回顾java Annotation（注解）

package com.annotation.zjc;
import java.lang.annotation.*;

//以下三行是“元注解”，用于指明此注解的生命周期、使用范围和可被文档化
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
public @interface Description {
	String value();
}

package com.annotation.zjc;
import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR,ElementType.METHOD})
@Documented
public @interface Resource {
	int id();
	String name();
	String type() default "Object";  //可以给出默认值
}

package com.annotation.zjc;

@Description("Inject use annotation")
//等同于@Description(value="Inject use annotation"),字段名称为value，可以用以上简写模式
public class ApplyAnnotation {
	
	@Resource(id=1,name="zhang",type="person")
	public ApplyAnnotation(){
		//init...
	}
	public void execute(Resource r){
		System.out.println(r.id()+"  "+r.name()+"  "+r.type());
	}
}

package com.annotation.zjc;

import java.lang.reflect.Constructor;
public class testMain {
	public static void main(String[] args){
		ApplyAnnotation aa=new ApplyAnnotation();
		Class<?> objclass=null;
		try{
			objclass = Class.forName("com.annotation.zjc.ApplyAnnotation");
		}catch(Exception e){}
		
		if(objclass!=null&&objclass.isAnnotationPresent(Description.class)){
			Description des=objclass.getAnnotation(Description.class);//获取“注解对象”
			System.out.println(des.value());
		}
		
		Resource r=null;
		if(objclass!=null){
			Constructor<?> cons[]=objclass.getConstructors();//反射取得类的构造函数
			for(Constructor<?> con:cons){
				if(con.isAnnotationPresent(Resource.class)){
					r=(Resource)con.getAnnotation(Resource.class);//获取“注解对象”
				}
			}
		}

		if(r!=null)
			aa.execute(r);
	}
}