org.cloudata.core.common.util.ByteCodeClassLoader.java Source code

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Here is the source code for org.cloudata.core.common.util.ByteCodeClassLoader.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.cloudata.core.common.util;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.cloudata.core.common.exception.GetFailException;

/**
 * @author jindolk
 *
 */
public class ByteCodeClassLoader extends ClassLoader {
    static final Log LOG = LogFactory.getLog(ByteCodeClassLoader.class.getName());

    private final Map<String, VersionedClass> classes = new HashMap<String, VersionedClass>();
    private ClassLoader parent;

    public ByteCodeClassLoader(ClassLoader parent) {
        super(parent);
        this.parent = parent;
    }

    public byte[] getClassBytesFromCache(Class<?> clazz, int version) {
        synchronized (classes) {
            if (classes.containsKey(clazz.getName())) {
                VersionedClass vClass = classes.get(clazz.getName());
                if (vClass.version == version) {
                    return vClass.classBytes;
                } else {
                    classes.remove(clazz.getName());
                    return null;
                }
            }
            return null;
        }
    }

    public void addClassBytes(String className, int version, byte[] classBytes) {
        synchronized (classes) {
            if (classes.containsKey(className)) {
                VersionedClass vClass = classes.get(className);
                if (vClass.version == version) {
                    return;
                } else {
                    classes.put(className, new VersionedClass(version, classBytes));
                }
            } else {
                classes.put(className, new VersionedClass(version, classBytes));
            }
        }
    }

    @Override
    protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
        Class<?> clazz = findClass(name);
        if (clazz == null) {
            return parent.loadClass(name);
        } else {
            return clazz;
        }
    }

    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {
        try {
            byte[] byteClass = null;
            synchronized (classes) {
                VersionedClass vClass = classes.get(name);
                if (vClass != null) {
                    byteClass = vClass.classBytes;
                } else {
                }
            }
            if (byteClass == null) {
                return null;
            }
            Class<?> clazz = defineClass(name, byteClass, 0, byteClass.length);
            return clazz;
        } catch (Error e) {
            LOG.error("Class load error:" + e.getMessage(), e);
            return super.findSystemClass(name);
        }
    }

    public byte[] getClassBytes(Class<?> clazz, int version) throws IOException {
        byte[] classBytes = getClassBytesFromCache(clazz, version);
        if (classBytes != null) {
            return classBytes;
        } else {
            classBytes = loadClassBytes(clazz);
            addClassBytes(clazz.getName(), version, classBytes);
            return classBytes;
        }
    }

    private byte[] loadClassBytes(Class<?> clazz) throws IOException {
        InputStream in = ByteCodeClassLoader.class.getClassLoader()
                .getResourceAsStream(clazz.getName().replaceAll("\\.", "/") + ".class");
        if (in == null) {
            throw new GetFailException("No class data:" + clazz);
        }

        BufferedInputStream bin = new BufferedInputStream(in);
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try {
            byte[] buf = new byte[4096];
            int read = 0;
            while ((read = bin.read(buf)) > 0) {
                out.write(buf, 0, read);
            }
        } finally {
            bin.close();
            out.close();
        }
        return out.toByteArray();
    }
}

class VersionedClass {
    int version;

    byte[] classBytes;

    public VersionedClass(int version, byte[] classBytes) {
        this.version = version;
        this.classBytes = classBytes;
    }
}