On 2017-12-31, Lasse Collin wrote:
> On 2017-12-30 Stefan Bodewig wrote:
>> if XZ for Java is used as a Java9 module java will derive the name of
>> the module from the jar name and will most likely be "xz". If you add
>> an "Automatic-Module-Name" entry to the jar's manifest you can
>> control the name yourself, without turing XZ into a proper Java9
>> module.
> I read a little about Java modules. I got an impression that
> Automatic-Module-Name is a good start and the minimum that libraries
> should do. So adding that entry sounds good.
> Would it be too complicated to turn XZ into a proper module? How useful
> is that?
As XZ hasn't got any dependencies you'd only benefit from an explicit
module info if you wanted to restrict the set of packages you
expose. Otherwise I think Automatic-Module-Name would achieve exactly
the same thing that you could achieve with an explicit
module-info.java. At least for now. module-info.java may give you more
control in the long term, though.
> From what I read, it needs module-info.java which should be easy to
> write as XZ doesn't depend on external packages. I don't know how to
> set it up with Ant. It would be very good if XZ could be built on
> older JDKs too, even if those compilers cannot build the
> module-info.java file.
You could check for JDK9 and only compile module-info.java if you found
it. That way XZ compiled with Java8 or earlier wouldn't be a proper
Java9 module and one compiled with Java9 would contain the module
descriptor.
Assuming you'd want to target Java7 and compile module-info.java if Ant
was actually on Java9 something like the patch below should do it. Here
module-info.java would be compiled by a separate javac task that comes
up with an empty set of sources to compile on Java8 and earlier.
Stefan
diff --git a/build.xml b/build.xml
index 52d3764..514e0e0 100644
--- a/build.xml
+++ b/build.xml
@@ -44,13 +44,22 @@
</target>
<target name="compile" description="Compiles the classes">
+ <available property="jdk9+"
classname="java.lang.module.ModuleDescriptor"/>
<mkdir dir="${classes_dir}"/>
<javac srcdir="." sourcepath="${src_dir}" destdir="${classes_dir}"
+ target="7" source="7"
includeAntRuntime="false" debug="${debug}"
includesfile="fileset-src.txt"
excludes="**/package-info.java">
<compilerarg compiler="modern" value="-Xlint"/>
</javac>
+ <javac srcdir="${src_dir}" destdir="${classes_dir}"
+ includeAntRuntime="false" debug="${debug}"
+ target="9" source="9"
+ taskname="compile-module-info">
+ <include name="**/module-info.java"/>
+ <exclude name="**/module-info.java" unless="jdk9+"/>
+ </javac>
</target>
<target name="jar" depends="compile"
@@ -71,6 +80,7 @@
<attribute name="Export-Package" value="org.tukaani.xz"/>
<attribute name="Bundle-Name" value="${title}"/>
<attribute name="Bundle-DocURL" value="${homepage}"/>
+ <attribute name="Automatic-Module-Name"
value="org.tukaani.xz"/>
</manifest>
</jar>
