Java设计模式中的代理设计模式详细解析

 
public class UserController {
  //...省略其他属性和方法...
  private MetricsCollector metricsCollector; // 依赖注入
  public UserVo login(String telephone, String password) {
    long startTimestamp = System.currentTimeMillis();
    // ... 省略login逻辑...
    long endTimeStamp = System.currentTimeMillis();
    long responseTime = endTimeStamp - startTimestamp;
    RequestInfo requestInfo = new RequestInfo("login", responseTime, startTimestamp);
    metricsCollector.recordRequest(requestInfo);
    //...返回UserVo数据...
  }
  public UserVo register(String telephone, String password) {
    long startTimestamp = System.currentTimeMillis();
    // ... 省略register逻辑...
    long endTimeStamp = System.currentTimeMillis();
    long responseTime = endTimeStamp - startTimestamp;
    RequestInfo requestInfo = new RequestInfo("register", responseTime, startTimestamp);
    metricsCollector.recordRequest(requestInfo);
    //...返回UserVo数据...
  }
}

 
public interface IUserController {
  UserVo login(String telephone, String password);
  UserVo register(String telephone, String password);
}
public class UserController implements IUserController {
  //...省略其他属性和方法...
  @Override
  public UserVo login(String telephone, String password) {
    //...省略login逻辑...
    //...返回UserVo数据...
  }
  @Override
  public UserVo register(String telephone, String password) {
    //...省略register逻辑...
    //...返回UserVo数据...
  }
}
public class UserControllerProxy implements IUserController {
  private MetricsCollector metricsCollector;
  private UserController userController;
  public UserControllerProxy(UserController userController) {
    this.userController = userController;
    this.metricsCollector = new MetricsCollector();
  }
  @Override
  public UserVo login(String telephone, String password) {
    long startTimestamp = System.currentTimeMillis();
    // 委托
    UserVo userVo = userController.login(telephone, password);
    long endTimeStamp = System.currentTimeMillis();
    long responseTime = endTimeStamp - startTimestamp;
    RequestInfo requestInfo = new RequestInfo("login", responseTime, startTimestamp);
    metricsCollector.recordRequest(requestInfo);
    return userVo;
  }
  @Override
  public UserVo register(String telephone, String password) {
    long startTimestamp = System.currentTimeMillis();
    UserVo userVo = userController.register(telephone, password);
    long endTimeStamp = System.currentTimeMillis();
    long responseTime = endTimeStamp - startTimestamp;
    RequestInfo requestInfo = new RequestInfo("register", responseTime, startTimestamp);
    metricsCollector.recordRequest(requestInfo);
    return userVo;
  }
}
//UserControllerProxy使用举例
//因为原始类和代理类实现相同的接口，是基于接口而非实现编程
//将UserController类对象替换为UserControllerProxy类对象，不需要改动太多代码
IUserController userController = new UserControllerProxy(new UserController());

public class MetricsCollectorProxy {
  private MetricsCollector metricsCollector;
  public MetricsCollectorProxy() {
    this.metricsCollector = new MetricsCollector();
  }
  public Object createProxy(Object proxiedObject) {
    Class<?>[] interfaces = proxiedObject.getClass().getInterfaces();
    DynamicProxyHandler handler = new DynamicProxyHandler(proxiedObject);
    return Proxy.newProxyInstance(proxiedObject.getClass().getClassLoader(), interfaces, handler);
  }
  private class DynamicProxyHandler implements InvocationHandler {
    private Object proxiedObject;
    public DynamicProxyHandler(Object proxiedObject) {
      this.proxiedObject = proxiedObject;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      long startTimestamp = System.currentTimeMillis();
      Object result = method.invoke(proxiedObject, args);
      long endTimeStamp = System.currentTimeMillis();
      long responseTime = endTimeStamp - startTimestamp;
      String apiName = proxiedObject.getClass().getName() + ":" + method.getName();
      RequestInfo requestInfo = new RequestInfo(apiName, responseTime, startTimestamp);
      metricsCollector.recordRequest(requestInfo);
      return result;
    }
  }
}
//MetricsCollectorProxy使用举例
MetricsCollectorProxy proxy = new MetricsCollectorProxy();
IUserController userController = (IUserController) proxy.createProxy(new UserController());