Java代理模式与动态代理之间的关系以及概念

// 接口
public interface Person {void giveMoney();}
// 学生类--> 被代理类
public class Student implements Person{
  private String name;
  public Student(String name) {this.name = name;}
  public void giveMoney() {
    System.out.println(name+"同学上交50元班费");
  }
}
// 学生代理类
public class StuProxy implements Person{
  private Student stu;
  public StuProxy(Student stu) {
    if (stu.getClass() == Student.class) {
      this.stu = stu;
    }
  }
  public void giveMoney() {stu.giveMoney();}
}

public static void main(String[] args) {
  // 获取学生实例  
  Student stu = new Student("张三");
  // 学生找交钱给班长  学生找到代理
  StuProxy stuProxy = new StuProxy(stu);
  // 班长交给老师  代理交钱(交的是学生的钱)
  stuProxy.giveMoney();
}

// 接口
public interface Rent {void doRent();}
// 被代理类
public class Renter implements Rent{
  public void doRent() {
    System.out.println("租客租房了");
  }
}
// 代理类
public class RentProxy implements Rent{
  private Renter renter;
  public RentProxy(Renter renter) {
    if (renter.getClass()==Renter.class)
      this.renter = renter;
  }
  public void doRent() {renter.doRent();}
}

public static void main(String[] args) {
  // 创建租客
  Renter renter = new Renter();
  // 租客找到中介
  RentProxy rentProxy = new RentProxy(renter);
  // 租客租房
  rentProxy.doRent();
}

// 下面是最经典的Service层的写法
public interface UserService {
    void del();
    void select();
}
public class UserServiceImpl implements UserService{
    public void del() {
        System.out.println("删除操作");
    }
    public void select() {
        System.out.println("查询操作");
    }
}

public class UserServiceImplProxy implements UserService{
  private UserServiceImpl userService;
  // set注入
  public void setUserService(UserServiceImpl userService) {
    this.userService = userService;
  }
  public void del() {
    printLog();
    userService.del();
  }
  public void select() {
    printLog();
    userService.select();
  }
  private void printLog(){
    System.out.println("执行时间="+new Date());
  }
}

// JDK动态代理中间类
public class ProxyInvocationHandler implements InvocationHandler {
  // 被代理的对象
  private Object target;
  // ser方法注入参数
  public void setTarget(Object target) {this.target = target;}
  // 生成动态代理类
  public Object getProxy(){
    return Proxy.newProxyInstance(this.getClass().getClassLoader(),
target.getClass().getInterfaces(),this);
  }
  // 处理代理实例，并返回结果
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    Object result = method.invoke(target,args);
    return result;
  }
}

public static void main(String[] args) {
  // 获取真实角色
  Student stu = new Student("张三三");
  // 动态代理中间类对象
  InvocationHandlerProxyStudent proxyStudent = new InvocationHandlerProxyStudent();
  proxyStudent.setStu(stu);
  // 代理类实例
  Person proxy = (Person) proxyStudent.getProxy();
  // 代理类实例调用方法
  proxy.giveMoney();
}

public Object getProxy(){
  return Proxy.newProxyInstance(this.getClass().getClassLoader(),
stu.getClass().getInterfaces(),this);
}