Compiling in Memory

Question

I am reading a book Java 6 Platform Revealed which describes using of Compiler API. Unfortunately Compiler API was changed during development of Mustang.
This sample stopped to work although I renamed names of classes into new ones.
I am able to compile the source of HelloWorld class, but I don't know how to invoke a new instance of this successfully compiled class (I get permanent ClassNotFoundException).
How to get it work?
Thank you for your help
Cavity
PS. I don't want to use extern files (as described here http://javainsel.blogspot.com/2006/03/example-for-using-java-6-compiler-api.html), I would like to make it as fast as possible (=in memory).
Java SE 6 final
import javax.tools.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.net.URI;
import java.util.Arrays;
public class CompileSource {
    private CompileSource() {
    public static void main(String args[]) throws IOException {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        DiagnosticCollector<JavaFileObject> diagnostics =
                new DiagnosticCollector<JavaFileObject>();
        StringWriter writer = new StringWriter();
        PrintWriter out = new PrintWriter(writer);
        out.println("public class HelloWorld {");
        out.println("  public static void main(String args[]) {");
        out.println("    System.out.println(\"Hello, World\");");
        out.println("  }");
        out.println("}");
        out.close();
        JavaFileObject file =
                new JavaSourceFromString("HelloWorld", writer.toString());
        Iterable<? extends JavaFileObject> compilationUnits =
                Arrays.asList(file);
        JavaCompiler.CompilationTask task = compiler.getTask(
                null, null, diagnostics, null, null, compilationUnits);
        boolean success = task.call();
        for (Diagnostic diagnostic : diagnostics.getDiagnostics())
            System.console().printf(
                    "Code: %s%n" +
                            "Kind: %s%n" +
                            "Position: %s%n" +
                            "Start Position: %s%n" +
                            "End Position: %s%n" +
                            "Source: %s%n" +
                            "Message:  %s%n",
                    diagnostic.getCode(), diagnostic.getKind(),
                    diagnostic.getPosition(), diagnostic.getStartPosition(),
                    diagnostic.getEndPosition(), diagnostic.getSource(),
                    diagnostic.getMessage(null));
        System.out.println("Success: " + success);
        if (success) {
            try {
                System.out.println("-----Output-----");
                Class.forName("HelloWorld").getDeclaredMethod("main",
                        new Class[]{String[].class}).invoke(null, new Object[]{null});
                System.out.println("-----Output-----");
            } catch (ClassNotFoundException e) {
                System.err.println("Class not found: " + e);
            } catch (NoSuchMethodException e) {
                System.err.println("No such method: " + e);
            } catch (IllegalAccessException e) {
                System.err.println("Illegal access: " + e);
            } catch (InvocationTargetException e) {
                System.err.println("Invocation target: " + e);
    static public class JavaSourceFromString extends SimpleJavaFileObject {
        final String code;
        JavaSourceFromString(String name, String code) {
            super(URI.create(
                    "string:///" + name.replace('.', '/') + Kind.SOURCE.extension),
                    Kind.SOURCE);
            this.code = code;
        @Override
        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
            return code;
}Message was edited by:
Cavity

Answer 1

This is exactly what I was looking for the whole day. Thank you very much Peter.
Unfortunately I cannot give you your deserved dukes :-((.
This forum is buggy, i cannot log in under my previous account :-((( and reseting password without "security" question does not work either.