netty中使用protobuffer

关于protobuffer，作为数据传输，那是不二的选择，当然我是针对游戏开发，为了达到高效的传输且不牺牲性能，另外方便前后端协作，足以让我考虑用它了，netty提供了对pb的支持，是这样用的：

* <pre>
 * {@link ChannelPipeline} pipeline = ...;
 *
 * // Decoders
 * pipeline.addLast("frameDecoder",
 *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
 * pipeline.addLast("protobufDecoder",
 *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
 *
 * // Encoder
 * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
 * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
 * </pre>
 * and then you can use a {@code MyMessage} instead of a {@link ByteBuf}
 * as a message:
 * <pre>

一看 还好，上面根据协议解析数据，然后通过pb解码器将buf数据转化为对应的messageLite，接着逻辑处理，然后组装数据，编码为 messageLite数据，发送出去，额尼玛 还好；

接下来看源码：

protobuffer解码器：

@Sharable
public class ProtobufDecoder extends MessageToMessageDecoder<ByteBuf> {

    private static final boolean HAS_PARSER;

    static {
        boolean hasParser = false;
        try {
            // MessageLite.getParsetForType() is not available until protobuf 2.5.0.
            MessageLite.class.getDeclaredMethod("getParserForType");
            hasParser = true;
        } catch (Throwable t) {
            // Ignore
        }

        HAS_PARSER = hasParser;
    }

    private final MessageLite prototype;
    private final ExtensionRegistry extensionRegistry;

    /**
     * Creates a new instance.
     */
    public ProtobufDecoder(MessageLite prototype) {
        this(prototype, null);
    }

    public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) {
        if (prototype == null) {
            throw new NullPointerException("prototype");
        }
        this.prototype = prototype.getDefaultInstanceForType();
        this.extensionRegistry = extensionRegistry;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
        final byte[] array;
        final int offset;
        final int length = msg.readableBytes();
        if (msg.hasArray()) {
            array = msg.array();
            offset = msg.arrayOffset() + msg.readerIndex();
        } else {
            array = new byte[length];
            msg.getBytes(msg.readerIndex(), array, 0, length);
            offset = 0;
        }

        if (extensionRegistry == null) {
            if (HAS_PARSER) {
                out.add(prototype.getParserForType().parseFrom(array, offset, length));
            } else {
                out.add(prototype.newBuilderForType().mergeFrom(array, offset, length).build());
            }
        } else {
            if (HAS_PARSER) {
                out.add(prototype.getParserForType().parseFrom(array, offset, length, extensionRegistry));
            } else {
                out.add(prototype.newBuilderForType().mergeFrom(array, offset, length, extensionRegistry).build());
            }
        }
    }
}

一大堆，干了啥事，额就是我上面描述的，指定protoType,将buf数据整合到messagelite实体上组合为一个消息，就干了这个；其他没撒，添加到了List.然后回调逻辑处理中的handle,额这里应call back method public void channelRead(ChannelHandlerContext ctx, Object message)；这里逻辑数据处理，完毕，然后看

ProtobufEncoder：

@Sharable
public class ProtobufEncoder extends MessageToMessageEncoder<MessageLiteOrBuilder> {
    @Override
    protected void encode(
            ChannelHandlerContext ctx, MessageLiteOrBuilder msg, List<Object> out) throws Exception {
        if (msg instanceof MessageLite) {
            out.add(wrappedBuffer(((MessageLite) msg).toByteArray()));
            return;
        }
        if (msg instanceof MessageLite.Builder) {
            out.add(wrappedBuffer(((MessageLite.Builder) msg).build().toByteArray()));
        }
    }
}

干啥子呢？ 就是把你业务层上的数据封装的messagelite编码为buf呗，看到这里 一头雾水啊 有木有！

没有！很简单，就是把业务你构建的messageLite转化为buf，因为底层是操作的buf（netty这层），额一切看起来是那样的美好，可是问题来了，这个封装蛋疼了，为啥？

