Java NIO 实现进程通讯，解决用户自定义数据的组包和拆分粘包的问题

TCP通讯过程中，由于网络原因或者其他原因，经常出现粘包和半包现象。所以在具体编程中需要考虑。

下边的 java 代码是用 NIO 实现的一个Server端，消息的通讯格式为：

4字节int类型 [包头] + 包体.

包头描述出包体的长度。

package com.sof.nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.util.Set;import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class Reactor implements Runnable{private static Logger logger = LoggerFactory.getLogger(Reactor.class);final Selector selector;final ServerSocketChannel serverSocket;public Reactor(String ip, int port) throws IOException{selector = Selector.open();serverSocket = ServerSocketChannel.open();serverSocket.socket().bind(new InetSocketAddress(port));serverSocket.configureBlocking(false);SelectionKey sk = serverSocket.register(selector, SelectionKey.OP_ACCEPT);sk.attach(new Acceptor());}public void run(){try{while (!Thread.interrupted()){logger.debug("selector is waitting  event....");selector.select();Set<SelectionKey> keys = selector.selectedKeys();if (keys.size() == 0){logger.debug("nothing happened");continue;}for (SelectionKey key : keys){if (key.isAcceptable()){logger.debug("Acceptable event happened");}else if (key.isReadable()){logger.debug("Readable event happened");}else if (key.isWritable()){logger.debug("Writeable event happened");}else{logger.debug("others event happened");}dispatch((SelectionKey) key);}keys.clear();}}catch (IOException ex){logger.error(ex.getMessage());ex.printStackTrace();}}void dispatch(SelectionKey k){Runnable r = (Runnable) (k.attachment());if (r != null){r.run();}}public class Acceptor implements Runnable{public synchronized void run(){try{SocketChannel c = serverSocket.accept();logger.info("got a new connection from:  " + c.socket().toString());if (c != null){new Handler(selector, c);}}catch (IOException ex){logger.error(ex.getMessage());ex.printStackTrace();}}}}

package com.sof.nio;import java.io.IOException;import java.nio.ByteBuffer;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import com.sof.bas.Bytes2util;import com.sof.bas.Util2Bytes;final public class Handler implements Runnable{private static Logger logger = LoggerFactory.getLogger(Handler.class);final SocketChannel socket;final SelectionKey sk;static final int MESSAGE_LENGTH_HEAD = 4;byte[] head = new byte[4];int bodylen = -1;Handler(Selector selector, SocketChannel socket) throws IOException{this.socket = socket;socket.configureBlocking(false);sk = socket.register(selector, 0);sk.attach(this);sk.interestOps(SelectionKey.OP_READ);selector.wakeup();}public void run(){try{read();}catch (IOException ex){try{socket.close();}catch (IOException e){e.printStackTrace();}logger.info("got a disconnect from " + socket.socket().toString());sk.cancel();}}public synchronized void read() throws IOException{ByteBuffer input = ByteBuffer.allocate(1024);socket.read(input);input.flip();//读取数据的原则: 要么读取一个完整的包头，要么读取一个完整包体。不满足这两种情况，不对ByteBuffer进行任何的get操作//但是要注意可能发生上次读取了一个完整的包头，下次读才读取一个完整包体情况。//所以包头部分必须用类的成员变量进行暂时的存储，当完整读取包头和包体后，在给业务处理部分。logger.debug("1: remain=" + input.remaining() + " bodylen=" + bodylen);while(input.remaining() > 0){if (bodylen < 0) //还没有生成完整的包头部分, 该变量初始值为-1，并且在拼凑一个完整的消息包以后，再将该值设置为-1{if ( input.remaining() >= MESSAGE_LENGTH_HEAD) //ByteBuffer缓冲区的字节数够拼凑一个包头{input.get(head, 0, 4);bodylen = Util2Bytes.bytes2bigint(head);logger.debug("2: remain=" + input.remaining() + " bodylen=" + bodylen);}else//ByteBuffer缓冲区的字节数不够拼凑一个包头，什么操作都不做，退出这次处理，继续等待{logger.debug("3: remain=" + input.remaining() + " bodylen=" + bodylen);break;}}else if(bodylen > 0) //包头部分已经完整生成. {if (input.remaining() >= bodylen) //缓冲区的内容够一个包体部分{byte[] body = new byte[bodylen];input.get(body, 0, bodylen);byte[] headandbody = new byte[MESSAGE_LENGTH_HEAD + bodylen];System.arraycopy(head, 0, headandbody, 0, head.length);System.arraycopy(body,0, headandbody, head.length, body.length);bodylen = -1;logger.debug("4: remain=" + input.remaining() + " bodylen=" + bodylen);Bytes2util.outputHex(headandbody, 16);}else  ///缓冲区的内容不够一个包体部分，继续等待，跳出循环等待下次再出发该函数{System.out.println("5: remain=" + input.remaining() + " bodylen=" + bodylen);break;}}else if(bodylen == 0) //没有包体部分，仅仅有包头的情况{byte[] headandbody = new byte[MESSAGE_LENGTH_HEAD + bodylen];System.arraycopy(head, 0, headandbody, 0, head.length);Bytes2util.outputHex(headandbody, 16);bodylen = -1;}}sk.interestOps(SelectionKey.OP_READ);}}

