FastJSON2 学习笔记
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FastJSON2 学习笔记
FASTJSON2是FASTJSON项目的重要升级，目标是为下一个十年提供一个高性能的JSON库。官方如是说。
pom.xml
查看新版本： maven.org 。
<dependency>
<groupId>com.alibaba.fastjson2</groupId>
<artifactId>fastjson2</artifactId>
<version>2.0.12</version>
</dependency>
非完美兼容 fastjson1
如果原来使用fastjson 1.2.x版本，可以使用兼容包，兼容包不能保证100%兼容，请仔细测试验证，发现问题请及时反馈。
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>2.0.14</version>
</dependency>
测试数据
JavaBean
在另一篇文章里有，直接取来用。
Json String
[
"name": "张三", "age": 10, "score": 23, "groupTag": "A",
"name": "李四", "age": 20, "score": 19, "groupTag": "A",
"name": "王五", "age": 30, "score": 20, "groupTag": "B",
"name": "赵六", "age": 40, "score": 21, "groupTag": "B",
"name": "洪七", "age": 50, "score": 25, "groupTag": "C",
"name": "重八", "age": 60, "score": 45, "groupTag": "C"
]
序列化
toJSONString
Hero hero = Hero.getList().get(0);
String jsonString = JSONObject.toJSONString(hero);
"age":10,"groupTag":"A","name":"张三","score":23
Features
更多详情，见参考资料：通过Features配置序列化和反序列化的行为
1. 格式化输出
Hero hero = Hero.getList().get(0);
String jsonString = JSON.toJSONString(hero, JSONWriter.Feature.PrettyFormat);
"age":10,
"groupTag":"A",
"name":"张三",
"score":23
2. 序列化时输出类型信息
Hero hero = Hero.getList().get(0);
String jsonString = JSON.toJSONString(hero, JSONWriter.Feature.WriteClassName);
"@type": "com.jerry.demo.fastjson2demo.entity.Hero",
"age": 10,
"groupTag": "A",
"name": "张三",
"score": 23
3. 使用单引号
JSONWriter.Feature.UseSingleQuotes
Hero hero = Hero.getList().get(0);
String jsonString = JSONObject.toJSONString(hero,
JSONWriter.Feature.PrettyFormat, // 格式化输出
JSONWriter.Feature.UseSingleQuotes); // 使用单引号
"age":10, 'groupTag':null, 'name':'张三', "score":23
4. 序列话时包含为 null 的字段
JSONWriter.Feature.WriteNulls
Hero hero = Hero.getList().get(0);
hero.setGroupTag(null);
String jsonString = JSONObject.toJSONString(hero,
JSONWriter.Feature.PrettyFormat, // 格式化输出
JSONWriter.Feature.UseSingleQuotes, // 使用单引号
JSONWriter.Feature.WriteNulls); // 序列话时包含为 null 的字段
"age":10, 'groupTag':null, 'name':'张三', "score":23
反序列化
JSONObject
jsonString 转 JavaBean
String jsonString = " 'age':10,'groupTag':'A','name':'张三','score':23 ";
Hero hero = JSONObject.parseObject(jsonString, Hero.class);
jsonString 转 JSONObject
String jsonString = " 'age':10,'groupTag':'A','name':'张三','score':23 ";
JSONObject jsonObject = JSONObject.parseObject(jsonString);
int id = jsonObject.getIntValue("age");
String name = jsonObject.getString("name");
JSONObject 转 JavaBean
String jsonString = " 'age':10,'groupTag':'A','name':'张三','score':23 ";
JSONObject jsonObject = JSONObject.parseObject(jsonString);
Hero hero = jsonObject.to(Hero.class);
JSONObject 获取 JavaBean
String jsonString = "" +
"'张三': 'age':10,'groupTag':'A','name':'张三','score':23 ," +
"'李四': 'age':11,'groupTag':'B','name':'李四','score':28 " +
"";
JSONObject jsonObject = JSONObject.parseObject(jsonString);
Object obj = jsonObject.get("张三");
