自定义清单在-post-jar中以通用依赖项多次添加

Question

I have a multi-module native Netbeans Java EE project. In it I have a Java Class Library project that is used by multiple other projects which in turn are packaged into the root .ear project.

I'm adding the "build timestamp" and the "build user" attributes to a custom manifest using the library's build.xml :

<target name="-post-jar">   
    <jar destfile="${dist.jar}" update="true">
        <manifest>

When I "clean and build" the root project, each project that refers the library calls:

<ant antfile="${call.script}" target="jar">

And my -post-jar target is called multiple times. This wouldn't be a problem, but sometimes the second invocation of the <jar> task fails with Unable to rename old file (probably due to Netbeans scanning the files in background, but I can't tell for sure).

There are repeating pairs of Building jar and Updating jar messages in Ant's output. However, if I remove my -post-jar target, the second invocation of the jar target does nothing, because it thinks that the jar is up to date and I see only one Building jar message.

How do I mark the updated jar up to date, so the second invocation of the jar target does nothing?

There's a github repo that demonstrates the problem.

Answer 1

I haven't found a way to not re-generate the manifest every time, but I found a way to make the generated file look the same as the zipped file (and we know that the <jar> task doesn't repack when the contents are the same).

Instead of updating the zipped manifest in -post-jar I now update the source file in -pre-jar . This way the final version of the manifest is zipped and since its contents don't change during build, subsequent <jar> invocations update nothing.

It worth mentioning that before adding the attributes Main-Class , Profile , etc. the build-impl.xml of Netbeans creates an empy manifest template, if the user doesn't provide a valid path in the manifest.file= property. The addition happens after -pre-jar , however the existence of the user-provided manifest is checked much earlier, during the init target and the result is saved to the manifest.available property.

My manifest template is not a static file. It contains the "build timestamp" and the "build user" attributes. Therefore the file doesn't exist during the init target, so I had to add the following line at the beginning of my build.xml :

<property name="manifest.available" value="true"/><!-- It will be available by the time we need it -->

Secondly, manifest.file still has to be set and I set it in project.properties (there's no UI for that setting yet and I wonder how it would behave in the presence of the variable in path)

manifest.file=${build.dir}/manifest.tmp

Next, I overwrite the manifest template in the -pre-jar target:

<tstamp>
    <format property="current.time" pattern="HH:mm:ss" locale="de,DE"/>
</tstamp>

<target name="-pre-jar" >
        <manifest file="${manifest.file}">
            <attribute name="MyApp-built-time" value="${current.time}"/>
            <attribute name="MyApp-built-by" value="${user.name}"/>
        </manifest> 

After that, the new problem became obvious: the timestamp was different for each invocation of

<ant antfile="mylib/build.xml" target="jar">

in the multi-module project and Ant had to repack the jar with the new timestamp in the manifest. I solved this by defining the timestamp property in every project's build.xml . Although the properties are not inherited due to inheritall="false" , Netbeans allows for overcoming that:

<property name="transfer.current.time" value="${current.time}"/>

This mechanism is broken in Java EE projects, but the workaround is simple:

<presetdef name="ant">
    <!-- workaround transfer.* not working in Java EE projects -->
    <ant>
        <propertyset>
            <propertyref prefix="transfer."/>
            <mapper from="transfer.*" to="*" type="glob"/>
        </propertyset>
    </ant>
</presetdef>