Question

这是示例代码

public OperationResult beforeEverything(BDDObject savingObject) {

  String checkAssetRole = doCheckAssetRole(savingObject);

  if (checkAssetRole != null && !checkAssetRole.equals("MissingAssetRole")) {
    return new OperationResult(new OperationExecutionError("SIP-37006",
                               new String[] {"Duplicate asset roles have been defined: " + checkAssetRole},
                               getLocalizationGate()));
  }
  ArrayList<String> warnings = new ArrayList<String>();
  boolean showWarning = false;

  if (checkAssetRole != null && checkAssetRole.equals("MissingAssetRole")) {
    mLogger.debug("Warning  of Asset role");
    warnings.add(new String(
                "Asset role is missing. Do you want to save the record?"));
    showWarning = true;
  }
  return OperationResult.OK;
}

问题是doCheckAssetRole方法返回null。那么如何在beforeEverything()方法中处理它呢？是否有一些异常处理要做？如果是这样，怎么样？

Answer 1

进行null检查，然后使用RuntimeException投放message。

 if(checkAssetRole==null)
      throw new RuntimeException ("AssetRole value is NULL.");

你的代码看起来像这样。

String checkAssetRole = doCheckAssetRole(savingObject);

if(checkAssetRole==null)
      throw new RuntimeException ("AssetRole value is NULL.");

if (checkAssetRole != null && !checkAssetRole.equals("MissingAssetRole")) {
return new OperationResult(new OperationExecutionError("SIP-37006",
                           new String[] {"Duplicate asset roles have been defined: " + checkAssetRole},
                           getLocalizationGate()));
}

Answer 2

如果doCheckAssetRole为null，则取决于您的业务逻辑：

它对应一个有效的业务用例，所以你有一个相应的OperationResult对象来返回这种情况，所以你会做类似的事情
```
if (checkAssetRole == null)
  return new NoAssetRoleOperationResult();
```
调用代码将处理这种结果。
它永远不会发生，除非用户犯了错误，然后你抛出一个检查过的异常。
```
if (checkAssetRole == null)
  throw new NoAssetRoleException(yourMessage);
```
然后进行方法声明throws NoAssetRoleExeption。然后，调用代码负责将此错误转发回用户。
由于环境错误（远程服务器关闭）而失败，您抛出了未经检查的异常，如RuntimeException，顶级代码将捕获它以指示存在环境故障。
由于开发错误而失败（理论上这段代码永远不会返回null），然后断言：
```
assert checkAssetRole != null : "assetRole should not be null"
```

选择你的案子：）

Answer 3

从方法中返回null是正常做法。呼叫者需要检查它。在您的情况下，您可以进行检查并采取相应措施。如果你想抛出和异常，那么你可以这样做。

   public OperationResult beforeEverything(BDDObject savingObject) {

     String checkAssetRole = doCheckAssetRole(savingObject);

     if (checkAssetRole == null) {
         // DO SOMETHING HERE. eg. throw new RuntimeException("Asset Role should not be null");
         //   or simply return null;

     }

Answer 4

这取决于返回null时您想要做什么。如果要在doCheckAssetRole返回null时返回值NotOK，则可以使用此片段。

public OperationResult beforeEverything(BDDObject savingObject) {

  String checkAssetRole = doCheckAssetRole(savingObject);

  if (checkAssetRole == null) {
    return OperationResult.NotOK; // Or something else that indicates to the calling method what happened.
  else {
    if (!checkAssetRole.equals("MissingAssetRole")) {
      return new OperationResult(new OperationExecutionError("SIP-37006",
                                 new String[] {"Duplicate asset roles have been defined: " + checkAssetRole},
                                 getLocalizationGate()));
    }
    ArrayList<String> warnings = new ArrayList<String>();
    boolean showWarning = false;

    if (checkAssetRole.equals("MissingAssetRole")) {
      mLogger.debug("Warning  of Asset role");
      warnings.add(new String(
                   "Asset role is missing. Do you want to save the record?"));
      showWarning = true;
    }
    return OperationResult.OK;
  }
}

如何在调用null返回方法的方法中处理null值？

4 个答案: