Scala Programming for Enterprise Web Development

Scala Source Code and Density

2012-02-27T10:16:00.001-08:00

I love Scala. It enables me to write concise / dense and clear code at the same time.

Take for example the piece of code below.

Had I written it in Java, it would be much longer, while at the same time less dense, and with much less clarity of what it is doing.

val site = config.sites.find(_.name == siteName).getOrElse(

throw new IllegalArgumentException("Cannot find site " + siteName))

val group = config.groups.find(_.name == groupName).getOrElse(

throw new IllegalArgumentException("Cannot find group " + groupName))

group.repositories.foreach { repo =>

val repoDir = new File(group.path, repo.name)

println("Backing up to repository %s at %s starting..." format (repo.name, repoDir))

if (repoDir.mkdir())

println("Created directory %s" format repoDir)

repo.facets.foreach { facet =>

println("Exporting facet %s..." format facet.name)

val source = site.databases.find(_.name == facet.source).getOrElse(

throw new IllegalArgumentException(

"Facet %s references non-existing database %s" format (facet.name, facet.source)))

println("Source database is %s:%s at %s" format (source.kind, source.name, source.url))

(source.kind, facet) match {

case ("neo4j", Facet(name, sourceName, "node", typeName, "json")) =>

val outFileName = new File(name + ".json")

println("Exporting %s nodes to %s" format (typeName, outFileName))

val dbDir = new File(new URI(source.url))

println("Neo4j database directory: %s" format dbDir)

val graphDb = new EmbeddedReadOnlyGraphDatabase(dbDir.getPath)

val (rowMeta, rows) = try {

val exporter = new Neo4jNodeExporter(graphDb, typeName)

println("Fetching meta...")

val rowMeta = exporter.fetchMeta()

println("Columns are: " + rowMeta.columns.mkString(", "))

val rows = exporter.export(rowMeta)

(rowMeta, rows)

} finally {

graphDb.shutdown()

}

println("Reading rows...")

val mapper = new ObjectMapper

mapper.getSerializationConfig.set(Feature.INDENT_OUTPUT, true)

val jsonRows = rows.map { row =>

val obj = mapper.createObjectNode()

for ((value, i) <- row.values.view.zipWithIndex) {

if (value != null)

obj.put(rowMeta.columns(i), value)

}

obj

}

val jsonArray = mapper.createArrayNode().addAll(jsonRows.toList)

val jsonData = mapper.createObjectNode()

jsonData.put("data", jsonArray)

val outFile = new File(repoDir, outFileName.toString)

print("Writing %s..." format outFile)

mapper.writeValue(outFile, jsonData)

println(" [OK]")

case x: Any => println("Skipping unrecognized facet: " + x)

}

println("Backing up to repository %s finished." format repo.name)

}

Scala is also fantastic at storing ad-hoc object graph / trees, check a look a this :

sites = List(

Site(name = "dev", databases = List(

Database(name = "graph", kind = "neo4j", url = "file:///together/project/SatukanCinta/satukancinta-neo4j-db_dev_1.6/"))),

Site(name = "test",

databases = List(Database(name = "graph", kind = "neo4j", url = "file:///together/project/SatukanCinta/dumptest/graph")))),

groups = List(Group(name = "main", path = "/together/project/SatukanCinta/dump_main",

repositories = List(

Repository(name = "like", kind = "*", facets = List(

Facet(name = "user", source = "graph", primitive = "node", typeName = "com.satukancinta.domain.User", format = "json"),

Facet(name = "topic", source = "graph", primitive = "node", typeName = "com.satukancinta.domain.Interest", format = "json"),

Facet(name = "like", source = "graph", primitive = "relationship", typeName = "LIKE", format = "graphml"))))))) {

Beat that, Java!

Still don't believe me? How about processing a bunch of collections, and sprinkle built-in parallel capability :

val indexHits = graphDb.getAllNodes.par.filter(_.getProperty("__type__") == typeName)

log.info("Index for {} returned {} nodes", typeName, indexHits.size)

val columnNames = indexHits.par.flatMap( node =>

node.getPropertyKeys.filter( _ != "__type__" ) ).toSet

val sortedColumns = columnNames.toList.sorted

log.info("Columns for {}: {}", typeName, sortedColumns.mkString(", "))

RowMeta(columns = sortedColumns)

I really can't imagine doing that (including the concurrency) in Java. Phew.

Verbose code == easy to read ? Not always. This one is much easier on the eyes.

Tip: To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

UnproxyableResolutionException Workaround when using Scala Closures and javax.inject CDI Beans Together

2012-02-15T08:50:00.001-08:00

Some powerful Scala programming language features like closures, pattern matching, and lazy vals don't work well with dependency injection frameworks like javax.inject aka CDI. This is due to stricter class structure requirements to enable proxying.

For example, this "innocent" code will not work:

@Inject private var fbPhotoImporterFactory: Instance[FacebookPhotoImporter] = _
@Produces @Named("facebookPhotoImporter") private var fbPhotoImporter: ActorRef = _

@PostConstruct
def init() {
    logger.debug("Starting FacebookPhotoImporter actor")
    fbPhotoImporter = Actor.actorOf(fbPhotoImporterFactory.get())
    fbPhotoImporter.start()
}

It will throw:

Caused by: org.jboss.weld.exceptions.UnproxyableResolutionException: WELD-001437 Normal scoped bean class com.satukancinta.web.Persistence is not proxyable because the type is final or it contains a final method public final javax.enterprise.inject.Instance com.satukancinta.web.Persistence.com$satukancinta$web$Persistence$$fbPhotoImporterFactory() - Managed Bean [class com.satukancinta.web.Persistence] with qualifiers [@Any @Default].
    at org.jboss.weld.util.Proxies.getUnproxyableClassException(Proxies.java:225)
    at org.jboss.weld.util.Proxies.getUnproxyableTypeException(Proxies.java:178)
    at org.jboss.weld.util.Proxies.getUnproxyableTypesExceptionInt(Proxies.java:193)
    at org.jboss.weld.util.Proxies.getUnproxyableTypesException(Proxies.java:167)
    at org.jboss.weld.bootstrap.Validator.validateBean(Validator.java:110)
    at org.jboss.weld.bootstrap.Validator.validateRIBean(Validator.java:126)
    at org.jboss.weld.bootstrap.Validator.validateBeans(Validator.java:345)
    at org.jboss.weld.bootstrap.Validator.validateDeployment(Validator.java:330)
    at org.jboss.weld.bootstrap.WeldBootstrap.validateBeans(WeldBootstrap.java:366)
    at org.jboss.as.weld.WeldContainer.start(WeldContainer.java:82)
    at org.jboss.as.weld.services.WeldService.start(WeldService.java:89)
    ... 5 more

As you can see, my use code isn't exactly "edge cases".

It's actually a pretty common use case: create a Akka actor and pass a factory function to it, as a closure.
The code above doesn't look like it's using a closure, but it actually is when written like this: (same functionality, but still breaks CDI)

fbPhotoImporter = Actor.actorOf { fbPhotoImporterFactory.get() }

I can see why CDI has a strict requirement, and I can also understand why Scala implements it the way it is (Scala developers definitely already has a lot of problems working around powerful Scala features into a very restrictive JVM bytecode requirements). This is the price we pay for having a somewhat inferior language (Java, please don't get offended) in the first place.

But I as an application developer want to have a quick fix for this issue. Re-coding the class in plain Java is one option, but it turns I don't need to. There is a workaround, by creating a helper method then using it:

@Inject private var fbPhotoImporterFactory: Instance[FacebookPhotoImporter] = _
@Produces @Named("facebookPhotoImporter") private var fbPhotoImporter: ActorRef = _

def createFbPhotoImporter() = fbPhotoImporterFactory.get()

@PostConstruct
def init() {
    logger.debug("Starting FacebookPhotoImporter actor")
    fbPhotoImporter = Actor.actorOf(createFbPhotoImporter)
    fbPhotoImporter.start()
}

Now Scala is happy and CDI is also happy. Yes it's a bit more verbose but not too bad. And I guess the code is now somewhat more understandable for Java guys. :)

Tip: To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Scala "Bug" with CDI Dependency Injection

2012-01-22T07:17:00.001-08:00

“Sometimes”, Scala creates public final methods, although the .scala source defines
no public final method at all.
There are two things that CDI doesn’t like (which Scala “sometimes” generates):
1. public final methods
2. public fields
To investigate and reproduce these problems I created a scala-cdi project at GitHub.

public final method: The Bug

Referencing a parent field from a closure / inner class triggers this behavior:

