Netty（25）Netty的序列化和反序列化机制是什么？

Victor3562025-12-22 20:10

Netty支持多种序列化和反序列化机制，包括Java原生的序列化机制、Google的Protocol Buffers、JSON、XML等。下面将详细介绍如何在Netty中实现序列化和反序列化，并结合代码示例进行说明。

Java原生序列化

Java原生序列化机制可以使用 ObjectEncoder 和 ObjectDecoder 来实现。

示例：使用Java原生序列化机制

  1. 定义一个可序列化的对象：
java 复制代码 
import java.io.Serializable;

public class MyMessage implements Serializable {
    private static final long serialVersionUID = 1L;
    private String content;

    public MyMessage(String content) {
        this.content = content;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public String toString() {
        return "MyMessage{" +
                "content='" + content + '\'' +
                '}';
    }
}
  1. 服务器端实现：
java 复制代码 
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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 io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;

public class SerializationServer {
    public static void main(String[] args) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new ObjectEncoder());
                     p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
                     p.addLast(new SerializationServerHandler());
                 }
             });

            b.bind(8080).sync().channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class SerializationServerHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Server received: " + msg);
        ctx.writeAndFlush(new MyMessage("Hello from server!"));
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}
  1. 客户端实现：
java 复制代码 
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;

public class SerializationClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new ObjectEncoder());
                     p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
                     p.addLast(new SerializationClientHandler());
                 }
             });

            b.connect("localhost", 8080).sync().channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class SerializationClientHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(new MyMessage("Hello from client!"));
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Client received: " + msg);
    }

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

使用Protocol Buffers

Protocol Buffers（Protobuf）是一种灵活、高效、自动化的序列化机制，适用于语言无关、平台无关的数据交换格式。以下是使用Protobuf的示例。

示例：使用Protobuf进行序列化和反序列化

  1. 定义Protobuf消息：

创建一个 message.proto 文件：

protobuf 复制代码 
syntax = "proto3";

option java_package = "com.example.protobuf";
option java_outer_classname = "MessageProtos";

message MyMessage {
    string content = 1;
}
  1. 生成Java类：

使用 protoc 编译 message.proto 文件：

sh 复制代码 
protoc --java_out=. message.proto
  1. 服务器端实现：
java 复制代码 
import com.example.protobuf.MessageProtos.MyMessage;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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 io.netty.handler.codec.protobuf.ProtobufDecoder;
import io.netty.handler.codec.protobuf.ProtobufEncoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;

public class ProtobufServer {
    public static void main(String[] args) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new ProtobufVarint32FrameDecoder());
                     p.addLast(new ProtobufDecoder(MyMessage.getDefaultInstance()));
                     p.addLast(new ProtobufVarint32LengthFieldPrepender());
                     p.addLast(new ProtobufEncoder());
                     p.addLast(new ProtobufServerHandler());
                 }
             });

            b.bind(8080).sync().channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

import com.example.protobuf.MessageProtos.MyMessage;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class ProtobufServerHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Server received: " + msg.getContent());
        MyMessage response = MyMessage.newBuilder().setContent("Hello from server!").build();
        ctx.writeAndFlush(response);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}
  1. 客户端实现：
java 复制代码 
import com.example.protobuf.MessageProtos.MyMessage;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.protobuf.ProtobufDecoder;
import io.netty.handler.codec.protobuf.ProtobufEncoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;

public class ProtobufClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new ProtobufVarint32FrameDecoder());
                     p.addLast(new ProtobufDecoder(MyMessage.getDefaultInstance()));
                     p.addLast(new ProtobufVarint32LengthFieldPrepender());
                     p.addLast(new ProtobufEncoder());
                     p.addLast(new ProtobufClientHandler());
                 }
             });

            b.connect("localhost", 8080).sync().channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
}

import com.example.protobuf.MessageProtos.MyMessage;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class ProtobufClientHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        MyMessage message = MyMessage.newBuilder().setContent("Hello from client!").build();
        ctx.writeAndFlush(message);
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Client received: " + msg.getContent());
    }

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

使用JSON

Netty也支持使用JSON进行序列化和反序列化。

示例：使用JSON进行序列化和反序列化

  1. 添加依赖：

在 pom.xml 中添加 Jackson 的依赖：

xml 复制代码 
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.0</version>
</dependency>
  1. 定义消息对象：
java 复制代码 
public class MyMessage {
    private String content;

    public MyMessage() {
    }

    public MyMessage(String content) {
        this.content = content;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public String toString() {
        return "MyMessage{" +
                "content='" + content + '\'' +
                '}';
    }
}
  1. 自定义编解码器：
java 复制代码 
import com.fasterxml.jackson.databind.ObjectMapper;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;

public class JsonEncoder extends MessageToByteEncoder<Object> {
    private final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
        byte[] bytes = objectMapper.writeValueAsBytes(msg);
        out.writeBytes(bytes);
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

import java.util.List;

public class JsonDecoder<T> extends ByteToMessageDecoder {
    private final ObjectMapper objectMapper = new ObjectMapper();
    private final Class<T> clazz;

    public JsonDecoder(Class<T> clazz) {
        this.clazz = clazz;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        byte[] bytes = new byte[in.readableBytes()];
        in.readBytes(bytes);
        T obj = objectMapper.readValue(bytes, clazz);
        out.add(obj);
    }
}
  1. 服务器端实现：
java 复制代码 
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class JsonServer {
    public static void main(String[] args) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new JsonDecoder<>(MyMessage.class));
                     p.addLast(new JsonEncoder());
                     p.addLast(new JsonServerHandler());
                 }
             });

            b.bind(8080).sync().channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class JsonServerHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Server received: " + msg);
        ctx.writeAndFlush(new MyMessage("Hello from server!"));
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}
  1. 客户端实现：
java 复制代码 
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class JsonClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .handler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast(new JsonDecoder<>(MyMessage.class));
                     p.addLast(new JsonEncoder());
                     p.addLast(new JsonClientHandler());
                 }
             });

            b.connect("localhost", 8080).sync().channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class JsonClientHandler extends SimpleChannelInboundHandler<MyMessage> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ctx.writeAndFlush(new MyMessage("Hello from client!"));
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MyMessage msg) throws Exception {
        System.out.println("Client received: " + msg);
    }

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

通过以上示例，您可以了解如何在Netty中使用Java原生序列化、Protocol Buffers和JSON进行序列化和反序列化。选择哪种方式取决于您的具体需求和环境。

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