jackson的objectMapper反序列化复杂对象TypeReference

objectMapper.readValue的三个重载方法

//简单型，就是 直接  UserBase.class 就可。
public <T> T readValue(String content, Class<T> valueType);

//valueTypeRef)；复杂的可以 用这个
public <T> T readValue(String content, TypeReference<T> 
//这个书写起来比较麻烦，就不说明了，不常用，前2个已经彻底满足了。

public <T> T readValue(String content, JavaType valueType);

demo

包名com.fasterxml.jackson.core.type.TypeReference

ObjectMapper objectMapper = new ObjectMapper();
String json1 = "{"userName":"小李飞刀","age":18,"addTime":1591851786568}";
String json2 = "[{"userName":"小李飞刀","age":18,"addTime":123}, {"userName":"小李飞刀2","age":182,"addTime":1234}]";


//1.最简单的常用方法，直接将一个json转换成实体类
UserBase userBase1 = objectMapper.readValue(json1, UserBase.class); //简单类型的时候，这样最方便
System.out.println("简单: " + userBase1.getUserName());
//用 TypeReference 也可以，但是麻烦 不如第一种直接 TypeReference 主要针对繁杂类型
//UserBase userBase2 = objectMapper.readValue(json1, new TypeReference<UserBase>() {});



//2.把Json转换成map，必须使用 TypeReference , map的类型定义 可以根据实际情况来定，比如若值都是String那么就可以 Map<String, String>
Map<String, Object> userBaseMap =  objectMapper.readValue(json1, new TypeReference<Map<String, Object>>() {
          
   });
System.out.println("map: " + userBaseMap.get("userName"));


//3.list<Bean>模式，必须用 TypeReference
List<UserBase> userBaseList = objectMapper.readValue(json2, new TypeReference<List<UserBase>>() {
          
   });
System.out.println("list: " + userBaseList.get(0).getUserName());


//4.Bean[] 数组，必须用 TypeReference
UserBase[] userBaseAry = objectMapper.readValue(json2, new TypeReference<UserBase[]>() {
          
   });
System.out.println("ary: " + userBaseAry[0].getUserName());