@RequestScoped @Named class IndexBean { private lazy val log = LoggerFactory.getLogger(classOf[IndexBean]) def testExecutor() = { val executor = Executors.newFixedThreadPool(4); executor.submit(new Runnable() { override def run(): Unit = log.debug("Executor is running") }) } }

Compiles to:

$ javap -p IndexBean Compiled from "IndexBean.scala" public class com.soluvas.scalacdi.IndexBean extends java.lang.Object implements scala.ScalaObject{ private org.slf4j.Logger com$soluvas$scalacdi$IndexBean$$log; ... public final org.slf4j.Logger com$soluvas$scalacdi$IndexBean$$log();

Deploying this app in Weld will throw:

org.jboss.weld.exceptions.UnproxyableResolutionException: WELD-001437 Normal scoped bean class com.soluvas.scalacdi.IndexBean is not proxyable because the type is final or it contains a final method public final org.slf4j.Logger com.soluvas.scalacdi.IndexBean.com$soluvas$scalacdi$IndexBean$$log() - Managed Bean [class com.soluvas.scalacdi.IndexBean] with qualifiers [@Any @Default @Named].         at org.jboss.weld.util.Proxies.getUnproxyableClassException(Proxies.java:225)         at org.jboss.weld.util.Proxies.getUnproxyableTypeException(Proxies.java:178)         at org.jboss.weld.util.Proxies.getUnproxyableTypesExceptionInt(Proxies.java:193)         at org.jboss.weld.util.Proxies.getUnproxyableTypesException(Proxies.java:167)         at org.jboss.weld.bootstrap.Validator.validateBean(Validator.java:110)

public final method: Workaround

Create a final local variable to hold the parent instance’s value:

def testExecutor() = { val executor = Executors.newFixedThreadPool(4); // this avoids 'log' becoming 'final' like: // private org.slf4j.Logger com$soluvas$scalacdi$IndexBean$$log; // public final org.slf4j.Logger com$soluvas$scalacdi$IndexBean$$log(); val log = this.log; executor.submit(new Runnable() { override def run(): Unit = log.debug("Executor is running") }) }

Which now compiles to:

$ javap -p IndexBean Compiled from "IndexBean.scala" public class com.soluvas.scalacdi.IndexBean extends java.lang.Object implements scala.ScalaObject{ private org.slf4j.Logger log; private org.slf4j.Logger log();

public field

I’m not able to reproduce this yet...
Tip: To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Implementing RichFaces ExtendedDataModel for JSF Paging with Spring Data Neo4j and Scala

2012-01-01T10:32:00.001-08:00

JSF 2.1 and JBoss RichFaces 4.1.0 make it easy to do server-side paging and sorting, which improves performance of Java EE web applications significantly compared to returning list of all rows from the database and filtering it later in the application.

By implementing ExtendedDataModel, the data model can be used directly by rich:dataTable and rich:dataScroller JSF components.

ExtendedDataModel for Spring Data Neo4j Finder/Query Methods

To implement this on Neo4j graph database, by using Spring Data Neo4j finder methods we can implement ExtendedDataModel like below: (in Scala programming language)

package com.satukancinta.web

import collection.JavaConversions._
import org.ajax4jsf.model.ExtendedDataModel
import javax.faces.context.FacesContext
import org.springframework.data.domain.Page
import org.ajax4jsf.model.DataVisitor
import org.springframework.data.neo4j.repository.GraphRepository
import org.springframework.data.domain.PageRequest
import org.springframework.data.neo4j.aspects.core.NodeBacked
import org.ajax4jsf.model.Range
import org.ajax4jsf.model.SequenceRange
import org.slf4j.LoggerFactory
import org.springframework.data.domain.Sort
import org.springframework.data.domain.Sort.Direction
import org.springframework.data.domain.Pageable

abstract class FinderModel[E]() extends ExtendedDataModel[E] {
private lazy val log = LoggerFactory.getLogger(classOf[FinderModel[E]])

private lazy val rowCount: Int = {
    val result= getRowCountLazy
    log.debug("Total rows: {}", result)
    result
}

private var rowIndex: Int = _
private var page: Page[E] = _
private var pageData: List[E] = _
private var lastRange: (Int, Int) = _

log.trace("Created {}", this.getClass)

def getRowCountLazy: Int
def find(pageable: Pageable): Page[E]

def setRowKey(key: Object): Unit = setRowIndex(key.asInstanceOf[Int])
def getRowKey: Object = getRowIndex: java.lang.Integer

private def loadData(range: Range): Unit = {
    val seqRange = range.asInstanceOf[SequenceRange]
    val curRange = (seqRange.getFirstRow, seqRange.getRows)
    if (lastRange == curRange) {
      log.debug("loadData returning cached")
      return
    }
    lastRange = curRange

    val pageNum = seqRange.getFirstRow / seqRange.getRows
    // ORDER BY name is painfully slow: https://groups.google.com/group/neo4j/t/f2219df41f5500a9
    val pageReq = new PageRequest(pageNum, seqRange.getRows/*, Direction.ASC, "y.name"*/)
    log.debug("loadData({}, {}) -> PageRequest({}, {})",
        Array[Object](seqRange.getFirstRow: java.lang.Long, seqRange.getRows: java.lang.Long,
            pageNum: java.lang.Long, seqRange.getRows: java.lang.Long))
    val startTime = System.currentTimeMillis
    page = find(pageReq)
    val findTime = System.currentTimeMillis - startTime
    log.debug("Page has {} rows of {} total in {} pages, took {}ms",
        Array[Object](page.getSize: java.lang.Long, page.getTotalElements: java.lang.Long,
            page.getTotalPages: java.lang.Long, findTime: java.lang.Long))
    pageData = page.toList
//    val pageIds = pageData.map( _.asInstanceOf[NodeBacked].getNodeId )
//    log.debug("Node IDs: {}", pageIds);
}

def walk(context: FacesContext, visitor: DataVisitor, range: Range, argument: Object): Unit = {
    loadData(range)
    for (val index <- 0 to pageData.size - 1) {
      visitor.process(context, index, argument)
    }
}

def isRowAvailable: Boolean = rowIndex < pageData.length

def getRowCount: Int = rowCount

def getRowData: E = {
    val result = pageData(rowIndex) // repository.findOne(rowKey.asInstanceOf[Long])
    val node = result.asInstanceOf[NodeBacked]
    log.trace("getRowData({}) = #{}: {}",
        Array[Object](rowIndex: java.lang.Long, node.getNodeId: java.lang.Long, node))
    result
}

def getRowIndex: Int = rowIndex
def setRowIndex(index: Int): Unit = rowIndex = index

def getWrappedData: Object = { null }
def setWrappedData(wrappedData: Object): Unit = { /* dummy */ }

}

To use the FinderModel, it's much easier if we create a repository first and add some finder/query methods returning count and Page:

public interface InterestRepository extends GraphRepository<Interest> {

@Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN COUNT(y)")
public Long findUserLikeCount(@Param("userId") long userId);

    // ORDER BY name is still slow: https://groups.google.com/group/neo4j/t/f2219df41f5500a9
//    @Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN y ORDER BY y.name")
    @Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN y")
    public Page<Interest> findUserLikes(@Param("userId") long userId, Pageable pageable);

}

How to create a FinderModel instance from Java :

@Inject InterestRepository interestRepo;
private FinderModel<Interest> userLikesModel;

@PostConstruct public void init() {
userLikesModel = new FinderModel<Interest>() {

            @Override
            public int getRowCountLazy() {
                return interestRepo.findUserLikeCount(user.getNodeId()).intValue();
            }

            @Override
            public Page<Interest> find(Pageable pageable) {
                return interestRepo.findUserLikes(user.getNodeId(), pageable);
            }
        };
    }

And how to use this data model from a JSF Template .xhtml file:

<rich:dataTable id="interestTable" var="interest" value="#{userLikes.userLikesModel}" rows="20">
    <rich:column>
        <f:facet name="header">Name</f:facet>
        <h:link outcome="/interests/show?id=#{interest.nodeId}" value="#{interest.name}"/>
    </rich:column>
    <f:facet name="footer"><rich:dataScroller/></f:facet>
</rich:dataTable>

Quite practical, isn't it?

ExtendedDataModel for Spring Data Neo4j Repository

FinderModel can then be further subclassed to handle any Spring Data Neo4j repository:

class GraphRepositoryModel[E]() extends FinderModel[E] {
private var repository: GraphRepository[E] = _

def getRowCountLazy: Int = repository.count.toInt
def find(pageable: Pageable): Page[E] = repository.findAll(pageable)

override def getWrappedData: Object = repository
override def setWrappedData(wrappedData: Object): Unit =
repository = wrappedData.asInstanceOf[GraphRepository[E]]

}

And use it like this:

@Inject InterestRepository interestRepo;
private GraphRepositoryModel<Interest> interestModel;

@PostConstruct public void init() {
    interestModel = new GraphRepositoryModel<Interest>();
    interestModel.setWrappedData(interestRepo);
}

Hope this helps.

