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From "Benjamin Reed (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-367) Static blocks do not automatically run when a class is loaded in Java 5.0
Date Thu, 27 Jul 2006 16:23:14 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-367?page=all ]

Benjamin Reed updated HADOOP-367:
---------------------------------

    Attachment: f.patch

Arg! It seems that public static methods on non-public classes cannot be called with reflection
:( So I took a different approach that is simpler and less code. (This patch removes 132 lines
and adds 18.)

I noticed that all of the factories simply created new objects. So now the WritableFactories.newInstance
method finds the factory that corresponds to the package of the class and lets that factory
create it. This means that there needs to be a WriteableFactory for each package that has
Writables. This lowers the number of overall factories while adding one visible factory per
package. It also simplifies the Writables since they don't need to worry about factories anymore.

> 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
>         Attachments: f.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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