一、概述
Netty是目前最流行的由JBOSS提供的一个Java开源框架NIO框架，Netty提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。
相比JDK原生NIO，Netty提供了相对十分简单易用的API，非常适合网络编程。Netty是完全基于NIO实现的，所以Netty是异步的。
Mina同样也是一款优秀的NIO框架，而且跟Netty是出自同一个人之手，但是Netty要晚一点，优点更多一些，想了解更多可以直接搜索mina和netty比较。
使用Netty，我们可以作为Socket服务器，也可以用来做Http服务器，同时也可以支持WebSocket，这里，我们将这三种方式都详细介绍一下。
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二、依赖Jar包
只需要引入Netty的jar包，为了方便json转换，我这里引入fastjson。
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.17.Final</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.40</version>
</dependency>三、通用的监听配置
不论是Socket、http还是websocket，都是基于tcp的，因此，netty需要配置EventLoopGroup做监听。
package cn.pomit.springwork.nettynew.server;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
public abstract class NettyServiceTemplate {
static private EventLoopGroup bossGroup = new NioEventLoopGroup();
static private EventLoopGroup workerGroup = new NioEventLoopGroup();
abstract protected ChannelHandler[] createHandlers();
abstract public int getPort();
abstract public String getName();
@PostConstruct
public void start() throws Exception {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelHandler[] handlers = createHandlers();
for (ChannelHandler handler : handlers) {
ch.pipeline().addLast(handler);
}
}
}).option(ChannelOption.SO_BACKLOG, 128).option(ChannelOption.SO_REUSEADDR, true)
.childOption(ChannelOption.SO_KEEPALIVE, true).childOption(ChannelOption.SO_REUSEADDR, true);
ChannelFuture cf = b.bind(getPort()).await();
// cf.channel().closeFuture().await();
if (!cf.isSuccess()) {
System.out.println("无法绑定端口：" + getPort());
throw new Exception("无法绑定端口：" + getPort());
}
System.out.println("服务[{" + getName() + "}]启动完毕，监听端口[{" + getPort() + "}]");
}
@PreDestroy
public void stop() {
bossGroup.shutdownGracefully().syncUninterruptibly();
workerGroup.shutdownGracefully().syncUninterruptibly();
System.out.println("服务[{" + getName() + "}]关闭。");
}
}
这里的配置，都是netty的常用配置：
- option和childOption是配置连接属性的。
- ChannelHandler是必须的，这里通过抽象方法，由子类负责配置。
启动的时候，new一个子类，调用start方法即可。
四、Netty的Socket监听
有了上面的NettyServiceTemplate，我们可以用几行代码构建一个tcp服务器。实现父类的抽象方法createHandlers，传递ChannelHandler数组。
下面的ChannelHandler数组包含：
- 换行分割解码器
- 字符串解码器
- 字符串编码器
- 自定义处理器，写自己逻辑用。
StringTcpServer ：
package cn.pomit.springwork.nettynew.server.tcp;
import cn.pomit.springwork.nettynew.handler.tcp.StringTcpServerHandler;
import cn.pomit.springwork.nettynew.server.NettyServiceTemplate;
import io.netty.channel.ChannelHandler;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.Delimiters;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
public class StringTcpServer extends NettyServiceTemplate {
private int port = 8088;
private String name = "String Server";
public StringTcpServer(int port) {
this.port = port;
}
@Override
protected ChannelHandler[] createHandlers() {
return new ChannelHandler[] {
new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()),
new StringDecoder(),
new StringEncoder(),
new StringTcpServerHandler() };
}
@Override
public int getPort() {
return port;
}
@Override
public String getName() {
return name;
}
public void setPort(int port) {
this.port = port;
}
public void setName(String name) {
this.name = name;
}
}
这样就是一个tcp服务器了，StringTcpServerHandler特别简单，打印并返回：
package cn.pomit.springwork.nettynew.handler.tcp;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
public class StringTcpServerHandler extends SimpleChannelInboundHandler<String> {
String charset = "UTF-8";
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println("内容:" + msg);
ctx.writeAndFlush("返回内容：" + msg);
}
}五、Netty的Http监听
Netty的http，稍微复杂点，复杂只是相对于返回值的控制，cookie的控制，session的控制，因为netty只负责帮你解析了http的所有信息，并没有像sevlet容器那样还给你控制session了啥的。
我这里只用netty做json数据转换，用来提供rest服务，如果想了解更多，可以看下我用netty实现的一个类似Spring容器的工具：https://gitee.com/ffch/teaboot, 这个工具解析html、rest等，提供了简单的session控制、security控制。代码属于早期内容，尚待维护。
5.1 Http服务器
这个服务器是专门面向rest服务的。有了上面的NettyServiceTemplate，我们可以用几行代码构建一个http服务器。实现父类的抽象方法createHandlers，传递ChannelHandler数组。