To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Scala closures vs Guava collection functions

2011-12-31T10:33:00.001-08:00

Let me show you the same method using list transformations (aka "map" in functional programming speak), one in Java programming language:

    @GET @Path("user/{userId}/likes") @Produces(MediaType.APPLICATION_JSON)
    public Payload<Iterable<Map<String, Object>>> getUserLikes(@PathParam("userId") long userId) {
        User user = neo4j.findOne(userId, User.class);
        Iterable<Interest> likeInterests = user.getLikeInterests();
        Iterable<Map<String, Object>> likes = Iterables.transform(likeInterests, new Function<Interest, Map<String, Object>>() {
            @Override
            public Map<String, Object> apply(Interest interest) {
                HashMap<String, Object> row = new HashMap<String, Object>();
                row.put("id", interest.getNodeId());
                row.put("name", interest.getName());
                return row;
            }
        });
        return new Payload<Iterable<Map<String, Object>>>(likes);
    }

And one in Scala programming language :

    @GET @Path("user/{userId}/likes") @Produces(Array(MediaType.APPLICATION_JSON))
    def getUserLikes(@PathParam("userId") userId: Long): Payload[Iterable[Map[String, Object]]] = {
        val user = neo4j.findOne(userId, classOf[User])
        val likeInterests = user.getLikeInterests
        val likes = likeInterests.map(interest =>
        Map("id"->interest.getNodeId, "name"->interest.getName) )
        new Payload(likes)
    }

Is Scala hard to read? I'll leave it to you to decide. :-)

To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Coding JSON REST JAX-RS Service Application to Access Neo4j Database in Scala

2011-12-31T09:21:00.001-08:00

Spring Data Neo4j makes it easy to accessing graph data in Neo4j graph database.

After separating the AspectJ-enhanced Spring Data Neo4j node entities, relationship entities, and repositories, it's very fun to access the entities from a Scala web application. In this case, I'll show you a JAX-RS application written in Scala programming language, consuming and producing JSON in REST-style. The application exposes Spring Data Neo4j through HTTP, which can be accessed via curl or any other web client.

Java programming language version:

@Path("node") @Stateless
public class NodeResource {

    private transient Logger logger = LoggerFactory.getLogger(NodeResource.class);
    @Inject Neo4jTemplate neo4j;
    @Inject InterestRepository interestRepo;

    @GET @Path("interest") @Produces(MediaType.APPLICATION_JSON)
    public Iterable<Interest> interest() {
        ClosableIterable<Interest> records = neo4j.findAll(Interest.class);
        return records;
    }

    @GET @Path("user") @Produces(MediaType.APPLICATION_JSON)
    public Payload<User> getUser() {
        return new Payload<User>(neo4j.findOne(5L, User.class));
    }

    @POST @Path("interest")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response createInterest(Payload<Interest> payload) {
        logger.debug("createInterest {}", payload.data);
        Interest interest = payload.data;
        interest.persist();
        return Response.created(URI.create(String.format("interest/%d", interest.getNodeId())))
                .entity(new Payload<Interest>(interest)).build();
    }

    @DELETE @Path("interest/{id}")
    public Response deleteInterest(@PathParam("id") long id) {
        try {
            Interest node = neo4j.findOne(id, Interest.class);
            node.remove();
            return Response.ok("deleted").build();
        } catch (DataRetrievalFailureException e) {
            return Response.status(Status.NOT_FOUND).entity(e.getMessage()).build();
        }
    }

    @GET @Path("interest/by/facebookId/{facebookId}")
    @Produces(MediaType.APPLICATION_JSON)
    public Payload<Interest> findInterestByFacebookId(@PathParam("facebookId") long facebookId) {
        logger.debug("findInterestByFacebookId {}", facebookId);
        Interest interest = interestRepo.findByFacebookId(facebookId);
        if (interest == null)
            throw new WebApplicationException(Response.status(Status.NOT_FOUND).entity("Interest with facebookId="+ facebookId +" not found").build());
        return new Payload<Interest>(interest);
    }

}

Scala programming language version:

@Path("node") @Stateless
class NodeResource {

   private lazy val logger = LoggerFactory.getLogger(classOf[NodeResource])
   @Inject var neo4j: Neo4jTemplate = _
   @Inject var interestRepo: InterestRepository = _

    @GET @Path("interest") @Produces(Array(MediaType.APPLICATION_JSON))
   def interest: Iterable[Interest] = neo4j.findAll(classOf[Interest])

@GET @Path("user") @Produces(Array(MediaType.APPLICATION_JSON))
def getUser: Payload[User] = new Payload[User](neo4j.findOne(5L, classOf[User]))

    @POST @Path("interest")
   @Consumes(Array(MediaType.APPLICATION_JSON))
   @Produces(Array(MediaType.APPLICATION_JSON))
   def createInterest(payload: Payload[Interest]): Response = {
       logger.debug("createInterest {}", payload.data)
       val interest = payload.data
        interest.persist
        Response.created(URI.create(String.format("interest/%d", interest.getNodeId)))
               .entity(new Payload[Interest](interest)).build
   }

    @DELETE @Path("interest/{id}")
   def deleteInterest(@PathParam("id") id: Long): Response = {
       try {
           val node = neo4j.findOne(id, classOf[Interest])
           node.remove
            Response.ok("deleted").build
       } catch {
          case e: DataRetrievalFailureException =>
           Response.status(Status.NOT_FOUND).entity(e.getMessage).build
       }
   }

   @GET @Path("interest/by/facebookId/{facebookId}")
   @Produces(Array(MediaType.APPLICATION_JSON))
   def findInterestByFacebookId(@PathParam("facebookId") facebookId: Long): Payload[Interest] = {
       logger.debug("findInterestByFacebookId {}", facebookId)
       val interest = interestRepo.findByFacebookId(facebookId)
       if (interest == null)
           throw new WebApplicationException(Response.status(Status.NOT_FOUND).entity("Interest with facebookId="+ facebookId +" not found").build
       new Payload[Interest](interest)
   }

}

Apart from less code and cruft, Scala code is not much different in structure.

If there are list processing functions or closures, then Scala code will read much easier, while the Java code will use Guava library and clunky syntax (at least until Java 8 arrives).

To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Graph Analysis with Scala and Spring Data Neo4j

2011-12-31T08:36:00.001-08:00

Neo4j graph database is the an awesome technology for graph data persistence. With Spring Data Neo4j accessing graph data becomes even easier.

The easiest way to use Spring Data Neo4j is by enabling its AspectJ weaving. Because I wanted to use both Scala and Spring Data Neo4j in my web application, using both languages (AspectJ and Scala) in the same project isn't possible for now. A tip for you, separate the AspectJ-enhanced classes (@NodeEntity, @RelationshipEntity, and repositories) into a separate AspectJ project, then depend on the AspectJ from the Scala application.

The result is I'm able to fully utilize the versatile Scala and the excellent Spring Data libraries with Neo4j.

Now for mandatory code comparison between Java and Scala :-)

Java programming language version:

package com.satukancinta.web;

import java.util.List;
import java.util.Map;

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import javax.inject.Named;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.neo4j.conversion.Result;
import org.springframework.data.neo4j.support.Neo4jTemplate;

import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.satukancinta.domain.User;

/**
* @author ceefour
* Various analysis of the social graph.
*/
@Named @ApplicationScoped
public class GraphAnalysis {

    private transient Logger logger = LoggerFactory.getLogger(GraphAnalysis.class);
    @Inject Neo4jTemplate neo4j;

    public List<MutualLikeRow> getMutualLikesLookup(User user) {
        logger.debug("getMutualLikesLookup {}/{}", user.getNodeId(), user);
        Result<Map<String, Object>> rows = neo4j.query("START x=node("+ user.getNodeId() +") MATCH x-[:LIKE]->i<-[:LIKE]-y RETURN id(y) AS id, y.name AS name, COUNT(*) AS mutualLikeCount", null);
        Iterable<MutualLikeRow> result = Iterables.transform(rows, new Function<Map<String, Object>, MutualLikeRow>() {
            @Override
            public MutualLikeRow apply(Map<String, Object> arg) {
                return new MutualLikeRow((Long)arg.get("id"), (Integer)arg.get("mutualLikeCount"),
                        (String)arg.get("name"));
            }
        });
        return Lists.newArrayList(result);
    }

