FastJson、Jackson处理Json转换对象、复杂对象问题
在开发过程中最常见的就是Json格式转化问题。包括Json转对象，转数据，转Map等等。常见处理json的类库FastJson，Jackson为此我针对他们做了一些总结，如有欠缺可以留言。希望可以帮助大家。
FastJson
准备两个套娃的类
@Data
@AllArgsConstructor
@NoArgsConstructor
public class FastJsonPerson {
private String name;
private Integer agexx;
private String other;
private List cards;
} @Data
@NoArgsConstructor
@AllArgsConstructor
public class Card {
private String cardName;
private Date cardTime;
}1.对象转字符串
@Test
public void transformString(){
FastJsonPerson person;
person = new FastJsonPerson();
person.setName("兵长");
person.setAgexx(18);
person.setOther("其他要被屏蔽");
person.setCards(Arrays.asList(new Card("招商",new Date()),
new Card("浦发",new Date())));
String personString = JSON.toJSONString(person);
System.out.println(personString);
}
// 结果：{"agexx":18,"cards":[{"cardName":"招商","cardTime":1631188795258},{"cardName":"浦发","cardTime":1631188795258}],"name":"兵长","other":"其他要被屏蔽"}在转化的过程不想要某个字段可以加上@JSONField(serialize = false)，注意不是@jsonIgnore,那个是jackson的。
在转化的过程中还想更换字段别名@JSONField(name="xxx")
格式化日期@JSONField(format="yyyy-MM-dd HH:mm:ss")
接下来改变对应的实体类完成上述三个要求。
@Data
@AllArgsConstructor
@NoArgsConstructor
public class FastJsonPerson {
private String name;
@JSONField(name="age")
private Integer agexx;
@JSONField(serialize = false)
private String other;
private List cards;
} @Data
@NoArgsConstructor
@AllArgsConstructor
public class Card {
private String cardName;
@JSONField(format="yyyy-MM-dd HH:mm:ss")
private Date cardTime;
}再次执行上边的测试方法，你会发现结果变成;agexx--->age ，时间格式变成了正常的，other字段被忽略。
{"age":18,"cards":[{"cardName":"招商","cardTime":"2021-09-09 20:12:26"},{"cardName":"浦发","cardTime":"2021-09-09 20:12:26"}],"name":"兵长"}2.字符串转对象,集合对象；
@Test
public void stringToObject() {
//针对于简单的字符串，我们可以通过转成Array，然后通过名字获取内容。
String s = "{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"}";
JSONObject object = JSON.parseObject(s);
System.out.println(object.get("age"));
System.out.println(object.get("name"));
System.out.println(object.get("cards"));
String list = "[{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"},{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"}]";
List personList = JSON.parseArray(list, FastJsonPerson.class);
System.out.println(personList);
} 3.字符串转Map
@Test
public void stringToMap(){
String s = "{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"}";
Map map = (Map)JSON.parseObject(s);
System.out.println(map);
} Jackson
准备两个套娃类
@Data
@NoArgsConstructor
@AllArgsConstructor
public class JacksonCard {
private String cardName;
private Date cardTime;
}@Data
@NoArgsConstructor
@AllArgsConstructor
public class JacksonPerson {
private String name;
private Integer agexx;
private String other;
private List cards;
} 1.对象转字符串
@SneakyThrows
@Test
public void transformToString (){
JacksonPerson person = new JacksonPerson();
person.setName("兵长");
person.setAgexx(18);
person.setOther("其他要被屏蔽");
person.setCards(Arrays.asList(new JacksonCard("招商",new Date()),
new JacksonCard("浦发",new Date())));
ObjectMapper objectMapper = new ObjectMapper();
System.out.println(objectMapper.writeValueAsString(person));
}
// 结果：{"name":"兵长","agexx":18,"other":"其他要被屏蔽","cards":[{"cardName":"招商","cardTime":1631242139184},{"cardName":"浦发","cardTime":1631242139184}]}在转化的过程不想要某个字段可以加上@JsonIgnore
在转化的过程中还想更换字段别名@JsonProperty("age")
格式化日期@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
根据上述描述改造对应的实体类
@Data
@NoArgsConstructor
