Ram's Technology Blog

SOLID Design Principles

2012-05-17T20:48:00.001-07:00

Single Responsibility Principle – A class should be developed such a way that it should not change for more than one reason in other words a class should have one and only one reason to change.

SRP (Single Responsibility Principle) focuses on one thing one responsibility. All the methods of a class which follows the SRP principle should relate to a single purpose. It is very easy to identify the violations of SRP in a class, that class is too big and complicated with doing too many things which are unrelated.

The easiest way to fix this is to split the class based on the functionality.

Open & Close Principle – A class should be open for extension, but closed for modifications. We can use traditional object oriented methodologies like inheritance and composition for this. Following are the two ways to achieve OCP for classes

Making all member variables private so that other parts of the code access those using getter and setter methods.
Second point is to avoid typecasting the classes at runtime.

Advantage of following OCP is developer can easily change the code by without breaking the existing behavior.

Liskov Substitution Principle – Liskov Substitution Principle explains about the behavioral subtyping which is more powerful than typical subtyping of functions. LSP tells us that derived class is substitutable for its parent class.

In simple terms we can say Liskov Substitution Principle is a contract between the base and derived classes, if base is satisfied with the contract so that derived class must satisfy with the contact.

Interface Segregation Principle – ISP tells about keeping the interfaces minimal and cohesive which can be maintainable.

Problem with huge interfaces is you are forcing the classes to implement all the methods which was a burden to the developer. To fix the ISP violations break down the interfaces by applying Single Responsibility Principle which makes fine grained interfaces.

Dependency Inversion Principle – DIP is very straight forward it says whenever a class is using other classes it should depend on the corresponding interfaces not on direct classes. Dependency Inversion Principle allows the classes to be isolated which makes low impact when we change the design.

EJB 3.1 Rocks!

2012-02-16T08:45:00.001-08:00

I got an opportunity to explore EJB 3.1 API after a long time. In that juncture i couldn't resist my self to post some of the features of EJB 3.1 API.

Singleton capability - Singleton feature of EJB3.1 allows one session bean instance per JVM. This feature allows concurrent access and it is totally thread safe.

We can access the Singleton bean similarly how we access the stateless session bean as follows.

No-interface view - Before EJB3.1 it is necessary to have an interface for creating a bean, but EJB3.1 api allows us to create beans without an interface which eases developers life.

Asynchronous - Another nice feature of this API, which allows us to invoke session beans asynchronously

There are more features added to EJB 3.1 API.

Spring Data Binding

2012-02-14T22:06:00.001-08:00

Data Binding happens in spring mvc when it submits a command object from a form. Command objects of any type used to transport data between presentation and controller layers.

When ever data transfers across these layers the core servlet (or servlet api) treats these parameters as string instead of objects of specific type.

Spring data binding enables the user to set the property values on a command object which are entered from a form.

DataBinder uses PropertyEditor (PropertyEditors basically part of Sun JavaBean API) for converting the object to string type and vice versa.

It is a better practice to explicitly register the PropertyEditor in initBinder() method for a particular controller class.

Vaadin integration with spring framework

2012-02-14T18:39:00.001-08:00

Vaadin is a new generation framework mainly used to develop web applications. I can say Vaadin is a pure java framework where developers can use minimal or no html & javascript code to build web applications.

Add the following dependencies in pom.xml file to import all the vaadin and spring related library files into your vaadin project.
The main intention to use 'SpringApplicationSevlet' in web.xml is to integrate Spring and Vaadin frameworks. The basic purpose of this servlet is to load all the vaadin related classes.
Spring context listener used to load the spring bean configuration files.

Follow https://vaadin.com to find more information on Vaadin framework.

Spring 3.1 Cache Abstraction

2012-01-31T20:46:00.001-08:00

Declarative Annotation based caching

@Cacheable - This is the new & important annotation that allows methods to cache the fetched data.
For each time when the method is triggered cache will check for the specific data.
Spring 3.1 caching strategy allows users to cache data based on certain conditions also called as 'Conditional caching'.

@CacheEvict annotation is very much useful to clear the unused data from the cache buffer.
Finally spring annotations cannot enable themselves automatically we have to enable it explicitly, similarly for caching also we have to enable the caching annotations by providing the following tag in our configuration file.

Spring AOP

2012-01-22T04:14:00.000-08:00

Aspect Oriented Programming (AOP) allows developers to think programming structure in another way. Here in my post i don't want to tell you what is the theory behind AOP, just i want to show you how easy to create aspects using spring framework.

Hope this demo helped you to understand how easy to create aspects using Spring AOP.

Why i like Spring Roo!

2012-01-20T22:14:00.001-08:00

Spring Roo - Next generation java application generator, possible for high quality and productivity of enterprise java applications.

From Roo 1.0 the contributions of Spring Source increased very significantly so that it supported lot of technologies.

The major advantage i found in Spring Roo 1.2.1 is cloud deployment. You can easily deploy your web application into cloud foundry. It is so easy to deploy into cloud - install cloud foundry add -on, logging in into cloud and then upload your web application that's it!.

Exception Handling

2009-11-17T19:35:00.000-08:00

Service Oriented Architecture classified exceptions into two ways System Faults and Business Faults.

System Faults
System Faults are thrown when a runtime error occurs at system or infrastructure level. Unreachable services at runtime are one of the occurrences of the runtime error.

Business Faults
Business Faults are generally thrown when a conditional exception occurred while processing the business logic of a particular service. These exceptions are generally raised due to the business rule violations, passing invalid data to the services etc.