}

Scala programming language version:

package com.satukancinta.web
import collection.JavaConversions._
import org.slf4j._
import javax.inject.Inject
import org.springframework.data.neo4j.support.Neo4jTemplate
import com.satukancinta.domain.User
import javax.enterprise.context.ApplicationScoped
import javax.inject.Named

/**
* @author ceefour
* Analysis functions of friend network graph.
*/
@Named @ApplicationScoped
class GraphAnalysis {

private lazy val logger = LoggerFactory.getLogger(classOf[GraphAnalysis])
@Inject private var neo4j: Neo4jTemplate = _

def getMutualLikesLookup(user: User): java.util.List[MutualLikeRow] = {
    logger.debug("getMutualLikesLookup {}/{}", user.getNodeId, user)
    val rows = neo4j.query(
        "START x=node("+ user.getNodeId() +") MATCH x-[:LIKE]->i<-[:LIKE]-y RETURN id(y) AS id, y.name AS name, COUNT(*) AS mutualLikeCount", null)
    val result = rows.map( r =>
        new MutualLikeRow(r("id").asInstanceOf[Long],
        r("mutualLikeCount").asInstanceOf[Integer].longValue,
        r("name").asInstanceOf[String]) )
        .toList
    result.sortBy(-_.mutualLikeCount)
}

}

As you can see, the Scala version is not only much more concise, easier to understand, but actually has added functionality (sorted using .sortBy) with less code. Thanks to collection functions and closure support.

To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

How to Exclude Scala/Java Source Files by Name in sbt

2011-10-12T19:04:00.001-07:00

I thought this small tip would be useful to someone as I recently needed to do this and didn't know how to.

The project base directory is by default a source directory in addition to src/main/scala. You can exclude source files by name (butler.scala in the example below) like:

excludeFilter in unmanagedSources := "butler.scala"

To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Using UnboundID LDAP SDK Directory API from Scala

2011-06-21T08:15:00.001-07:00

I'm very new in the world of LDAP Directory Services. After installing ApacheDS Server, Apache Directory Studio LDAP GUI Client, and trying the plain old ldapsearch and ldapcompare command-line utilities, it was time for me to do some integration with Java applications (I'm actually trying to query LDAP directory from Ant build script task).

The most popular and programmer-friendly LDAP API at the moment is UnboundID LDAP SDK. To get a feel of how it works, I decided to use Scala REPL interpreter. I really love this tool (and the Scala programming language itself) more and more every time I use it!

The screen captures below doesn't do justice to the Scala interpreter. The tab-completion works really well!
Indeed the UnboundID LDAP SDK is really easy to use, and it's better with powerful Scala & its versatile interpreter for a quick ride. :-)

Learn Scala programming language quicker! Get Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.

Connect & Bind using UnboundID LDAP SDK and Scala

ceefour@annafi:~/vendor/unboundid-ldapsdk-2.2.0-se$ scala -cp unboundid-ldapsdk-se.jar  Welcome to Scala version 2.9.0.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_25). Type in expressions to have them evaluated. Type :help for more information. scala> import com.unboundid.ldap.sdk._ import com.unboundid.ldap.sdk._ scala> val con = new LDAPConnection con: com.unboundid.ldap.sdk.LDAPConnection = LDAPConnection(not connected) scala> con.connect("localhost", 10389) scala> con.bind("uid=admin,ou=system","password") res5: com.unboundid.ldap.sdk.BindResult = LDAPResult(resultCode=0 (success), messageID=1)

Connect & Bind via SSL

scala> import com.unboundid.util.ssl._ import com.unboundid.util.ssl._ scala> var sslUtil = new SSLUtil( new TrustAllTrustManager() ) sslUtil: com.unboundid.util.ssl.SSLUtil = com.unboundid.util.ssl.SSLUtil@43763e0b scala> var socketFactory = sslUtil.createSSL createSSLContext createSSLServerSocketFactory createSSLSocketFactory scala> var socketFactory = sslUtil.createSSLSocketFactory socketFactory: javax.net.ssl.SSLSocketFactory = com.sun.net.ssl.internal.ssl.SSLSocketFactoryImpl@43d7a5a scala> val con = new LDAPConnection LDAPConnection LDAPConnectionInternals LDAPConnectionOptions LDAPConnectionPool LDAPConnectionPoolHealthCheck LDAPConnectionPoolHealthCheckThread LDAPConnectionPoolStatistics LDAPConnectionReader LDAPConnectionStatistics scala> val con = new LDAPConnection(socketFactory, "localhost", 10636) con: com.unboundid.ldap.sdk.LDAPConnection = LDAPConnection(connected to localhost:10636) scala> con.bind("uid=admin,ou=system","password") res18: com.unboundid.ldap.sdk.BindResult = LDAPResult(resultCode=0 (success), messageID=1)

Search

scala> val results=con.search("ou=system",SearchScope.SUB,"(uid=admin)") results: com.unboundid.ldap.sdk.SearchResult = SearchResult(resultCode=0 (success), messageID=3, entriesReturned=1, referencesReturned=0) scala> results.getSearchEntries res8: java.util.List[com.unboundid.ldap.sdk.SearchResultEntry] = [SearchResultEntry(dn='uid=admin,ou=system', messageID=3, attributes={Attribute(name=uid, values={'admin'}), Attribute(name=keyAlgorithm, values={'RSA'}), Attribute(name=sn, values={'administrator'}), Attribute(name=objectClass, values={'person', 'organizationalPerson', 'inetOrgPerson', 'tlsKeyInfo', 'top'}), Attribute(name=displayName, values={'Directory Superuser'}), Attribute(name=cn, values={'system administrator'}), Attribute(name=publicKey, base64Values={'MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJjX2EbUDyBZYFPfsSNMZRsW3mLc/KiKRO6pck3J3eFMKErXA7jxpiho/Eoc6RWgxut2K3aITnQZIl1hHF6Hv30CAwEAAQ=='}), Attribute(name=privateKeyFormat, values={'PKCS#8'}), Attribute(name=publicKeyFormat, values={'X.509'}), Attribute(name=privateKey, ba... scala> results.getSearchEntries.get(0) res11: com.unboundid.ldap.sdk.SearchResultEntry = SearchResultEntry(dn='uid=admin,ou=system', messageID=3, attributes={Attribute(name=uid, values={'admin'}), Attribute(name=keyAlgorithm, values={'RSA'}), Attribute(name=sn, values={'administrator'}), Attribute(name=objectClass, values={'person', 'organizationalPerson', 'inetOrgPerson', 'tlsKeyInfo', 'top'}), Attribute(name=displayName, values={'Directory Superuser'}), Attribute(name=cn, values={'system administrator'}), Attribute(name=publicKey, base64Values={'MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJjX2EbUDyBZYFPfsSNMZRsW3mLc/KiKRO6pck3J3eFMKErXA7jxpiho/Eoc6RWgxut2K3aITnQZIl1hHF6Hv30CAwEAAQ=='}), Attribute(name=privateKeyFormat, values={'PKCS#8'}), Attribute(name=publicKeyFormat, values={'X.509'}), Attribute(name=privateKey, base64Values={'MII...

Compare

scala> con.compare("uid=admin,ou=system", "userPassword", "password") res12: com.unboundid.ldap.sdk.CompareResult = LDAPResult(resultCode=5 (compare false), messageID=4, opType='compare', matchedDN='uid=admin,ou=system') scala> con.compare("uid=admin,ou=system", "uid", "admin") res13: com.unboundid.ldap.sdk.CompareResult = LDAPResult(resultCode=6 (compare true), messageID=5, opType='compare', matchedDN='uid=admin,ou=system')

Get Entry & Attribute Value

scala> val entry = con.getEntry("uid=admin,ou=system") entry: com.unboundid.ldap.sdk.SearchResultEntry = SearchResultEntry(dn='uid=admin,ou=system', messageID=7, attributes={Attribute(name=uid, values={'admin'}), Attribute(name=keyAlgorithm, values={'RSA'}), Attribute(name=sn, values={'administrator'}), Attribute(name=objectClass, values={'person', 'organizationalPerson', 'inetOrgPerson', 'tlsKeyInfo', 'top'}), Attribute(name=displayName, values={'Directory Superuser'}), Attribute(name=cn, values={'system administrator'}), Attribute(name=publicKey, base64Values={'MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJjX2EbUDyBZYFPfsSNMZRsW3mLc/KiKRO6pck3J3eFMKErXA7jxpiho/Eoc6RWgxut2K3aITnQZIl1hHF6Hv30CAwEAAQ=='}), Attribute(name=privateKeyFormat, values={'PKCS#8'}), Attribute(name=publicKeyFormat, values={'X.509'}), Attribute(name=privateKey, base64Values={'MII... scala> entry.getAttribute getAttribute getAttributeValue getAttributeValueAsBoolean getAttributeValueAsDN getAttributeValueAsDate getAttributeValueAsInteger getAttributeValueAsLong getAttributeValueByteArrays getAttributeValueBytes getAttributeValues getAttributes getAttributesWithOptions scala> entry.getAttribute def getAttribute(String): Attribute def getAttribute(String, schema.Schema): Attribute scala> entry.getAttribute("userPassword") res16: com.unboundid.ldap.sdk.Attribute = Attribute(name=userPassword, values={'{SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g='}) scala> entry.getAttributeValue("userPassword") res17: java.lang.String = {SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g=

Scala 2.9.0.1 final version released: programming language with parallel features for Java VM

2011-06-21T08:14:00.001-07:00

UPDATE: Scala 2.9.0.1 has replaced 2.9.0 as it hot-fixed several important bugs.

