jackson objectMapper json字符串、对象bean、map、数组list互相转换常用的方法列举

原创已于 2024-02-01 14:25:01 修改 · 1.8k 阅读

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#json #list #java

于 2022-01-05 15:53:18 首次发布

本文详细列举了使用Jackson库进行Java对象、JSON字符串、Map及List之间的转换方法，包括对象转实体、对象转JSON、Map转JSON、数组转JSON、JSON转对象、JSON转Map、JSON转对象数组、JSON转Map数组、默认转换为LinkedHashMap以及JSON字符串与List或Map的互转。这些转换在实际开发中非常常见，是Java后端开发必备技能之一。

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jackson objectMapper json字符串、对象bean、map、数组list互相转换常用的方法列举：

ObjectMapper mapper = new ObjectMapper();

1.object 转实体对象

ObjectMapper objectMapper = new ObjectMapper();
RequestImagesDto requestImages = objectMapper.convertValue(lGetRight,  RequestImagesDto.class);

2.对象转json字符串

User user=new User();
String userJson=mapper.writeValueAsString(user);

3.Map转json字符串

  Map map=new HashMap();  
  String json=mapper.writeValueAsString(map);

4.数组list转json字符串

Student[] stuArr = {student1, student3};  
String jsonfromArr =  mapper.writeValueAsString(stuArr);

5.json字符串转对象

String expected = "{\"name\":\"Test\"}";
User user = mapper.readValue(expected, User.class);

6.json字符串转Map

String expected = "{\"name\":\"Test\"}";
Map userMap = mapper.readValue(expected, Map.class);

7.json字符串转对象数组List

String expected="[{\"a\":12},{\"b\":23},{\"name\":\"Ryan\"}]";
CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, User.class);
List<User> userList = mapper.readValue(expected, listType);

8.json字符串转Map数组List<Map<String,Object>>

String expected="[{\"a\":12},{\"b\":23},{\"name\":\"Ryan\"}]";
CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, Map.class);
List<Map<String,Object>> userMapList = mapper.readValue(expected, listType);

9.jackson默认将对象转换为LinkedHashMap

String expected = "[{\"name\":\"Ryan\"},{\"name\":\"Test\"},{\"name\":\"Leslie\"}]";
ArrayList arrayList = mapper.readValue(expected, ArrayList.class);

10.json字符串与list或map互转的方法

ObjectMapper objectMapper = new ObjectMapper();
 //遇到date按照这种格式转换
 SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 objectMapper.setDateFormat(fmt);
 String preference = "{name:'侯勇'}";
  //json字符串转map
  Map<String, String> preferenceMap = new HashMap<String, String>();
  preferenceMap = objectMapper.readValue(preference, preferenceMap.getClass());
  //map转json字符串
  String result=objectMapper.writeValueAsString(preferenceMap);

11.bean转换为map

List<Map<String,String>> returnList=new ArrayList<Map<String,String>>();
List<Menu> menuList=menuDAOImpl.findByParentId(parentId);
ObjectMapper mapper = new ObjectMapper();
//用jackson将bean转换为map
returnList=mapper.convertValue(menuList,new TypeReference<List<Map<String, String>>>(){});