通过前面的学习，我们了解到数据在网络中传输的都是二进制字节码数据，因而在发送数据时就需要编码，接收数据时就需要解码。

codec(编解码器)的组成部分有两个：decoder(解码器)和encoder(编码器)。encoder负责把业务数据转换成字节码数据，decoder负责把字节码数据转换成业务数据

Netty中本身也提供了一些编解码器,如：

• StringEncoder/StringDecoder 对字符串进行编解码
• ObjectEncoder/ObjectDecoder 对Java对象进行编解码
• …

通过了解可以发现，Netty编解码器底层使用Java序列化技术来实现的。 但是Java序列化技术本身效率不高，而且无法跨语言，序列化后的体积太大(是二进制编码的5倍多)，序列化性能太低。因此转而选择使用 ProtoBuf 来实现序列化。

ProtoBuf的优点/特性：

1. ProtiBuf以message的方式来管理数据
2. 支持跨平台、跨语言
3. 高性能、高可靠性
4. 适合做数据存储或RPC

ProtoBuf的使用

 <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.6.1</version>
  </dependency>
2、编写Student.proto文件(IDEA的话 可以装Proto插件)
 
syntax = "proto3"; //版本
option java_outer_classname = "StudentPOJO"; //生成的外部类名 同时也是文件名
//protobuf使用message管理数据
message Student { //会在StudentPOJO外部类生成一个内部类Student，真正用到的对象
      int32 id=1;//student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
      string name=2;
如上创建一个proto文件，Student类是真正用到的对象，将是以一个内部类的方式展现在Java文件中，其中定义了两个成员变量：int id;String name。
 
3、使用编译器编译proto文件
 
注意：这里依赖的protobuf是3.6.1版本，因此编译器也要是3.6.1版本的,我这里下载的是osx-3.6.1版本的
 
protoc编译器下载
 
由于这里使用的是Java语言，因此执行命令如下：
 
 
将Student.proto文件拷贝到protoc编译器同级目录
 
 
protoc --java_out=. Student.proto
 
生成的StudengPOJO.Java文件如下:
 
