Question

I use the class javax.tools.JavaCompiler (jdk6) to compile a source file, but the source file depends on some jar file. How to set the classpath of the javax.tools.JavaCompiler?

Answer 1

The javax.tools.JavaCompiler#getTask() method takes an options parameter that allows to set compiler options. The following message describes an easy way to set them in order to access the calling program’s classpath:

You need to configure the standard
java file manager to know about the
jar files(s) – you use the compiler
options argument to do that.

By default the java compiler object
only seems to know about the default
locations for bootclasspath, extdirs
and endorseddirs directories in terms
of its classpath.

You need to add the calling program’s
current classpath to the java compiler
instance’s which gets passed on the
the standard file manager, which will
then find classes in the jar files.

Here’s how I do it in the compiler
wrapper I wrote

List<String> optionList = new ArrayList<String>();
// set compiler's classpath to be same as the runtime's
optionList.addAll(Arrays.asList("-classpath",System.getProperty("java.class.path")));

// any other options you want
optionList.addAll(Arrays.asList(options));

JavaCompiler.CompilationTask task = compiler.getTask(out,jfm,diagnostics,optionList,null,jfos);

All you’ll need then is to get the proper classpath set when running the calling program.