Compile code fully in memory with javax.tools.JavaCompiler

Question

I'm using the JavaCompiler from the javax.tools package (JDK 1.7) to compile some stuff on the fly, like this:

compiler.run(null, null, "-cp", paths, "path/to/my/file.java");

It works but I would like to do it all in memory (e.g. pass a string with the code, not the source file, and get the byte code back not a .class file). I found that extending the InputStream and OutputStream parameters is no use since it's probably just the same as in the console. Do you know a way to make the run method work like this? Or do you know a confirmed way to do this with the getTask() method? (extending the FileManager looks easy but isn't that easy :)

Answer 1

I've run the above code in Mac OS Java 7. None of them works. So i wrote one https://github.com/trung/InMemoryJavaCompiler

StringBuilder source = new StringBuilder()
    .append("package org.mdkt;\n")
    .append("public class HelloClass {\n")
    .append("   public String hello() { return \"hello\"; }")
    .append("}");

Class<?> helloClass = InMemoryJavaCompiler.compile("org.mdkt.HelloClass", source.toString());