请看哈：

看到没有  ，你只能处理一个pb文件，换句话就一个pb消息，我顿时菊花紧了；

上面说了一大堆，细心的读者应该会有解决方案了，netty不过是提供了网络传输以及解析数据方案，解析数据我们可以自己定义 ，同时也可以选择解析时机是那个时候，既然现在我要解析pb，且有多个，那么我选择解析pb的时候是在逻辑处理回调函数Calls {@link io.netty.channel.ChannelHandlerContext#fireChannelRead(Object)} 的时候，这个时候的数据是一个buf，怎样来将buf来转化为pb呢，netty提供的解码器给我答案了，只要拿到要转化的pb实体类型，就可以，这里我的消息定义是这样：header+ID+message;  header:包长，ID：pb区分标记；message：要处理的真正需要的内容；

pb的命名方式：

package protoData;

import "vo/netCardVO.proto";

option java_package = "protoData";
option java_outer_classname = "battleProto";


//请求PK玩家编号
message BattleRequest {
    enum msgID {
        ID = 4;
    } //消息编号
    required bool accpet = 1; //是否接受pk
    required uint32 playerID = 2; //发起挑战的ID
}

//响应战斗（匹配完成进入战斗流程）
message BattleResponse {
    enum msgID {
        ID = 4;
    } //消息编号
    required bool accpet = 1; //是否接受pk
    required uint32 playerID = 2;   // 请求挑战的ip
    optional netCardVO cardList = 3;   //牌列表  如果没有接受pk，则为null
}

 在程序启动的时候注册消息，然后放在一个messageLite[]数组上，解析buf数据先解析出ID，通过数组来直接索引到要解析数据类型的实体！这样就可以处理多个pb实体了；

关于protobuffer生成工具，目前有多方面的语音支持：as3，python，java，c++  ... ... 这里我就说java的，

你可以集成插件idea-plugin-protobuffer ，http://www.oschina.net/p/idea-plugin-protobuf；然后只管编写pb，编译下就生成java文件， eclipse  ，google提供有插件的，网上自己找找；

最后附上一个prot文件，google官网上的 这里面可以找到你想要的pb写法，这上面最直接：

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Author: [email protected] (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// The messages in this file describe the definitions found in .proto files.
// A valid .proto file can be translated directly to a FileDescriptorProto
// without any other information (e.g. without reading its imports).



package google.protobuf;
option java_package = "com.google.protobuf";
option java_outer_classname = "DescriptorProtos";

// descriptor.proto must be optimized for speed because reflection-based
// algorithms don't work during bootstrapping.
option optimize_for = SPEED;

// The protocol compiler can output a FileDescriptorSet containing the .proto
// files it parses.
message FileDescriptorSet {
  repeated FileDescriptorProto file = 1;
}

// Describes a complete .proto file.
message FileDescriptorProto {
  optional string name = 1;       // file name, relative to root of source tree
  optional string package = 2;    // e.g. "foo", "foo.bar", etc.

  // Names of files imported by this file.
  repeated string dependency = 3;

  // All top-level definitions in this file.
  repeated DescriptorProto message_type = 4;
  repeated EnumDescriptorProto enum_type = 5;
  repeated ServiceDescriptorProto service = 6;
  repeated FieldDescriptorProto extension = 7;

  optional FileOptions options = 8;
}

// Describes a message type.
message DescriptorProto {
  optional string name = 1;

  repeated FieldDescriptorProto field = 2;
  repeated FieldDescriptorProto extension = 6;

  repeated DescriptorProto nested_type = 3;
  repeated EnumDescriptorProto enum_type = 4;

  message ExtensionRange {
    optional int32 start = 1;
    optional int32 end = 2;
  }
  repeated ExtensionRange extension_range = 5;

  optional MessageOptions options = 7;
}

// Describes a field within a message.
message FieldDescriptorProto {
  enum Type {
    // 0 is reserved for errors.
    // Order is weird for historical reasons.
    TYPE_DOUBLE         = 1;
    TYPE_FLOAT          = 2;
    TYPE_INT64          = 3;   // Not ZigZag encoded.  Negative numbers
                               // take 10 bytes.  Use TYPE_SINT64 if negative
                               // values are likely.
    TYPE_UINT64         = 4;
    TYPE_INT32          = 5;   // Not ZigZag encoded.  Negative numbers
                               // take 10 bytes.  Use TYPE_SINT32 if negative
                               // values are likely.
    TYPE_FIXED64        = 6;
    TYPE_FIXED32        = 7;
    TYPE_BOOL           = 8;
    TYPE_STRING         = 9;
    TYPE_GROUP          = 10;  // Tag-delimited aggregate.
    TYPE_MESSAGE        = 11;  // Length-delimited aggregate.

