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");

}

}