[[ltwdump]]
= Dumping classes during load-time weaving

[[ltwdump-introduction]]
== Introduction

Very rarely problems may be encountered with classes that have been
load-time woven. Symptoms will include incorrect program function or a
Java exception such as `java.lang.VerifyError`. In these situations it's
most helpful to include the offending class in the bug report. When
using load-time weaving the woven classes are in memory only so to save
them to disk configure `META-INF/aop.xml` to dump the classes (by
default to an `_ajdump` subdirectory of the current working directory).
Also if the input class file is not available (e.g. it is a generated
proxy or has already been instrumented by another agent) you can
configure the weaver to dump the input classes as well.

[[ltw-examples]]
=== Configuring bytecode dumping in load-time weaving

For details of how to configure byte-code dumping, see the AspectJ
Development Environment Guide section on
xref:../devguide/ltw.adoc#configuring-load-time-weaving-with-aopxml-files[Configuring
Load-time Weaving]. Following is a simple example.

[[ltwdump-examples]]
=== LTW Dump Examples

The following `META-INF/aop.xml` will weave classes in the `com.foo`
package (and subpackages) but not CGLIB generated classes in the
`com.foo.bar` package (and subpackages). It will also ensure all woven
byte-code is dumped both before and after weaving.

[source, xml]
....
<aspectj>
    <aspects>
        <aspect name="ataspectj.EmptyAspect"/>
    </aspects>
    <weaver options="-verbose -debug">
        <dump within="com.foo.bar..*" beforeandafter="true"/>
        <include within="com.foo..*"/>
        <exclude within="com.foo.bar..*CGLIB*"/>
    </weaver>
</aspectj>
....

You should see messages similar to this:

[source, text]
....
[WeavingURLClassLoader] info AspectJ Weaver Version 1.5.3 built on Thursday Oct 26, 2006 at 17:22:31 GMT
[WeavingURLClassLoader] info register classloader org.aspectj.weaver.loadtime.WeavingURLClassLoader
[WeavingURLClassLoader] info using configuration /C:/tempMETA-INF/aop.xml
[WeavingURLClassLoader] info register aspect ataspectj.EmptyAspect
[WeavingURLClassLoader] debug not weaving 'com.foo.bar.Test$$EnhancerByCGLIB$$12345'
[WeavingURLClassLoader] debug weaving 'com.foo.bar.Test'
....

On disk you would find the following files:

[source, text]
....
_ajdump/_before/com/foo/bar/Test.class
_ajdump/com/foo/bar/Test.class
....