// Generated by the protocol buffer compiler.  DO NOT EDIT!
// source: Student.proto
public final class StudentPOJO {
  private StudentPOJO() {}
  public static void registerAllExtensions(
      com.google.protobuf.ExtensionRegistryLite registry) {
  public static void registerAllExtensions(
      com.google.protobuf.ExtensionRegistry registry) {
    registerAllExtensions(
        (com.google.protobuf.ExtensionRegistryLite) registry);
  public interface StudentOrBuilder extends
      // @@protoc_insertion_point(interface_extends:Student)
      com.google.protobuf.MessageOrBuilder {
     * <pre>
     *student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
     * </pre>
     * <code>int32 id = 1;</code>
    int getId();
     * <code>string name = 2;</code>
    String getName();
     * <code>string name = 2;</code>
    com.google.protobuf.ByteString
        getNameBytes();
   * <pre>
   *protobuf使用message管理数据
   * </pre>
   * Protobuf type {@code Student}
  public  static final class Student extends
      com.google.protobuf.GeneratedMessageV3 implements
      // @@protoc_insertion_point(message_implements:Student)
      StudentOrBuilder {
  private static final long serialVersionUID = 0L;
    // Use Student.newBuilder() to construct.
    private Student(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
      super(builder);
    private Student() {
      id_ = 0;
      name_ = "";
    @Override
    public final com.google.protobuf.UnknownFieldSet
    getUnknownFields() {
      return this.unknownFields;
    private Student(
        com.google.protobuf.CodedInputStream input,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      this();
      if (extensionRegistry == null) {
        throw new NullPointerException();
      int mutable_bitField0_ = 0;
      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
          com.google.protobuf.UnknownFieldSet.newBuilder();
      try {
        boolean done = false;
        while (!done) {
          int tag = input.readTag();
          switch (tag) {
            case 0:
              done = true;
              break;
            case 8: {
              id_ = input.readInt32();
              break;
            case 18: {
              String s = input.readStringRequireUtf8();
              name_ = s;
              break;
            default: {
              if (!parseUnknownFieldProto3(
                  input, unknownFields, extensionRegistry, tag)) {
                done = true;
              break;
      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
        throw e.setUnfinishedMessage(this);
      } catch (java.io.IOException e) {
        throw new com.google.protobuf.InvalidProtocolBufferException(
            e).setUnfinishedMessage(this);
      } finally {
        this.unknownFields = unknownFields.build();
        makeExtensionsImmutable();
    public static final com.google.protobuf.Descriptors.Descriptor
        getDescriptor() {
      return StudentPOJO.internal_static_Student_descriptor;
    @Override
    protected FieldAccessorTable
        internalGetFieldAccessorTable() {
      return StudentPOJO.internal_static_Student_fieldAccessorTable
          .ensureFieldAccessorsInitialized(
              Student.class, Builder.class);
    public static final int ID_FIELD_NUMBER = 1;
    private int id_;
     * <pre>
     *student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
     * </pre>
     * <code>int32 id = 1;</code>
    public int getId() {
      return id_;
    public static final int NAME_FIELD_NUMBER = 2;
    private volatile Object name_;
     * <code>string name = 2;</code>
    public String getName() {
      Object ref = name_;
      if (ref instanceof String) {
        return (String) ref;
      } else {
        com.google.protobuf.ByteString bs = 
            (com.google.protobuf.ByteString) ref;
        String s = bs.toStringUtf8();
        name_ = s;
        return s;
     * <code>string name = 2;</code>
    public com.google.protobuf.ByteString
        getNameBytes() {
      Object ref = name_;
      if (ref instanceof String) {
        com.google.protobuf.ByteString b = 
            com.google.protobuf.ByteString.copyFromUtf8(
                (String) ref);
        name_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
    private byte memoizedIsInitialized = -1;
    @Override
    public final boolean isInitialized() {
      byte isInitialized = memoizedIsInitialized;
      if (isInitialized == 1) return true;
      if (isInitialized == 0) return false;
      memoizedIsInitialized = 1;
      return true;
    @Override
    public void writeTo(com.google.protobuf.CodedOutputStream output)
                        throws java.io.IOException {
      if (id_ != 0) {
        output.writeInt32(1, id_);
      if (!getNameBytes().isEmpty()) {
        com.google.protobuf.GeneratedMessageV3.writeString(output, 2, name_);
      unknownFields.writeTo(output);
    @Override
    public int getSerializedSize() {
      int size = memoizedSize;
      if (size != -1) return size;
      size = 0;
      if (id_ != 0) {
        size += com.google.protobuf.CodedOutputStream
          .computeInt32Size(1, id_);
      if (!getNameBytes().isEmpty()) {
        size += com.google.protobuf.GeneratedMessageV3.computeStringSize(2, name_);
      size += unknownFields.getSerializedSize();
      memoizedSize = size;
      return size;
    @Override
    public boolean equals(final Object obj) {
      if (obj == this) {
       return true;
      if (!(obj instanceof Student)) {
        return super.equals(obj);
      Student other = (Student) obj;
      boolean result = true;
      result = result && (getId()
          == other.getId());
      result = result && getName()
          .equals(other.getName());
      result = result && unknownFields.equals(other.unknownFields);
      return result;
    @Override
    public int hashCode() {
      if (memoizedHashCode != 0) {
        return memoizedHashCode;
      int hash = 41;
      hash = (19 * hash) + getDescriptor().hashCode();
      hash = (37 * hash) + ID_FIELD_NUMBER;
