Java Annotation

很实用几个例子，在Java开发中，灵活运用可以解决很多问题，比如说持久化实现，还可以配合Struts拦截器解决权限问题，可以控制到方法。

package cn.annotation;
/**
 * Define Annotation key words is '@interface' so as class
 * If you don't set default value to attribute of field
 * when you quote defined Annotation,you should clear and define
 * attributes that you define in the Annotation
 * @author Administrator
 * @since 2011/12/21
 *
 */
@interface Myannotation{
	public String key();
	public String tableName();
	public int year();
}
public class AnnotationDemo01 {
	@Myannotation(key="yangyang",tableName="talbe",year=23)
	public void getInfo(){
		System.out.println("自定义Annotation");
	}
	public static void main(String args[]){
		AnnotationDemo01 a1 = new AnnotationDemo01();
		a1.getInfo() ;
	}
}

package cn.annotation;
/**
 * Define Annotation key words is '@interface' so as class
 * If you don't set default value to attribute of field
 * when you quote defined Annotation,you should clear and define
 * attributes that you define in the Annotation
 * @author Administrator
 *
 */
@interface Myannotation02{
	public String key() default "key";
	public String tableName() default "table";
	public int year() default 0;
}
public class AnnotationDemo02 {
	@Myannotation02
	public void printInfo(){
		System.out.println("自定Annotation,并设置默认值!");
	}
	
	public static void main(String[] args) {
		AnnotationDemo02 a2 = new AnnotationDemo02();
		a2.printInfo();
	}

}

package cn.annotation;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
 * Annoation范围：
 * RetentionPolicy.SOURCE 此Annotation信息只保留在程序源文件中(.java)
 * RetentionPolicy.CLASS 此Annotation信息保留在源程序(.java)和编译之后的类文件(.class)中,不加载到Jvm中。默认方式
 * RetentionPolicy.RUNTIME 此Annotation信息保留在源程序(.java)和编译之后的类文件(.class)中,运行时加载到Jvm中
 * @author Administrator
 *
 */
@Retention(value=RetentionPolicy.RUNTIME)
@interface Myannotation04{
	public String name() default "yangyang";
}
 

package cn.annotation;

import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
/**
 * 通过JAVA反射取Annotation
 * 只有执行时才会加载到Jvm中，才可以取得Annotation信息
 * @author Administrator
 *
 */
@Retention(value=RetentionPolicy.RUNTIME)
@interface Myannotation05{
	public String name() default "name";
	public String sex() default "男";
	public int age() default 20;
}
class Simple{
	public void printInfo(){
		System.out.println("***");
	}
}
class SimpleBean extends Simple{
	@SuppressWarnings("Unchecked")
	@Deprecated
	@Override
	@Myannotation05(name="张三",sex="男",age=25)
	public void printInfo(){
		System.out.println("获取Annotaion信息");
	}
}
public class AnnotationDemo04 {
	public static void main(String[] args) {
		Class<SimpleBean> classz = SimpleBean.class;
		try{
			Method method = classz.getMethod("printInfo", null);
			if(method.isAnnotationPresent(Myannotation05.class)){
				Myannotation05 info = method.getAnnotation(Myannotation05.class);
				System.out.println("姓名："+info.name()+"、 性别："+info.sex()+"、  年龄："+info.age());
			}
		}catch(Exception e){
			System.out.println(e.getMessage());
		}
	}
}