Exception handling in BPEL services
BPEL supports two levels of exception handlers with respect to the scope

Scope level
Process level

BPEL having a list of runtime exceptions as per the specifications. Following are the default fault handlers available in BPEL specifications.
BPEL's default Compensation handler
Default Termination handler
Exception handling in mediator components
Mediator components support runtime exceptions and they are categorized into groups -

All Exceptions
Data-related exceptions
Database or infrastructure exceptions
Recoverable/Retry-able errors

SOA Governance Model Framework

2009-11-01T23:17:00.000-08:00

For any successful SOA project Governance is mandatory. In General governance is the process of making appropriate decisions on behalf of the stakeholders.

What is SOA Governance refers to -'SOA Governance' manages the organization processes and policies to execute SOA smoothly. In addition, SOA governance also establishes behavioral rules and guidelines for the stakeholders who are participating in the SOA. Normally, these policies cover the organizations business, security, technology and compliance operating within the SOA sphere.

While designing the SOA Governance, Governance Model Framework helps us to identify the critical SOA concerns and also determine how best to establish governance for those concerns. Find the useful entities/artifacts of the SOA Governance Model Framework -

SOA Lifecycle

2009-10-21T19:57:00.001-07:00

We can find a gap or an improper alignment between IT and business processes in traditional software development an approach which leads to huge gap. Analysis says due to this gap business-critical software services are not able to react quickly and efficiently to the business changes.

Service oriented architecture reduces this semantic gap through a new development model which align the business process services with software development. Let’s look into SOA Lifecyle and the relevant technology we use. Basically SOA Lifecycle divided into four phases:

Process Modeling -
Process Modeling is a critical phase where process analysts work with respective process managers to analyze and get the requirements. In this phase process analysts spent most of their time to define the Key Performance Indicators (KPI), Business Policies and Business rules.

We use Business Process Modeling notation (BPMN) to design business process models.

Process Implementation -
In this phase programmers implement basic services for the business processes and integrate them with the help of analysts. We use Business Process Execution Language(BPEL) to develop the business process. It is very important to preserve the SOA essence factors like 'Reusable Services', 'Loose Coupling','Integration of Services' etc.

Process Execution & Control-
In Process Execution and Control phase, we will execute the developed processes. When execution of process happens they will interact with various external services.

Process Control also important part in this phase where process managers involve in checking whether processes are executing properly and efficiently.

Process Monitoring and Optimization -
Monitoring and Optimization phase is also an important phase where process owners monitor the key performance indicators. Generally we go for Business Activity Monitor (BAM) in this phase to monitor the important parameters and KPI's.

If any service need to raise its optimization level, again the process or that particular service send back to the starting phase i.e. modeling to identify and improve its efficiency levels. All the processes follow similar phases which we discussed above and this happens iteratively without impacting the business.

Creating Simple Oracle BPEL Process

2009-10-16T00:37:00.000-07:00

This article shows how to create, deploy and test a simple BPEL process on Oracle SOA suite 10g using JDeveloper.

1. Right click on the Applications on Application Navigation and enter the Application name in this case 'MyFirstBPELApplication'.

2. In Step 2 right click on the MyFirstBPELApplication and create a new Project. Enter the project name using proper naming conventions.

3. Once your project is ready, now create a BPEL project through BPEL Project Creation Wizard and name it as 'AddBPELProcess'.

Select the Asynchronous BPEL Process in the template select box.

4. Now our BPEL Service is ready, in our business logic we will add a variable with a constant value. Drag and drop the Assign activity onto the design area.

5. Double click on the Assign activity to configure our add operation. Select the Copy Operation option in Create select box to incorporate our business logic.

6. Now in operation wizard choose Expression as a Type at input variable side.

7. For our simplicity JDeveloper provided wide range of functions, now select Mathematical Functions option so that we can use the add operation in our process. In our bpel process we add a constant value (120) with the input value, so pass the constant value and input variable to the add function.

8. Once you done with the business logic now assign the output to the output variable and click on OK.

9. Your BPEL process is ready to deploy on the Oracle SOA Suite 10g. Make sure that your server is running and you are able to see the server instance under the ServerConnection.

10. If every thing is OK then you are able to see successful Build on the Ant console.

11. Now lets test our BPEL process in the Oracle BPEL Process Manager. Open the BPM and login using default login authentication. Find our BPEL instance under BPEL Process tab here it is AddBPELProcess.

12. Click on the AddBPELProcess instance to initiate the testing process. Pass the input value in the text box here it is 120 and click on the Post XML Message button.

13. Finally, lets check for the result under flow tab which shows the visual representation of the bpel process. Double click on the assign activity to check the output variable value.

See, it is 240 (120 (Constant) + 120 (input value))that means our first bpel process worked well!!!.

Hope, this article useful for the developers who just started learning Oracle SOA Suite. Do not hesitate to reach me for any queries on this workout.

What, Where and Why

2009-10-14T20:54:00.001-07:00

What -
Lets start with 'What is SOA?' - Service Oriented Architecture is an architectural approach to develop ad-hoc services and connect them to form an information management system. SOA allows us to create distributed services and exposes themselves to other services with an predefined service contract.

So what is a Service here - Yes, A service is an independent software component having business logic and expose itself through self-describing interface.

Where -
Why we bother about SOA, because of its decoupling nature. As we know if any system coupled tightly with the services it is very difficult to modify without disturbing the other services.

The cost of maintenance raises as the count of services increasing in tightly coupled distributed system. In the maintenance cost perspective SOA gives you the feasibility to minimize the cost factor.

Why -
So where we can use this SOA? basically most of the SOA projects are integration based projects where we can use the loose coupling concept to integrate the services.

SOA perfectly fits in the area where we reuse and composite the services to create new business processes. When a business extending, modifying its services or switching to other service providers or consumers SOA is the best option.