      hash = (53 * hash) + getId();
      hash = (37 * hash) + NAME_FIELD_NUMBER;
      hash = (53 * hash) + getName().hashCode();
      hash = (29 * hash) + unknownFields.hashCode();
      memoizedHashCode = hash;
      return hash;
    public static Student parseFrom(
        java.nio.ByteBuffer data)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data);
    public static Student parseFrom(
        java.nio.ByteBuffer data,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data, extensionRegistry);
    public static Student parseFrom(
        com.google.protobuf.ByteString data)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data);
    public static Student parseFrom(
        com.google.protobuf.ByteString data,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data, extensionRegistry);
    public static Student parseFrom(byte[] data)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data);
    public static Student parseFrom(
        byte[] data,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws com.google.protobuf.InvalidProtocolBufferException {
      return PARSER.parseFrom(data, extensionRegistry);
    public static Student parseFrom(java.io.InputStream input)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseWithIOException(PARSER, input);
    public static Student parseFrom(
        java.io.InputStream input,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseWithIOException(PARSER, input, extensionRegistry);
    public static Student parseDelimitedFrom(java.io.InputStream input)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseDelimitedWithIOException(PARSER, input);
    public static Student parseDelimitedFrom(
        java.io.InputStream input,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
    public static Student parseFrom(
        com.google.protobuf.CodedInputStream input)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseWithIOException(PARSER, input);
    public static Student parseFrom(
        com.google.protobuf.CodedInputStream input,
        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
        throws java.io.IOException {
      return com.google.protobuf.GeneratedMessageV3
          .parseWithIOException(PARSER, input, extensionRegistry);
    @Override
    public Builder newBuilderForType() { return newBuilder(); }
    public static Builder newBuilder() {
      return DEFAULT_INSTANCE.toBuilder();
    public static Builder newBuilder(Student prototype) {
      return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
    @Override
    public Builder toBuilder() {
      return this == DEFAULT_INSTANCE
          ? new Builder() : new Builder().mergeFrom(this);
    @Override
    protected Builder newBuilderForType(
        BuilderParent parent) {
      Builder builder = new Builder(parent);
      return builder;
     * <pre>
     *protobuf使用message管理数据
     * </pre>
     * Protobuf type {@code Student}
    public static final class Builder extends
        com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
        // @@protoc_insertion_point(builder_implements:Student)
        StudentOrBuilder {
      public static final com.google.protobuf.Descriptors.Descriptor
          getDescriptor() {
        return StudentPOJO.internal_static_Student_descriptor;
      @Override
      protected FieldAccessorTable
          internalGetFieldAccessorTable() {
        return StudentPOJO.internal_static_Student_fieldAccessorTable
            .ensureFieldAccessorsInitialized(
                Student.class, Builder.class);
      // Construct using StudentPOJO.Student.newBuilder()
      private Builder() {
        maybeForceBuilderInitialization();
      private Builder(
          BuilderParent parent) {
        super(parent);
        maybeForceBuilderInitialization();
      private void maybeForceBuilderInitialization() {
        if (com.google.protobuf.GeneratedMessageV3
                .alwaysUseFieldBuilders) {
      @Override
      public Builder clear() {
        super.clear();
        id_ = 0;
        name_ = "";
        return this;
      @Override
      public com.google.protobuf.Descriptors.Descriptor
          getDescriptorForType() {
        return StudentPOJO.internal_static_Student_descriptor;
      @Override
      public Student getDefaultInstanceForType() {
        return Student.getDefaultInstance();
      @Override
      public Student build() {
        Student result = buildPartial();
        if (!result.isInitialized()) {
          throw newUninitializedMessageException(result);
        return result;
      @Override
      public Student buildPartial() {
        Student result = new Student(this);
        result.id_ = id_;
        result.name_ = name_;
        onBuilt();
        return result;
      @Override
      public Builder clone() {
        return (Builder) super.clone();
      @Override
      public Builder setField(
          com.google.protobuf.Descriptors.FieldDescriptor field,
          Object value) {
        return (Builder) super.setField(field, value);
      @Override
      public Builder clearField(
          com.google.protobuf.Descriptors.FieldDescriptor field) {
        return (Builder) super.clearField(field);
      @Override
      public Builder clearOneof(
          com.google.protobuf.Descriptors.OneofDescriptor oneof) {
        return (Builder) super.clearOneof(oneof);
      @Override
      public Builder setRepeatedField(
          com.google.protobuf.Descriptors.FieldDescriptor field,
          int index, Object value) {
        return (Builder) super.setRepeatedField(field, index, value);
      @Override
      public Builder addRepeatedField(
          com.google.protobuf.Descriptors.FieldDescriptor field,
          Object value) {
        return (Builder) super.addRepeatedField(field, value);
      @Override
      public Builder mergeFrom(com.google.protobuf.Message other) {
        if (other instanceof Student) {
          return mergeFrom((Student)other);
        } else {
          super.mergeFrom(other);
          return this;
