DSON

Build Status

DSON is a dart library which converts Dart Objects into their JSON representation. It helps you keep your code clean of fromJSON and toJSON functions by using dart:mirrors reflection. It works after dart2js compiling using @MirrorUsed annotation.

This library was initially a fork from Dartson. Now it contains some differences: * Dartson uses transformers to convert objects to JSON. This produce faster and smaller code after dart2Js. This is a feature that I also would like to add to DSON. * DSON has the ability to serialize cyclical objects by mean of depth parameter, which allows user to specify how deep in the object graph he wants to serialize. * DSON has the ability to exclude attributes for serialziation in a more flexible way. I mean, not using @ignore over every attribute. This make excluding attributes two global and hardcoded, so users can only specify one exclusing schema.

Serialization

To serialize objects (convert objects to JSON strings) you only need to use the serialize function and pass the object to serialize as parameter:

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

class Person {
  int id;
  String firstName;
  var lastName; //This is a dynamic attribute could be String, int, duble, num, date or another type
  double height;
  DateTime dateOfBirth;

  @Property("renamed")
  String otherName;
  

  @ignore
  String notVisible;

  // private members are never serialized
  String _private = "name";

  String get doGetter => _private;
}

void main() {
  Person object = new Person()
    ..id = 1
    ..firstName = "Jhon"
    ..lastName = "Doe"
    ..height = 1.8
    ..dateOfBirth = new DateTime(1988, 4, 1, 6, 31)
    ..otherName = "Juan"
    ..notVisible = "hallo";

  String jsonString = serialize(object);
  print(jsonString);
  // will print: '{"id":1,"firstName":"Jhon","lastName":"Doe","height":1.8,"dateOfBirth":"1988-04-01T06:31:00.000","renamed":"Juan","doGetter":"name"}'
}

Converting objects to Maps

To convert objects to Maps you only need to use the objectToSerializable function and pass the object to serialize as parameter:

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

class Person {
  int id;
  String firstName;
  var lastName; //This is a dynamic attribute could be String, int, duble, num, date or another type
  double height;
  DateTime dateOfBirth;

  @Property("renamed")
  String otherName;
  

  @ignore
  String notVisible;

  // private members are never serialized
  String _private = "name";

  String get doGetter => _private;
}

void main() {
  Person object = new Person()
    ..id = 1
    ..firstName = "Jhon"
    ..lastName = "Doe"
    ..height = 1.8
    ..dateOfBirth = new DateTime(1988, 4, 1, 6, 31)
    ..otherName = "Juan"
    ..notVisible = "hallo";

  Map map = objectToSerializable(object);
  print(map);
  // will print: '{id:1, firstName: Jhon, lastName: Doe, height: 1.8, dateOfBirth: 1988-04-01T06:31:00.000, renamed: Juan, doGetter: name}'
}

Serializing Cyclical Objects

To serialize objects that contains Cyclical References it would be needed to use the annotation @cyclical. If this annotation is present and the depth variable is not set then the non-primitive objects are not going to be parsed and only the id or hashmap is going to be present. Let's see next example:

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

@cyclical
class Employee {
  int id;
  String firstName;
  String lastName;
  
  Address address;
  
  Employee manager;
}

@cyclical
class Address {
  int id;
  String street;
  String city;
  String country;
  String postalCode;
  
  Employee owner;
}


void main() {
  var manager = new Employee()
    ..id = 1
    ..firstName = 'Jhon'
    ..lastName = 'Doe';
  manager.address = new Address()
      ..id = 1
      ..street = 'some street'
      ..city = 'Miami'
      ..country = 'USA'
      ..owner = manager;

  var employee = new Employee()
    ..id = 2
    ..firstName = 'Luis'
    ..lastName = 'Vargas'
    ..manager = manager;
  employee.address = new Address()
    ..id = 2
    ..street = 'some street'
    ..city = 'Miami'
    ..country = 'USA'
    ..owner = employee;
    
  print(serialize(employee)); //will print: '{"id":2,"firstName":"Luis","lastName":"Vargas","address":{"id":2},"manager":{"id":1}}'
  
  print(serialize(employee.address)); // will print: '{"id":2,"street":"some street","city":"Miami","country":"USA","owner":{"id":2}}'
  
