[Netty學習筆記]九、ProtoBuf的入門使用

概述

通過前面的學習，我們瞭解到數據在網絡中傳輸的都是二進制字節碼數據，因而在發送數據時就需要編碼，接收數據時就需要解碼。

codec(編解碼器)的組成部分有兩個：decoder(解碼器)和encoder(編碼器)。encoder負責把業務數據轉換成字節碼數據，decoder負責把字節碼數據轉換成業務數據

Netty中本身也提供了一些編解碼器,如：

• StringEncoder/StringDecoder 對字符串進行編解碼
• ObjectEncoder/ObjectDecoder 對Java對象進行編解碼
• …

通過了解可以發現，Netty編解碼器底層使用Java序列化技術來實現的。 但是Java序列化技術本身效率不高，而且無法跨語言，序列化後的體積太大(是二進制編碼的5倍多)，序列化性能太低。因此轉而選擇使用ProtoBuf來實現序列化。

ProtoBuf的優點/特性：

1. ProtiBuf以message的方式來管理數據
2. 支持跨平臺、跨語言
3. 高性能、高可靠性
4. 適合做數據存儲或RPC

ProtoBuf的使用

使用步驟：

1、引入ProtoBuf依賴

2、編寫.proto文件

3、使用protoc編譯器將.proto文件自動生成爲對應語言的文件(也可使用grpc來自動生成)

下面創建一個簡單的proto文件並自動生成爲Java文件：

1、引入3.6.1版本的依賴

 <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.6.1</version>
  </dependency>

2、編寫Student.proto文件(IDEA的話 可以裝Proto插件)

syntax = "proto3"; //版本

option java_outer_classname = "StudentPOJO"; //生成的外部類名 同時也是文件名
//protobuf使用message管理數據
message Student { //會在StudentPOJO外部類生成一個內部類Student，真正用到的對象
      int32 id=1;//student類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
      string name=2;
			
}

如上創建一個proto文件，Student類是真正用到的對象，將是以一個內部類的方式展現在Java文件中，其中定義了兩個成員變量：int id;String name。

3、使用編譯器編譯proto文件

注意：這裏依賴的protobuf是3.6.1版本，因此編譯器也要是3.6.1版本的,我這裏下載的是osx-3.6.1版本的

protoc編譯器下載

由於這裏使用的是Java語言，因此執行命令如下：

將Student.proto文件拷貝到protoc編譯器同級目錄

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類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
     * </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管理數據
   * </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類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
     * </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管理數據
     * </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類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
       * </pre>
       *
       * <code>int32 id = 1;</code>
       */
      public int getId() {
        return id_;
      }
      /**
       * <pre>
       *student類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
       * </pre>
       *
       * <code>int32 id = 1;</code>
       */
      public Builder setId(int value) {
        
        id_ = value;
        onChanged();
        return this;
      }
      /**
       * <pre>
       *student類中有一個屬性 名字爲id 類型爲int32(protibuf類型) 1表示屬性序號
       * </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)
}

將序列化後的Java類放到項目中即可使用

示例：基於ProtoBuf實現簡單的通訊

1. 客戶端發送一個Student對象到服務器
2. 服務器端接收到Student對象 並顯示信息
3. 使用ProtoBuf編解碼

服務器端

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();

                            //對哪種類型進行解碼
                            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));
    }
}

客戶端代碼

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();
                            //編碼器
                            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：這裏在客戶端和服務器端加上了與ProtoBuf有關的編解碼器

上面的例子服務器端只會生成一種特定類型的對象，如果服務器端想要根據業務獲取不同類型的對象可參見下面的例子

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;
}

服務端代碼

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();

                            // 這裏服務器端添加的是針對protoBuf的解碼器
                            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("獲取到客戶端發送的信息：" + student.getId() + "," + student.getName());

        } else if (Objects.equals(dataType, RolePOJO.Role.DataType.Worker)) {
            RolePOJO.Worker worker = msg.getWorker();
            System.out.println("獲取到客戶端發送的信息：" + worker.getAge() + "," + worker.getName());
        } else {
            System.out.println("獲取到客戶端發送的信息");
        }

    }

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

客戶端代碼

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中的語法enum,如果想查看ProtoBuf語法的其他用法可參見ProtoBuf語法