ChannelHandler数组中：
- HttpResponseEncoder是netty自己的响应编码器，报文级别
- HttpRequestDecoder是netty自己的请求解码器，报文级别
- HttpObjectAggregator是完全的解析Http POST请求用的。
- HttpMsgResponseEncoder是自定义的响应编码器，为的是对响应做简单的控制。应用级别
- HttpMsgRequestDecoder是自定义的请求解码器，是对http请求转换为json。应用级别
- JsonHttpServerHandler是自定义逻辑处理器，写自己业务用。
JsonHttpServer :
package cn.pomit.springwork.nettynew.server.http;
import cn.pomit.springwork.nettynew.coder.http.HttpMsgRequestDecoder;
import cn.pomit.springwork.nettynew.coder.http.HttpMsgResponseEncoder;
import cn.pomit.springwork.nettynew.handler.http.JsonHttpServerHandler;
import cn.pomit.springwork.nettynew.server.NettyServiceTemplate;
import io.netty.channel.ChannelHandler;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
public class JsonHttpServer extends NettyServiceTemplate {
int port = 8888;
String name = "Json Server";
private String charset = "UTF-8";
private int timeout = 60;
public JsonHttpServer(int port) {
this.port = port;
}
@Override
protected ChannelHandler[] createHandlers() {
return new ChannelHandler[] {
new HttpResponseEncoder(),
new HttpRequestDecoder(),
new HttpObjectAggregator(1048576),
new HttpMsgResponseEncoder(charset, timeout),
new HttpMsgRequestDecoder(charset),
new JsonHttpServerHandler() };
}
@Override
public int getPort() {
return port;
}
@Override
public String getName() {
return name;
}
}
5.2 自定义的请求解码器
请求解码器就是转换下数据，变成字符串。
HttpMsgRequestDecoder:
package cn.pomit.springwork.nettynew.coder.http;
import java.nio.charset.Charset;
import java.util.List;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.HttpObject;
public class HttpMsgRequestDecoder extends MessageToMessageDecoder<HttpObject>{
private String charset;
public HttpMsgRequestDecoder(String charset) {
super();
this.charset = charset;
}
@Override
protected void decode(ChannelHandlerContext ctx, HttpObject in,
List<Object> out) throws Exception {
FullHttpRequest request = (FullHttpRequest) in;
ByteBuf buf = request.content();
String jsonStr = buf.toString(Charset.forName(charset));
out.add(jsonStr);
}
}5.3 自定义的响应编码器
响应编码器中，定义了连接的配置信息，http头信息、内容类型等。
HttpMsgResponseEncoder:
package cn.pomit.springwork.nettynew.coder.http;
import java.util.List;
import cn.pomit.springwork.nettynew.model.http.HttpResponseMsg;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpHeaderValues;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
public class HttpMsgResponseEncoder extends MessageToMessageEncoder<HttpResponseMsg> {
private String charset;
private int timeout;
public HttpMsgResponseEncoder(String charset, int timeout) {
super();
this.charset = charset;
this.timeout = timeout;
}
@Override
protected void encode(ChannelHandlerContext ctx, HttpResponseMsg message, List<Object> out) {
try {
DefaultFullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.valueOf(message.getResCode()),
Unpooled.wrappedBuffer(message.getMessage().getBytes(charset)));
response.headers().set(HttpHeaderNames.CONTENT_TYPE, message.getResType()+";charset=" + charset);
response.headers().set(HttpHeaderNames.CONTENT_LENGTH, response.content().readableBytes());
// 强制keep-alive
response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
response.headers().set("Keep-Alive", "timeout=" + timeout);
out.add(response);
} catch (Exception e) {
e.printStackTrace();
}
}
}
5.4 业务处理器
这里的业务处理器很简单，就打印返回。
JsonHttpServerHandler:
package cn.pomit.springwork.nettynew.handler.http;
import cn.pomit.springwork.nettynew.model.http.HttpResponseMsg;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
public class JsonHttpServerHandler extends SimpleChannelInboundHandler<String> {
String charset = "UTF-8";
@Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
System.out.println("post内容:" + msg);
HttpResponseMsg hrm = new HttpResponseMsg();
hrm.setResType(HttpResponseMsg.ResType.JSON.getValue());
hrm.setResCode(HttpResponseMsg.ResCode.OK.getValue());
hrm.setMessage(msg);
ctx.writeAndFlush(hrm);
}
}
六、Netty的WebSocket监听
Netty的WebSocket，相对于http还稍微简单点。
Netty对WebSocket做了完全控制，你需要做的只是对WebSocket的用户进行控制，能根据用户找到相应的通道即可。
