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I have a GUI application. In my main class I have a method (called createAndShow()) to initialize all my GUI classes. Inside each GUI class, I have static initializer to read properties files(resource bundles or configuration files). If a file or entry is missing or value is wrong, I catch the exception and then throws a MissingResourceException to upper level on purpose. In my createAndShow() method of the main class, I put a try-catch to catch Exception. But somehow JVM refuse to get there. Whenever a file is missing, that MissingResourceException is thrown and then the application just hang. I expected the createAndShow() method will catch that exception and exit gracefully. Is there anything special for exceptions throws from the static initializer?

I am using XP and java 1.6.

Raedwald
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5YrsLaterDBA
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3 Answers3

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Static initializers are invoked by the class loader, not by any user code.

You will not be able to capture those exceptions, and since the classes you need are not able to be loaded, your application will crash.

My recommendation would be to do a Configuration singleton class. You could use What is an efficient way to implement a singleton pattern in Java?. Create an init() or load() method in that class which will be able to throw the exceptions that can be caught in your createAndShow() method.

Pang
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Marcelo
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    ...which means that you cannot to catch your exception and is the main reason why you should avoid using static initializers. – Nicola Musatti Aug 16 '11 at 15:29
  • @Nicola You were probably commenting while I was editing that into the answer. – Marcelo Aug 16 '11 at 15:30
  • but from the exception stack we can see the sequence which indicates it went through my createAndShow() before reach the point exception is thrown. – 5YrsLaterDBA Aug 16 '11 at 15:38
  • @5YrsLaterDBA That is because your `createAndShow()` method is the first one trying to load the classes. Your method is *indirectly* executing your static initializer because the JVM *coincidentally* is loading your classes for the first time. – Marcelo Aug 16 '11 at 15:43
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The static initializer block will be called when the class is loaded. If it throws an exception, the class will not be loaded and you will end up with a NoClassDefFoundException.

You should simply log errors and move on when you have missing resources. Or, you don't do the loading in static initializer blocks, but instead do it in a separate class whose sole purpose is to load these resource bundles.

Kal
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Exceptions thrown in static initializer blocks result in the class not being loaded, which means that your calling class that uses the class can't be loaded either, unless you are using some very careful defensive coding techniques.

Sean Patrick Floyd
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