package com.sof.bas;import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class Bytes2util {private static Logger logger = LoggerFactory.getLogger(Bytes2util.class);public static byte[] biginttobytes(int value) {byte[] stream = new byte[4];for (int i = 0; i < 4; i++) {stream[i] = (byte) ((value & (0xFF << (4 - i - 1) * 8)) >> ((4 - i - 1) * 8));}outputHex(stream, 16);return stream;}public static byte[] bigshorttobytes(short value) {byte stream[] = new byte[2];for (int i = 0; i < 2; i++) {stream[i] = (byte) ((value & (0xFF << (2 - i - 1) * 8)) >> ((2 - i - 1) * 8));}outputHex(stream, 16);return stream;}public static byte[] smallinttobytes(int value) {byte stream[] = new byte[4];for (int i = 0; i < 4; i++) {stream[4 - i - 1] = (byte) ((value & (0xFF << (4 - i - 1) * 8)) >> ((4 - i - 1) * 8));}outputHex(stream, 16);return stream;}public static byte[] smallshorttobytes(short value) {byte stream[] = new byte[2];for (int i = 0; i < 2; i++) {stream[2 - i - 1] = (byte) ((value & (0xFF << (2 - i - 1) * 8)) >> ((2 - i - 1) * 8));}outputHex(stream, 16);return stream;}public static void outputHex(byte[] stream, int number) {String content = "stream display, length=" + stream.length + "\n";for (int i = 0; i < stream.length; i++) {if (i / number != 0 && i % number == 0) {content += "\n";}String tempstr = Integer.toHexString(stream[i] & 0xFF).toUpperCase();if (tempstr.length() == 1)tempstr = "0" + tempstr;content += tempstr + " ";}logger.debug(content);}}

package com.sof.bas;public class Util2Bytes{public static int bytes2smallint(byte stream[]){int value = 0;int temp = 0;for (int i = 3; i >= 0; i--){if ((stream[i]) >= 0){temp = stream[i];}else{temp = stream[i] + 256;}temp <<= (i * 8);value += temp;}return value;}public static short bytes2smallshort(byte stream[]){short value = 0;int temp = 0;for (int i = 1; i >= 0; i--){if ((stream[i]) >= 0){temp = stream[i];}else{temp = stream[i] + 256;}temp <<= (i * 8);value += temp;}return value;}public static int bytes2bigint(byte stream[]){int value = 0;int temp = 0;for (int i = 0; i < 4; i++){if ((stream[i]) >= 0){temp = stream[i];}else{temp = stream[i] + 256;}temp <<= ((4 - i - 1) * 8);value += temp;}return value;}public static short bytes2bigshort(byte stream[]){short value = 0;int temp = 0;for (int i = 0; i < 2; i++){if ((stream[i]) >= 0){temp = stream[i];}else{temp = stream[i] + 256;}temp <<= ((2 - i - 1) * 8);value += temp;}return value;}}