Scala 2.9.0 final:

We are happy to announce the release of the new stable release of the Scala distribution. The new Scala 2.9.0 final is available from our Download Page. The Scala 2.9.0 codebase includes several additions, notably the new Parallel Collections, but it also introduces improvements on many existing features, and contains many bug fixes.

Scala 2.9.0 binaries are available for the following libraries:

Dispatch 0.7.8 and 0.8.1
Unfiltered 0.3.2
Spde 0.3.1

Of course.

Here are some recommended learning resources on Scala programming language:

Also, the Typesafe Stack is also out, which brings together Scala, Akka, and a few other things to get one up-and-running quickly. Much fun.

On the collection side of things, one of the first questions I saw was: do parallel collections share a common interface with standard collections. The answer is yes, they do, but not one that existed in 2.8.1.

You see, a trouble with parallel collections is that, now that they are available, people will probably be passing them around. If they could be passed to old code -- as it was briefly contemplated -- that old code could crash in mysterious ways. In fact, it happens with REPL itself.

For that reason, ALL of your code comes with a guarantee that it will only accept sequential collections. In other words, Iterable, Seq, Set, etc, they all now share a guarantee to be sequential, which means you cannot pass a parallel sequence to a method expecting Seq.

The parallel collections start with Par: ParIterable, ParSeq, ParSet and ParMap. No ParTraversable for now. These are guaranteed to be parallel. They can be found inside scala.collection.parallel, scala.collection.parallel.immutable, etc.

You can also get a parallel collection just by calling the ".par" method on it, and, similarly, the ".seq" method will return a sequential collection.

Now, if you want your code to not care whether it receives a parallel or sequential collection, you should prefix it with Gen: GenTraversable, GenIterable, GenSeq, etc. These can be either parallel or sequential.

And, now, something fun to try out:

def p[T](coll: collection.GenIterable[T]) = coll foreach println; p(1 to 20); p((1 to 20).par)

I highly recommend the following books for more information about Scala programming language:

Copied mostly verbatim from this announcement and that announcement.

How to Dump/Inspect Object or Variable in Java

2010-12-26T05:54:00.001-08:00

Scala (console) has a very useful feature to inspect or dump variables / object values :

scala> def b = Map("name" -> "Yudha", "age" -> 27)
b: scala.collection.immutable.Map[java.lang.String,Any]

scala> b
res1: scala.collection.immutable.Map[java.lang.String,Any] = Map((name,Yudha), (age,27))

Inside our application, especially in Java programming language (although the techniques below obviously works with any JVM language like Scala and Groovy) sometimes we want to inspect/dump the content of an object/value. Probably for debugging or logging purposes.

My two favorite techniques is just to serialize the Java object to JSON and/or XML. An added benefit is that it's possible to deserialize the dumped object representation back to an actual object if you want.

JSON Serialization with Jackson

Depend on Jackson (using Maven):
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.6.3</version>
</dependency>
Then use it:
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

..
Logger logger = LoggerFactory.getLogger(getClass());

@Test
public void level() throws ServiceException, JsonGenerationException, JsonMappingException, IOException {
MagentoServiceLocator locator = new MagentoServiceLocator();
Mage_Api_Model_Server_HandlerPortType port = locator.getMage_Api_Model_Server_HandlerPort();
String sessionId = port.login("...", "...");
logger.info(String.format("Session ID = %s", sessionId));
Map[] categories = (Map[]) port.call(sessionId, "catalog_category.level", new Object[] { null, null, 2 } );
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationConfig.Feature.INDENT_OUTPUT, true);
logger.info( mapper.writeValueAsString(categories) );
}

Example output :

6883 [main] INFO id.co.bippo.shop.magentoclient.AppTest - [ {
"position" : "1",
"level" : "2",
"is_active" : "1",
"name" : "Gamis",
"category_id" : "3",
"parent_id" : 2
}, {
"position" : "2",
"level" : "2",
"is_active" : "1",
"name" : "Celana",
"category_id" : "5",
"parent_id" : 2
} ]

XML Serialization with XStream

As a pre-note, XStream can also handle JSON with either Jettison or its own JSON driver, however people usually prefer Jackson than XStream for JSON serialization.

Maven dependency for XStream:
<dependency>
<groupId>xstream</groupId>
<artifactId>xstream</artifactId>
<version>1.2.2</version>
</dependency>
Use it:
import java.io.IOException;
import java.rmi.RemoteException;
import java.util.Map;

import javax.xml.rpc.ServiceException;

import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.thoughtworks.xstream.XStream;
...
@Test
public void infoXml() throws ServiceException, RemoteException {
MagentoServiceLocator locator = new MagentoServiceLocator();
Mage_Api_Model_Server_HandlerPortType port = locator.getMage_Api_Model_Server_HandlerPort();
String sessionId = port.login("...", "...");
logger.info(String.format("Session ID = %s", sessionId));
Map category = (Map) port.call(sessionId, "catalog_category.info",
new Object[] { 3 } );
XStream xstream = new XStream();
logger.info( xstream.toXML(category) );
}

Sample output:

5949 [main] INFO id.co.bippo.shop.magentoclient.AppTest - <map>
<entry>
    <string>position</string>
    <string>1</string>
</entry>
<entry>
    <string>custom_design</string>
    <string></string>
</entry>
<entry>
    <string>custom_use_parent_settings</string>
    <string>0</string>
</entry>
<entry>
    <string>custom_layout_update</string>
    <string></string>
</entry>
<entry>
    <string>include_in_menu</string>
    <string>1</string>
</entry>
<entry>
    <string>custom_apply_to_products</string>
    <string>0</string>
</entry>
<entry>
    <string>meta_keywords</string>
    <string>gamis, busana muslim</string>
</entry>
<entry>
    <string>available_sort_by</string>
    <string></string>
</entry>
<entry>
    <string>url_path</string>
    <string>gamis.html</string>
</entry>
<entry>
    <string>children</string>
    <string></string>
</entry>
<entry>
    <string>landing_page</string>
    <null/>
</entry>
<entry>
    <string>display_mode</string>
    <string>PRODUCTS</string>
</entry>
<entry>
    <string>level</string>
    <string>2</string>
</entry>
<entry>
    <string>description</string>
    <string>Gamis untuk muslimah</string>
</entry>
<entry>
    <string>name</string>
    <string>Gamis</string>
</entry>
<entry>
    <string>path</string>
    <string>1/2/3</string>
</entry>
<entry>
    <string>created_at</string>
    <string>2010-12-24 11:37:41</string>
</entry>
<entry>
    <string>children_count</string>
    <string>0</string>
</entry>
<entry>
    <string>is_anchor</string>
    <string>1</string>
</entry>
<entry>
    <string>url_key</string>
    <string>gamis</string>
</entry>
<entry>
    <string>parent_id</string>
    <int>2</int>
</entry>
<entry>
    <string>filter_price_range</string>
    <null/>
</entry>
<entry>
    <string>all_children</string>
    <string>3</string>
</entry>
<entry>
    <string>is_active</string>
    <string>1</string>
</entry>
<entry>
    <string>page_layout</string>
    <string></string>
</entry>
<entry>
    <string>image</string>
    <null/>
</entry>
<entry>
    <string>category_id</string>
    <string>3</string>
</entry>
<entry>
    <string>default_sort_by</string>
    <null/>
</entry>
<entry>
    <string>custom_design_from</string>
    <null/>
</entry>
<entry>
    <string>updated_at</string>
    <string>2010-12-24 11:37:41</string>
</entry>
<entry>
    <string>meta_description</string>
    <string>Jual baju gamis untuk muslim</string>
</entry>
<entry>
    <string>custom_design_to</string>
    <null/>
</entry>
<entry>
    <string>path_in_store</string>
    <null/>
</entry>
<entry>
    <string>meta_title</string>
    <string>Gamis</string>
</entry>
<entry>
    <string>increment_id</string>
    <null/>
</entry>
</map>

Which one is better?

