Question

[TL; DR] 问题是，在AWrapper和AType中我必须复制几乎整个函数，其中总是存在语法：

public [TYPE/void] METHOD([OPT: args]) throws TestFailedException {
[OPT: TYPE result = null;]
long startTime = System.currentTimeMillis();
while (true) {
  try {
    beforeOperation();
    [OPT: result =] ((WrappedType) element).METHOD([OPT: args]);
    handleSuccess();
    break;
  } catch (Exception e) {
     handleSoftFailure(e);
     if (System.currentTimeMillis() - startTime > TIMEOUT) {
       handleFailure(e);
       break;
     } else {
       try {
         Thread.sleep(WAIT_FOR_NEXT_TRY);
       } catch (InterruptedException ex) {
       }
     }
   }
 }
 [OPT: return result;]
}

假设我有2个课程，我不拥有：

public class IDontOwnThisType {

  public void doA(String string) { System.out.println("doA"); }
  public String doB();  {System.out.println("doB"); return "doB";}
  public OtherTypeIDoNotOwn doC() {System.out.println("doC"); return new OtherTypeIDoNotOwn();}

}

public OtherTypeIDoNotOwn {

  public void doD() { System.out.println("doD"); }
  public String doE() { System.out.println("doE); }
  public OtherTypeIDoNotOwn  doF(String string) {System.out.println("doF"); return new OtherTypeIDoNotOwn();}

}

所以，我有一个界面：

public interface OperationManipulator {

  void beforeOperation(); //called before operation
  void handleSuccess(); //called after success
  void handleSoftFailure(Exception e); //called after every failure in every try
  void handleFailure(Exception e) throws TestFailedException; //called after reaching time limit 

}

然后接口扩展到一个，“模仿”外部类的方法，但抛出自定义异常：

public interface IWrapper<T extends IType> extends OperationManipulator {

  public void doA(String string) throws TestFailedException;
  public String doB() throws TestFailedException;    
  public T doC() throws TestFailedException;

}

然后我们有IType，它还扩展了OperationManipulator：

public interface IType<T extends IType> extends OperationManipulator {

  public void doD() throws TestFailedException; 
  public String doE() throws TestFailedException;    
  public T doF(String string) throws TestFailedException;

}

然后，我们有上述接口的抽象实现：

public abstract class AType<T extends IType> implements IType{

  Object element; // I do not own type of this object, cant modify it.
  Class typeClass;
  long TIMEOUT = 5000;
  long WAIT_FOR_NEXT_TRY = 100;

  public AType(Object element) {
    this.element = element;
    elementClass = this.getClass();
  }

/* ... */

}

然后，我们覆盖接口的函数，不包括OperationManipulator接口：

功能不返回任何版本：

@Override
public void doD() throws TestFailedException {
  long startTime = System.currentTimeMillis();
  while (true) {
    try {
      beforeOperation();
      ((OtherTypeIDoNotOwn) element).doD();
      handleSuccess();
      break;
    } catch (Exception e) {
      handleSoftFailure(e);
      if (System.currentTimeMillis() - startTime > TIMEOUT) {
        handleFailure(e);
        break;
      } else {
        try {
          Thread.sleep(WAIT_FOR_NEXT_TRY);
        } catch (InterruptedException ex) {
        }
      }
    }
  }

返回正常参考版本的函数：

@Override
public String doE() throws TestFailedException {
  String result = null;
  long startTime = System.currentTimeMillis();
  while (true) {
    try {
      beforeOperation();
      result = ((OtherTypeIDoNotOwn) element).doE();
      handleSuccess();
      break;
    } catch (Exception e) {
      handleSoftFailure(e);
      if (System.currentTimeMillis() - startTime > TIMEOUT) {
        handleFailure(e);
        break;
      } else {
        try {
          Thread.sleep(WAIT_FOR_NEXT_TRY);
        } catch (InterruptedException ex) {
        }
      }
    }
  }
  return result;
}

函数返回类型参数的对象：

@Override
public T doF(String string) throws TestFailedException {
  T result = null;
  long startTime = System.currentTimeMillis();
  while (true) {
    try {
      beforeOperation();
      OtherTypeIDoNotOwn temp = ((OtherTypeIDoNotOwn) element).doF(string);
      result = (T) elementClass.getDeclaredConstructor(Object.class).newInstance(temp);
      handleSuccess();
      break;
    } catch (Exception e) {
      handleSoftFailure(e);
      if (System.currentTimeMillis() - startTime > TIMEOUT) {
        handleFailure(e);
        break;
      } else {
        try {
          Thread.sleep(WAIT_FOR_NEXT_TRY);
        } catch (InterruptedException ex) {
        }
      }
    }
  }
  return result;
}

