DartVM服务器开发（二十一）-Dart中的Gson(jaguar_serializer)

Dart 后端 2019/02/10

今天我们来学习一下如何使用jaguar_serializer包，这里说明一下，该包在三端平台都是可用的(Flutter，dart web ,dart vm)，学习过安卓的，都知道gson吧，该包类似于gson

1.引入包

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#pubspec.yaml
dependencies:
  jaguar_serializer: ^2.2.0

dev_dependencies:
  build_runner:
  jaguar_serializer_cli:

执行pub get命令
获取成功.png
导包

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import 'package:jaguar_serializer/jaguar_serializer.dart';

2.初始化

  • 新增一个实体类

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    class Person {
      String name;
      int age;
    }

  • 添加生成脚本标记

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    @GenSerializer()
    class PersonSerializer extends Serializer<Person> with _$PersonSerializer {
    }

  • 运行脚本
    使用脚本命令pub run build_runner build
    image.png

  • 导入生成代码
    回到person这个类的文件中，添加
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    part 'person.jser.dart';

##　3．使用

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main() async {
  Jaguar(port: 1000)
    ..get('/person', (ctx){
      PersonSerializer personSerializer=new PersonSerializer();
      Person person=new Person()
      ..name='rhyme'
      ..age=18;
 //personSerializer.toMap(person)获取到map对象
      return Response.json( personSerializer.toMap(person));
    })
    ..log.onRecord.listen(print)
    ..serve(logRequests: true);
}

然后我们来请求一下
image.png
成功返回了json数据

4.使用详解

  • json与对象相互转换

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    import 'dart:convert';
    main(){
      String jsonString='{"name":"rhyme","age":18}';
      PersonSerializer personSerializer=new PersonSerializer();

      // json to entity
      Person person=personSerializer.fromMap(json.decode(jsonString));
      print('name:${person.name} ,age: ${person.age}');

      //entity to json
      String toJson= json.encode( personSerializer.toMap(person));
      print(toJson);
    }

  • json 与对象列相互转换

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    main(){
      String jsonString='[{"name":"rhyme","age":18},{"name":"ben","age":21}]';
      PersonSerializer personSerializer=new PersonSerializer();
      
      // list: json to entity
      //因为目前fromList不支持dynamic的值，所以，我们需要吧json.decode出来的List<dynamic>转化为List<Map>，不然会报异常
      List<Map> mapList=(json.decode(jsonString) as List<dynamic>).map((dy)=>dy as Map).toList();
      List<Person> persons=personSerializer.fromList(mapList);
      for(Person p in persons){
        print('name:${p.name} ,age: ${p.age}');
      }
      //list: entity to json
      String fromJson=json.encode(personSerializer.toList(persons));
      print(fromJson);
    }

  • 对象内嵌对象与json相互转换

    在对象内添加一个对象

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    class Person {
      String name;
      int age;
    //new
      Info info;
    //new
    }

    //new
    class Info{
       String address;
       String phoneNumber;
    }
    //edit
    @GenSerializer( serializers: [ InfoSerializer])
    //edit
    class PersonSerializer extends Serializer<Person> with _$PersonSerializer {
    }

    //new
    @GenSerializer()
    class InfoSerializer extends Serializer<Info> with _$InfoSerializer {
    }
    //new

运行命令pub run build_runner build
image.png
转换跟上面相同

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String jsonString='{"name":"rhyme","age":18,"info":{"address":"广州","phoneNumber":"159xxxxxxxx"}}';
 PersonSerializer personSerializer=new PersonSerializer();

 // json to entity
 Person person=personSerializer.fromMap(json.decode(jsonString));
 print('name:${person.name} ,age: ${person.age}');

 //entity to json
 String toJson= json.encode(personSerializer.toMap(person));
 print(toJson);

  • 对象内嵌对象列

    将上面的Info改为List<Info>
    重新运行命令pub run build_runner build
    转换跟上面一样

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    String jsonString='[{"name":"rhyme","age":18,"info":[{"address":"广州","phoneNumber":"159xxxxxxxx"},{"address":"北京","phoneNumber":"158xxxxxxxx"}]},{"name":"ben","age":21}]';
    PersonSerializer personSerializer=new PersonSerializer();

    // list: json to entity
    //因为目前fromList不支持dynamic的值，所以，我们需要吧json.decode出来的List<dynamic>转化为List<Map>，不然会报异常
    List<Map> mapList=(json.decode(jsonString) as List<dynamic>).map((dy)=>dy as Map).toList();
    List<Person> persons=personSerializer.fromList(mapList);
    for(Person p in persons){
      print('name:${p.name} ,age: ${p.age}');
    }
    //list: entity to json
    String fromJson=json.encode(personSerializer.toList(persons));
    print(fromJson);

  • 对象内嵌多个对象

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    class Person {
      String name;
      int age;
      List<Info> info;
    //new
      Avatar avatar;
    //new
    }


    class Info{
       String address;
       String phoneNumber;
    }
    //new
    class Avatar{
      String url;
      String path;

    }
    //new

    //edit
    @GenSerializer( serializers: [ InfoSerializer,AvatarSerializer])
    //edit
    class PersonSerializer extends Serializer<Person> with _$PersonSerializer {
    }

    @GenSerializer()
    class InfoSerializer extends Serializer<Info> with _$InfoSerializer {
    }
    //new
    @GenSerializer()
    class AvatarSerializer extends Serializer<Avatar> with _$AvatarSerializer {
    }
    //new

然后重新运行命令pub run build_runner build
使用也是跟上面相同

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String jsonString='[{"name":"rhyme","age":18,"avatar":{"url":"http://www.baidu.com","path":"baidu"},"info":[{"address":"广州","phoneNumber":"159xxxxxxxx"},{"address":"北京","phoneNumber":"158xxxxxxxx"}]},{"name":"ben","age":21}]';
PersonSerializer personSerializer=new PersonSerializer();

// list: json to entity
//因为目前fromList不支持dynamic的值，所以，我们需要吧json.decode出来的List<dynamic>转化为List<Map>，不然会报异常
List<Map> mapList=(json.decode(jsonString) as List<dynamic>).map((dy)=>dy as Map).toList();
List<Person> persons=personSerializer.fromList(mapList);
for(Person p in persons){
  print('name:${p.name} ,age: ${p.age}');
}
//list: entity to json
String fromJson=json.encode(personSerializer.toList(persons));
print(fromJson);

  • 别名

    有时候，我们的实体类成员变量名跟json数据中对应的字段不相同，可以使用@Alias('')对需要的字段进行标记，里面的值为json对应的字段
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    class Person {
      @Alias('Name')
      String name;
      int age;
      List<Info> info;
      Avatar avatar;
    }

要使上面生效，需要重新运行命令pub run build_runner build

  • Build命令

    我们可以发现，当我每次做一个修改，都需要执行pub run build_runner build命令，这样是非常容易导致疏忽的，jaguar_serializer已经为我们考虑到了，
    我们可以使用命令
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    pub run build_runner watch

当该命令运行后，我们的每次点击保存，都会重新激活一次脚本，如下图
image.png
如果你是Flutter开发，可以使用下面的build命令

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flutter packages pub run build_runner build

Flutter的监听命令

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flutter packages pub run build_runner watch

ok，今天就到这里了，我们明天见!

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