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From "Markus Wiederkehr (JIRA)" <mime4j-...@james.apache.org>
Subject [jira] Commented: (MIME4J-139) DelegatingFieldParser NPE problem
Date Sun, 15 Nov 2009 20:07:48 GMT

    [ https://issues.apache.org/jira/browse/MIME4J-139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12778166#action_12778166

Markus Wiederkehr commented on MIME4J-139:

@Stefano: thanks for the explanation.

This is what seems to happen chronologically in Stefanos DefaultFieldParserTest:

 1) static initializer of DelegatingFieldParser
 2) static initializer of DefaultFieldParser
 3) static initializer of AbstractField
 4) constructor of DelegatingFieldParser (invoked by AbstractField)
   4.1) variable defaultParser is null (probably because UnstructuredField has not been completely
 5) static initializer of UnstructuredField
 6) constructor of DelegatingFieldParser (invoked by DefaultFieldParserTest)
  6.1) variable defaultParser is not null (refers to an UnstructuredField instance)
 7) Unit tests invokes AbstractField.parse()
 8) NPE because of defaultParser being null in 3.1

Now what's funny is if you change defaultParser to private static the variable defaultParser
is still null in 4.1!

But after initialization has completed the variable points to the right object and the test

> DelegatingFieldParser NPE problem
> ---------------------------------
>                 Key: MIME4J-139
>                 URL: https://issues.apache.org/jira/browse/MIME4J-139
>             Project: JAMES Mime4j
>          Issue Type: Bug
>    Affects Versions: 0.6
>         Environment: jre 1.6.11
>            Reporter: Andrzej Rusin
>            Priority: Minor
>   Original Estimate: 0.08h
>  Remaining Estimate: 0.08h
> We have custom ContentHandlers that extend AbstractContentHandler and add some custom
Fields that extend AbstractField.
> We were getting:
> java.lang.NullPointerException
>  at org.apache.james.mime4j.field.DelegatingFieldParser.parse(DelegatingFieldParser.java:51)
>  at org.apache.james.mime4j.field.AbstractField.parse(AbstractField.java:171)
>  at org.apache.james.mime4j.field.AbstractField.parse(AbstractField.java:63)
>  at org.apache.james.mime4j.message.MessageBuilder.field(MessageBuilder.java:101)
>  at org.apache.james.mime4j.parser.MimeStreamParser.parse(MimeStreamParser.java:121)
>  at org.apache.james.mime4j.message.Message.<init>(Message.java:141)
>  at org.apache.james.mime4j.message.Message.<init>(Message.java:100)
> always AFTER the MimeStreamParser got invoked with our content handlers (so, not on our
parsing, but eg. later, on normal 
> new Message(InputStream).
> Looked like we are currupting something inside MimeStreamParser.
> Then I noticed that DelegatingFieldParser.defaultParser is defined as:
> private FieldParser defaultParser = UnstructuredField.PARSER;
> while other field parsers have:
> static final FieldParser PARSER = new FieldParser() {...}
> So I changed DelegatingFieldParser.defaultParser to static final  and the NPEs do not
occur anymore.
> I do not undestand exactly why this happens, but that are the facts.
> Is there any reason why DelegatingFieldParser.defaultParser can't be static final?

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