java中动态代理的实现

package com.example.service;
public interface UserService {
  public String getName(int id);
  public Integer getAge(int id);
}

package com.example.service.impl;
import com.example.service.UserService;
public class UserServiceImpl implements UserService {
  public String getName(int id) {
    System.out.println("------getName------");
    return "cat";
  }
  public Integer getAge(int id) {
    System.out.println("------getAge------");
    return 10;
  }
}

package com.example.jdk;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public class MyInvocationHandler implements InvocationHandler {
  private Object target;
  /**
   * 绑定委托对象并返回一个代理类
   *
   * @param target
   * @return
   */
  public Object bind(Object target) {
    this.target = target;
    //取得代理对象
    return Proxy.newProxyInstance(target.getClass().getClassLoader(),
        target.getClass().getInterfaces(), this);  //要绑定接口(这是一个缺陷，cglib弥补了这一缺陷)
  }
  @Override
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    if ("getName".equals(method.getName())) {
      System.out.println("------before " + method.getName() + "------");
      Object result = method.invoke(target, args);
      System.out.println("------after " + method.getName() + "------");
      return result;
    } else {
      Object result = method.invoke(target, args);
      return result;
    }
  }
}

package com.example.jdk;

import com.example.service.UserService;
import com.example.service.impl.UserServiceImpl;

/**
 * 测试类
 */
public class RunJDK {
  public static void main(String[] args) {
    MyInvocationHandler proxy = new MyInvocationHandler();
    UserService userServiceProxy = (UserService) proxy.bind(new UserServiceImpl());
    System.out.println(userServiceProxy.getName(1));
    System.out.println(userServiceProxy.getAge(1));
  }
}

package com.example.cglib;
import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CGLIBProxy implements MethodInterceptor {
  private Object target;
  /**
   * 创建代理对象
   *
   * @param target
   * @return
   */
  public Object getInstance(Object target) {
    this.target = target;
    Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(this.target.getClass());
    // 回调方法
    enhancer.setCallback(this);
    // 创建代理对象
    return enhancer.create();
  }
  @Override
  public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
    System.out.println("++++++before " + methodProxy.getSuperName() + "++++++");
    System.out.println(method.getName());
    Object result = methodProxy.invokeSuper(o, objects);
    System.out.println("++++++after " + methodProxy.getSuperName() + "++++++");
    return result;
  }
}

package com.example.cglib;
import com.example.service.UserService;
import com.example.service.impl.UserServiceImpl;
/**
 * 测试CGLIB
 */
public class RunCGLIB {
  public static void main(String[] args) {
    CGLIBProxy cglibProxy = new CGLIBProxy();
    UserService userService = (UserService) cglibProxy.getInstance(new UserServiceImpl());
    userService.getName(1);
    userService.getAge(1);
  }
}