Detailed explanation of the application of dynamic proxy in Java

This article mainly introduces the relevant information on the implementation and application of Java dynamic proxy in detail. I hope that through this article, everyone can understand and master the use of Java dynamic proxy. Friends in need can refer to it

Detailed explanation of the implementation and application of Java dynamic proxy

Java dynamic proxy is actually not commonly used to write daily business code, but it is very common and important to use the RPC framework client at the framework layer. The core idea of ​​spring and the implementation of the underlying principles of aop use java's dynamic proxy technology.

Using a proxy can realize remote calling of objects and implementation of aop.

The implementation of Java's dynamic proxy mainly relies on InvoctionHandler (interface) and Proxy (class).

The following is an example

The agent implemented generally needs an interface

##

package com.yasin.ProxyLearn;

public interface IStudy {

  public void learn();

  public String getKonwledge();

}

The class that implements the interface

package com.yasin.ProxyLearn;

public class Study implements IStudy{

  public void learn() {
    System.out.println("我要开始学习了!");
  }

  public String getKonwledge() {

    return "Java真的强";
  }

}

Proxy class, which needs to implement the InvacationHandler interface

package com.yasin.ProxyLearn;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class StudyProxy implements InvocationHandler{

  //真实要被代理的对象
  private Object study;

  public StudyProxy(Object study){
    this.study=study;
  }

  /**
   * 当被代理对象执行自己的方法时，便会执行这个方法
   */
  public Object invoke(Object object, Method method, Object[] args) throws Throwable {

    Object obj=null;

    System.out.println("代理执行前我可以执行一些操作");

    //执行被代理对象的方法
    obj = method.invoke(study, args);


    System.out.println("代理执行后我还可以执行一些操作");

    return obj;
  }

}

Test class

package com.yasin.JavaLearn;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;
import org.apache.log4j.xml.DOMConfigurator;

import com.yasin.ProxyLearn.IStudy;
import com.yasin.ProxyLearn.Study;
import com.yasin.ProxyLearn.StudyProxy;

/**
 * Hello world!
 *
 */
public class App {

  public static void main(String[] args) {

    IStudy study = new Study();

    InvocationHandler handler = new StudyProxy(study);

    IStudy proxyStudy =(IStudy)Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class[] {IStudy.class}, handler);

    proxyStudy.learn();

    System.out.println(proxyStudy.getKonwledge());

  }
}

The above is the basic use of java dynamic proxy. The implementation of spring aop and rpc remote server is more complicated than this, which will be discussed in depth later.

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