      public Builder mergeFrom(Student other) {
        if (other == Student.getDefaultInstance()) return this;
        if (other.getId() != 0) {
          setId(other.getId());
        if (!other.getName().isEmpty()) {
          name_ = other.name_;
          onChanged();
        this.mergeUnknownFields(other.unknownFields);
        onChanged();
        return this;
      @Override
      public final boolean isInitialized() {
        return true;
      @Override
      public Builder mergeFrom(
          com.google.protobuf.CodedInputStream input,
          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
          throws java.io.IOException {
        Student parsedMessage = null;
        try {
          parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
          parsedMessage = (Student) e.getUnfinishedMessage();
          throw e.unwrapIOException();
        } finally {
          if (parsedMessage != null) {
            mergeFrom(parsedMessage);
        return this;
      private int id_ ;
       * <pre>
       *student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
       * </pre>
       * <code>int32 id = 1;</code>
      public int getId() {
        return id_;
       * <pre>
       *student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
       * </pre>
       * <code>int32 id = 1;</code>
      public Builder setId(int value) {
        id_ = value;
        onChanged();
        return this;
       * <pre>
       *student类中有一个属性 名字为id 类型为int32(protibuf类型) 1表示属性序号
       * </pre>
       * <code>int32 id = 1;</code>
      public Builder clearId() {
        id_ = 0;
        onChanged();
        return this;
      private Object name_ = "";
       * <code>string name = 2;</code>
      public String getName() {
        Object ref = name_;
        if (!(ref instanceof String)) {
          com.google.protobuf.ByteString bs =
              (com.google.protobuf.ByteString) ref;
          String s = bs.toStringUtf8();
          name_ = s;
          return s;
        } else {
          return (String) ref;
       * <code>string name = 2;</code>
      public com.google.protobuf.ByteString
          getNameBytes() {
        Object ref = name_;
        if (ref instanceof String) {
          com.google.protobuf.ByteString b = 
              com.google.protobuf.ByteString.copyFromUtf8(
                  (String) ref);
          name_ = b;
          return b;
        } else {
          return (com.google.protobuf.ByteString) ref;
       * <code>string name = 2;</code>
      public Builder setName(
          String value) {
        if (value == null) {
    throw new NullPointerException();
        name_ = value;
        onChanged();
        return this;
       * <code>string name = 2;</code>
      public Builder clearName() {
        name_ = getDefaultInstance().getName();
        onChanged();
        return this;
       * <code>string name = 2;</code>
      public Builder setNameBytes(
          com.google.protobuf.ByteString value) {
        if (value == null) {
    throw new NullPointerException();
  checkByteStringIsUtf8(value);
        name_ = value;
        onChanged();
        return this;
      @Override
      public final Builder setUnknownFields(
          final com.google.protobuf.UnknownFieldSet unknownFields) {
        return super.setUnknownFieldsProto3(unknownFields);
      @Override
      public final Builder mergeUnknownFields(
          final com.google.protobuf.UnknownFieldSet unknownFields) {
        return super.mergeUnknownFields(unknownFields);
      // @@protoc_insertion_point(builder_scope:Student)
    // @@protoc_insertion_point(class_scope:Student)
    private static final Student DEFAULT_INSTANCE;
    static {
      DEFAULT_INSTANCE = new Student();
    public static Student getDefaultInstance() {
      return DEFAULT_INSTANCE;
    private static final com.google.protobuf.Parser<Student>
        PARSER = new com.google.protobuf.AbstractParser<Student>() {
      @Override
      public Student parsePartialFrom(
          com.google.protobuf.CodedInputStream input,
          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
          throws com.google.protobuf.InvalidProtocolBufferException {
        return new Student(input, extensionRegistry);
    public static com.google.protobuf.Parser<Student> parser() {
      return PARSER;
    @Override
    public com.google.protobuf.Parser<Student> getParserForType() {
      return PARSER;
    @Override
    public Student getDefaultInstanceForType() {
      return DEFAULT_INSTANCE;
  private static final com.google.protobuf.Descriptors.Descriptor
    internal_static_Student_descriptor;
  private static final 
    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
      internal_static_Student_fieldAccessorTable;
  public static com.google.protobuf.Descriptors.FileDescriptor
      getDescriptor() {
    return descriptor;
  private static  com.google.protobuf.Descriptors.FileDescriptor
      descriptor;
  static {
    String[] descriptorData = {
      "\n\rStudent.proto\"#\n\007Student\022\n\n\002id\030\001 \001(\005\022\014" +
      "\n\004name\030\002 \001(\tB\rB\013StudentPOJOb\006proto3"
    com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
        new com.google.protobuf.Descriptors.FileDescriptor.    InternalDescriptorAssigner() {
          public com.google.protobuf.ExtensionRegistry assignDescriptors(
              com.google.protobuf.Descriptors.FileDescriptor root) {
            descriptor = root;
            return null;
    com.google.protobuf.Descriptors.FileDescriptor
      .internalBuildGeneratedFileFrom(descriptorData,
        new com.google.protobuf.Descriptors.FileDescriptor[] {
        }, assigner);
    internal_static_Student_descriptor =
      getDescriptor().getMessageTypes().get(0);
    internal_static_Student_fieldAccessorTable = new
      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
        internal_static_Student_descriptor,
        new String[] { "Id", "Name", });
  // @@protoc_insertion_point(outer_class_scope)
将序列化后的Java类放到项目中即可使用