6.1 WebSocket服务器
有了上面的NettyServiceTemplate，我们可以用几行代码构建一个WebSocket服务器。实现父类的抽象方法createHandlers，传递ChannelHandler数组。
ChannelHandler数组中：
- HttpServerCodec是netty自己的http解码器，报文级别
- ChunkedWriteHandler是用于大数据的分区传输。
- HttpObjectAggregator是完全的解析Http消息体请求用的。
- WebSocketServerProtocolHandler是配置websocket的监听地址。
- WebSocketServerHandler是自定义逻辑处理器，写自己业务用。
WebSocketServer :
package cn.pomit.springwork.nettynew.server.websocket;
import cn.pomit.springwork.nettynew.handler.websocket.WebSocketServerHandler;
import cn.pomit.springwork.nettynew.server.NettyServiceTemplate;
import io.netty.channel.ChannelHandler;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
public class WebSocketServer extends NettyServiceTemplate {
int port = 9999;
String name = "WebSocket";
public WebSocketServer(int port) {
this.port = port;
}
@Override
protected ChannelHandler[] createHandlers() {
return new ChannelHandler[] {
new HttpServerCodec(),
new ChunkedWriteHandler(),
new HttpObjectAggregator(1048576),
new WebSocketServerProtocolHandler("/ws"),
new WebSocketServerHandler() };
}
@Override
public int getPort() {
return port;
}
@Override
public String getName() {
return name;
}
}
6.2 WebSocket的聊天室逻辑
下面是用websocket做聊天室的逻辑：
- 使用MessageDTO 做消息的传递实体；
- WebSocketUser存储了每个连接上来的WebSocket用户，保存对应段分Channel。
- 前端要求填入用户后，模拟登录，并返回用户列表。前端根据用户列表选择人发送信息。
- 根据MessageDTO中的发送人和接收人，找到对应的Channel并发送消息。
WebSocketServerHandler:
package cn.pomit.springwork.nettynew.handler.websocket;
import java.util.List;
import com.alibaba.fastjson.JSONObject;
import cn.pomit.springwork.nettynew.model.websocket.MessageDTO;
import cn.pomit.springwork.nettynew.model.websocket.WebSocketUser;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
public class WebSocketServerHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
MessageDTO messageDTO = JSONObject.parseObject(msg.text(), MessageDTO.class);
if (messageDTO.getMessageType().equals(MessageDTO.Type.TYPE_NEW.getMessageType())) {
WebSocketUser.add(messageDTO.getFromUserName(), ctx.channel());
messageDTO.setTargetUserName(messageDTO.getFromUserName());
messageDTO.setFromUserName("SYSTEM");
messageDTO.setMessage(JSONObject.toJSONString(WebSocketUser.getUserList()));
ctx.channel().writeAndFlush(new TextWebSocketFrame(JSONObject.toJSONString(messageDTO)));
} else {
List<Channel> webUsers = WebSocketUser.getSessionByUserName(messageDTO.getTargetUserName());
if (webUsers == null || webUsers.size() == 0) {
System.out.print("发送给" + messageDTO.getTargetUserName() + ",当前无session");
MessageDTO messageDTOError = new MessageDTO();
messageDTOError.setFromUserName("SYSTEM");
messageDTOError.setTargetUserName(messageDTO.getFromUserName());
messageDTOError.setMessageType(MessageDTO.Type.TYPE_ERROR.getMessageType());
messageDTOError.setMessage("发送失败！");
ctx.channel().writeAndFlush(new TextWebSocketFrame(JSONObject.toJSONString(messageDTOError)));
return;
}
System.out.print("发送给" + messageDTO.getTargetUserName() + ",当前session个数为：" + webUsers.size());
for (int i = 0; i < webUsers.size(); i++) {
Channel session = webUsers.get(i);
if (!session.isOpen()) {
WebSocketUser.removeWebSocketSession(messageDTO.getTargetUserName(), session);
}
session.writeAndFlush(new TextWebSocketFrame(JSONObject.toJSONString(messageDTO)));
}
}
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
System.out.println("用户：" + ctx.channel().id().asLongText() + "上线");
}
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
System.out.println("用户下线: " + ctx.channel().id().asLongText());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.channel().close();
}
}
6.3 用户信息保存
用一个并发map保存所有用户和对应的Channel。
WebSocketUser:
package cn.pomit.springwork.nettynew.model.websocket;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import io.netty.channel.Channel;
public class WebSocketUser {
private static Map<String, List<Channel>> userNameWebsession = new ConcurrentHashMap<>();
public static void add(String userName, Channel webSocketSession) {
