Dinesh on Java

The Core J2EE patterns deal with testing on the presentation tier as offered by Sun Java Center. J2EE stands for Java 2 Enterprise Edition currently known as Java Enterprise Edition (J EE). It consists of many APIs that provide software developers with the capabilities to write server-side code. These design patterns are specifically concerned with the following listed layers.

• Presentation Layer
• Business Layer
• Integration Layer

Presentation Tier

• Intercepting Filter
  It is used to provide interception and manipulation of requests as well as response prior to and preceding the processing of the request.   
• Context Object
  Context Object is present to keep from using system information that is specific to the protocol and doesn’t coincide with its context.   
• Front Controller
  A centralized access point allows for non-duplication of the control logic needed to handle a request. Front Controller is to handle such request by acting as an initial point.   
• Application Controller
  It provides support for action reuse and code to view-management. The code is made more readable and maintainable as well as modular. Request handling is also improved and made more extensible.   
• View Helper
  It is used to provide a different view, hiding the logic present in the code. Now the logic and the view are completely independent to provide ease for developers and designers.   
• Composite View
  Small sub views can be created using the composite view. These sub views can be integrated to create a singular view.   
• Dispatcher View
  To be able to support a small amount of multitasking, dispatcher view is used. It provides handling and response generation for requests while a business processing is taking place.   
• Service to Worker
  It is used to perform handling of requests as well as processing of the business transaction and after that, the control is transferred to the View.   

Business Tier

• Business Delegate
  The business delegate pattern is one of the Java EE design patterns. It is used in order to decouple or reduce the coupling between the presentation tier and business services.   
• Service Locator
  The design pattern, service locator is an important part in software development. Looking up for a service is one of the core features of service locator. A robust abstraction layer performs this function. The design pattern uses a central registry called Service Locator.   
• Session Facade
  The session façade pattern’s core application is development of enterprise apps. You can also call it a logical extension of GoF designs. The pattern encases the interactions which are happening between the low-level components, which is Entity EJB.   
• Business Object
  Object-oriented programming makes use of the business object. It represents the parts of a business. A business object is able to represent things like event, person, business process, place, and concept. The business object can exist in certain forms like a product, an invoice, and the details of a particular part of a transaction.   
• Composite Entity
  It is one if the Java EE software-design patterns. The composite entity pattern performs modeling, managing and representing a set of interrelated persistent objects. It does not represent them as separate fine-grained entity beans. Composite entity beans are able to represent a graph of objects.   
• Transfer Object
  It is one of the Java EE design patterns. We need transfer object when we need to pass the data across various attributes in a packet to the server. Value Object is another name for transfer object. The transfer object is just a class of POJO which has a method of the getter and setter.   

Integration Tier

• Data Access Object
  The data access object in a computer software which is as an object which is responsible for providing abstract interface for communication to a specific form of database.   
• Service Activator
  The service activator design pattern is one of the Java EE patterns. It is an SI (spring integration) component. It is responsible for triggering or activating a service object or bean which is managed by the spring. A service activator searches through the message channel in order to look for messages.   
• Web Service Broker
  The web service broker uses web protocols and XML. We can use this pattern to expose and broker the services. Assume a circumstance, where multiple organizations are lined up in order to request info from a number of service providers.