So I recently learned of the new JavaCompiler API available in JDK 1.6. This makes it very simple to compile a String
to a .class
file directly from running code:
String className = "Foo";
String sourceCode = "...";
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
List<JavaSourceFromString> unitsToCompile = new ArrayList<JavaSourceFromString>()
{{
add(new JavaSourceFromString(className, sourceCode));
}};
StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
compiler.getTask(null, fileManager, null, null, null, unitsToCompile).call();
fileManager.close();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
FileInputStream fis = new FileInputStream(className + ".class");
IOUtils.copyStream(fis, bos);
return bos.toByteArray();
You can grab the source to JavaSourceFromString
from the Javadoc.
This will very handily compile sourceCode
to Foo.class
in the current working directory.
My question is: is it possible to compile straight to a byte[]
array, and avoid the messiness of dealing with File
I/O altogether?
Maybe you could create your own
javax.tools.JavaFileManager
implementing class where you would return your own implementation ofjavax.tools.FileObject
which would then write it out to memory instead to disk. So for your subclass ofjavax.tools.FileObject
Writer openWriter() throws IOException
method you would return ajava.io.StringWriter
. All the methods should be converted to theirString
counterparts.