Netty自定义实现粘包与粘包
TCP粘包与拆包 问题的展现程序
默认不适应任何编解码器的情况下
Server
public class MyServer {
public static void main(String[] args) throws Exception {
HashMap<Object, Object> objectObjectHashMap = new HashMap<>();
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new MyServerInitializer());
ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
//----------------------------------------------------------------------
public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
/**
每连接一个客户端initChannel就会被调用一次
*/
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new MyServerHandler());
}
}
//----------------------------------------------------------------------
public class MyServerHandler extends SimpleChannelInboundHandler<ByteBuf> {
/**记录服务器端接收到了几次*/
private int count;
/**
* @param ctx 上下文，可以获取远程的信息，地址、连接对象
* @param msg 客户端发来的请求对象
* @throws Exception
*/
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
byte[] buffer = new byte[msg.readableBytes()];
msg.readBytes(buffer);
String message = new String(buffer, Charset.forName("utf-8"));
System.out.println("服务器端接收到的消息内容：" + message);
System.out.println("服务器端接收到的消息数量：" + (++count));
//向客户端返回数据
ByteBuf responseByteBuf = Unpooled.copiedBuffer(UUID.randomUUID().toString(), Charset.forName("utf-8"));
ctx.writeAndFlush(responseByteBuf);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
Client
public class MyClient {
public static void main(String[] args) throws Exception {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
.handler(new MyClientInitializer());
//与对应的url建立连接通道
ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
eventLoopGroup.shutdownGracefully();
}
}
}
//----------------------------------------------------------------------
public class MyClientInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new MyClientHandler());
}
}
//----------------------------------------------------------------------
public class MyClientHandler extends SimpleChannelInboundHandler<ByteBuf> {
private int count;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
for (int i = 0; i < 5; i++) {
ByteBuf buffer = Unpooled.copiedBuffer("sent from client", Charset.forName("utf-8"));
ctx.writeAndFlush(buffer);
}
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
byte[] buffer = new byte[msg.readableBytes()];
msg.readBytes(buffer);
String message = new String(buffer, Charset.forName("utf-8"));
System.out.println("客户端接收到的消息内容：" + message);
System.out.println("客户端接收到的消息数量：" + (++count));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
测试
Server输出
服务器端接收到的消息内容：sent from clientsent from clientsent from clientsent from clientsent from client
服务器端接收到的消息数量：1
Client输出
客户端接收到的消息内容：9226b8cf-0e10-41db-9e0e-684310854fc1
客户端接收到的消息数量：1
很明显是错误的，我们一共发送了5条消息但是服务器端却把它当成了一条消息进行接收了
解决问题自定义粘包与拆包
协议对象
/**
* 协议对象
*/
public class PersonProtocol {
/**value 消息体的长度，向后再读取length个字节为一个消息，content的长度*/
private int length;
/**消息体，length表示的长度就是它的内容长度*/
private byte[] content;
public int getLength() {
return length;
}
public void setLength(int length) {
this.length = length;
}
public byte[] getContent() {
return content;
}
public void setContent(byte[] content) {
this.content = content;
}
}
消息解码器
/**
* 消息解码器，用于定义接收一个消息的粘包的规则
*/
public class MyPersonDecoder extends ReplayingDecoder<Void> {
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
System.out.println("MyPersonDecoder decoder invoked !");
//读取一个int(4个字节)，它表示消息体的长度
int length = in.readInt();
//用于消息体内容
byte[] content = new byte[length];
in.readBytes(content);
PersonProtocol personProtocol = new PersonProtocol();
personProtocol.setLength(length);
personProtocol.setContent(content);
out.add(personProtocol);
}
}
消息编码器
public class MyPersonEncoder extends MessageToByteEncoder<PersonProtocol> {
@Override
protected void encode(ChannelHandlerContext ctx, PersonProtocol msg, ByteBuf out) throws Exception {
System.out.println("MyPersonEncoder encode invoked !");
out.writeInt(msg.getLength());
out.writeBytes(msg.getContent());
}
}
Server
public class MyServer {
public static void main(String[] args) throws Exception {
HashMap<Object, Object> objectObjectHashMap = new HashMap<>();
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new MyServerInitializer());
ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
//----------------------------------------------------------------------
public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
/**
每连接一个客户端initChannel就会被调用一次
*/
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new MyPersonDecoder());
pipeline.addLast(new MyPersonEncoder());
pipeline.addLast(new MyServerHandler());
}
}
//----------------------------------------------------------------------
public class MyServerHandler extends SimpleChannelInboundHandler<PersonProtocol> {
/**记录服务器端接收到了几次*/
private int count;
/**
* @param ctx 上下文，可以获取远程的信息，地址、连接对象
* @param msg 客户端发来的请求对象
* @throws Exception
*/
@Override
protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
int length = msg.getLength();
byte[] content = msg.getContent();
System.out.println("服务端接收到的数据：");
System.out.println("长度：" + length);
System.out.println("内容：" + new String(content, Charset.forName("utf-8")));
System.out.println("服务器端接收到的消息数量：" + (++count));
//向客户端返回数据
String responseMessage = UUID.randomUUID().toString();
byte[] responseContent = responseMessage.getBytes(Charset.forName("utf-8"));
int responseLength = responseContent.length;
PersonProtocol personProtocol = new PersonProtocol();
personProtocol.setLength(responseLength);
personProtocol.setContent(responseContent);
ctx.writeAndFlush(personProtocol);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}
Client
public class MyClient {
public static void main(String[] args) throws Exception {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new MyPersonDecoder());
pipeline.addLast(new MyPersonEncoder());
pipeline.addLast(new MyClientHandler());
}
});
//与对应的url建立连接通道
ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
channelFuture.channel().closeFuture().sync();
}finally {
eventLoopGroup.shutdownGracefully();
}
}
}
//----------------------------------------------------------------------
public class MyClientHandler extends SimpleChannelInboundHandler<PersonProtocol> {
private int count;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
for (int i = 0; i < 5; i++) {
String messageToBeSent = "sent from client";
byte[] content = messageToBeSent.getBytes(Charset.forName("utf-8"));
int length = content.length;
PersonProtocol personProtocol = new PersonProtocol();
personProtocol.setLength(length);
personProtocol.setContent(content);
ctx.writeAndFlush(personProtocol);
}
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, PersonProtocol msg) throws Exception {
int length = msg.getLength();
byte[] content = msg.getContent();
System.out.println("客户端接收到的消息： ");
System.out.println("长度：" + length);
System.out.println("内容：" + new String(content,Charset.forName("utf-8")));
System.out.println("客户端接收到的消息数量：" + (++count));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
cause.printStackTrace();
ctx.close();
}
}