I personally prefer JSON, but fortunately, you always have a choice. :-)

Eclipse RAP Single Sourcing Awesomeness (with EMF Editor and Teneo+Hibernate as bonus!)

2010-12-20T15:15:00.001-08:00

Eclipse Rich Client Platform has come a looong way since it was first introduced (and used in Eclipse IDE). The new Eclipse RAP (Rich Application Platform) is also becoming more and more attractive for deploying existing or new Eclipse RCP applications to the web.

One of my the projects I'm working on is developed on top of Eclipse RCP. It uses additional plugins such as EMF (Eclipse Modeling Framework) including EMF Editor UI, Teneo (EMF Persistence for Relational Databases), and Hibernate.

After some work, I managed to run the whole application on both Eclipse RCP (desktop) and Eclipse RAP (web-based). See the screenshots for proof.

Thanks to the recently released EMF Support for RAP I don't have to let go any of the nice EMF generated editor UIs for the web-based RAP version.

What's amazing is how little the work I have to do to port the RCP app to RAP.

The changes I needed to do is not changing code, but juggling dependencies to plugins and/or packages. Also creating a few platform-specific plugins (different based on whether I deploy on RCP or RAP).

It boils down to:

Do not hard-depend on org.eclipse.ui plugin. Either depend on both org.eclipse.ui and org.eclipse.rap.ui plugins as optional dependencies, or import the specific packages. I prefer optional dependency on both plugins because it's much faster and easier.
Be aware that there will be multiple sessions at once.
2D Drawing functions are not yet fully available. (and I guess will never be available)

See the Eclipse RAP FAQ on Single Sourcing for more information.

See and download the full gallery on posterous

Fixing error: The type org.eclipse.core.runtime.IAdaptable cannot be resolved. It is indirectly referenced from required .class files.

2010-12-20T00:01:00.001-08:00

If you get one of the following errors :

The type org.eclipse.core.runtime.IAdaptable cannot be resolved. It is indirectly referenced from required .class files.

The type org.eclipse.core.runtime.CoreException cannot be resolved. It is indirectly referenced from required .class files.

First of all, check that your plugins depend on org.eclipse.core.runtime plugin.

The classes above are located in org.eclipse.equinox.common plugin, and should be included (along with org.eclipse.core.runtime plugin) in your target platform.

If it still occurs, most likely you get your target platform plugins mixed up. I got this error because I tried to mix plugins from my Eclipse IDE installation (Helios 3.6-SR-1) with Eclipse 3.7M4 Platform plugins.

Simply unchecking the plugins from target platform Contents tab is not enough. I have to actually remove the location. If you notice duplicate plugins in your Target Platform Definition's Contents tab, then you're getting this problem.

Remove the offending plugins location from the target platform definition. If you must add plugins from Eclipse IDE location, cherry pick each plugin from the Locations UI, instead of just adding the whole SDK and unchecking them from the Contents tab.

Creating an About Dialog for your Eclipse RCP Application

2010-12-19T11:41:00.001-08:00

Displaying an About box in your Eclipse RCP Application/Product is actually very simple. However as is typical of a framework ("don't call us, we'll call you" principle), there are conventions you must follow.

Before you do this, you must already create an Eclipse RCP Application class that implements IApplication and register it as an Eclipse extension in your plugin.xml.

Adding the Help > About Menu Item

First, edit your ApplicationActionBarAdvisor class (which extends org.eclipse.ui.application.ActionBarAdvisor base class), as follows:

    protected void makeActions(IWorkbenchWindow window) {
        aboutAction = ActionFactory.ABOUT.create(window);
        register(aboutAction);
    }

That will register the About action. You will also need to add the menu action itself to the menu bar:

    protected void fillMenuBar(IMenuManager menuBar) {
        MenuManager helpMenu = new MenuManager("&Help", IWorkbenchActionConstants.M_HELP);

        menuBar.add(helpMenu);
        helpMenu.add(aboutAction);
    }

Launch your Eclipse RCP application and you can display the About dialog.

Customizing the About Dialog Box

To customize the About dialog box's contents, first you must create an Eclipse RCP Product Configuration.
Click File > New > Product Configuration and define your product.

This should also add your product to extension point 'org.eclipse.core.runtime.products'.

Edit your project's Launch Configuration to use the your Product Configuration instead of Eclipse Application. Verify that it works well.

Now you can customize the About box contents by editing your Product Configuration (.product file), go to Branding tab and About Dialog section. Specify the About Image and About Text there.

To specify the image, import an image resource (PNG, GIF, JPG) to your plugin project (e.g. inside an /icons folder). Important: Your image will need to be included inside your resulting plugin binary. Edit your plugin's manifest, go to Build tab, and make sure your images/icons are included (checked) for the binary build and source build.

After editing your Product Configuration, you must synchronize it with the plugin manifest. Go to the Product's Overview tab and click Synchronize (under Testing).

That action will update several properties in the org.eclipse.core.runtime.products extension, for example:

   <extension
         id="abispulsa_rcp"
         point="org.eclipse.core.runtime.products">
      <product
            application="com.abispulsa.bisnis.rcp.application"
            description="Layanan bagi korporasi untuk dapat dengan mudah mengisi pulsa."
            name="AbisPulsa Bisnis RCP">
         <property
               name="appName"
               value="AbisPulsa Bisnis RCP">
         </property>
         <property
               name="aboutText"
               value="AbisPulsa Bisnis merupakan layanan bagi korporasi untuk dapat dengan mudah mengisi pulsa.">
         </property>
         <property
               name="aboutImage"
               value="icons/AbisPulsa_icon_75x75.png">
         </property>
      </product>
   </extension>

For your information: Other properties you can use include:

windowImages
aboutImage
aboutText
appName
welcomePage
preferenceCustomization

References:

Fixing Eclipse RCP Launch Error: Application "org.eclipse.ui.ide.workbench" could not be found in the registry.

2010-12-19T09:56:00.001-08:00

If you encounter the following error message when launching your Eclipse RCP application/plugin :

!ENTRY org.eclipse.osgi 4 0 2010-12-20 00:49:08.433
!MESSAGE Application error
!STACK 1
java.lang.RuntimeException: Application "org.eclipse.ui.ide.workbench" could not be found in the registry. The applications available are: org.eclipse.ant.core.antRunner, org.eclipse.jdt.core.JavaCodeFormatter, org.eclipse.help.base.infocenterApplication, org.eclipse.help.base.helpApplication, org.eclipse.help.base.indexTool, com.abispulsa.bisnis.rcp.application, org.eclipse.equinox.app.error.
at org.eclipse.equinox.internal.app.EclipseAppContainer.startDefaultApp(EclipseAppContainer.java:248)
at org.eclipse.equinox.internal.app.MainApplicationLauncher.run(MainApplicationLauncher.java:29)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
at org.eclipse.equinox.launcher.Main.main(Main.java:1383)

It means that you haven't added the following plugin to your target platform / enabled plugins:

org.eclipse.ui.ide.application

That means you'll use the default "workbench" application as used by Eclipse IDE.

When you've created your own application class which implements org.eclipse.equinox.app.IApplication interface, you need to register an Eclipse extension to org.eclipse.core.runtime.applications in your plugin.xml like the following example:

   <extension id="application"
         point="org.eclipse.core.runtime.applications">
      <application>
         <run class="com.abispulsa.bisnis.rcp.Application">
         </run>
      </application>
   </extension>

Then edit your Eclipse Application launch configuration to use your own application class.

Mirroring an Eclipse Update Site to a Local p2 Repository

2010-12-19T05:09:00.003-08:00

Installing or updating Eclipse plugins/features is easy using Eclipse p2 Update Sites. However, since it requires downloading from the Internet the process is often very slow.

Some projects provide an archived update site (.zip file) but the rest do not provide them. When installing or updating features for multiple Eclipse IDE or RCP Application installations, downloading the same files multiple times from the Internet can get annoying. Not to mention it definitely wastes precious time AND bandwidth.

Thankfully there is a way to create a local p2 repository that acts as a mirror site to the original Eclipse p2 Update Sites.

This is useful for making available a full Eclipse release or a set of Eclipse features/plugins to internal corporate users, for example, reducing the bandwidth normally used with dozens of users downloading the same bits from external Eclipse p2 Update sites.