    // New in version 2.
    TYPE_BYTES          = 12;
    TYPE_UINT32         = 13;
    TYPE_ENUM           = 14;
    TYPE_SFIXED32       = 15;
    TYPE_SFIXED64       = 16;
    TYPE_SINT32         = 17;  // Uses ZigZag encoding.
    TYPE_SINT64         = 18;  // Uses ZigZag encoding.
  };

  enum Label {
    // 0 is reserved for errors
    LABEL_OPTIONAL      = 1;
    LABEL_REQUIRED      = 2;
    LABEL_REPEATED      = 3;
    // TODO(sanjay): Should we add LABEL_MAP?
  };

  optional string name = 1;
  optional int32 number = 3;
  optional Label label = 4;

  // If type_name is set, this need not be set.  If both this and type_name
  // are set, this must be either TYPE_ENUM or TYPE_MESSAGE.
  optional Type type = 5;

  // For message and enum types, this is the name of the type.  If the name
  // starts with a '.', it is fully-qualified.  Otherwise, C++-like scoping
  // rules are used to find the type (i.e. first the nested types within this
  // message are searched, then within the parent, on up to the root
  // namespace).
  optional string type_name = 6;

  // For extensions, this is the name of the type being extended.  It is
  // resolved in the same manner as type_name.
  optional string extendee = 2;

  // For numeric types, contains the original text representation of the value.
  // For booleans, "true" or "false".
  // For strings, contains the default text contents (not escaped in any way).
  // For bytes, contains the C escaped value.  All bytes >= 128 are escaped.
  // TODO(kenton):  Base-64 encode?
  optional string default_value = 7;

  optional FieldOptions options = 8;
}

// Describes an enum type.
message EnumDescriptorProto {
  optional string name = 1;

  repeated EnumValueDescriptorProto value = 2;

  optional EnumOptions options = 3;
}

// Describes a value within an enum.
message EnumValueDescriptorProto {
  optional string name = 1;
  optional int32 number = 2;

  optional EnumValueOptions options = 3;
}

// Describes a service.
message ServiceDescriptorProto {
  optional string name = 1;
  repeated MethodDescriptorProto method = 2;

  optional ServiceOptions options = 3;
}

// Describes a method of a service.
message MethodDescriptorProto {
  optional string name = 1;

  // Input and output type names.  These are resolved in the same way as
  // FieldDescriptorProto.type_name, but must refer to a message type.
  optional string input_type = 2;
  optional string output_type = 3;

  optional MethodOptions options = 4;
}

// ===================================================================
// Options

// Each of the definitions above may have "options" attached.  These are
// just annotations which may cause code to be generated slightly differently
// or may contain hints for code that manipulates protocol messages.
//
// Clients may define custom options as extensions of the *Options messages.
// These extensions may not yet be known at parsing time, so the parser cannot
// store the values in them.  Instead it stores them in a field in the *Options
// message called uninterpreted_option. This field must have the same name
// across all *Options messages. We then use this field to populate the
// extensions when we build a descriptor, at which point all protos have been
// parsed and so all extensions are known.
//
// Extension numbers for custom options may be chosen as follows:
// * For options which will only be used within a single application or
//   organization, or for experimental options, use field numbers 50000
//   through 99999.  It is up to you to ensure that you do not use the
//   same number for multiple options.
// * For options which will be published and used publicly by multiple
//   independent entities, e-mail [email protected] to reserve extension
//   numbers.  Simply tell me how many you need and I'll send you back a
//   set of numbers to use -- there's no need to explain how you intend to
//   use them.  If this turns out to be popular, a web service will be set up
//   to automatically assign option numbers.


message FileOptions {

  // Sets the Java package where classes generated from this .proto will be
  // placed.  By default, the proto package is used, but this is often
  // inappropriate because proto packages do not normally start with backwards
  // domain names.
  optional string java_package = 1;


  // If set, all the classes from the .proto file are wrapped in a single
  // outer class with the given name.  This applies to both Proto1
  // (equivalent to the old "--one_java_file" option) and Proto2 (where
  // a .proto always translates to a single class, but you may want to
  // explicitly choose the class name).
  optional string java_outer_classname = 8;

