关于在controller中json数据与对象,map,list的相互转换 jackson

关于在controller中json数据与对象,map,list的相互转换

步骤：
1.导入jackson相关jar包

• jackson-annotations.jar
• jackson-core.jar
• jackson-databind.jar

---

com.fasterxml.jackson.core
jackson-core
2.7.3


com.fasterxml.jackson.core
jackson-databind
2.7.3


com.fasterxml.jackson.core
jackson-annotations
2.7.3

2.创建jackson的核心对象：ObjectMapper
ObjectMapper mapper = new ObjectMapper();

3.调用mapper的相关方法

对象转json

User user = new User("Tom","沈阳")；
String json = mapper.writeValueAsString(user);
System.out.print(json); //输出：{"name":"Tom","city","沈阳"}

Map<String,String>转json

HashMap<String,String> map = new HashMap<String,String>();
map.put("name","Kris");
map.put("city","沈阳");
String json = mapper.writeValueAsString(map);
System.out.print(json); //输出：{"city":"沈阳","name":"Kris"} （HashMap是无序的）

---

Map<String,Object>转json

Map<String,User> map = new HashMap<String,User>();
map1.put("01",new User("Tom","沈阳"));
map1.put("02",new User("Kris","上海"));
String json = mapper.writeValueAsString(map1);
System.out.println(json);
输出：
{
"01":{"name":"Tom","city":"沈阳"},
"02":{"name":"Kris","city":"上海"}
}

ArrayList转为json

ArrayList al = new ArrayList();
al.add("Tom");
al.add("沈阳");
String json = mapper.writeValueAsString(al);
System.out.print(json); //输出：["TOM","SHENYANG"]

ArrayList转为json

ArrayList al = new ArrayList();
al.add(new User("Tom","沈阳"));
al.add(new User("Kris","上海"));
String json = mapper.writeValueAsString(al);
System.out.print(json);
输出：
[
{"name":"Tom","city":"沈阳"},
{"name":"Kris","city":"上海"}
]

json转对象
String json = "{"name":"Tom","city":"沈阳"}";
User user = mapper.readValue(json, User.class);
System.out.println(user);

json转map<String,String>

HashMap<String,String> map = mapper.readValue(json, HashMap.class);
System.out.println(map);

json转map<String,Object>

Map<String,User> map= mapper.readValue(json, HashMap.class);
System.out.println(map);

json转list

ArrayList list= mapper.readValue(json, ArrayList.class);
System.out.println(list);

json转list

List list= mapper.readValue(json, ArrayList.class);
System.out.println(list);