System.out.println(obj); // "age":10,"groupTag":"A","name":"张三","score":23
Hero hero = jsonObject.getObject("李四", Hero.class);
System.out.println(hero); // Hero(name=李四, age=11, score=28, groupTag=B)
JSONArray
jsonString 转 JSONArray
String jsonString = "[" +
" 'age':10,'groupTag':'A','name':'张三','score':23 ," +
" 'age':11,'groupTag':'B','name':'李四','score':28 " +
"]";
JSONArray jsonArray = JSONArray.parseArray(jsonString);
Object o = jsonArray.get(0);
System.out.println(o); // "age":10,"groupTag":"A","name":"张三","score":23
Hero hero = jsonArray.getObject(0, Hero.class);
System.out.println(hero); // Hero(name=张三, age=10, score=23, groupTag=A)
JSONArray 转 List
String jsonString = "[" +
" 'age':10,'groupTag':'A','name':'张三','score':23 ," +
" 'age':11,'groupTag':'B','name':'李四','score':28 " +
"]";
JSONArray jsonArray = JSON.parseArray(jsonString);
List<Hero> list = jsonArray.toJavaList(Hero.class);
System.out.println(list);
// [Hero(name=张三, age=10, score=23, groupTag=A), Hero(name=李四, age=11, score=28, groupTag=B)]
jsonString 转 List
String jsonString = "[" +
" 'age':10,'groupTag':'A','name':'张三','score':23 ," +
" 'age':11,'groupTag':'B','name':'李四','score':28 " +
"]";
List<Hero> list = JSON.parseArray(jsonString, Hero.class);
System.out.println(list);
// [Hero(name=张三, age=10, score=23, groupTag=A), Hero(name=李四, age=11, score=28, groupTag=B)]
jsonString 转 Map
String jsonString = "" +
"'张三': 'age':10,'groupTag':'A','name':'张三','score':23 ," +
"'李四': 'age':11,'groupTag':'B','name':'李四','score':28 " +
"";
TypeReference<HashMap<String, Hero>> tr = new TypeReference<HashMap<String, Hero>>() ;
HashMap<String, Hero> map = JSONObject.parseObject(jsonString, tr);
System.out.println(map);
// 李四=Hero(name=李四, age=11, score=28, groupTag=B), 张三=Hero(name=张三, age=10, score=23, groupTag=A)
JSONPath
eval
JSONPath.eval(JavaBean, "JSONPathStr")
List<Hero> list = Hero.getList();
String jsonString = JSONObject.toJSONString(list);
Hero hero = (Hero)JSONPath.eval(list, "$[0]");
System.out.println(hero); // Hero(name=张三, age=10, score=23, groupTag=A)
JSONObject jsonObject = (JSONObject)JSONPath.eval(jsonString, "$[0]");
Hero hero = jsonObject.to(Hero.class);
System.out.println(hero); // Hero(name=张三, age=10, score=23, groupTag=A)
String name = (String)JSONPath.eval(jsonString, "$[0].name");
System.out.println(name); // 张三
of
JSONReader.of("jsonString");
JSONReader parser = JSONReader.of("[ \\"age\\":10,\\"groupTag\\":\\"A\\",\\"name\\":\\"张三\\",\\"score\\":23 ]");
JSONPath path = JSONPath.of("$[0].name"); // 缓存起来重复使用能提升性能
String name = (String)path.extract(parser);
System.out.println(name); // 张三
参考资料
Fastjson_学习笔记
GitHub：alibaba/fastjson2
Gitee：wenshao：fastjson2
Gitee：astjson2文档
- FASTJSON2提供的Annotations
- FASTJSON 2 Autotype机制介绍
- 通过Features配置序列化和反序列化的行为（格式化、别名等。。。）
- FASTJSON v2 JSONSchema的支持
- FASTJSON2 JSONPath支持介绍
- 使用Mixin注入Anntation定制序列化和反序列化
- 列化时对字段名做处理的扩展接口 NameFilter
- 在 Spring 中集成 Fastjson2
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