AWrapper也是如此，但不同之处在于：

构造函数具有存储类型的类参数
对象转换为IDoNotOwnThisType而不是OtherTypeIDoNotOwn。此对象的功能也可能返回OtherTypeIDoNotOwn。

IDoNotOwnThisType是AWrapper正在包装的类型。

OtherTypeIDoNotOwn是AType正在包装的类型。

然后，我们实现了这些抽象类：

public class AssertingType extends AType<AssertingType> {

  public AssertingType(Object element) {
    super(element);
  }

  @Override
  public void beforeOperation() {
    //System.out.println("Asserting type before operation!");
  }

  @Override
  public void handleSuccess() {
    //TODO: add to log file and log to output
    System.out.println("Asserting type success!");
  }

  @Override
  public void handleFailure(Exception e) throws TestFailedException {
    //TODO: add to log file, log to output and throw exception
    System.out.println("Asserting type failure!");
    e.printStackTrace();
    throw new TestFailedException();
  }

  @Override
  public void handleSoftFailure(Exception e) {
    //TODO: add to log file, log to output
    System.out.println("Asserting type soft failure!");
    e.printStackTrace();
  }

}

和

public class AssertingWrapper extends AWrapper<AssertingType> {

  public AssertingWrapper (Object driver) {
    super(driver, AssertingType.class);
  }

  @Override
  public void beforeOperation() {
    //TODO
    System.out.println("Asserting wrapper success!");
  }

  @Override
  public void handleSuccess() {
    //TODO: add to log file and log to output
    System.out.println("Asserting wrapper success!");
  }

  @Override
  public void handleFailure(Exception e) throws TestFailedException {
    //TODO: add to log file, log to output and throw exception
    System.out.println("Asserting wrapper failure!");
    throw new TestFailedException();
  }

  @Override
  public void handleSoftFailure(Exception e) {
    //TODO: add to log file, log to output
    System.out.println("Asserting wrapper soft failure!");
    e.printStackTrace();
  }
}

所以，我们可以这样使用它：

AssertingWrapper wrapper = new AssertingWrapper(new IDoNotOwnThisType());

AssertingType type = wrapper.doC();

AssertingType type2 = type.doF();

输出：

Asserting wrapper before operation!
doC
Asserting wrapper success!
Asserting type before operation!
doF
Asserting type success!

完整的工作代码在这里： LIVE

问题是，我总是在while和try中写catch，AType AWrapper等，我能以某种方式减少代码重复吗？在示例中，我每个类只提供3个函数，但在我的实际代码中，我有50多个方法。我可以以某种方式包装这些函数，以便重复的部分不重复吗？

Answer 1

你的问题似乎很复杂，我不能声称已经能够成功地把它包裹起来，但我会试一试，因为它似乎是一个非常有趣的问题，因为我碰巧有处理你看来类似的情况的一些经验。

如果由于我的误解，我的回答结果完全不合适，请原谅。

因此，您正在寻找的是一个通用的解决方案，用于在调用之前和之后注入您自己的代码，其中调用可以是任何方法，接受任意数量的参数，并返回任何类型的返回值

在java中，存在一个动态代理工具，您可以在java.lang.reflect.Proxy下找到它。

有了它，您可以执行以下操作：

ClassLoader classLoader = myInterfaceClass.getClassLoader();
T temp = (T)Proxy.newProxyInstance( classLoader, new Class<?>[] { myInterfaceClass }, 
    invocationHandler );

invocationHandler由您提供，其格式如下：

private final InvocationHandler invocationHandler = new InvocationHandler()
{
    @Override
    public Object invoke( Object proxy, Method method, Object[] arguments )
        throws Throwable
    {
        /* your pre-invocation code goes here */
        /* ... */

        /* invoke original object */
        Object result = method.invoke( myObject, arguments );

        /* your post-invocation code goes here */
        /* ... */

        /* return the result (will probably be null if method was void) */
        return result;
    }
};

所以，我认为您可以用最少量的代码来解决问题。

动态代理的创建和对method.invoke()的调用都没有表现得非常好，（你知道，反射有点慢），但是如果你用它进行测试，它应该没关系。

如何在使用不兼容的包装器时减少代码重复

1 个答案: