maartenc edited a comment on pull request #134:
URL: https://github.com/apache/ant/pull/134#issuecomment-671239026
Hi @bodewig ,
You are right, here is a bit more context of the problem.
Our applications are installed like this:
```
<some root dir>
/Shared
/org/apache/commons-io/commons-io-2.4.jar
/org/apache/commons-lang/commons-lang-2.6.jar
...
/ApplicationA
main.jar
lib1.jar
lib2.jar
...
/ApplicationB
main.jar
lib1.jar
lib3.jar
...
```
Our biggest application uses about 500 jars. To speed up classloading, we
are adding an INDEX.LIST to main.jar.
The INDEX.LIST spec says that the jar file paths in the INDEX.LIST should be
relative to main.jar. So the INDEX.LIST should look like:
```
JarIndex-Version: 1.0
main.jar
[...]
lib1.jar
[...]
../Shared/org/apache/commons-io/commons-io-2.4.jar
[...]
../Shared/org/apache/commons-lang/commons-lang-2.6.jar
[...]
```
With the current Ant `<jar>` task, there are 2 possibilities to configure
the jar file paths in the INDEX.LIST.
1. if main.jar doesn't contain a `Class-Path` attribute (our use-case), all
jar file paths are flattened.
2. if main.jar does contain a `Class-Path` attribute, the jar file path is
taken from that `Class-Path` attribute.
Since we don't have a `Class-Path` attribute (which is intentionaly), we end
up with a flatten path names in INDEX.LIST.
A workaround could probably be to:
1. add a `Class-Path` attribute to the MANIFEST.MF with the wanted mapping
for INDEX.LIST
2. generate the INDEX.LIST
3. remove the `Class-Path` attribute from the MANIFEST.MF
This is off course a suboptimal solution making the build script needlessly
complex.
The attached patch tries to address the issue by making it possible to
specify a filename-mapper **inside** the `<indexjars>` element. If this mapper
isn't specified, the default mapping (as specified above) is used.
```
<jar ...>
<indexjars>
<fileset dir="build/lib/**/*.jar"/>
<firstmatchmapper>
<globmapper from="${basedir}/build/lib/${application}/*" to="*"
handledirsep="true" />
<globmapper from="${basedir}/build/lib/Shared/*"
to="../Shared/*" handledirsep="true"/>
</firstmatchmapper>
</indexjars>
</jar>
```
An alternative patch could be to add an extra mapper subelement to the
`<jar>` task directly (and not inside the `<indexjars>` element), something
like:
```
<jar ...>
<indexjars>
<fileset dir="build/lib/**/*.jar"/>
</indexjars>
<indexjarsmapper>
<firstmatchmapper>
<globmapper from="${basedir}/build/lib/${application}/*" to="*"
handledirsep="true" />
<globmapper from="${basedir}/build/lib/Shared/*"
to="../Shared/*" handledirsep="true"/>
</firstmatchmapper>
</indexjarsmapper>
</jar>
```
I think the first solutions results in a cleaner build.xml. But with perhaps
a little bit more complex java code (and with a not 100% backwards compatible
API change). But the second solution is also a possibility, I can create a new
patch if you prefer that solution.
Maarten
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