Java Development

Small Technique on using Java Decompiler in Eclipse

2012-02-22T11:19:00.000+08:00

Here's my common use way on the Java Decompiler..

Method 1: Direct Access to the class by shortcut
1. Click Ctrl + T, and then input the class and input the class name

2. Eclipse will bring you to the class implementation.

Method 2: Direct Access to the class by Open Declaration (F3)
1. Mouse over to the corresponding class in the Java File and click F3
For example, mouse over javax.ejb.SessionBean and then click F3

2. Eclipse will bring you to the class implementation.

Method 3: Use Java Browsing Perspective
1. Click the icon in the Red Box below to Open a new perspective

2. Choose Java Browsing

3. You may find your class implementation as below.

Install Decompiler in Eclipse Indgio

2012-02-20T10:54:00.001+08:00

This article will show you how to install a Java Decompiler to Eclipse.. We will use JadClipse in this example.

JadClipse
Maintainer:	Vladimir Grishchenko, Johann Gyger
Platform:	Platform independent
Genre:	Java, Decompiler, Eclipse plug-in
License:	CPL
Languages:	English, Russian
Website:	JadClipse.sf.net

1. Download JAD

http://www.softpedia.com/progDownload/JAD-Download-85911.html

2. Download JADEclipse in sourceforge

http://sourceforge.net/projects/jadclipse/

3. Put the JAR to Eclipse Plugin Folder

For example: D:\eclipse_indigo\plugins\net.sf.jadclipse_3.3.0.jar

4. Start and Configure Eclipse for the JAD Plugin
In Eclipse, Click Window –> Preference –> Java –> Jadclipse

For example:

Path to decompiler: D:\warez\JAD\jadnt158\jad.exe

Directory for temporary files: D:\tmp\Decompiler

5. Done and test
Open a file, mouse over the javax.ejb.SessionBean, click F3 to go to the class definition.

The Decompiled Java file will be shown.

The project was not built due to "Could not delete 'XXXXXX'". Fix the problem, then try refreshing this project and building it since it may be inconsistent.

2012-02-16T23:47:00.000+08:00

The project was not built due to "Could not delete 'XXXXXX'". Fix the problem, then try refreshing this project and building it since it may be inconsistent.

This problem is due to the cache of the old class file in eclipse, to clean the cache..

1. Project -> Clean

2. Clean all projects

3. The error is gone.

How to avoid calling huge number of Java program

2012-02-16T10:46:00.000+08:00

Background
When the mail server receive email, it would trigger a java program by calling a shell script.
However, as the volumne of email is large, the java program will be triggered serveral times...

Better Design
Have a search in google and found something is useful to improve the current design.

The following is extracted from stackoverflow:
----------------------------------------------------------------------------------------------------

Standalone Java application is already running, so command line parameters are out of question.

Simplest alternatives remaining are polling for files, sockets and HTTP server.

Polling for files:

Make you java app to read a specific directory once in a few seconds. If a file appears in that directory, read it and do as it says. Make your shell script to form that file.

Socket:

Make you java app to listen on a socket. Use netcat or a similar utility to send commands to that socket.

HTTP Server:

Start an HTTP listener within the Java process. Use wget or similar utility to post your commands to that listener:

HttpServer httpServer = HttpServer.create(new InetSocketAddress(port), 5);
httpServer.createContext("/", new TileServerRequestHandler());
httpServer.setExecutor(Executors.newCachedThreadPool());
httpServer.start();

Other options:
JMS

Reference
http://stackoverflow.com/questions/5913400/how-to-communicate-with-existing-java-process

[Resolved] Do not use APIs from sun.* packages (WAS Upgrade)

2012-02-15T13:12:00.002+08:00

This is a short note for my WAS upgrade project V6.0 to V7.0

Recommendation by the WebSphere Application Migration Tool:
Do not use APIs from sun.* packages

Package: sun.misc.BASE64Encoder

*** Code changes as below:

Before
import sun.misc.BASE64Decoder;

import sun.misc.BASE64Encoder;

String text = "Hello!";

// Encode

sun.misc.BASE64Encoder base64encoder = new sun.misc.BASE64Encoder();

String encodedText = base64encoder.encode(text.getBytes());

// Decode

sun.misc.BASE64Decoder base64decoder = new sun.misc.BASE64Decoder();

byte[] output= base64decoder.decodeBuffer(encodedText);

After

import org.apache.commons.codec.binary.Base64;

String text = "Hello!";

// Encode (static method)

String encodedText = Base64.encodeBase64String(text.getBytes());

// Decode (static method)

byte[] output= Base64.decodeBase64(encodedText);

Website to find the public jar - findjar.com

2012-02-14T10:07:00.003+08:00

This website helps you to find out the common jar file stored in http://mirrors.ibiblio.org/

Website: http://www.findjar.com/

1. Go to the website

2. Input the Jar name, e.g. j2ee-1.4.jar

3. Click JAR/Class Search

[Resolved] Use the BigDecimal toPlainString() method explicitly when deriving a string value (WAS Upgrade)

2012-02-13T18:10:00.000+08:00

This is a short note for my WAS upgrade project V6.0 to V7.0

Recommendation by the WebSphere Application Migration Tool:
Use the BigDecimal toPlainString() method explicitly when deriving a string value

The behavior of the method toString() in BigDecimal is changed from J2SE 1.4 to 1.5

Java 1.4.2

String toString()
Returns the string representation of this BigDecimal.

Java 1.5

String toString()
Returns the string representation of this BigDecimal, using scientific notation if an exponent is needed.

Reference:
Java 1.4.2: http://docs.oracle.com/javase/1.4.2/docs/api/java/math/BigDecimal.html
Jave 1.5: http://docs.oracle.com/javase/1.5.0/docs/api/java/math/BigDecimal.html