设计模式之代理模式

代理模式

代理模式分为静态代理和动态代理．下图为静态代理结构图：

静态代理示例代码：

// 抽象主题接口
public interface Subject {

    void request();
}

// 具体主题角色
public class RealSubject implements Subject{
    @Override
    public void request() {
        System.out.println("真实对象处理请求．．．");
        Random random = new Random();
        try {
            Thread.sleep(random.nextInt(1000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

// 代理角色
public class Proxy implements Subject{

    private Subject subject;

    public Proxy(Subject subject) {
        this.subject = subject;
    }

    @Override
    public void request() {
        System.out.println("代理对象开始处理请求．．．");
        before();
        subject.request();
        after();
    }

    private void after() {
        System.out.println("proxy end...");
    }

    private void before() {
        System.out.println("proxy start...");
    }
}
// 测试
public class ProxyTest {

    public static void main(String[] args) {

        Proxy proxy = new Proxy(new RealSubject());
        proxy.request();
    }
}

JDK动态代理示例代码：

// 抽象接口
public interface Person {

    void findWork();
}

// 具体对象
public class Worker implements Person{
    @Override
    public void findWork() {
        System.out.println("打工人要找工作．．．");
    }
}

// 代理类，实现的是InvocationHandler接口
public class JdkHr implements InvocationHandler {

    private Person target;

    public Person getInstance(Person person){
        this.target = person;
        Class<? extends Person> targetClass = target.getClass();
        return (Person) Proxy.newProxyInstance(targetClass.getClassLoader(), targetClass.getInterfaces(), this);
    }

    @Override
    public Object invoke(Object o, Method method, Object[] objects) throws Throwable {
        before();
        Object invoke = method.invoke(this.target, objects);
        after();
        return invoke;
    }

    private void after() {
        System.out.println("proxy end...");
    }

    private void before() {
        System.out.println("proxy start...");
    }
}

// 测试
public class JdkProxyTest {

    public static void main(String[] args) {
        // 这一行设置保存程序运行时的动态代理类class文件，方便查看
        System.getProperties().put("jdk.proxy.ProxyGenerator.saveGeneratedFiles", "true");
        JdkHr hr = new JdkHr();
        Person person = hr.getInstance(new Worker());
        person.findWork();
    }
}

CGLib动态代理示例代码：

  ```java
  // 抽象接口
  public interface Person {
  
      void findWork();
  }
  
  // 具体对象
  public class Worker implements Person{
      @Override
      public void findWork() {
          System.out.println("打工人要找工作．．．");
      }
  }
  
  // 代理类，实现的是MethodInterceptor接口
  public class CglibHr implements MethodInterceptor {
  
      public Object getInstance(Class<?> clazz){
          Enhancer enhancer = new Enhancer();
          enhancer.setSuperclass(clazz);
          enhancer.setCallback(this);
          return enhancer.create();
      }
  
      @Override
      public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
          before();
          Object obj = methodProxy.invokeSuper(o, objects);
          after();
          return obj;
      }
  
      private void after() {
          System.out.println("proxy end...");
      }
  
      private void before() {
          System.out.println("proxy start...");
      }
  
  }
  
  // 测试
  public class CglibProxyTest {
  
      public static void main(String[] args) {
          // 这一行设置保存程序运行时的动态代理类class文件
          System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "cglibProxy/");
          CglibHr hr = new CglibHr();
          Person person = (Person) hr.getInstance(Worker.class);
          person.findWork();
      }
  }
  
  ```