  // depth is a optional parameter that could be a list that should contains strings or Maps<String, Map>
  print(serialize(employee, depth: ['address']));
  /* will print:
           '{"id":2,"firstName":"Luis","lastName":"Vargas",'
              '"address":{"id":2,"street":"some street","city":"Miami","country":"USA","owner":{"id":2}},'
              '"manager":{"id":1}}'
  */
  
  print(serialize(employee, depth: [{'manager': ['address']}, 'address']));
  /* will print:
         '{"id":2,"firstName":"Luis","lastName":"Vargas",'
            '"address":{"id":2,"street":"some street","city":"Miami","country":"USA",'
              '"owner":{"id":2}},'
            '"manager":{"id":1,"firstName":"Jhon","lastName":"Doe",'
              '"address":{"id":1,"street":"some street","city":"Miami","country":"USA","owner":{"id":1}}}}');
  */
}

as you can see employee has an address, and the address has an owner of type Employee. If the property id is not present in the object then it is going to take the hashcode value from the object as reference. And finally, the depth parameter passed to serialize function tells serializer how deep you want to go throw the reference. This help us not only to avoid cyclical reference, but to determine what referenced objects should be serialized.

The same applies for lists:

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

@cyclical
class Student {
  int id;
  String name;
  
  List<Course> courses;
}

@cyclical
class Course {
  int id;
  
  DateTime beginDate;
  
  List<Student> students;
}

void main() {
  
  var student1 = new Student()
      ..id = 1
      ..name = 'student1',
    student2 = new Student()
      ..id = 2
      ..name = 'student2',
    student3 = new Student()
      ..id = 3
      ..name = 'student3',
    course1 = new Course()
      ..id = 1
      ..beginDate = new DateTime.utc(2015, 1, 1)
      ..students = [student1, student2],
    course2 = new Course()
      ..id = 2
      ..beginDate = new DateTime.utc(2015, 1, 2)
      ..students = [student2, student3],
    course3 = new Course()
      ..id = 3
      ..beginDate = new DateTime.utc(2015, 1, 3)
      ..students = [student1, student3];
  
  student1.courses = [course1, course3];
  student2.courses = [course1, course2];
  student3.courses = [course2, course3];
  
  var students = [student1, student2, student3]; 
  
  print(serialize(student1)); // will print: '{"id":1,"name":"student1","courses":[{"id":1},{"id":3}]}'

  print(serialize(student1, depth: ['courses']));
  /* will print:
      '{'
        '"id":1,'
        '"name":"student1",'
        '"courses":['
          '{"id":1,"beginDate":"2015-01-01T00:00:00.000Z","students":[{"id":1},{"id":2}]},'
          '{"id":3,"beginDate":"2015-01-03T00:00:00.000Z","students":[{"id":1},{"id":3}]}'
        ']'
      '}');
   */

  print(serialize(student1.courses)); 
  /* will print:
      '['
        '{"id":1,"beginDate":"2015-01-01T00:00:00.000Z","students":[{"id":1},{"id":2}]},'
        '{"id":3,"beginDate":"2015-01-03T00:00:00.000Z","students":[{"id":1},{"id":3}]}'
      ']');
  */
  
  print(serialize(student2.courses, depth: ['students']));
  /* will print: 
      '['
        '{"id":1,"beginDate":"2015-01-01T00:00:00.000Z","students":['
          '{"id":1,"name":"student1","courses":[{"id":1},{"id":3}]},'
          '{"id":2,"name":"student2","courses":[{"id":1},{"id":2}]}'
        ']},'
        '{"id":2,"beginDate":"2015-01-02T00:00:00.000Z","students":['
          '{"id":2,"name":"student2","courses":[{"id":1},{"id":2}]},'
          '{"id":3,"name":"student3","courses":[{"id":2},{"id":3}]}'
        ']}'
      ']'
   */
}

Without the annotation @cyclical the program is going to throw a stack overflow error caused by the serializing of cyclical objects.

Excluding attributes from being serialized

To exclude parameter from being serialized we have two options the first option is using @ignore over the attribute to ignore. However this approach is too global. What I want to say with this is that the attribute is going to be ignored always.

Another way to exclude attributes is adding the parameter exclude to serialize function. In this way we only exclude those attributes during that serialization.

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

@cyclical
class Student {
  int id;
  String name;
  
  List<Course> courses;
}

@cyclical
class Course {
  int id;
  
  DateTime beginDate;
  
