CompilerUtils.java

/*
 *      Copyright (C) 2015, 2016  higherfrequencytrading.com
 *      Copyright (C) 2016 Roman Leventov
 *
 *      This program is free software: you can redistribute it and/or modify
 *      it under the terms of the GNU Lesser General Public License as published by
 *      the Free Software Foundation, either version 3 of the License.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU Lesser General Public License for more details.
 *
 *      You should have received a copy of the GNU Lesser General Public License
 *      along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.openhft.chronicle.values;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * This class support loading and debugging Java Classes dynamically.
 */
enum CompilerUtils {
    ;
    public static final CachedCompiler CACHED_COMPILER = new CachedCompiler();

    private static final Method DEFINE_CLASS_METHOD;
    static JavaCompiler s_compiler;
    static StandardJavaFileManager s_standardJavaFileManager;

    static {
        try {
            DEFINE_CLASS_METHOD = ClassLoader.class.getDeclaredMethod(
                    "defineClass", String.class, byte[].class, int.class, int.class);
            DEFINE_CLASS_METHOD.setAccessible(true);
        } catch (NoSuchMethodException e) {
            throw new AssertionError(e);
        }
    }

    static {
        reset();
    }

    private static void reset() {
        s_compiler = ToolProvider.getSystemJavaCompiler();
        if (s_compiler == null) {
            try {
                Class<?> javacTool = Class.forName("com.sun.tools.javac.api.JavacTool");
                Method create = javacTool.getMethod("create");
                s_compiler = (JavaCompiler) create.invoke(null);
            } catch (Exception e) {
                throw new AssertionError(e);
            }
        }

        s_standardJavaFileManager = s_compiler.getStandardFileManager(null, null, null);
    }

    /**
     * Define a class for byte code.
     *
     * @param classLoader to load the class into.
     * @param className   expected to load.
     * @param bytes       of the byte code.
     */
    public static Class defineClass(
            @Nullable ClassLoader classLoader, @NotNull String className, @NotNull byte[] bytes) {
        try {
            return (Class) DEFINE_CLASS_METHOD
                    .invoke(classLoader, className, bytes, 0, bytes.length);
        } catch (IllegalAccessException e) {
            throw new AssertionError(e);
        } catch (InvocationTargetException e) {
            //noinspection ThrowInsideCatchBlockWhichIgnoresCaughtException
            throw new AssertionError(e.getCause());
        }
    }
}