netty之LengthFieldBasedFrameDecoder解码器

官方api:http://netty.io/4.1/api/io/netty/handler/codec/LengthFieldBasedFrameDecoder.html

package com.eshore.ismp.hbinterface.sps;

import java.nio.charset.Charset;

import org.apache.log4j.Logger;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.eshore.ismp.hbinterface.service.BizCommonService;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class SpsServer4 {
	 private static final Logger logger = Logger.getLogger(SpsServer4.class);
	    private static int PORT = 10002;
	    /**用于分配处理业务线程的线程组个数 */
	    protected static final int BIZGROUPSIZE = Runtime.getRuntime().availableProcessors()*2; //默认
	    /** 业务出现线程大小*/
	    protected static final int BIZTHREADSIZE = 4;
	        /*
	     * NioEventLoopGroup实际上就是个线程池,
	     * NioEventLoopGroup在后台启动了n个NioEventLoop来处理Channel事件,
	     * 每一个NioEventLoop负责处理m个Channel,
	     * NioEventLoopGroup从NioEventLoop数组里挨个取出NioEventLoop来处理Channel
	     */
	    private static final EventLoopGroup bossGroup = new NioEventLoopGroup(BIZGROUPSIZE);
	    private static final EventLoopGroup workerGroup = new NioEventLoopGroup(BIZTHREADSIZE);  

	    protected static void run(final BizCommonService bizCommonService) throws Exception {
	    	//String PORTs=ConfigLoadUtil.getValue("toSpsServerPort");
	    	//PORT=Integer.parseInt(PORTs);
	    	//logger.info("PORT IS:"+PORT);
	        ServerBootstrap b = new ServerBootstrap();
	        b.group(bossGroup, workerGroup);
	        b.channel(NioServerSocketChannel.class);
	        b.childHandler(new ChannelInitializer<SocketChannel>() {
	            @Override
	            public void initChannel(SocketChannel ch) throws Exception {
	                ChannelPipeline pipeline = ch.pipeline();
	               /* pipeline.addLast("decoder", new StringDecoder(CharsetUtil.UTF_8));
	                pipeline.addLast("encoder", new StringEncoder(CharsetUtil.UTF_8));  */
	                pipeline.addLast(new MessageDecoder(Integer.MAX_VALUE,18,4,-22,0));
	                pipeline.addLast("decoder", new StringDecoder(Charset.forName("GBK")));
	                pipeline.addLast("encoder", new StringEncoder(Charset.forName("GBK")));
	                pipeline.addLast(new SpsServerHandler(bizCommonService));
	            }
	        });  

	        b.bind(PORT).sync();
	        logger.info("TCP服务器已启动");
	    }  

	    protected static void shutdown() {
	        workerGroup.shutdownGracefully();
	        bossGroup.shutdownGracefully();
	    }  

	    public static void main(String[] args) throws Exception {
	    	try{
	    		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
	    				new String[] { "applicationContext.xml" });
	    		context.start();
	    		BizCommonService bizCommonService = (BizCommonService) context.getBean("bizCommonService");
	    		SpsServer4.run(bizCommonService);
	    	}catch(Exception e){
	    		logger.error("start sps interface server error:",e);
	    		System.exit(-1);
	    	}
	    }
}

MessageDecoder:

package com.eshore.ismp.hbinterface.sps;

import java.io.UnsupportedEncodingException;
import java.nio.ByteOrder;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

public class MessageDecoder extends LengthFieldBasedFrameDecoder{
	private final  Logger logger = LoggerFactory.getLogger(this.getClass());
	public MessageDecoder(int maxFrameLength, int lengthFieldOffset, int lengthFieldLength, int lengthAdjustment,
			int initialBytesToStrip) {
		super(maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment, initialBytesToStrip);
	}

	@Override
	protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception{
		return super.decode(ctx, in);
	}
	@Override
	protected long getUnadjustedFrameLength(ByteBuf buf, int offset, int length, ByteOrder order){
		long frameLength;
	    switch (length) {
	    case 1:
	        frameLength = buf.getUnsignedByte(offset);
	        break;
	    case 2:
	        frameLength = buf.getUnsignedShort(offset);
	        break;
	    case 3:
	        frameLength = buf.getUnsignedMedium(offset);
	        break;
	    case 4:
	        //frameLength = buf.getUnsignedInt(offset);
	    	frameLength=buf.readableBytes();
	    	logger.info("==="+frameLength);
	    	byte[] cc=new byte[buf.readableBytes()];
	    	ByteBuf tmp=buf.copy();
	    	tmp.readBytes(cc);
	    	try {
				String ss=new String(cc,"GBK");
				frameLength=Integer.parseInt(ss.substring(offset,offset+length));
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}
	        break;
	    case 8:
	        frameLength = buf.getLong(offset);
	        break;
	    default:
	        throw new DecoderException(
	                "unsupported lengthFieldLength: "
	         + length + " (expected: 1, 2, 3, 4, or 8)");
	    }
	    return frameLength;
	}

}

其中，报文长度为6位：17-22

参考 https://blog.csdn.net/bestone0213/article/details/47108419

参考：https://www.jianshu.com/p/a0a51fd79f62

参考：https://blog.csdn.net/zougen/article/details/79037675