java json

map 转json 
       Map<String, Object> map = new HashMap<>();
        map.put("key1", "value1");
        map.put("key2", 123);
        map.put("key3", new Object());
        System.out.println(JSON.toJSON(map));

json转对象

ObjectMapper mapper = new ObjectMapper();
GssbCardExtraInfo obj = null;
try {
　　obj = mapper.readValue(jsonStr, GssbCardExtraInfo.class);
} catch (JsonProcessingException e) {
　　throw new RuntimeException(e);
}