netty初探(2)

上一篇 netty(1)

一、TCP/IP 流式传输

　　在上文演示了2进制流式传输引起的TCP拆包问题，这里继续演示文本型的传输问题，文本型的可以有以下几种策略

　

1.1 以特殊字符表示结尾

HTTP协议中以\r\n\r\n表示请求首部结束，这里也以\r\n\r\n表示特殊字符，非常容易理解，没有碰到\r\n\r\n就继续写入缓冲，碰到了表明是一个完整的逻辑数据，可以处理了。

Server端代码

public class Server {

    public static final String SERVER_DELIMITER = "\r\n\r\n";

    public static void main(String[] args) throws Exception {
        //1 创建2个线程，一个是负责接收客户端的连接。一个是负责进行数据传输的
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        //2 创建服务器辅助类
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 1024)
                .option(ChannelOption.SO_SNDBUF, 32 * 1024)
                .option(ChannelOption.SO_RCVBUF, 32 * 1024)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        //设置特殊分隔符
                        ByteBuf buf = Unpooled.copiedBuffer(SERVER_DELIMITER.getBytes());
                        sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));
                        //设置字符串形式的解码
                        sc.pipeline().addLast(new StringDecoder());
                        sc.pipeline().addLast(new ServerHandler());
                    }
                });

        //4 绑定连接
        ChannelFuture cf = b.bind(8765).sync();

        //等待服务器监听端口关闭
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }

}

public class ServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(" server channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String request = (String)msg;
        System.out.println("Server :" + msg);
        String response = "服务器响应：" + msg + Server.SERVER_DELIMITER;
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable t) throws Exception {
        ctx.close();
    }
}

客户端代码：

public class Client {

    public static final String CLIENT_DELIMITER = "\r\n\r\n";

    public static void main(String[] args) throws Exception {

        EventLoopGroup group = new NioEventLoopGroup();

        Bootstrap b = new Bootstrap();
        b.group(group)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        //
                        ByteBuf buf = Unpooled.copiedBuffer(CLIENT_DELIMITER.getBytes());
                        sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));
                        sc.pipeline().addLast(new StringDecoder());
                        sc.pipeline().addLast(new ClientHandler());
                    }
                });

        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();
        StringBuffer sb = new StringBuffer("GET " + "/index.jsp" + " HTTP/1.1\r\n");
        sb.append("Host: www.javathinker.org\r\n");
        sb.append("Accept: */*\r\n");
        sb.append("Accept-Language: zh-cn\r\n");
        sb.append("Accept-Encoding: gzip, deflate\r\n");
        sb.append("User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)\r\n");
        sb.append("Connection: Keep-Alive\r\n\r\n");
        cf.channel().writeAndFlush(Unpooled.wrappedBuffer(sb.toString().getBytes()));
//        Thread.sleep(1000);
//        cf.addListener(ChannelFutureListener.CLOSE);

        //等待客户端端口关闭
        cf.channel().closeFuture().sync();
        group.shutdownGracefully();
    }
}

public class ClientHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            String response = (String)msg;
            System.out.println("Client: " + response);
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}

1.2 以FixedLength的方式

跟上述代码类似，只需要修改下Decoder即可

b.group(group)
         .channel(NioSocketChannel.class)
         .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new FixedLengthFrameDecoder(5));
                sc.pipeline().addLast(new StringDecoder());
                sc.pipeline().addLast(new ClientHandler());
            }
        });

二、使用Java对象传输

官网Object demo：http://netty.io/4.1/xref/io/netty/example/objectecho/package-summary.html

使用Java对象传输，只需要配置对应的encoder: Object->byte[] 和对应的decoder: byte[]->Object即可

2.1 使用java searilizable

先写个工具类，提供GZIP压缩功能，以及发送请求和处理请求的通用方法

package netty;

import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import netty.marshalling.Req;
import netty.marshalling.Resp;

import java.io.*;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

/**
 * Created by carl.yu on 2016/11/7.
 */
public class Utils {
    public static byte[] gzip(byte[] data) throws Exception{
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        GZIPOutputStream gzip = new GZIPOutputStream(bos);
        gzip.write(data);
        gzip.finish();
        gzip.close();
        byte[] ret = bos.toByteArray();
        bos.close();
        return ret;
    }

    public static byte[] ungzip(byte[] data) throws Exception{
        ByteArrayInputStream bis = new ByteArrayInputStream(data);
        GZIPInputStream gzip = new GZIPInputStream(bis);
        byte[] buf = new byte[1024];
        int num = -1;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while((num = gzip.read(buf, 0 , buf.length)) != -1 ){
            bos.write(buf, 0, num);
        }
        gzip.close();
        bis.close();
        byte[] ret = bos.toByteArray();
        bos.flush();
        bos.close();
        return ret;
    }