Documentation

First, you need to mirror the site (or a particular feature), so take a look at the mirror command described here:
Running Update Manager from Command Line

then create a site policy (a type of redirection) as described here:
Controlling the Eclipse Update Policy

Command Examples

You can start the update manager in a standalone mode to create a mirror of an update site by using
this command:

java -Dhttp.proxyHost=yourProxy -Dhttp.proxyPort=yourProxyPort \
-jar plugins/org.eclipse.equinox.launcher_<version>.jar \
-application org.eclipse.update.core.standaloneUpdate -command mirror \
-from %updateSiteToMirror% -mirrorUrl %urlOfYourUpdateSite% \
-to %fileLocationToMirrorTo%

Run this command from Eclipse install directory (i.e. where startup.jar is).
Replace %fileLocationToMirrorTo% with the local directory where the update site contents will be copied to, and %urlOfYourUpdateSite% with a URL which will point to the directory you informed.

Of course you will need to install a local web server, like Apache HTTPD and configure it according the directory/URL you specified before.

It even supports to create one mirror-site of multiple sites if you specify the same location for multiple sites it will append them to the site.xml giving you one big (and messy) update site.

An easy way to use this is use a dos or bash scipt ofcourse. For example the following script to mirror the relevant update sites:

set LAUNCHER=C:\opt\springsource-2.1\sts-2.1.0.RELEASE\plugins/plugins/org.eclipse.equinox.launcher_1.0.200.v20090520.jar

goto:eof

:updateSite
java -Dhttp.proxyHost=yourProxy -Dhttp.proxyPort=yourProxyPort -jar %LAUNCHER% -application org.eclipse.update.core.standaloneUpdate -command mirror -from %1 -mirrorUrl http://server/eclipseupdatesite/%2 -to Y:\%2 &goto:eof
goto:eof
This gives us multiple update sites under http://server/eclipseupdatesite/ like http://server/eclipseupdatesite/m2eclipse etc. Of course you still need 1 computer to have unrestricted/fast internet access, but you can always create those sites at home.

Aggregating Specific Features

You can also aggregate several features from other update sites to your own, using either p2.mirror, p2 Composite Repositories, b3, or Nexus Pro.

See http://stackoverflow.com/questions/4378112/p2-repositories-aggregator

Sources:

Mirroring an Eclipse Update Site to a Local p2 Repository

2010-12-19T05:09:00.001-08:00

Installing or updating Eclipse plugins/features is easy using Eclipse p2 Update Sites. However, since it requires downloading from the Internet the process is often very slow.

Thankfully there is a way to create a local p2 repository that acts as a mirror site to the original Eclipse p2 Update Sites.

Documentation

First, you need to mirror the site (or a particular feature), so take a look at the mirror command described here:
Running Update Manager from Command Line

then create a site policy (a type of redirection) as described here:
Controlling the Eclipse Update Policy

Command Examples

You can start the update manager in a standalone mode to create a mirror of an update site by using
this command:

Of course you will need to install a local web server, like Apache HTTPD and configure it according the directory/URL you specified before.

It even supports to create one mirror-site of multiple sites if you specify the same location for multiple sites it will append them to the site.xml giving you one big (and messy) update site.

An easy way to use this is use a dos or bash scipt ofcourse. For example the following script to mirror the relevant update sites:

set LAUNCHER=C:\opt\springsource-2.1\sts-2.1.0.RELEASE\plugins/plugins/org.eclipse.equinox.launcher_1.0.200.v20090520.jar

goto:eof

Aggregating Specific Features

You can also aggregate several features from other update sites to your own, using either p2.mirror, p2 Composite Repositories, b3, or Nexus Pro.

See http://stackoverflow.com/questions/4378112/p2-repositories-aggregator

Sources:

Making Software Literate: The Parser, The Interpreter, and The Literal

2010-12-19T02:51:00.001-08:00

In my last post, the title suggests "teaching code to read itself". However all I wrote was about Interpreter.

For code to read itself, it must be able to generate a model from itself. Therefore, you need the metamodel of the programming lanaguage the software is written in, and the grammar of that language. By using those two ingredients and the proper tools, you can generate a model from the software.

An example of a comprehensive tool for doing this is Eclipse MoDisco. It comes with a complete tooling for discovering / reflecting / introspecting a Java project.

However, for software to understand the model, it must also have an Interpreter/Evaluator, which can do something with the model.

In a way, a generator is a specialized kind of interpreter which simply outputs the concrete representation ("artifact") of the model being processed.

To not only read a model but also to make changes to it, we need a Manipulator (what a scary name), which is a kind of interpreter that performs actions on a model. Sample action: delete an EClass node named 'Car'.

After making changes, the resulting model can be generated back to file artifacts using generator. The project can then be rebuilt, only the changed artifacts are needed.

To rebuild the project from scratch though, we need a complete set of project files.

A typical software project, not only consists of a single language (hence metamodel) but several other artifacts including:
- build.xml (Ant build)
- plugin.xml, MANIFEST.MF (PDE project)
- pom.xml (Maven project)
- build.gradle (Gradle build)
- .project, .classpath, build.properties (Eclipse JDT project)

Depending on requirements, it may not be needed (sometimes not even desirable) to model all of those artifacts properly. Sometimes, it's enough to model a file as a 'Literal':

File: EClass
-----------------------
name: EString
directory: EString
contents: EString

Which in practice means, that these artifacts are not part of the model-driven lifecycle at all. (i.e. You can actually ignore it and it won't evenmatter)

Model-driven is all about transformation, or processing, or shapeshifting, or (meta)morphing. If an artifact or model stays the same throughout the lifecycle, and it's not being used as a metamodel for transformation of its instances, then it's the same thing as if modeling is not used at all.

When all project artifacts are understood, 'literalled', or generated, the project can be rebuilt from scratch using the model. With a good headless build system such as Maven or Gradle, this should be simple.

The other part to include is the information "in programmer's head". We deal with this everyday that it seldom occurs to us that it *is* information.

Things like:
- the directory location of the project
- project name
- location and name of the generated binaries
- SCM user, password, URL
- SCM tool
- test status (whether the tests pass, how many tests, how many fails, how many passes)

These information should be modeled, and a specialized interpreter can be created to act on the project.

A final behavior is 'replaceSelf', which requires the following information:
1. self source location
2. self binary location
3. self descriptor model
4. location of *this* self descriptor model
5. prototype source location
6. prototype binary location
7. prototype descriptor model

where 'prototype' is the project that we've discussed and built above.

The replaceSelf behavior, given the 'self descriptor model' will update/replace itself using the prototype locations, and also update the self descriptor model (e.g. Update the version number).

If the software runs continuously (as a server/daemon), it can then fork a new version of itself, then terminate its own instance.

I guess now the lifecycle is complete. ;-)

Making Software Literate: Teaching Code to Read Itself

2010-12-19T01:56:00.001-08:00

My previous post introduces the concept of Grammar, Template, and the Metamodel.

Creating metamodel is easy for humans, there is Ecore editor and Ecore Tools for that.

Generating artifacts from a model is also relatively easier... When compared to "reading" artifacts and generating a model.

In the machine world, almost everything is harder to read than to write.

For example, it is easy for a generator to output this:

lastName = "Irawan"
name = "Hendy " + lastName

However, it's not easy to "read" the above artifact. By that I mean that the parser software should "understand" that 'name' contains "Hendy Irawan".

And it brings us to... Interpreter.

Interpreter is an enhanced parser that knows what to do with a model. Advanced interpreters may have behaviors, but the most commonly used functionality is Evaluating Expressions.

An Evaluator transforms expressions in the metamodel to actual values (which are still expressions, called value expression, but do not need further processing). After the example artifact above are parsed AND interpreted/evaluated, the 'name' object will rightly contain 'Hendy Irawan'.

Grammar and Template's Role in Modeling

2010-12-19T01:35:00.001-08:00

Grammar and Template are two essential components for model-driven reflection and generation.

Note that this article relates to high-level, abstract view of Model Driven Engineering. And it's going to be boring and theoretical, but I have to write it down so I won't forget. ;-)

With a Grammar, you can 'read' or understand or introspect or reflect or parse or deconstruct or reverse-engineer or (in a way) deserialize... from a concrete artifact, and generating a model as an output.

With a Template, you can 'write' or generate or create or build or construct or (in a way) serialize... an artifact as an output, from a model.

The third element which is required by both processes, is the metamodel. It's actually a prerequirement.

These three are the core ingredients for model driven engineering.

Now to actually bake these ingredients, you need equipment, the tools. Fortunately these are all provided by Eclipse Modeling Framework projects.

