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Java EE5 and Java EE 6 support for annotations

2012-02-09 12:02 162 查看

Java EE5 and Java EE 6 support for annotations

The goal of Java™ EE5 and Java EE 6 platform development is to minimizethe number of artifacts that you have to create and maintain, therebysimplifying the development process. Java EE5 and Java EE 6 support the injection of annotationsinto
your source code, so that you can embed resources, dependencies,services, and life-cycle notifications in your source code, withouthaving to maintain these artifacts elsewhere.
An annotation is a modifier or Metadata tag that provides additionaldata to Java classes, interfaces, constructors,methods, fields, parameters, and local variables. Annotations replaceboilerplate code, common code that is required by certain applications.For
example, an annotation can replace the paired interface and implementationrequired for a Web service. Annotations can also replace additionalfiles that programs require, which are maintained separately. By usingan annotation, this separate file is no longer
required. For example,annotations can replace the need for a separately maintained deploymentdescriptor for JavaBeans™.

Annotations
Replace descriptors for most purposes
Remove the need for marker interfaces (like java.rmi.Remote)
Allow application settings to be visible in the component theyaffect

Java EE 5 provides annotations for the following tasks, among others:
Developing Enterprise JavaBean applications
Defining and using Web services
Mapping Java technology classes to XML
Mapping Java technology classes to databases
Mapping methods to operations
Specifying external dependencies
Specirying deployment information, including security attributes

Java EE 5 defines a number of annotations thatcan be injected into your source code. To declare an annotation, yousimply precede the keyword with an "at" sign (@).
package com.ibm.counter;

import javax.ejb.Stateless;

@Stateless

public class CounterBean {

}
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