userNameWebsession.computeIfAbsent(userName, v -> new ArrayList<Channel>()).add(webSocketSession);
}
/**
* 根据昵称拿WebSocketSession
*
* @param nickName
* @return
*/
public static List<Channel> getSessionByUserName(String userName) {
return userNameWebsession.get(userName);
}
/**
* 移除失效的WebSocketSession
*
* @param webSocketSession
*/
public static void removeWebSocketSession(String userName, Channel webSocketSession) {
if (webSocketSession == null)
return;
List<Channel> webSessoin = userNameWebsession.get(userName);
if (webSessoin == null || webSessoin.isEmpty())
return;
webSessoin.remove(webSocketSession);
}
public static Set<String> getUserList() {
return userNameWebsession.keySet();
}
}
七、过程中用到的其他实体、启动类及页面
7.1 启动类
TestApp:
package cn.pomit.springwork.nettynew;
import cn.pomit.springwork.nettynew.server.http.JsonHttpServer;
import cn.pomit.springwork.nettynew.server.tcp.StringTcpServer;
import cn.pomit.springwork.nettynew.server.websocket.WebSocketServer;
public class TestApp {
public static void main(String args[]) throws ClassNotFoundException, InstantiationException, IllegalAccessException{
StringTcpServer stringTcpServerTest = new StringTcpServer(8088);
JsonHttpServer jsonHttpServer = new JsonHttpServer(8880);
WebSocketServer webSocketServer = new WebSocketServer(9999);
try {
stringTcpServerTest.start();
jsonHttpServer.start();
webSocketServer.start();
} catch (Exception e) {
e.printStackTrace();
}
}
}
7.2 Http响应实体
HttpResponseMsg:
package cn.pomit.springwork.nettynew.model.http;
public class HttpResponseMsg {
public enum ResType {
HTML("text/html"),
JSON("application/json"),
JS("application/javascript"),
PNG("image/png"),
JPG("image/jpg");
String value = null;
ResType(String value) {
this.value = value;
}
public String getValue() {
return value;
}
}
public enum ResCode {
NOT_FOUND(404),
OK(200),
INTERNAL_ERROR(500);
int value = 200;
ResCode(int value) {
this.value = value;
}
public int getValue() {
return value;
}
}
public int resCode;
public String resType;
public String message;
public int getResCode() {
return resCode;
}
public void setResCode(int resCode) {
this.resCode = resCode;
}
public String getResType() {
return resType;
}
public void setResType(String resType) {
this.resType = resType;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}7.3 WebSocket传递实体
MessageDTO:
package cn.pomit.springwork.nettynew.model.websocket;
public class MessageDTO {
private String fromUserName;
private String targetUserName;
private String message;
private String messageType;
public String getFromUserName() {
return fromUserName;
}
public void setFromUserName(String fromUserName) {
this.fromUserName = fromUserName;
}
public String getTargetUserName() {
return targetUserName;
}
public void setTargetUserName(String targetUserName) {
this.targetUserName = targetUserName;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public String getMessageType() {
return messageType;
}
public void setMessageType(String messageType) {
this.messageType = messageType;
}
public static enum Type {
TYPE_NEW("0000"), TYPE_TEXT("1000"), TYPE_BYTE("1001"), TYPE_ERROR("1111");
private String messageType;
Type(String messageType) {
this.messageType = messageType;
}
public String getMessageType() {
return messageType;
}
public void setMessageType(String messageType) {
this.messageType = messageType;
}
}
}
7.4 WebSocket前端页面
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<title>品茗IT-WebSocket测试</title>
<!-- CSS -->
<link href="https://lib.baomitu.com/material-design-icons/3.0.1/iconfont/material-icons.min.css" rel="stylesheet">
<link href="https://lib.baomitu.com/materialize/0.100.2/css/materialize.min.css" type="text/css" rel="stylesheet" media="screen,projection"/>
<style>
body { text-align:left; margin:0; font:normal 12px Verdana, Arial;
background:#FFEEFF } form { margin:0; font:normal 12px Verdana,
Arial; } table,input { font:normal 12px Verdana, Arial; }
a:link,a:visited{ text-decoration:none; color:#333333; } a:hover{
text-decoration:none;