MINA2中的拆包组包的处理及一些方法

1.position 

例： 

position()

第一次使用返回值为当前位置：0 


position(8) 返回第8个字节以后的数据（包括第8个）可以和 limit　联合使用 
如： 

buffer.position(3);
buffer.limit(7);
ByteBuffer slice = buffer.slice();

再次调用 position() 返回：8 


2.remaining 

例： 

ByteBuffer byt = ByteBuffer.allocate(128,false);

第一次调用 
byt.remaining(); 返回 128 

A、使用：byt.putInt(5);或者byt.getInt()或者byt.get(字节数组)等方法 

之后调用 byt.remaining(); 返回 124 

B、但使用 byt.putInt(5,4);或者byt.getInt(0) 之后，调用方法 
byt.remaining();返回 128 


3.prefixedDataAvailable 

prefixedDataAvailable(4) int 

该方法很好用。判断前四字节的整型值是否大于等于整个缓冲区的数据。可以方便的判断一次 
messageReceived 过来的数据是否完整。（前提是自己设计的网络通讯协议前四字节等于发送数据的长度） 

prefixedDataAvailable(2) Short int 


网上找到的例子： 

protected boolean doDecode(IoSession session, IoBuffer in,
           ProtocolDecoderOutput out) throws Exception {
       if (in.prefixedDataAvailable(4, Constants.MAX_COMMAND_LENGTH)) {
           int length = in.getInt();
           byte[] bytes = new byte[length];
           in.get(bytes);
           int commandNameLength = Constants.COMMAND_NAME_LENGTH;
           byte[] cmdNameBytes = new byte[commandNameLength];
           System.arraycopy(bytes, 0, cmdNameBytes, 0, commandNameLength);
           String cmdName = (new String(cmdNameBytes)).trim();
           AbstractTetrisCommand command = TetrisCommandFactory
               .newCommand(cmdName);
           if (command != null) {
               byte[] cmdBodyBytes = new byte[length - commandNameLength];
               System.arraycopy(bytes, commandNameLength, cmdBodyBytes, 0,
                   length - commandNameLength);
               command.bodyFromBytes(cmdBodyBytes);
               out.write(command);
           }
           return true;
       } else {
           return false;
       }
   }

MINA中分段读取数据的方法： 


2. ProtobufRPCRequestProtocolDecoder.java 

package com.lizongbo.protobufrpc;

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

public class ProtobufRPCRequestProtocolDecoder implements ProtocolDecoder {

private static final AttributeKey BUF_BYTE = new AttributeKey(
ProtobufRPCRequestProtocolDecoder.class, "bufb");

public void decode(IoSession ioSession, IoBuffer ioBuffer,
ProtocolDecoderOutput protocolDecoderOutput) throws
Exception {
try {
IoBuffer bufTmp = null;
byte[] buf = (byte[]) ioSession.getAttribute(BUF_BYTE);
if (buf == null) {
System.out.println("没有尚未处理的数据" + ioBuffer.remaining());
bufTmp = ioBuffer;
} else {
System.out.println("合并尚未处理的数据" + ioBuffer.remaining());
bufTmp = IoBuffer.allocate(buf.length + ioBuffer.remaining());
bufTmp.setAutoExpand(true);
bufTmp.put(buf);
bufTmp.put(ioBuffer);
bufTmp.flip();
} while (bufTmp.remaining() >= 4
&& bufTmp.remaining() >= bufTmp.getInt(bufTmp.position())) { // 循环处理数据包
System.out.println("循环处理数据包");
int dataLen = bufTmp.getInt(bufTmp.position());
byte[] b = new byte[dataLen];
bufTmp.get(b);
ProtobufRPCRequest pak = new ProtobufRPCRequest();
pak.setReqByteLen(b.length);
pak.readFrom(b, 4);
System.out.println("往下传递");
protocolDecoderOutput.write(pak);
}
if (bufTmp.hasRemaining()) { // 如果有剩余的数据，则放入Session中
System.out.println("如果有剩余的数据，则放入Session中" + bufTmp.remaining());
byte[] tmpb = new byte[bufTmp.remaining()];
bufTmp.get(tmpb);
ioSession.setAttribute(BUF_BYTE, tmpb);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}

public void dispose(IoSession session) throws Exception {
System.out.println("dispose");

}

public void finishDecode(IoSession session, ProtocolDecoderOutput out) throws
Exception {
System.out.println("finishDecode");
}

}