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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-367) Static blocks do not automatically run when a class is loaded in Java 5.0
Date Wed, 02 Aug 2006 18:36:16 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-367?page=comments#action_12425331 ] 
            
Doug Cutting commented on HADOOP-367:
-------------------------------------

I committed the reflection patch, but am not yet closing this.

Hairong, will you provide a patch replacing WritableFactory with ReflectionUtils?

> Static blocks do not automatically run when a class is loaded in Java 5.0
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-367
>                 URL: http://issues.apache.org/jira/browse/HADOOP-367
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.4.0
>         Environment: Java 5.0
>            Reporter: Benjamin Reed
>             Fix For: 0.5.0
>
>         Attachments: f.patch, reflection.patch
>
>
> There seems to be a change that happened between 1.4 and 1.5 with respect to static initializers.
I can't find this documented, but I can reproduce with a very simple program. Basically, a
static initializer is not called unless a static member/method of the class is accessed or
an instance is created. This is actually what the JLS says, but until 1.5 the static initializers
ran when the class was loaded. Note that this behavior only occurs when running with the 1.5
JRE AND compiling for 1.5.
> For many Writables this isn't an issue, so the fallback behavior of the WritableFactory
works, but Block is package private, so loadEdits fails when called from org.apache.hadoop.io.ArrayWritable.readFields()
yielding the following trace:
> Caused by: java.lang.RuntimeException: java.lang.IllegalAccessException: Class org.apache.hadoop.io.WritableFactories
can not access a member of class org.apache.hadoop.dfs.Block with modifiers "public"
>         at org.apache.hadoop.io.WritableFactories.newInstance(WritableFactories.java:49)
>         at org.apache.hadoop.io.ArrayWritable.readFields(ArrayWritable.java:81)
>         at org.apache.hadoop.dfs.FSDirectory.loadFSEdits(FSDirectory.java:532)
>         at org.apache.hadoop.dfs.FSDirectory.loadFSImage(FSDirectory.java:470)
>         at org.apache.hadoop.dfs.FSDirectory.<init>(FSDirectory.java:307)
>         at org.apache.hadoop.dfs.FSNamesystem.<init>(FSNamesystem.java:177)
>         at org.apache.hadoop.dfs.NameNode.<init>(NameNode.java:91)
>         at org.apache.hadoop.dfs.NameNode.<init>(NameNode.java:84)
>         at org.apache.hadoop.dfs.NameNode.main(NameNode.java:491)

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