    public static void send(ChannelFuture cf) throws Exception{
        for (int i = 1; i <= 2; i++) {
            Req req = new Req();
            req.setId("" + i);
            req.setName("pro" + i);
            req.setRequestMessage("数据信息" + i);
            String path = "G:\\projects-helloworld\\lucene\\src\\main\\resources\\in\\" + i + ".jpg";
            String fileName = i + ".jpg";
            req.setFileName(fileName);
            File file = new File(path);
            FileInputStream in = new FileInputStream(file);
            byte[] data = new byte[in.available()];

            in.read(data);
            in.close();
            req.setAttachment(Utils.gzip(data));
            cf.channel().writeAndFlush(req);
        }
    }

    public static void recv(ChannelHandlerContext ctx, Object msg) throws Exception{
        Req req = (Req) msg;
        System.out.println("req:"+req);
        System.out.println("Server : " + req.getId() + ", " + req.getName() + ", " + req.getRequestMessage());
        byte[] attachment = Utils.ungzip(req.getAttachment());
        String fileName = req.getFileName();
        String path = "G:\\projects-helloworld\\lucene\\src\\main\\resources\\out\\" + fileName;
        FileOutputStream fos = new FileOutputStream(path);
        fos.write(attachment);
        fos.close();

        Resp resp = new Resp();
        resp.setId(req.getId());
        resp.setName("resp" + req.getId());
        resp.setResponseMessage("响应内容" + req.getId());
        ctx.writeAndFlush(resp);//.addListener(ChannelFutureListener.CLOSE);
    }

    public static void main(String[] args) throws Exception{

        //读取文件
        String readPath = System.getProperty("user.dir") + File.separatorChar + "sources" +  File.separatorChar + "006.jpg";
        File file = new File(readPath);
        FileInputStream in = new FileInputStream(file);
        byte[] data = new byte[in.available()];
        in.read(data);
        in.close();

        System.out.println("文件原始大小:" + data.length);
        //测试压缩

        byte[] ret1 = gzip(data);
        System.out.println("压缩之后大小:" + ret1.length);

        byte[] ret2 = ungzip(ret1);
        System.out.println("还原之后大小:" + ret2.length);

        //写出文件
        String writePath = System.getProperty("user.dir") + File.separatorChar + "receive" +  File.separatorChar + "006.jpg";
        FileOutputStream fos = new FileOutputStream(writePath);
        fos.write(ret2);
        fos.close();

    }
}

Req:

import java.io.Serializable;

public class Req implements Serializable {

    private static final long SerialVersionUID = 1L;

    private String id;
    private String name;
    private String requestMessage;
    private byte[] attachment;
    private String fileName;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRequestMessage() {
        return requestMessage;
    }

    public void setRequestMessage(String requestMessage) {
        this.requestMessage = requestMessage;
    }

    public byte[] getAttachment() {
        return attachment;
    }

    public void setAttachment(byte[] attachment) {
        this.attachment = attachment;
    }

    public String getFileName() {
        return fileName;
    }

    public void setFileName(String fileName) {
        this.fileName = fileName;
    }

    @Override
    public String toString() {
        return "Req{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", requestMessage='" + requestMessage + '\'' +
                ", fileName='" + fileName + '\'' +
                '}';
    }
}

Resp:

import java.io.Serializable;

public class Resp implements Serializable{

    private static final long serialVersionUID = 1L;

    private String id = "1";
    private String name ="aaa";
    private String responseMessage ="this is demo";

    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getResponseMessage() {
        return responseMessage;
    }
    public void setResponseMessage(String responseMessage) {
        this.responseMessage = responseMessage;
    }

    @Override
    public String toString() {
        return "Resp{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", responseMessage='" + responseMessage + '\'' +
                '}';
    }
}

Server端代码：

public class ObjectEchoServer {
    static final boolean SSL = System.getProperty("ssl") != null;
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.
        final SslContext sslCtx;
        if (SSL) {
            SelfSignedCertificate ssc = new SelfSignedCertificate();
            sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
        } else {
            sslCtx = null;
        }

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            if (sslCtx != null) {
                                p.addLast(sslCtx.newHandler(ch.alloc()));
                            }
                            p.addLast(
                                    new ObjectEncoder(),
                                    new ObjectDecoder(ClassResolvers.cacheDisabled(null)),
                                    new ObjectEchoServerHandler());
                        }
                    });

            // Bind and start to accept incoming connections.
            b.bind(PORT).sync().channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

public class ObjectEchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // Echo back the received object to the client.
        Utils.recv(ctx, msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

client端代码：

public final class ObjectEchoClient {

    static final boolean SSL = System.getProperty("ssl") != null;
    static final String HOST = System.getProperty("host", "127.0.0.1");
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
    static final int SIZE = Integer.parseInt(System.getProperty("size", "256"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.
        final SslContext sslCtx;
        if (SSL) {
            sslCtx = SslContextBuilder.forClient()
                    .trustManager(InsecureTrustManagerFactory.INSTANCE).build();
        } else {
            sslCtx = null;
        }