    
 
示例：基于ProtoBuf实现简单的通讯
 
客户端发送一个Student对象到服务器
服务器端接收到Student对象 并显示信息
使用ProtoBuf编解码
 
public class NettyProtoBufServer {
    public static void main(String[] args) {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            //对哪种类型进行解码
                            pipeline.addLast("decoder", new ProtobufDecoder(StudentPOJO.Student.getDefaultInstance()));
                            pipeline.addLast(new NettyProtoBufHandler());
                    });
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
//handler
public class NettyProtoBufHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        StudentPOJO.Student student = (StudentPOJO.Student) msg;
        System.out.println("from client:" + student.getId() + "====>" + student.getName());
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("msg from server", CharsetUtil.UTF_8));
客户端代码




    
 
public class NettyProtoBufClient {
    public static void main(String[] args) {
        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();
                            //编码器
                            pipeline.addLast("encoder", new ProtobufEncoder());
                            pipeline.addLast(new NettyProtoBufClientHandler());
                    });
            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8899).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
//handler
public class NettyProtoBufClientHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        StudentPOJO.Student student = StudentPOJO.Student.newBuilder().setId(1).setName("abc").build();
        ctx.writeAndFlush(student);
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf= (ByteBuf) msg;
        System.out.println(buf.toString(CharsetUtil.UTF_8));
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        super.exceptionCaught(ctx, cause);
注意：这里在客户端和服务器端加上了与ProtoBuf有关的编解码器
 
上面的例子服务器端只会生成一种特定类型的对象，如果服务器端想要根据业务获取不同类型的对象可参见下面的例子
 
syntax = "proto3";
option java_outer_classname = "RolePOJO";
option java_package = "com.wojiushiwo.protobuf.multi";
message Role {
    //declare enum
    enum DataType {
        Student = 0;
        Worker = 1;
    //first field
    DataType dataType = 1;
    //can select one of declared field
    oneof dataBody {
        Student student = 2;
        Worker worker = 3;
message Student {
    int32 id = 1;
    string name = 2;
message Worker {
    string name = 1;
    int32 age = 2;
服务端代码
 
public class NettyMultiProtoBufTypeServer {
    public static void main(String[] args) {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            // 这里服务器端添加的是针对protoBuf的解码器
                            pipeline.addLast("decoder", new ProtobufDecoder(RolePOJO.Role.getDefaultInstance()));
                            pipeline.addLast(new MultiProtoBufServerHandler());
                    });
            ChannelFuture channelFuture = serverBootstrap.bind(8900).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
//handler
public class MultiProtoBufServerHandler extends SimpleChannelInboundHandler<RolePOJO.Role> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, RolePOJO.Role msg) throws Exception {
        RolePOJO.Role.DataType dataType = msg.getDataType();
        if (Objects.equals(dataType, RolePOJO.Role.DataType.Student)) {
            RolePOJO.Student student = msg.getStudent();
            System.out.println("获取到客户端发送的信息：" + student.getId() + "," + student.getName());
        } else if (Objects.equals(dataType, RolePOJO.Role.DataType.Worker)) {
            RolePOJO.Worker worker = msg.getWorker();
            System.out.println("获取到客户端发送的信息：" + worker.getAge() + "," + worker.getName());
        } else {
            System.out.println("获取到客户端发送的信息");
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
客户端代码




