Chris01: Reverted edit of Zenek, changed back to last version by RangerRick

2007-02-20T14:44:00Z

Reverted edit of Zenek, changed back to last version by RangerRick

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There is no official "policy" per se for packaging Java software in Fink, but there are a number of best practices that make it easier.

== The '''''Type''''' Field ==

By default, if you use <code>Type: java</code> without specifying a version, Fink will use the '''lowest''' JDK found in /System/Library/Frameworks/JavaVM.framework/Versions. So if you have a 1.3.1, 1.4.2, and 1.5.0 JDK on your system, it will use the 1.3.1.

If you use <code>Type: java('''version''')</code> (i.e., <code>Type: java(1.4)</code>), it will use the '''highest''' JDK found that matches that version. So if you have both a 1.4.1 and 1.4.2 JDK on your system, it will use the 1.4.2 JDK.

Regardless of whether you use the versioned or unversioned field, as long as you're setting <code>Type: java</code>, the build environment inside your package will have the following extra environment variables set:

JAVA_HOME /System/Library/Frameworks/JavaVM.framework/Versions/''<code>detected_version</code>''/Home
PATH /System/Library/Frameworks/JavaVM.framework/Versions/''<code>detected_version</code>''/Home/bin:$PATH

== Using the '''''Type''''' Field Effectively ==

There are 2 major ways it is recommended to package Java software, depending on whether you want to require a specific JDK, or you want to target a specific JDK or higher.

=== Requiring a Specific JDK ===

If you want to ensure your software is compiled with, say, the 1.4 JDK, use:

Type: java(1.4)

This will detect a JDK of that specific major and minor version number, and set <code>JAVA_HOME</code> and <code>PATH</code> respectively. If the software you are packaging uses <code>javac -target</code> (or ant's <javac target=""/> notation), it will still use the JDK that you specified, but generate bytecode compatible with the target given.

=== Using The Available JDK (recommended) ===

The problem with using <code>Type: java(1.4)</code> is that it requires a specific JDK, even if later ones are available. The primary reason to do so is to be able to create bytecode usable by older JDKs.

Instead, it is recommended to do the following:

Package: myjavapackage
Type: java
Depends: system-java (>= 1.4-1)
BuildDepends: system-java-dev (>= 1.4-1)
Patch: %n.patch

Create a patch that makes sure that javac is being called with a target of 1.4. In the case of an ant build.xml, change any entries like:

<javac srcdir="foo">
<patternset refid="foo.files" />
</javac>

...into...

<javac target="1.4" srcdir="foo">
<patternset refid="foo.files" />
</javac>

In the case of some other tool calling <code>javac</code>, you can pass "<code>-target</code>" on the <code>javac</code> command-line.

This lets you not care what JDK is installed, as long as it's 1.4 or newer.

== Problems with specific JDKs ==

; as of release 1.5, 'enum' is a keyword, and may not be used as an identifier : The 1.5 JDK adds some new keywords to the language, like <code>enum</code>. In some cases, you might need to add <code>source="1.4"</code> to your build.xml (or <code>-source 1.4</code> on the javac command-line) to make things work correctly.

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[[Category: Fink|Policy:Packaging Java]]
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Fink:Policy:Packaging Java - Revision history

Chris01: Reverted edit of Zenek, changed back to last version by RangerRick