/*
 * Copyright 2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gradle.api.internal.tasks.compile.jdk6;

import org.gradle.api.internal.tasks.compile.*;
import org.gradle.api.internal.tasks.compile.Compiler;
import org.gradle.api.tasks.WorkResult;
import org.gradle.api.tasks.compile.CompileOptions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.Serializable;
import java.nio.charset.Charset;
import java.util.List;

public class Jdk6JavaCompiler implements Compiler<JavaCompileSpec>, Serializable {
    private static final Logger LOGGER = LoggerFactory.getLogger(Jdk6JavaCompiler.class);

    public WorkResult execute(JavaCompileSpec spec) {
        LOGGER.info("Compiling with JDK 6 Java compiler API.");

        JavaCompiler.CompilationTask task = createCompileTask(spec);
        boolean success = task.call();
        if (!success) {
            throw new CompilationFailedException();
        }

        return new SimpleWorkResult(true);
    }

    private JavaCompiler.CompilationTask createCompileTask(JavaCompileSpec spec) {
        List<String> options = new JavaCompilerArgumentsBuilder(spec).build();
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        CompileOptions compileOptions = spec.getCompileOptions();
        StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, compileOptions.getEncoding() != null ? Charset.forName(compileOptions.getEncoding()) : null);
        Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjectsFromFiles(spec.getSource());
        return compiler.getTask(null, null, null, options, null, compilationUnits);
    }
}

@@ -662,16 +662,55 @@
 .jdk6;%0A%0A
+import org.gradle.api.GradleException;%0A
 import o
@@ -1951,24 +1951,276 @@
 Compiler();%0A
+        if(compiler==null)%7B%0A            throw new RuntimeException(%22Cannot find System Java Compiler. Ensure that you have installed a JDK (not just a JRE) and configured your JAVA_HOME system variable to point to the according directory.%22);%0A        %7D%0A
         Comp

Add a more helpful error message to Jdk6Compiler when executed within a JRE and no JDK installed.