  // If set true, then the Java code generator will generate a separate .java
  // file for each top-level message, enum, and service defined in the .proto
  // file.  Thus, these types will *not* be nested inside the outer class
  // named by java_outer_classname.  However, the outer class will still be
  // generated to contain the file's getDescriptor() method as well as any
  // top-level extensions defined in the file.
  optional bool java_multiple_files = 10 [default=false];

  // Generated classes can be optimized for speed or code size.
  enum OptimizeMode {
    SPEED = 1;      // Generate complete code for parsing, serialization, etc.
    CODE_SIZE = 2;  // Use ReflectionOps to implement these methods.
  }
  optional OptimizeMode optimize_for = 9 [default=CODE_SIZE];



  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message MessageOptions {
  // Set true to use the old proto1 MessageSet wire format for extensions.
  // This is provided for backwards-compatibility with the MessageSet wire
  // format.  You should not use this for any other reason:  It's less
  // efficient, has fewer features, and is more complicated.
  //
  // The message must be defined exactly as follows:
  //   message Foo {
  //     option message_set_wire_format = true;
  //     extensions 4 to max;
  //   }
  // Note that the message cannot have any defined fields; MessageSets only
  // have extensions.
  //
  // All extensions of your type must be singular messages; e.g. they cannot
  // be int32s, enums, or repeated messages.
  //
  // Because this is an option, the above two restrictions are not enforced by
  // the protocol compiler.
  optional bool message_set_wire_format = 1 [default=false];

  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message FieldOptions {
  // The ctype option instructs the C++ code generator to use a different
  // representation of the field than it normally would.  See the specific
  // options below.  This option is not yet implemented in the open source
  // release -- sorry, we'll try to include it in a future version!
  optional CType ctype = 1;
  enum CType {
    CORD = 1;

    STRING_PIECE = 2;
  }
  // The packed option can be enabled for repeated primitive fields to enable
  // a more efficient representation on the wire. Rather than repeatedly
  // writing the tag and type for each element, the entire array is encoded as
  // a single length-delimited blob.
  optional bool packed = 2;

  // EXPERIMENTAL.  DO NOT USE.
  // For "map" fields, the name of the field in the enclosed type that
  // is the key for this map.  For example, suppose we have:
  //   message Item {
  //     required string name = 1;
  //     required string value = 2;
  //   }
  //   message Config {
  //     repeated Item items = 1 [experimental_map_key="name"];
  //   }
  // In this situation, the map key for Item will be set to "name".
  // TODO: Fully-implement this, then remove the "experimental_" prefix.
  optional string experimental_map_key = 9;

  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message EnumOptions {
  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message EnumValueOptions {
  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message ServiceOptions {

  // Note:  Field numbers 1 through 32 are reserved for Google's internal RPC
  //   framework.  We apologize for hoarding these numbers to ourselves, but
  //   we were already using them long before we decided to release Protocol
  //   Buffers.

  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

message MethodOptions {

  // Note:  Field numbers 1 through 32 are reserved for Google's internal RPC
  //   framework.  We apologize for hoarding these numbers to ourselves, but
  //   we were already using them long before we decided to release Protocol
  //   Buffers.

  // The parser stores options it doesn't recognize here. See above.
  repeated UninterpretedOption uninterpreted_option = 999;

  // Clients can define custom options in extensions of this message. See above.
  extensions 1000 to max;
}

// A message representing a option the parser does not recognize. This only
// appears in options protos created by the compiler::Parser class.
// DescriptorPool resolves these when building Descriptor objects. Therefore,
// options protos in descriptor objects (e.g. returned by Descriptor::options(),
// or produced by Descriptor::CopyTo()) will never have UninterpretedOptions
// in them.
message UninterpretedOption {
  // The name of the uninterpreted option.  Each string represents a segment in
  // a dot-separated name.  is_extension is true iff a segment represents an
  // extension (denoted with parentheses in options specs in .proto files).
  // E.g.,{ ["foo", false], ["bar.baz", true], ["qux", false] } represents
  // "foo.(bar.baz).qux".
  message NamePart {
    required string name_part = 1;
    required bool is_extension = 2;
  }
  repeated NamePart name = 2;

  // The value of the uninterpreted option, in whatever type the tokenizer
  // identified it as during parsing. Exactly one of these should be set.
  optional string identifier_value = 3;
  optional uint64 positive_int_value = 4;
  optional int64 negative_int_value = 5;
  optional double double_value = 6;
  optional bytes string_value = 7;
}