Google protobuf

个人理解:

定义.proto文件就是指明消息里包含的成员和类型，protoc会compile成相应的java文件包含interface和implementation class，然后在构建message的时候要使用builder，然后写到outputstream里。

应用实例：

ByteArrayOutputStream out = new ByteArrayOutputStream(BYTE_ARRAY_SIZE);
CodedOutputStream codedOut = CodedOutputStream.newInstance(out);
GothamAuthProto.ExclusiveGroupChoices.newBuilder().setUsername(getActor().getUserId()).addChoices(GothamAuthProto.NameValuePair.newBuilder().setName(GROUP_KEY).setValue(role)).build().writeTo(codedOut);
codedOut.flush();
String uri = solaceRoleSetupUri + getActor().getUserId();
LOGGER.info("Select role: " + out.toString() + " -> " + uri);
batman.createProducerTemplate().sendBody(uri, out.toByteArray());

From Google.protobuf tutorial:https://developers.google.com/protocol-buffers/docs/javatutorial

1, With protocol buffers, you write a .proto description of the data structure you wish to store. 

 2, From that, the protocol buffer compiler creates a class that implements automatic encoding and parsing of the protocol buffer data with an efficient binary format.

 3, The generated class provides getters and setters for the fields that make up a protocol buffer and takes care of the details of reading and writing the protocol buffer as a unit.

a. START with a .proto file:

=====================================

package tutorial;

option java_package = "com.example.tutorial";
option java_outer_classname = "AddressBookProtos";

message Person {
  required string name = 1;
  required int32 id = 2;
  optional string email = 3;

  enum PhoneType {
    MOBILE = 0;
    HOME = 1;
    WORK = 2;
  }

  message PhoneNumber {
    required string number = 1;
    optional PhoneType type = 2 [default = HOME];
  }

  repeated PhoneNumber phone = 4;
}

message AddressBook {
  repeated Person person = 1;
}

====================================================

b.  Run the protocol buffer compiler protoc on your .proto:(generate the classes you'll need to read and write AddressBook)
Here are some of the accessors for the Person class:

// required string name = 1;
public boolean hasName();
public String getName();

// required int32 id = 2;
public boolean hasId();
public int getId();

// optional string email = 3;
public boolean hasEmail();
public String getEmail();

c, To construct a message, you must first construct a builder, set any fields you want to set to your chosen values, then call the builder's build() method.

Person john =
  Person.newBuilder()
    .setId(1234)
    .setName("John Doe")
    .setEmail("jdoe@example.com")
    .addPhone(
      Person.PhoneNumber.newBuilder()
        .setNumber("555-4321")
        .setType(Person.PhoneType.HOME))
    .build();