get Class File from ClassLoader - Java Reflection

Java examples for Reflection:Class

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Description

get Class File from ClassLoader

Demo Code

/*/*from  w  w  w  .  j a  va  2  s . c  o m*/
 * Copyright 2014 NAVER Corp.
 *
 * 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 com.java2s;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;

import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

public class Main {
    public static byte[] getClassFile(ClassLoader classLoader,
            String className) {
        if (classLoader == null) {
            classLoader = ClassLoader.getSystemClassLoader();
        }
        if (className == null) {
            throw new NullPointerException("className must not be null");
        }

        final InputStream is = classLoader.getResourceAsStream(className
                .replace('.', '/') + ".class");
        if (is == null) {
            throw new RuntimeException("No such class file: " + className);
        }

        ReadableByteChannel channel = Channels.newChannel(is);
        ByteBuffer buffer;

        try {
            buffer = ByteBuffer.allocate(is.available());

            while (channel.read(buffer) >= 0) {
                if (buffer.remaining() == 0) {
                    buffer.flip();
                    ByteBuffer newBuffer = ByteBuffer.allocate(buffer
                            .capacity() * 2);
                    newBuffer.put(buffer);
                    buffer = newBuffer;
                }
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            close(is);
        }

        return buffer.array();
    }

    private static void close(Closeable closeable) {
        if (closeable != null) {
            try {
                closeable.close();
            } catch (IOException ignore) {
                // skip
            }
        }
    }
}

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