java-classic-code/serializer/ProtobufSerializer.java

package com.sdyc.ndmp.protobuf.serializer;

import com.google.protobuf.GeneratedMessage;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;

/**
 * <pre>
 *
 * Created by IntelliJ IDEA.
 * User: zhenqin
 * Date: 14-7-28
 * Time: 下午3:36
 * To change this template use File | Settings | File Templates.
 *
 * </pre>
 *
 * @author zhenqin
 */
public class ProtobufSerializer implements Serializer<GeneratedMessage> {

    private static final long serialVersionUID = 1L;
    /**
     * 字符编码
     */
    protected String charset = "UTF-8";


    /**
     * 内部缓存
     */
    protected final static Map<Class<?>, Method>
            CLASS_METHOD_MAP = new HashMap<Class<?>, Method>(3);


    public ProtobufSerializer() {

    }


    public ProtobufSerializer(String charset) {
        this.charset = charset;
    }

    @Override
    public byte[] serialize(GeneratedMessage o) {
        if (o == null) {
            return null;
        }

        byte[] bytes = o.toByteArray();

        String clazz = o.getClass().getName();
        byte[] bytes1 = clazz.getBytes(Charset.forName(charset));

        ByteBuf channelBuffer = Unpooled.buffer(4 + bytes.length + bytes1.length);
        channelBuffer.writeInt(bytes1.length);
        channelBuffer.writeBytes(bytes1);
        channelBuffer.writeBytes(bytes);
        return channelBuffer.array();
    }

    @Override
    public GeneratedMessage deserialize(byte[] bytes) {
        if (bytes == null || bytes.length == 0) {
            return null;
        }

        ByteBuf channelBuffer = Unpooled.wrappedBuffer(bytes);

        channelBuffer.resetReaderIndex();
        int classNameLength = channelBuffer.readInt();

        ByteBuf classBuf = channelBuffer.readBytes(classNameLength);
        String clazzName = classBuf.toString(Charset.forName(charset));

        ByteBuf objectBuf = channelBuffer.readBytes(channelBuffer.readableBytes());

        // 检查一下Netty Protobuf解码器是怎么写的
        try {
            return reflact(clazzName, objectBuf.array());
        } catch (ClassNotFoundException e) {
            throw new IllegalStateException("class: " + clazzName + " not found!", e);
        } catch (NoSuchMethodException e) {
            throw new IllegalStateException("class: " + clazzName + " has not method: parseFrom(byte[]).", e);
        } catch (Exception e) {
            throw new IllegalStateException("reflection error!", e);
        }
    }


    protected static GeneratedMessage reflact(String clazz, byte[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        Class<?> aClass = Class.forName(clazz);
        Method method = CLASS_METHOD_MAP.get(aClass);
        if (method == null) {
            method = aClass.getMethod("parseFrom", byte[].class);
            CLASS_METHOD_MAP.put(aClass, method);
        }
        return (GeneratedMessage) method.invoke(null, args);
    }


    public String getCharset() {
        return charset;
    }

    public void setCharset(String charset) {
        this.charset = charset;
    }
}