addressbook.proto

//For Java, the compiler generates a .java file with a class for each message type, 
//as well as a special Builder classes for creating message class instances.


syntax = "proto2";
//package declarations, helps to prevent naming conflicts between diffrent projects
package tutorial;


//in what java package name your generated class should live
option java_package = "com.example.tutorial";
//define the class name which should contain all of the classes in this file
option java_outer_classname = "AddressBookProtos";

message Person {

// " = 1", " = 2" markers on each element identify the unique "tag" that field uses in the binary encoding. 
//Tag numbers 1-15 require one less byte to encode than higher numbers,
//Forimization you can decide to use those tags for the commonly used or repeated elements, 
//leaving tags 16 and higher for less-commonly used optional elements.
//Each element in a repeated field requires re-encoding the tag number, 
//so repeated fields are particularly good candidates for this optimization.
  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 phones = 4;
}

message AddressBook {
  repeated Person people = 1;
}