@AllArgsConstructor
public class JacksonPerson {
private String name;
@JsonProperty("age")
private Integer agexx;
@JsonIgnore
private String other;
private List cards;
} @Data
@NoArgsConstructor
@AllArgsConstructor
public class JacksonCard {
private String cardName;
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
private Date cardTime;
}2.字符串转对象,对象集合,复杂对象
@Test
public void transformToObject() throws IOException {
String s = "{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"}";
String list = "[{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"},{\"age\":18,\"cards\":[{\"cardName\":\"招商\",\"cardTime\":\"2021-09-09 20:12:26\"},{\"cardName\":\"浦发\",\"cardTime\":\"2021-09-09 20:12:26\"}],\"name\":\"兵长\"}]";
ObjectMapper objectMapper = new ObjectMapper();
System.out.println(objectMapper.readValue(s, JacksonPerson.class));
List personList = (List)objectMapper.readValue(list, objectMapper.getTypeFactory().constructParametricType(List.class, JacksonPerson.class));
System.out.println(personList);
// 如果多层套娃，你可以使TypeReference，万能想要的都有
List> personList1 = objectMapper.readValue(list, new TypeReference>>(){});
System.out.println(personList1);
} 下边是JsonUtils工具类。
package com.cn.zj.json;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;
import java.text.SimpleDateFormat;
/**
* @description:
* @author: wangdakai
* @date: 2021/9/10
*/
@Slf4j
public class JsonUtils {
private static ObjectMapper objectMapper = new ObjectMapper();
static {
//序列化的时候序列对象的所有属性
objectMapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);
//反序列化的时候如果多了其他属性,不抛出异常
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
//如果是空对象的时候,不抛异常
objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
//取消时间的转化格式,默认是时间戳,可以取消,同时需要设置要表现的时间格式
objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
}
/**
* 对象转Json
* @param obj
* @param
* @return
*/
public static String objectToJson(T obj){
if(obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
} catch (Exception e) {
log.warn("Parse Object to Json error",e);
e.printStackTrace();
return null;
}
}
/**
* json转对象
* @param src
* @param clazz
* @param
* @return
*/
public static T jsonToObject(String src,Class clazz){
if(StringUtils.isEmpty(src) || clazz == null){
return null;
}
try {
return clazz.equals(String.class) ? (T) src : objectMapper.readValue(src,clazz);
} catch (Exception e) {
log.warn("Parse Json to Object error",e);
e.printStackTrace();
return null;
}
}
/**
* json转想要的对象；应对各种复杂格式的对象很万能。
* @param src
* @param typeReference
* @param
* @return
*/
public static T jsonToObject(String src, TypeReference typeReference){
if(StringUtils.isEmpty(src) || typeReference == null){
return null;
}
try {
return (T)(typeReference.getType().equals(String.class) ? src : objectMapper.readValue(src, typeReference));
} catch (Exception e) {
log.warn("Parse Json to Object error",e);
e.printStackTrace();
return null;
}
}
/**
* json转成对象
* @param str
* @param collectionClass
* @param elementClasses
* @param
* @return
*/
public static T jsonToTransfer(String str, Class collectionClass, Class... elementClasses) {
try {
return (T)objectMapper.readValue(str, objectMapper.getTypeFactory().constructParametricType(collectionClass, elementClasses));
} catch (Exception e) {
log.warn("Parse Json to Object error",e);
e.printStackTrace();
}
return null;
}
} 另外也可以用其他人写好的工具包，https://hutool.cn/docs/#/json...感性去的可以去看看。如果只是处理json就没必要，里边的东西太多。人生一世难得糊涂。