Java设计模式之代理模式原理及实现代码分享

/**方式一：聚合式静态代理
 * @author Goser  (mailto:goskalrie@163.com)
 * @Since 2016年9月7日
 */
//1.抽象主题接口
public interface Manager {
  void doSomething();
}
//2.真实主题类
public class Admin implements Manager {
  public void doSomething() {
    System.out.println("Admin do something.");
  }
}
//3.以聚合方式实现的代理主题
public class AdminPoly implements Manager{
  private Admin admin;
  
  public AdminPoly(Admin admin) {
    super();
    this.admin = admin;
  }
 
  public void doSomething() {
    System.out.println("Log:admin操作开始");
    admin.doSomething();
    System.out.println("Log:admin操作结束");
  }
}
//4.测试代码
    Admin admin = new Admin();
    Manager m = new AdminPoly(admin);
    m.doSomething();
//方式二：继承式静态代理
//与上面的方式仅代理类和测试代码不同
//1.代理类
public class AdminProxy extends Admin {
  @Override
  public void doSomething() {
    System.out.println("Log:admin操作开始");
    super.doSomething();
    System.out.println("Log:admin操作开始");
  }
}
//2.测试代码
    AdminProxy proxy = new AdminProxy();
    proxy.doSomething();

//1. 抽象主题
public interface Moveable {
  void move() throws Exception;
}
//2. 真实主题
public class Car implements Moveable {
  public void move() throws Exception {
    Thread.sleep(new Random().nextInt(1000));
    System.out.println("汽车行驶中…");
  }
}
//3.事务处理器
public class TimeHandler implements InvocationHandler {
  private Object target;
  public TimeHandler(Object target) {
    super();
    this.target = target;
  }
  /**
   * 参数：
   *proxy 被代理的对象
   *method 被代理对象的方法
   *args 方法的参数
   * 返回：
   *Object 方法返回值
   */
  public Object invoke(Object proxy, Method method, Object[] args)
      throws Throwable {
    long startTime = System.currentTimeMillis();
    System.out.println("汽车开始行驶…");
    method.invoke(target, args);
    long stopTime = System.currentTimeMillis();
    System.out.println("汽车结束行驶…汽车行驶时间：" + (stopTime - startTime) + "毫秒！");
    return null;
  }
}
//测试类
public class Test {
  public static void main(String[] args) throws Exception{
    Car car = new Car();
    InvocationHandler h = new TimeHandler(car);
    Class cls = car.getClass();
    /**
     *loader 类加载器
     *interfaces 实现接口
     *h InvocationHandler
     */
    Moveable m = (Moveable) Proxy.newProxyInstance(cls.getClassLoader(),cls.getInterfaces(), h);
    m.move();
  }
}

public static Object newProxyInstance(ClassLoader loader,
                     Class[] interfaces,
                     InvocationHandler h)
    throws IllegalArgumentException{
    if (h == null) {
      throw new NullPointerException();
    }
    final Class[] intfs = interfaces.clone();
    final SecurityManager sm = System.getSecurityManager();
    if (sm != null) {
      checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
    }
    /*查找或生成指定的代理类*/
    Class cl = getProxyClass0(loader, intfs);
    /*用指定的调用处理程序调用它的构造函数.*/
    try {
    //获得类的构造函数
      final Constructor cons =cl.getConstructor(constructorParams);
      final InvocationHandler ih = h;
      if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) {
       //当需要代理的类实现了一个非public的接口时，因为这样的接口需要特殊的权限，因此调用doPrivilege（native 修饰的方法）创建代理实例。
        return AccessController.doPrivileged(newPrivilegedAction