"如果"声明与OO设计

问题描述：

我有枚举说错误代码

public enum ErrorCodes { 
       INVALID_LOGIN(100),
       INVALID_PASSWORD(101),
       SESSION_EXPIRED(102) ...;

       private int errorCode;

       private ErrorCodes(int error){
              this.errorCode = error;
       }    //setter and getter and other codes
}

现在我检查我的异常错误代码与此错误代码。如果这样做，我不想写。我如何解决这个问题（写10+如果块）

now I check my exception error codes with this error codes. I don't want to write if this do this, if this do this. How I can solve this problem (writing 10+ if blocks)

有没有任何设计模式，这种情况？

Is there any design patter to that situation ?

谢谢

答

如Spoike所指出的，使用多态选择正确的错误处理方法是一个选项。通过定义一个类层次结构，这种方法基本上可以通过定义一个类层次结构来推迟10个以上的JVM虚拟方法查找。

As pointed out by Spoike, using polymorphism to pick the right error handling method is an option. This approach basically defers the 10+ if blocks to the JVM's virtual method lookup, by defining a class hierarchy.

但是，在进行完整的类层次结构之前，还要考虑使用枚举方法。如果您计划在每种情况下做的事情是非常相似的，那么此选项将很有效。

But before going for a full-blown class hierarchy, also consider using enum methods. This option works well if what you plan to do in each case is fairly similar.

例如，如果要为每个 ErrorCode ，你可以这样做：

For example, if you want to return a different error message for each ErrorCode, you can simply do this:

// Note singular name for enum
public enum ErrorCode { 
   INVALID_LOGIN(100, "Your login is invalid"),
   INVALID_PASSWORD(101, "Your password is invalid"),
   SESSION_EXPIRED(102, "Your session has expired");

   private final int code;
   private final String 

   private ErrorCode(int code, String message){
          this.code = code;
          this.message = message;
   }

   public String getMessage() {
       return message;
   }
}

然后，您的错误处理代码变为：

Then your error handling code becomes just:

ErrorCode errorCode = getErrorCode();
prompt(errorCode.getMessage());

这种方法的一个缺点是如果要添加其他案例，则需要修改枚举本身，而使用类层次结构，您可以添加新的案例，而无需修改现有代码。

One drawback of this approach is that if you want to add additional cases, you'll need to modify the enum itself, whereas with a class hierarchy you can add new cases without modifying existing code.

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