Flutter JSON序列化插件json_serializable_generator的使用

json_serializable_generator

json_serializable_generator 提供了用于处理 JSON 的 Dart 构建系统构建器。此库会读取 .model.json 文件，并自动生成对应的 Dart 模型类文件（.model.dart）。

目前模型应该位于同一目录下，否则需要显式指定路径，如后文所述。

使用方法

简单情况

对于 int, double, bool, String, List, 和 Map 类型，该库依赖于默认的 Dart JSON 序列化。对于其他类型，则假定存在名为 fromJson(Map<String, dynamic> json) 的命名构造函数。

示例

{
  ...,
  "reference": "SomeGeneratedResource",
  "some_other_prop": "String"
}

复杂类型

以下是复杂类型的字段及其说明：

示例

{
  ...,
  "externalResource": {
    "type": "ExternalResource",
    "writeMethod": "prettyWrite",
    "readMethod": "prettyRead",
    "importPath": "package:my_app/external_resources/ExternalResource.dart"
  }
}

构建配置 (build.yaml)

缓存模式（默认；不适用于 Flutter）

targets:
  $default:
    builders:
      json_serializable_generator:
        generate_for:
          include:
            - lib/**

源码模式（Flutter 必须使用）

targets:
  $default:
    builders:
      _generator:
        generate_for:
          include:
            - lib/**

builders:
  _generator:
    import: "package:json_serializable_generator/json_serializable_generator.dart"
    builder_factories:
      - "jsonSerializableGenerator"
    build_extensions: {".model.json": [".model.dart"]}
    auto_apply: root_package
    build_to: source

示例代码

以下是一个完整的示例，展示如何使用 json_serializable_generator 插件。

示例代码

example/main.dart

import 'dart:convert';
import 'dart:io';
import 'package:json_serializable_generator/json_serializable.dart'; // 引入插件
import './Example.model.dart'; // 引入生成的模型类

void main() {
  // 示例 JSON 数据
  String json = '''
  {
    "id": "abcdefg",
    "isRequired": true,
    "count": 42,
    "simpleSchema": {
      "id": 123456,
      "isRequired": false,
      "name": "Test Model Simple"
    },
    "someExternal": "some-id;string;false;123;",
    "anotherExternal": "another-id;string;false;123;",
    "someList": ["Adam", "Benjamin"],
    "someMapping": {
      "Adam": 1,
      "Benjamin": 2
    }
  }''';

  // 反序列化 JSON 数据
  Example deserializedModelInstance = JsonSerializable.fromJson<Example>(json);

  // 序列化模型数据为 JSON
  String serializedModelJson = jsonEncode(deserializedModelInstance.toJson());
  print(serializedModelJson);

  // 退出程序
  exit(0);
}

生成的模型类文件 (Example.model.dart)

// 自动生成的模型类
class Example {
  final String id;
  final bool isRequired;
  final int count;
  final SimpleSchema simpleSchema;
  final String someExternal;
  final String anotherExternal;
  final List<String> someList;
  final Map<String, int> someMapping;

  Example({
    required this.id,
    required this.isRequired,
    required this.count,
    required this.simpleSchema,
    required this.someExternal,
    required this.anotherExternal,
    required this.someList,
    required this.someMapping,
  });

  factory Example.fromJson(Map<String, dynamic> json) {
    return Example(
      id: json['id'],
      isRequired: json['isRequired'],
      count: json['count'],
      simpleSchema: SimpleSchema.fromJson(json['simpleSchema']),
      someExternal: json['someExternal'],
      anotherExternal: json['anotherExternal'],
      someList: List<String>.from(json['someList']),
      someMapping: Map<String, int>.from(json['someMapping']),
    );
  }

  Map<String, dynamic> toJson() => {
        'id': id,
        'isRequired': isRequired,
        'count': count,
        'simpleSchema': simpleSchema.toJson(),
        'someExternal': someExternal,
        'anotherExternal': anotherExternal,
        'someList': someList,
        'someMapping': someMapping,
      };
}

// 内部模型类
class SimpleSchema {
  final int id;
  final bool isRequired;
  final String name;

  SimpleSchema({
    required this.id,
    required this.isRequired,
    required this.name,
  });

  factory SimpleSchema.fromJson(Map<String, dynamic> json) {
    return SimpleSchema(
      id: json['id'],
      isRequired: json['isRequired'],
      name: json['name'],
    );
  }

  Map<String, dynamic> toJson() => {
        'id': id,
        'isRequired': isRequired,
        'name': name,
      };
}