  List<Student> students;
}

void main() {
  
  var student1 = new Student()
      ..id = 1
      ..name = 'student1',
    student2 = new Student()
      ..id = 2
      ..name = 'student2',
    student3 = new Student()
      ..id = 3
      ..name = 'student3',
    course1 = new Course()
      ..id = 1
      ..beginDate = new DateTime.utc(2015, 1, 1)
      ..students = [student1, student2],
    course2 = new Course()
      ..id = 2
      ..beginDate = new DateTime.utc(2015, 1, 2)
      ..students = [student2, student3],
    course3 = new Course()
      ..id = 3
      ..beginDate = new DateTime.utc(2015, 1, 3)
      ..students = [student1, student3];
  
  student1.courses = [course1, course3];
  student2.courses = [course1, course2];
  student3.courses = [course2, course3];
  
  var students = [student1, student2, student3]; 
  
  print(serialize(student1)); // will print: '{"id":1,"name":"student1","courses":[{"id":1},{"id":3}]}'

  print(serialize(student1, depth: 'courses', exclude: 'name'));
  /* will print:
      '{'
        '"id":1,'
        '"courses":['
          '{"id":1,"beginDate":"2015-01-01T00:00:00.000Z","students":[{"id":1},{"id":2}]},'
          '{"id":3,"beginDate":"2015-01-03T00:00:00.000Z","students":[{"id":1},{"id":3}]}'
        ']'
      '}');
   */

  print(serialize(student1.courses, exclude: 'beginDate')); 
  /* will print:
      '['
        '{"id":1,"students":[{"id":1},{"id":2}]},'
        '{"id":3,"students":[{"id":1},{"id":3}]}'
      ']');
  */
  
  print(serialize(student2.courses, depth: 'students', exclude: {'students': 'name'}));
  /* will print: 
      '['
        '{"id":1,"beginDate":"2015-01-01T00:00:00.000Z","students":['
          '{"id":1,"courses":[{"id":1},{"id":3}]},'
          '{"id":2,"courses":[{"id":1},{"id":2}]}'
        ']},'
        '{"id":2,"beginDate":"2015-01-02T00:00:00.000Z","students":['
          '{"id":2,"name":"student2","courses":[{"id":1},{"id":2}]},'
          '{"id":3,"name":"student3","courses":[{"id":2},{"id":3}]}'
        ']}'
      ']'
   */
   
   print(serialize(student2.courses, depth: 'students', exclude: ['beginDate', {'students': 'name'}]));
  /* will print: 
      '['
        '{"id":1,"students":['
          '{"id":1,"courses":[{"id":1},{"id":3}]},'
          '{"id":2,"courses":[{"id":1},{"id":2}]}'
        ']},'
        '{"id":2,"students":['
          '{"id":2,"name":"student2","courses":[{"id":1},{"id":2}]},'
          '{"id":3,"name":"student3","courses":[{"id":2},{"id":3}]}'
        ']}'
      ']'
   */
}

Deserialization

To deserialize objects (convert JSON strings to objects) you only need to use the parse and parseList function and pass the json string to deserialize and the Type of the object as parameters:

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

class EntityClass {
  String name;
  String _setted;
  
  @Property(name:"renamed")
  bool otherName;
  
  @ignore
  String notVisible;
  
  List<EntityClass> children;
  
  set setted(String s) => _setted = s;
  String get setted => _setted;
}

void main() {
  EntityClass object = parse('{"name":"test","renamed":"blub","notVisible":"it is", "setted": "awesome"}', EntityClass);
  
  print(object.name); // > test
  print(object.otherName); // > blub
  print(object.notVisible); // > it is
  print(object.setted); // > awesome
  
  // to parse a list of items use [parseList]
  List<EntityClass> list = parseList('[{"name":"test", "children": [{"name":"child1"},{"name":"child2"}]},{"name":"test2"}]', EntityClass);
  print(list.length); // > 2
  print(list[0].name); // > test
  print(list[0].children[0].name); // > child1
}

Converting Maps and Lists<Map> to dart objects

Frameworks like Angular.dart come with several HTTP services which already transform the HTTP response to a map using JSON.encode. To use those encoded Maps or Lists use map and mapList.

library example;

import 'package:dson/dson.dart';

@MirrorsUsed(targets:const['example'],override:'*')
import 'dart:mirrors';

class EntityClass {
  String name;
  String _setted;
  
  @Property(name:"renamed")
  bool otherName;
  
  @ignore
  String notVisible;
  
  List<EntityClass> children;
  
  set setted(String s) => _setted = s;
  String get setted => _setted;
}

void main() {
  EntityClass object = map({"name":"test","renamed":"blub","notVisible":"it is", "setted": "awesome"}, EntityClass);  
  print(object.name); // > test
  print(object.otherName); // > blub
  print(object.notVisible); // > it is
  print(object.setted); // > awesome
  
  // to parse a list of items use [parseList]
  List<EntityClass> list = mapList([{"name":"test", "children": [{"name":"child1"},{"name":"child2"}]},{"name":"test2"}], EntityClass);
  print(list.length); // > 2
  print(list[0].name); // > test
  print(list[0].children[0].name); // > child1
}

Libraries

dson