1、Gson
1）添加依赖
com.google.code.gson
gson
2.2.4
2）转化方法
（1）对象转Json
Gson gson = new Gson();
String json = gson.toJson(Object object);
（2）Json转对象
gson.fromJson(String json, Class classOfT)
（3）集合转Json
Gson gson = new Gson();
String json = gson.toJson(Object object);
（4）Json转集合
TypeToken typeOfT = new TypeToken(){};
T fromJson = (T)gson.fromJson(json, typeOfT.getType());
2、Json-Lib
1）添加依赖
net.sf.json-lib
json-lib
2.4
jdk15
2）转化方法
（1）对象转Json
JSONObject fromObject = JSONObject.fromObject(Object object);
String string = fromObject.toString();
（2）Json转对象
JSONObject fromObject2 = JSONObject.fromObject(string);
Object bean =JSONObject.toBean(JSONObject jsonObject, Class beanClass)
（3）集合转Json
JSONArray fromObject = JSONArray.fromObject(Object object);
String string = fromObject.toString();
（4）Json转集合
JSONArray fromObject2 = JSONArray.fromObject(string);
Collection collection = JSONArray.toCollection
(JSONArray jsonArray, Class objectClass)
3、Fastjson
Fastjson是阿里巴巴公司开发的，Java语言编写的，JSON的处理器。
1）添加依赖
com.alibaba
fastjson
1.2.31
2）转化方法
（1）对象转Json
JSON.toJSONString(Object object);
（2）Json转对象
JSON.parseObject(String text,Class Class);
（3）集合转Json
JSON.toJSONString(Object object)
（4）Json转集合
JSON.parseArray(String text,Class Class);
4、Jackson
1）添加依赖
com.fasterxml.jackson.core
jackson-databind
2.8.8
2）转换方法
public static String object_to_json(Object object) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
return mapper.writeValueAsString(object);
}
public static T json_to_object(String json, Class mainClass, Class... parametricClasses) throws JsonParseException, JsonMappingException, IOException {
ObjectMapper mapper = new ObjectMapper();
JavaType parametricType = mapper.getTypeFactory().constructParametricType(mainClass, parametricClasses);
T readValue = mapper.readValue(json, parametricType);
return readValue;
}