        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            if (sslCtx != null) {
                                p.addLast(sslCtx.newHandler(ch.alloc(), HOST, PORT));
                            }
                            p.addLast(
                                    new ObjectEncoder(),
                                    new ObjectDecoder(ClassResolvers.cacheDisabled(null)),
                                    new ObjectEchoClientHandler());
                        }
                    });

            // Start the connection attempt.
            ChannelFuture cf = b.connect(HOST, PORT).sync();
            Utils.send(cf);
            cf.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
}

public class ObjectEchoClientHandler extends ChannelInboundHandlerAdapter {

    private final List<Integer> firstMessage;

    /**
     * Creates a client-side handler.
     */
    public ObjectEchoClientHandler() {
        firstMessage = new ArrayList<Integer>(ObjectEchoClient.SIZE);
        for (int i = 0; i < ObjectEchoClient.SIZE; i++) {
            firstMessage.add(Integer.valueOf(i));
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        try {
            Resp resp = (Resp)msg;
            System.out.println("Client : " + resp.getId() + ", " + resp.getName() + ", " + resp.getResponseMessage());
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

2.2 使用jboss marshalling序列化

        <dependency>
            <groupId>org.jboss.marshalling</groupId>
            <artifactId>jboss-marshalling-serial</artifactId>
            <version>2.0.0.Beta2</version>
        </dependency>

jboss marshalling自动支持netty的codec

public final class MarshallingCodeCFactory {

    /**
     * 创建Jboss Marshalling解码器MarshallingDecoder
     * @return MarshallingDecoder
     */
    public static MarshallingDecoder buildMarshallingDecoder() {
        //首先通过Marshalling工具类的精通方法获取Marshalling实例对象 参数serial标识创建的是java序列化工厂对象。
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        //创建了MarshallingConfiguration对象，配置了版本号为5
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        //根据marshallerFactory和configuration创建provider
        UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
        //构建Netty的MarshallingDecoder对象，俩个参数分别为provider和单个消息序列化后的最大长度
        MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024 * 1024 * 1);
        return decoder;
    }

    /**
     * 创建Jboss Marshalling编码器MarshallingEncoder
     * @return MarshallingEncoder
     */
    public static MarshallingEncoder buildMarshallingEncoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
        //构建Netty的MarshallingEncoder对象，MarshallingEncoder用于实现序列化接口的POJO对象序列化为二进制数组
        MarshallingEncoder encoder = new MarshallingEncoder(provider);
        return encoder;
    }
}

直接在server中配置codec即可，其他都类似

b.group(pGroup, cGroup)
         .channel(NioServerSocketChannel.class)
         .option(ChannelOption.SO_BACKLOG, 1024)
         //设置日志
         .handler(new LoggingHandler(LogLevel.INFO))
         .childHandler(new ChannelInitializer<SocketChannel>() {
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ServerHandler());
            }
        });

        b.group(group)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                        sc.pipeline().addLast(new ClientHandler());
                    }
                });

2.3 其他序列化框架

其他序列化框架都类似，只要有对应的encoder和decoder，比如Kryo和Google protocol Buf

三、其他

3.1 read_time_out和write_time_out

　　在用netty进行socket通信时，通常也会遇到read time out和write time out的设置问题，netty也是通过handler来实现的，netty默认提供了2个类

// The connection is closed when there is no inbound traffic
   // for 30 seconds.

   public class MyChannelInitializer extends ChannelInitializer<Channel> {
       public void initChannel(Channel channel) {
           channel.pipeline().addLast("readTimeoutHandler", new ReadTimeoutHandler(30);
           channel.pipeline().addLast("myHandler", new MyHandler());
       }
   }

   // Handler should handle the ReadTimeoutException.
   public class MyHandler extends ChannelDuplexHandler {
        @Override
       public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
               throws Exception {
           if (cause instanceof ReadTimeoutException) {
               // do something
           } else {
               super.exceptionCaught(ctx, cause);
           }
       }
   }

   ServerBootstrap bootstrap = ...;
   ...
   bootstrap.childHandler(new MyChannelInitializer());
   ...
   

当读超时，可以捕获该异常，也可以丢弃此连接，防止占用服务器资源。

同样的

   // The connection is closed when a write operation cannot finish in 30 seconds.

   public class MyChannelInitializer extends ChannelInitializer<Channel> {
       public void initChannel(Channel channel) {
           channel.pipeline().addLast("writeTimeoutHandler", new WriteTimeoutHandler(30);
           channel.pipeline().addLast("myHandler", new MyHandler());
       }
   }

   // Handler should handle the WriteTimeoutException.
   public class MyHandler extends ChannelDuplexHandler {
        @Override
       public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
               throws Exception {
           if (cause instanceof WriteTimeoutException) {
               // do something
           } else {
               super.exceptionCaught(ctx, cause);
           }
       }
   }

   ServerBootstrap bootstrap = ...;
   ...
   bootstrap.childHandler(new MyChannelInitializer());
   ...