How to handle null value in a method from which a null returning method is called?

Question

This is the sample code piece

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; }

The thing is that doCheckAssetRole method returns null. So how can I handle it in beforeEverything() method. Is there some exception handling to be done? if so, how?

amicngh · Accepted Answer · 2012-07-26 09:50:09Z

1

Put a null check and then throw a RuntimeException with message .

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

And your code look like this.

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())); }

answered Jul 26, 2012 at 9:50

amicngh

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5 Comments

assylias Over a year ago

I think IllegalArgumentException is better than RuntimeException in that case (more specific).

Axel Over a year ago

1. you should also remove the null check in the following if-conditions too because they aren't necessary any more. 2. I think IllegalArgumentException isn't more specific - after all the error is not because of an illegal argument. 3. If you just remove the null checks for checkAssetRole altogether, you would get an NullPointerException - now that's what I call specific.

amicngh Over a year ago

@Axel : As per the code posted by OP null checks are already there in all if block so he won't get NullPointerException.

dev Over a year ago

This is a good answer. Can u pls tell me whether I have to handle the RuntimeException after throwing it? I mean, a try-catch block is necessary, right?

Axel Over a year ago

@amicngh: Yes, that's why I suggested removing the null checks.

jolivier · Accepted Answer · 2012-07-26 09:57:33Z

It depends what you want is your business logic if doCheckAssetRole is null:

it corresponds to a valid business use case, so you have a corresponding OperationResult object to return for this case, so you would do something like
```
if (checkAssetRole == null) return new NoAssetRoleOperationResult(); 
```
And the calling code will handle this kind of result.
its never supposed to happen, except if the user made a mistake, then you throw a checked exception.
```
if (checkAssetRole == null) throw new NoAssetRoleException(yourMessage); 
```
and you make your method declaration throws NoAssetRoleExeption. The calling code is then responsible of forwarding this error back to the user.
it failed because of a environment error (a remote server is down), you throw an unchecked exception like RuntimeException, an top level code will catch it to indicate there is an environment failure.
it failed because of a development error (theorically this code should never return null), then you assert:
```
assert checkAssetRole != null : "assetRole should not be null" 
```

Pick your case :)

In your first case, return new NoAssetRoleOperationResult(); the NoAssetRoleOperationResult() needs to be cast to the desired object type.

jasop · Accepted Answer · 2012-07-26 09:53:00Z

Returning null from a method is normal practice. The caller needs to check for it. In your case you can just do a check and act accordingly. If you want to throw and Exception, then you can do so.

 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; }

Can u pls tell me whether I have to handle the RuntimeException after throwing it? I mean, a try-catch block is necessary, right?
Runtime exceptions do not require a try/catch block. If you are building a web-app you need to decide what to do with that error. You can create your own exception class (sub-class RuntimeException) and then catch it further down and display a message to the user.

Rajesh J Advani · Accepted Answer · 2012-07-26 09:56:30Z

It depends on what you want to do when null is returned. If you want to return a value NotOK when null is returned from doCheckAssetRole, then you can use this fragment.

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; } }

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