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【第15章：Java反射机制】_动态代理

发布时间：2021-01-07 17:19:04编辑：雪饮阅读（）

 普通的静态代理实现

package org.kasumi;
interface Subject{
       public String say(String name,int age);
}
class RealSubject implements Subject{
       public String say(String name ,int age){
              return "姓名:"+name+"，年龄:"+age;
       }
}
class ProxySubject implements Subject{
       private Subject sub=null;
       public ProxySubject(Subject sub){
              this.sub=sub;
       }
       public String say(String name,int age){
              return this.sub.say(name,age);
       }
}
public class Hello{
   public static void main(String args[]){
              Subject sub=new ProxySubject(new RealSubject());
              System.out.println(sub.say("kasumi",24));
       }
};

获取类加载器
class RealSubject{}
public class Hello{
   public static void main(String args[]){
              RealSubject r=new RealSubject();
              System.out.println(r.getClass().getClassLoader().getClass().getName());
       }
};
D:\>javac Hello.java
D:\>java Hello
sun.misc.Launcher$AppClassLoader
动态代理的实现
import java.lang.reflect.InvocationHandler ;
import java.lang.reflect.Proxy ;
import java.lang.reflect.Method ;
interface Subject{
       public String say(String name,int age);
}
class RealSubject implements Subject{
       public String say(String name,int age){
              return "姓名：" + name + "，年龄：" + age ;
       }
};
class MyInvocationHandler implements InvocationHandler{
       private Object obj ;
       public Object bind(Object obj){
              this.obj = obj ;       // 真实主题类
              //一个对象的类加载器的类、一个对象所实现的所有接口、InvocationHandler实例
              return Proxy.newProxyInstance(obj.getClass().getClassLoader(),obj.getClass().getInterfaces(),this) ;
       }
       // 在执行方法之前执行
       public void before() {
        System.out.println("before kasumi");
    }
       //执行方法
       public Object invoke(Object proxy,Method method,Object[] args) throws Throwable{
              this.before();
              System.out.println("method: " + method); 
              System.out.println("args:");
              for(Object x:args){
                     System.out.println("\tx:"+x);
              }
              Object temp = method.invoke(this.obj,args) ;   // 调用方法 
              return temp ;
       }
};
public class Hello{
   public static void main(String args[]){
              Subject sub = (Subject)new MyInvocationHandler().bind(new RealSubject()) ;
              String info = sub.say("kasumi",24) ;
              System.out.println(info) ;
       }
};
D:\>javac Hello.java
D:\>java Hello
before kasumi
method: public abstract java.lang.String Subject.say(java.lang.String,int)
args:
        x:kasumi
        x:24
姓名：kasumi，年龄：24