是用mina自定义解析器

我们在自定义传输协议时，通常都是采用字节数组的方式进行传送，如何正确接收和解码byte数组？

假设我们自定义了传输协议: 字节数组的前4个字节是要传输的数据长度，后面跟数据。我们用mina可以这样处理

1.自定义编码器ByteArrayEncoder.java

import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
import org.apache.mina.filter.codec.ProtocolEncoderOutput;

/**
 *  编码器将数据直接发出去(不做处理)
 */
public class ByteArrayEncoder extends ProtocolEncoderAdapter {

    @Override
    public void encode(IoSession session, Object message,
            ProtocolEncoderOutput out) throws Exception {
        out.write(message);
        out.flush();
        
    }
}

2.自定义解码器(确保能读取到完整的包)

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.CumulativeProtocolDecoder;
import org.apache.mina.filter.codec.ProtocolDecoderOutput;

import com.talkweb.meeting.tools.IntByteConvert;

public class ByteArrayDecoder extends CumulativeProtocolDecoder  {

    @Override
    public boolean doDecode(IoSession session, IoBuffer in, ProtocolDecoderOutput out)
            throws Exception {
        
        if(in.remaining() > 4){//前4字节是包头
            //标记当前position的快照标记mark，以便后继的reset操作能恢复position位置
            in.mark();
            byte[] l = new byte[4];
            in.get(l);

            //包体数据长度
            int len = MyTools.bytes2int(l);//将byte转成int
           

            //注意上面的get操作会导致下面的remaining()值发生变化
            if(in.remaining() < len){
                //如果消息内容不够，则重置恢复position位置到操作前,进入下一轮, 接收新数据，以拼凑成完整数据
                in.reset();   
                return false;
            }else{
                //消息内容足够
                in.reset();//重置恢复position位置到操作前
                int sumlen = 4+len;//总长 = 包头+包体
                byte[] packArr = new byte[sumlen];
                in.get(packArr, 0 , sumlen);
                
                IoBuffer buffer = IoBuffer.allocate(sumlen);
                buffer.put(packArr);
                buffer.flip();
                out.write(buffer);
                buffer.free();
                
                if(in.remaining() > 0){//如果读取一个完整包内容后还粘了包，就让父类再调用一次，进行下一次解析
                    return true;
                }
            }
        }
        return false;//处理成功，让父类进行接收下个包
    }
    
}

3.编解码工厂类

import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.ProtocolCodecFactory;
import org.apache.mina.filter.codec.ProtocolDecoder;
import org.apache.mina.filter.codec.ProtocolEncoder;


/**
 * @author BruceYang
 *
 */
public class ByteArrayCodecFactory implements ProtocolCodecFactory {
    
    private ByteArrayDecoder decoder;
    private ByteArrayEncoder encoder;
    
    public ByteArrayCodecFactory() {
        encoder = new ByteArrayEncoder();
        decoder = new ByteArrayDecoder();
    }

    @Override
    public ProtocolDecoder getDecoder(IoSession session) throws Exception {
        return decoder;
    }

    @Override
    public ProtocolEncoder getEncoder(IoSession session) throws Exception {
        return encoder;
    }

}

4.调用编解码工厂进行编解码

NioSocketAcceptor acceptor = new NioSocketAcceptor();

acceptor.getFilterChain().addLast("mycoder", new ProtocolCodecFilter(new ByteArrayCodecFactory()));