    
 
package com.wojiushiwo.protobuf.multi;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
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.ProtobufEncoder;
 * Created by myk
 * 2020/1/29 下午5:40
public class NettyMultiProtoBufTypeClient {
    public static void main(String[] args) {
        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 ProtobufEncoder());
                            pipeline.addLast(new MultiProtoBufClientHandler());
                    });
            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8900).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
//handler
package com.wojiushiwo.protobuf.multi;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
 * Created by myk
 * 2020/1/29 下午5:41
public class MultiProtoBufClientHandler extends ChannelInboundHandlerAdapter {
    public static void main(String[] args) {
        System.out.println((int) (Math.random() * 10));
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        int randomNum = (int) (Math.random() * 10);
        RolePOJO.Role role;
        if (randomNum % 2 == 0) {
            RolePOJO.Student student = RolePOJO.Student.newBuilder().setId(1).setName("student").build();
            role = RolePOJO.Role.newBuilder().setDataType(RolePOJO.Role.DataType.Student)
                    .setStudent(student).build();
        } else {
            RolePOJO.Worker worker = RolePOJO.Worker.newBuilder().setAge(20).setName("worker").build();
            role = RolePOJO.Role.newBuilder().setDataType(RolePOJO.Role.DataType.Worker)
                    .setWorker(worker).build();
        ctx.writeAndFlush(role);
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
上面使用到了ProtoBuf中的语法enum,如果想查看ProtoBuf语法的其他用法可参见ProtoBuf语法
                    概述通过前面的学习，我们了解到数据在网络中传输的都是二进制字节码数据，因而在发送数据时就需要编码，接收数据时就需要解码。codec(编解码器)的组成部分有两个：decoder(解码器)和encoder(编码器)。encoder负责把业务数据转换成字节码数据，decoder负责把字节码数据转换成业务数据Netty中本身也提供了一些编解码器,如：StringEncoder/StringD...
如果想使用protobuf，首先需要下载protobuf的编译器
下载地址：https://github.com/protocolbuffers/protobuf/releaseshttps://github.com/protocolbuffers/protobuf/releases
根据系统选择对应的protoc编译器下载完成后，需要在项目中声明一个*.proto的文件作为数据格式的声明文件
新建：Student.proto
				
public final Builder setUnknownFields(
    final com.google.protobuf.UnknownFieldSet unknownFields) {
  return super.setUnknownFieldsProto3(unknownFields);
}public static cn.nhorizon.ads.server.domain...
使用从给定输入流解析的协议缓冲区填充消息。读取错误或输入格式错误时返回false。
成功返回并不表示整个输入已使用，请确保调用ConsumedEntireMessage（）检查是否已使用（如果适用）。
  PROTOBUF_ATTRIBUTE_REINITIALIZES bool ParseFromCodedStream(
      io::CodedInputStream* input);
//跟上面那个功能一样，不过允许 repeated 部分不填充，.
				
ProtoBuf—— 序列化 & 反序列化过程序列化 & 反序列化过程1、序列化：toByteArray()2、反序列化：parseFrom(byteArray)
序列化 & 反序列化过程
1、序列化：toByteArray()
序列化过程描述：  编码 & 数据存储两个过程
1、创建一个输出流
2、计算出序列化后的二进制流长度，分配该长度的空间，以备以后将每个字段填充到该空间
3、判断每个字段是否有设置值，有值才会进行编码
若optional 或 repeated 字段
				
可以使用Springboot作为框架，protobuf作为数据序列化工具，Netty作为网络通信框架来实现文件传输。以下是简要的实现步骤：
1. 定义protobuf消息格式：首先定义一个消息格式，包含文件名、文件大小和文件内容等信息。
2. 编写Netty服务端和客户端：服务端和客户端之间通过Netty进行通信。服务端接收客户端传来的文件请求，读取文件并发送给客户端；客户端接收服务端发送的文件并保存到本地。
3. 在Springboot中使用Netty：将Netty服务端和客户端集成到Springboot中，可以使用Springboot提供的注解和配置来简化Netty的配置和启动。
4. 实现文件传输功能：在Netty服务端和客户端的处理逻辑中，实现文件的读取和写入，并使用protobuf来序列化和反序列化文件信息。
总的来说，使用Springboot+protobuf+Netty实现文件传输相对来说比较复杂，需要对三个框架都有一定的了解。但是，这种方式可以实现更高效、更安全的文件传输，特别是针对大文件和高并发场景。