[java] Java - ignore exception and continue

For my Java application, I am creating an instance of a user information object and populating it with a service that I don't control the source for.

The code looks like this:

// username given as parameter
UserInfo ui = new UserInfo();
try {
    DirectoryUser du = LDAPService.findUser(username);
    if (du!=null) {
       ui.setUserInfo(du.getUserInfo());
    }
} catch (Exception e) {
    // Whatever
}

If LDAPService.findUser() can't locate a user, it will throw a NullPointerException and grind the rest of my application to a stop. It's okay if the user information isn't populated, so I want to be able to continue without causing everything else to start throwing exceptions.

Is there a way to do this?

You are already doing it in your code. Run this example below. The catch will "handle" the exception, and you can move forward, assuming whatever you caught and handled did not break code down the road which you did not anticipate.

 try{
      throw new Exception();
 }catch (Exception ex){
   ex.printStackTrace();
 }
 System.out.println("Made it!");

However, you should always handle an exception properly. You can get yourself into some pretty messy situations and write difficult to maintain code by "ignoring" exceptions. You should only do this if you are actually handling whatever went wrong with the exception to the point that it really does not affect the rest of the program.

You are actually ignoring exception in your code. But I suggest you to reconsider.

Here is a quote from Coding Crimes: Ignoring Exceptions

For a start, the exception should be logged at the very least, not just written out to the console. Also, in most cases, the exception should be thrown back to the caller for them to deal with. If it doesn't need to be thrown back to the caller, then the exception should be handled. And some comments would be nice too.

The usual excuse for this type of code is "I didn't have time", but there is a ripple effect when code is left in this state. Chances are that most of this type of code will never get out in the final production. Code reviews or static analysis tools should catch this error pattern. But that's no excuse, all this does is add time to the maintainance and debugging of the software.

Even if you are ignoring it I suggest you to use specific exception names instead of superclass name. ie., Use NullPointerException instead of Exception in your catch clause.

It's generally considered a bad idea to ignore exceptions. Usually, if it's appropriate, you want to either notify the user of the issue (if they would care) or at the very least, log the exception, or print the stack trace to the console.

However, if that's truly not necessary (you're the one making the decision) then no, there's no other way to ignore an exception that forces you to catch it. The only revision, in that case, that I would suggest is explicitly listing the the class of the Exceptions you're ignoring, and some comment as to why you're ignoring them, rather than simply ignoring any exception, as you've done in your example.

LDAPService should contain method like LDAPService.isExists(String userName) use it to prevent NPE to be thrown. If is not - this could be a workaround, but use Logging to post some warning..

You can write a try - catch block around the line you want to have ignored.

Like in the example code of yours. If you just continue your code below the closing bracket of the catch block everythings fine.

You could catch the NullPointerException explicitly and ignore it - though its generally not recommended. You should not, however, ignore all exceptions as you're currently doing.

UserInfo ui = new UserInfo();
try {
    DirectoryUser du = LDAPService.findUser(username);
    if (du!=null) {
       ui.setUserInfo(du.getUserInfo());
    }
} catch (NullPointerException npe) {
    // Lulz @ your NPE
    Logger.log("No user info for " +username+ ", will find some way to cope");
}

Printing the STACK trace, logging it or send message to the user, are very bad ways to process the exceptions. Does any one can describe solutions to fix the exception in proper steps then can trying the broken instruction again?