CODEWITHSUNDEEP
javaprotocol-buffers
Max Usanin
Max Usanin

Reputation: 2499

how use protocol buffers?

I watched a lot of tutorials, but I can not understand how to use protocol buffers

Why "message User "? why not "class User "? and how Eclipse has created such a message? and why name = 2 ? not name = "Max"

ption java_outer_classname="ProtoUser";

message User {

   required int32  id = 1;  // DB record ID
   required string name = 2;
   required string firstname = 3;
   required string lastname = 4;
   required string ssn= 5; 



   // Embedded Address message spec

    message Address {
      required int32 id = 1;
      required string country = 2 [default = "US"];; 
      optional string state = 3;
      optional string city = 4;
      optional string street = 5;
      optional string zip = 6;



      enum Type {
         HOME = 0;

         WORK = 1; 

       }

       optional Type addrType = 7 [default = HOME]; 

 }
   repeated Address addr = 16;
}

Upvotes: 2

Views: 6428

Answers (2)

Sneha Mule
Sneha Mule

Reputation: 715

Protobuffer use message(keyword) instead of class Inside the class you define the structure of. schema. For example

 message Person{
  string name = 1;
  repeated string id = 2;
  Type phoneType = 3;
 }

enum Type{
 CellPhone = 0;
 HomePhone = 1;
 }

In the above example, we are defining the structure of the Person Message. It has name which datatype is a string, id which is an array of the string and type(when you expect only certain values then use an enum. In this case, we assume that phoneNumber can be either CellPhone or HomePhone. If someone is sending any other value then IT will through UNKNOWN proto value exception)

required: means parameter is required

To use proto first create proto classes using mvn clean install Then create protobuilder Protobuilder to set for above proto

 Person person = Person.newBuilder().setName("testName")
 .setPhoneType(Type.CellPhone)
 .addAllId(listIds)
 .build;

Once you set the value you can not change it. If you want to change the value then you need to create another proto. Pesron person1 = Person.newBuilder(person).setName("ChangeName").build;

person1 will have the name ChangeName, phoneType CellPhone, and ids arrays of strings.

More information: https://developers.google.com/protocol-buffers

Upvotes: 0

Nikolay Kuznetsov
Nikolay Kuznetsov

Reputation: 9579

Why "message User "? why not "class User "?

Google Protocol Buffers (GPB) does not have class in its syntax, it has message instead. https://developers.google.com/protocol-buffers/docs/style

This file is just text file, it should have .proto extension. After all you will run a utility on it which would generate real Java classes which you can import and easily use in your project.

https://developers.google.com/protocol-buffers/docs/javatutorial

Compiling Your Protocol Buffers

protoc -I=$SRC_DIR --java_out=$DST_DIR $SRC_DIR/addressbook.proto

required string lastname = 4;

4 stands for the field id, not a value, it is going to be used to generate a bit stream.

Upvotes: 4

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