The first ingredient you need to create is the metamodel, which usually means an Ecore model. In later phases, the metamodel is not always the first artifact, it can be a generated artifact.

To read an artifact, you need a tool, the parser, that can read your metamodel. And create a grammar in a language that the tool understands. An example is Xtext with its Xtext grammar language. And Xtext, of course, understands Ecore models as the metamodel.

Given: metamodel + grammar --> Xtext, you will get a Parser.

A parser is an artifact reader that is customized to your grammar and metamodel. Given concrete artifact(s) as input, it generates a model as output.

To write to an artifact, you need a tool, that is a generator, that can read your metamodel. Then you create a template in a language that the generator understands.

Such a generator is Eclipse M2T Xpand, and its Xpand language.

Given metamodel + model + template --> Xpand, you get: (textual) artifact!

Actually, the concrete examples above assume one thing: the other metamodel (the "artifact") is a filesystem with text files.

In an abstract way, all transformations are model-to-model (M2M) transformations, hence conceptually requiring two metamodels, not just one. M2T (generation) and T2M (parsing) are conceptually M2M where one side is textual files, or "textual metamodel".

In order for code to understand itself, it must be able to generate a model from its own code.

2010-12-19T00:32:00.001-08:00

In order for code to understand itself, it must be able to generate a model (reverse engineer / discover / import) from its own code.

Its model can then be used to generate code and build it, thus understanding and building itself.

What You Need to Start Model-to-Text Transformation with Xpand

2010-12-18T13:15:00.001-08:00

Setup your Model-driven Development Environment:

Get Eclipse IDE, Modeling distribution.
Install Xpand to Eclipse IDE
Install MWE to Eclipse IDE
Ecore Tools is optional, but it helps you to create your metamodel (Ecore model) using a nicer visual diagram editor.

Now you can create your project:

Create your metamodel (.ecore file). Better just use Ecore Tools, and create .ecorediag diagram alongside .ecore file.
Create a .genmodel from your metamodel.
Generate your Model package and classes from the .genmodel.
Create a sample model (instance).
Open the .ecore model file, right click on a EClass and choose Create Dynamic Instance.
Create a Xpand template.
Create a MWE workflow file (.mwe).
Add necessary plugin dependencies to the MANIFEST.MF.

Now you can run the workflow.

The steps above the high-level steps. It sounds complicated and indeed it can be confusing at first. (the reason why I'm blogging this here is so that I won't get confused in the future) ;-)

If you want the simplest thing, use the New Xpand Project Wizard - Sample Xpand Project and it'll provide up a ready-to-use Ecore+Xpand+MWE setup for you. :-)

Note: MWE and Xpand package names has changed since moved from openArchitectureWare to Eclipse Modeling Framework umbrella, so be aware of this when following older tutorials.

How to Solve MWE/Xpand Workflow Problems/Errors

2010-12-18T12:42:00.001-08:00

What to Check :

1. Check your model file (.xmi). See: http://spring-java-ee.blogspot.com/2010/12/fixing-eclipse-mwe-error-workflow.html

2. Check your plugin.xml file, make sure it contains extension on org.eclipse.emf.ecore.generated_package . Sample:

   <extension point="org.eclipse.emf.ecore.generated_package">
      <package
            uri="http://www.bippo.co.id/shop/3.0/magentoconfig/1.0"
            class="id.co.bippo.magento.config.MagentoConfigPackage"/>
   </extension>

3. Check that you've (re-)generated your model classes. Open your .genmodel and regenerate the Model.

Fixing Eclipse MWE Error: Workflow interrupted. Reason: Couldn't load resource under platform:/resource/.xmi : org.eclipse.emf.ecore.xmi.PackageNotFoundException: Package with uri 'http://' not found.

2010-12-18T12:27:00.001-08:00

If you ever tried to run an Eclipse MWE Workflow, most likely to do M2T (Model-to-Text) transformation using Xpand from an EMF Ecore model to text files, you'll surely encounter several errors at first (or later).

For my case, the error is as follows:

0    INFO WorkflowRunner     - --------------------------------------------------------------------------------------
7    INFO WorkflowRunner     - EMF Modeling Workflow Engine 1.0.0, Build v201008251122
7    INFO WorkflowRunner     - (c) 2005-2009 openarchitectureware.org and contributors
7    INFO WorkflowRunner     - --------------------------------------------------------------------------------------
8    INFO WorkflowRunner     - running workflow: /home/ceefour/project/Bippo/modeling_workspace/id.co.bippo.models/src/workflow/makegradle.mwe
8    INFO WorkflowRunner     -
542 INFO StandaloneSetup    - Registering platform uri '/home/ceefour/project/Bippo/modeling_workspace'
686 INFO CompositeComponent - Reader: Loading model from platform:/resource/id.co.bippo.models/src/demo.bippo.co.id.xmi
780 ERROR WorkflowRunner     - Workflow interrupted. Reason: Couldn't load resource under platform:/resource/id.co.bippo.models/src/demo.bippo.co.id.xmi : org.eclipse.emf.ecore.xmi.PackageNotFoundException: Package with uri 'http://www.bippo.co.id/shop/3.0/magentoconfig/1.0' not found. (platform:/resource/id.co.bippo.models/src/demo.bippo.co.id.xmi, 2, 312)

This seemed like the dreaded platform:/resource URI common pitfall.

However, in my case the problem was inside the .xmi model file itself :

xsi:schemaLocation="http://www.bippo.co.id/shop/3.0/magentoconfig/1.0 ../metamodel/magento-config.ecore"

I was moving the metamodel (Ecore model) to another folder/package, however the XMI file's schemaLocation was hardcoded to a specific path.

Fix the schemaLocation, and it would work fine.

Gradle Build Script (build.gradle) for Writing Gradle Plugins

2010-12-15T07:45:00.001-08:00

Gradle is a great build system written in Groovy programming language and that uses build scripts written in Groovy as well.

There are several ways to write a Gradle plugin and the most extensible one (also the most complicated) is to build the plugin as a separate project.

I tried to find documentation on how to do this but I can only find actual guide for writing "embedded" Gradle plugins (the plugins are contained inside buildSrc folder). But to move the plugin out of buildSrc folder and make it independent, you can use a build.gradle build script file like this in your plugin:

apply { plugin 'java' plugin 'groovy' plugin 'maven' plugin 'eclipse' } group = 'gradle-plugin-javafx' version = '0.2.0-SNAPSHOT' dependencies { compile gradleApi() groovy localGroovy() }
Change group and version properties with your own.

Also, you can leave out applying the 'java', 'eclipse', and 'maven' plugins if you don't use them.

Source: http://code.google.com/p/gradle-plugin-javafx/source/browse/build.gradle

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public final method: The Bug

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public field

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How to Exclude Scala/Java Source Files by Name in sbt

Using UnboundID LDAP SDK Directory API from Scala

Connect & Bind using UnboundID LDAP SDK and Scala

Connect & Bind via SSL

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How to Dump/Inspect Object or Variable in Java

JSON Serialization with Jackson

XML Serialization with XStream

Eclipse RAP Single Sourcing Awesomeness (with EMF Editor and Teneo+Hibernate as bonus!)

Fixing error: The type org.eclipse.core.runtime.IAdaptable cannot be resolved. It is indirectly referenced from required .class files.

Creating an About Dialog for your Eclipse RCP Application

Adding the Help > About Menu Item

Customizing the About Dialog Box

Fixing Eclipse RCP Launch Error: Application "org.eclipse.ui.ide.workbench" could not be found in the registry.

Mirroring an Eclipse Update Site to a Local p2 Repository

Documentation

Command Examples

Aggregating Specific Features

Mirroring an Eclipse Update Site to a Local p2 Repository

Documentation

Command Examples

Aggregating Specific Features

Making Software Literate: The Parser, The Interpreter, and The Literal

Making Software Literate: Teaching Code to Read Itself

Grammar and Template's Role in Modeling

In order for code to understand itself, it must be able to generate a model from its own code.

What You Need to Start Model-to-Text Transformation with Xpand

How to Solve MWE/Xpand Workflow Problems/Errors

Fixing Eclipse MWE Error: Workflow interrupted. Reason: Couldn't load resource under platform:/resource/*.xmi : org.eclipse.emf.ecore.xmi.PackageNotFoundException: Package with uri 'http://*' not found.

Gradle Build Script (build.gradle) for Writing Gradle Plugins

Fixing Eclipse MWE Error: Workflow interrupted. Reason: Couldn't load resource under platform:/resource/.xmi : org.eclipse.emf.ecore.xmi.PackageNotFoundException: Package with uri 'http://' not found.