How can I debug this NullPointerException

Question

I have an error when unmarshaling XML to Java object with JAXB:

java.lang.NullPointerException
    at com.sun.xml.internal.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$1.parse(RuntimeBuiltinLeafInfoImpl.java:188)
    at com.sun.xml.internal.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$1.parse(RuntimeBuiltinLeafInfoImpl.java:186)
    at com.sun.xml.internal.bind.v2.runtime.reflect.TransducedAccessor$CompositeTransducedAccessorImpl.parse(TransducedAccessor.java:230)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.LeafPropertyLoader.text(LeafPropertyLoader.java:50)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.text(UnmarshallingContext.java:483)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.InterningXmlVisitor.text(InterningXmlVisitor.java:78)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.StAXEventConnector.handleCharacters(StAXEventConnector.java:173)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.StAXEventConnector.bridge(StAXEventConnector.java:127)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:392)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:368)

How can I find the cause?

some more details:

part of the xml that I am trying to parse is:

<member_resources>
                    <__field_location__>
                            <directive>
                                    sun-sat
                            </directive>
                            <file>
                                    null
                            </file>
                            <line>
                                    0
                            </line>
                    </__field_location__>
                    <sun-sat>
                            00:00-24:00 tester2
                    </sun-sat>
                    <__field_location__>
                            <directive>
                                    isLine
                            </directive>
                            <file>
                                    null
                            </file>
                            <line>
                                    0
                            </line>
                    </__field_location__>
                    <isLine>
                            true
                    </isLine>
            </member_resources>

when stopping at the event that caused this I get:

next event <__field_location__>
next event <directive>
next event sun-sat
next event <file>
next event null

What IDE are you using? if it's Eclipse or Netbeans you can just use their debuggers. — talnicolas
– talnicolas, Commented Feb 27, 2012 at 14:05
found the problem: I am using my own xml events for unmarshal. the code new CharactersImpl(key) will cause this exception if key is null. — oshai
– oshai, Commented Feb 27, 2012 at 14:19

Florent Guillaume · Accepted Answer · 2012-02-27 14:12:26Z

3

Add an exception breakpoint for NullPointerException. When it's hit, explore a few levels higher in the call stack to find out the state of the local variables, you'll probably get a clue as to what is null.

answered Feb 27, 2012 at 14:12

Florent Guillaume

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Sam · Accepted Answer · 2012-02-27 14:12:15Z

3

A good approach is using source of JAXB(its implementation) and a IDE for debugging.

answered Feb 27, 2012 at 14:12

Sam

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fdierre · Accepted Answer · 2012-02-27 14:05:00Z

1

Well, a starting point could be setting a breakpoint at the call to the unmarshaler and check exactly which arguments it is being passed.

First thing I'd check is that what you're passing is actually xml, and that it is both well-formed and valid.

answered Feb 27, 2012 at 14:05

fdierre

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