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Why does code execution never enter catch block (java)?

I am trying to throw a (custom) ImportException from the importUsers method in the UserHelper class. I can see in the debugger that the throw clause is being executed, but the method from which the importUsers method is called never gets caught.

Here is the method in which the exception is thrown:

public static AccessorValidator importUsers(List<String> data, WebUser actor) throws ImportException {

    //(irrelevant code removed)

    try {
        isSuccess = insertUserData(st, blocks, db, actor);
    } catch (Exception e) {
        throw new ImportException("Could not insert user on line " + rowCounter);
    }

}

Here's where I'm trying unsuccessfully to catch the thrown exception from the execute method in the AccessorValidator class:

    public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request,
        HttpServletResponse response) throws Exception {
    //(irrelevant code removed)
    try{
        av = UserHelper.importUsers(data, admin);
        System.out.print("test2");
    } catch (ImportException ie) {
        System.out.print("testE");
        returnMessageValue = ie.getMessage();
    } catch (Exception e) {
        System.out.print("testE2");
    }

The result is "test2" and the code execution never hits any of the catch blocks. What am I doing wrong?

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8 answers


try changing your method to

try {
    isSuccess = insertUserData(st, blocks, db, actor);
    system.out.print("after insertUserData");
} catch (Exception e) {
    System.out.print("before throwing");
    throw new ImportException("Could not insert user on line " + rowCounter);
}


so you can verify that what you see when debugging is what is actually being executed (by checking your console) and whether insertUserData is throwing an exception or not.

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If "test2" is printed, no exception will be thrown by importUsers ().



The line information in the debugger may not be accurate. Try putting a breakpoint in the Exception constructor to see if it was actually thrown.

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Perhaps insertUserData () isn't throwing any exceptions in your test setup? It would help if this method was included in your question as well ...

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Are you sure you are insertUserData

actually throwing an exception and not only returning true / false boolean? Seeing the debugger step on the "throw" line does not mean that something is being thrown, since the line information is not always completely accurate.

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Check the following:

  • make sure your breakpoints are in sync with your source
  • insertUserData()

    does not throw an exception at all, check if it should throw an exception at all or not. It looks like you are expecting something that will never happen.
  • Make sure it is ImportException

    indeed the same object in both cases when you refer to it
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If the output is "test2" then of course no exception was thrown.

Just guess ...

Sometimes your IDE may not be in sync with the source code that is actually being executed, especially if your code is part of an external library ... If you change the library code and do not update the actual one classpath

, or if this change occurs while debugging, the lines of code may change and you can see that an exception will be thrown even though it doesn't really happen.

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The problem has been resolved. It looks like the try-catch block in the importUsers method was surrounded by another try-catch block that did not throw an ImportException. So the first catch block worked correctly, I just missed the second one.

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try to catch Throwable, the root of the exception and error, with:

try{
        av = UserHelper.importUsers(data, admin);
        System.out.print("test2");
    } catch (ImportException ie) {
        System.out.print("testE");
        returnMessageValue = ie.getMessage();
    } catch (Exception e) {
        System.out.print("testE2");
    } catch (Throwable t) {
        // Here you'll catch *anything* else
        System.out.print("testTE");
    }
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