use system classpath for ant javac task

Question

I want the javac task to use jars from the system classpath, by which I mean the classpath that is set in the shell's environment before ant is started. That classpath is

CLASSPATH=D:\local\lib\java\*;.;C:\lib\java\*;C:\lib\java\db\*

on my system. I have popular jars there that are used by many projects. The basic snippet I use in the build file is

<target name="build">
    <mkdir dir="${obj}" />
    <javac srcdir="${src}" destdir="${obj}"
        includes="**/*.java"
        excludes="**/package-info.java **/deprecated/*.java"
        includeAntRuntime="no" debug="true" debuglevel="source,lines"
    >
        <compilerarg value="-Xlint"/>
    </javac>
</target>

That way ant only passes the output directory as classpath.

[javac] '-classpath'
[javac] 'D:\dev\tbull-projects\jsonc\obj'

(jsonc is the project I'm working on, and D:\dev\tbull-projects\jsonc is the working directory.) I browsed the documentation for a while and came up with two attempts. First one was adding the attribute classpath="${java.class.path}" to the javac tag. That would pass a tremendously long classpath to the compiler, listing every single jar from ant's own lib directory and finally tools.jar from the JDK. Not the classpath that I wanted.

The second shot was setting

    <property name="build.sysclasspath" value="first" />

before javac was invoked, and that got me in the right direction. Now these lines were among the output:

dropping D:\dev\tbull-projects\jsonc\D:\local\lib\java\* from path as it doesn't exist
dropping D:\dev\tbull-projects\jsonc\C:\lib\java\* from path as it doesn't exist
dropping D:\dev\tbull-projects\jsonc\C:\lib\java\db\* from path as it doesn't exist
dropping D:\dev\tbull-projects\jsonc\C:\Program Files\Java\jdk1.6.0_18\jre\lib\sunrsasign.jar from path as it doesn't exist
dropping D:\dev\tbull-projects\jsonc\C:\Program Files\Java\jdk1.6.0_18\jre\classes from path as it doesn't exist

Well, you can imagine that these paths really don't exist. I just don't get why ant constructed them this way. It would know how to do path arithmetic on Windows, would it?

Maybe my approach is flawed more fundamentally, so I'll let you know what I'm actually after. So I'm developing this project (a library), which uses another library. The project is gonna be open source, so I want other developers to be able to build it after they have downloaded the dependency library and placed it somewhere in their classpath.

From what I saw in other questions about ant+classpath, it appears that it's a custom fashion to distribute the dependency libs with the source code (so the classpath can be just like ./libs). But I surely don't want to have jars in my git repo. So how could that be done?

Answer 1

Set includeJavaRuntime=true in javac task.

<target name="build">
    <mkdir dir="${obj}" />
    <javac srcdir="${src}" destdir="${obj}"
        includes="**/*.java"
        excludes="**/package-info.java **/deprecated/*.java"
        includeAntRuntime="no" includeJavaRuntime="true"
        debug="true" debuglevel="source,lines">
        <compilerarg value="-Xlint"/>
    </javac>
</target>