com.javacreed.examples.lang.DynamicClassLoader.java Source code

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Here is the source code for com.javacreed.examples.lang.DynamicClassLoader.java

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/**
 * Copyright 2012-2014 Java Creed.
 * 
 * Licensed under the Apache License, Version 2.0 (the "<em>License</em>");
 * 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 com.javacreed.examples.lang;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DynamicClassLoader extends ClassLoader {

    private static final Logger LOGGER = LoggerFactory.getLogger(DynamicClassLoader.class);

    private final ConcurrentMap<String, byte[]> loadedClasses = new ConcurrentHashMap<>();

    public DynamicClassLoader() {
    }

    public DynamicClassLoader(final ClassLoader parent) {
        super(parent);
    }

    @Override
    protected Class<?> findClass(final String name) throws ClassNotFoundException {
        DynamicClassLoader.LOGGER.debug("Finding class: {}", name);
        if (loadedClasses.containsKey(name)) {
            final byte[] b = loadedClasses.get(name);
            return defineClass(name, b, 0, b.length);
        }

        return super.findClass(name);
    }

    public void loadJar(final InputStream in) throws IOException {
        try (BufferedInputStream bis = new BufferedInputStream(in); ZipInputStream zis = new ZipInputStream(bis)) {
            for (ZipEntry ze = zis.getNextEntry(); ze != null; ze = zis.getNextEntry()) {
                if (ze.isDirectory()) {
                    continue;
                }

                final String name = ze.getName();
                final String canonicalName = StringUtils.removeEnd(name, ".class").replaceAll("[\\/]", ".");
                final byte[] classBytes = IOUtils.toByteArray(zis);
                if (loadedClasses.putIfAbsent(canonicalName, classBytes) == null) {
                    DynamicClassLoader.LOGGER.debug("Loading class: {} of {} bytes", canonicalName,
                            classBytes.length);
                } else {
                    DynamicClassLoader.LOGGER.debug("Skipping class: {} of {} bytes as onle already exists",
                            canonicalName, classBytes.length);
                }
            }
        }
    }
}