Jackson中ObjectMapper简介说明

Jackson常用操作实现思路

实现思路:
    1.引入jackson依赖
	2.获取一个ObjectMapper对象
	3.使用ObjectMapper对象中的方法对
	    对象和json之间操作

jackson依赖

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.10.0</version>
</dependency>

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-annotations</artifactId>
  <version>2.10.0</version>
</dependency>

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-core</artifactId>
  <version>2.10.0</version>
</dependency>

实例化ObjectMapper

ObjectMapper mapper=new ObjectMapper();

1.对象转json字符串

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

2.Map转json字符串

Map<String,Object> map=new HashMap();
String json=mapper.writeValueAsString(map);

3.数组和list转json字符串

List<User> list=new ArrayList();
String json=mapper.writeValueAsString(list);

4.json字符串转对象

String user="{\"name\":\"java265-maomao\"}";
User user=mapper.readValue(user,User.class);

5.json字符串转Map

String json="{\"name\":\"java265-maomao\"}";
Map<String,String> map=mapper.readValue(json,Map.class);

6.json字符串转对象数组和List

String json="[{\"name\":\"java265-maomao\"},{\"name\":\"java"}]";
CollectionType listType=mapper.getTypeFactory().constructCollectionType(ArrayList.class,User.class);
List<User> list=mapper.readValue(json,listType);

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

String json="[{\"name\":\"java265-maomao\"},{\"name\":\"java\"}]";
CollectionType listType=mapper.getTypeFactory().constructCollectionType(ArrayList.class,Map.class);
List<Map<String,Object>> list=mapper.readValue(json,listType);