Add 'nixpkgs/' from commit '2436c27541b2f52deea3a4c1691216a02152e729'

git-subtree-dir: nixpkgs
git-subtree-mainline: 1148b1d122bc03e9a3665856c9b7bb96bd4e3994
git-subtree-split: 2436c27541b2f52deea3a4c1691216a02152e729

1 files changed, 63 insertions, 0 deletions

diff --git a/nixpkgs/doc/languages-frameworks/java.xml b/nixpkgs/doc/languages-frameworks/java.xml
new file mode 100644
index 00000000000..bf0fc488392
--- /dev/null
+++ b/nixpkgs/doc/languages-frameworks/java.xml
@@ -0,0 +1,63 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xml:id="sec-language-java">
+ <title>Java</title>
+
+ <para>
+  Ant-based Java packages are typically built from source as follows:
+<programlisting>
+stdenv.mkDerivation {
+  name = "...";
+  src = fetchurl { ... };
+
+  nativeBuildInputs = [ jdk ant ];
+
+  buildPhase = "ant";
+}
+</programlisting>
+  Note that <varname>jdk</varname> is an alias for the OpenJDK (self-built where available, or pre-built via Zulu). Platforms with OpenJDK not (yet) in Nixpkgs (<literal>Aarch32</literal>, <literal>Aarch64</literal>) point to the (unfree) <literal>oraclejdk</literal>.
+ </para>
+
+ <para>
+  JAR files that are intended to be used by other packages should be installed in <filename>$out/share/java</filename>. JDKs have a stdenv setup hook that add any JARs in the <filename>share/java</filename> directories of the build inputs to the <envar>CLASSPATH</envar> environment variable. For instance, if the package <literal>libfoo</literal> installs a JAR named <filename>foo.jar</filename> in its <filename>share/java</filename> directory, and another package declares the attribute
+<programlisting>
+buildInputs = [ libfoo ];
+nativeBuildInputs = [ jdk ];
+</programlisting>
+  then <envar>CLASSPATH</envar> will be set to <filename>/nix/store/...-libfoo/share/java/foo.jar</filename>.
+ </para>
+
+ <para>
+  Private JARs should be installed in a location like <filename>$out/share/<replaceable>package-name</replaceable></filename>.
+ </para>
+
+ <para>
+  If your Java package provides a program, you need to generate a wrapper script to run it using the OpenJRE. You can use <literal>makeWrapper</literal> for this:
+<programlisting>
+nativeBuildInputs = [ makeWrapper ];
+
+installPhase =
+  ''
+    mkdir -p $out/bin
+    makeWrapper ${jre}/bin/java $out/bin/foo \
+      --add-flags "-cp $out/share/java/foo.jar org.foo.Main"
+  '';
+</programlisting>
+  Note the use of <literal>jre</literal>, which is the part of the OpenJDK package that contains the Java Runtime Environment. By using <literal>${jre}/bin/java</literal> instead of <literal>${jdk}/bin/java</literal>, you prevent your package from depending on the JDK at runtime.
+ </para>
+
+ <para>
+  Note all JDKs passthru <literal>home</literal>, so if your application requires environment variables like <envar>JAVA_HOME</envar> being set, that can be done in a generic fashion with the <literal>--set</literal> argument of <literal>makeWrapper</literal>:
+<programlisting>
+--set JAVA_HOME ${jdk.home}
+</programlisting>
+ </para>
+
+ <para>
+  It is possible to use a different Java compiler than <command>javac</command> from the OpenJDK. For instance, to use the GNU Java Compiler:
+<programlisting>
+nativeBuildInputs = [ gcj ant ];
+</programlisting>
+  Here, Ant will automatically use <command>gij</command> (the GNU Java Runtime) instead of the OpenJRE.
+ </para>
+</section>