FastJson链接
一、JackSon介绍Jackson 是用来序列化和反序列化 Json 的 Java 的开源框架。
Spring MVC 的默认 Json 解析器便是 Jackson。
与其他 Java 的 Json 框架 Gson 等相比， Jackson 解析大的 Json 文件速度比较快。
Jackson 运行时占用内存比较低，性能比较好。
Jackson 有灵活的 API，可以很容易进行扩展和定制。
笔记参考出处https://www.bilibili.com/video/BV1gJ411d7ai?p=6
二、JackSon序列化和反序列化
1、实体类
@Data
public class DgjTestEntity {
private String name;
private int age;
private String sex;
private Date birthday;
private String email;
private String address;
public DgjTestEntity(String name, int age, String sex, Date birthday, String email, String address) {
this.name = name;
this.age = age;
this.sex = sex;
this.birthday = birthday;
this.email = email;
this.address = address;
}
}public void jacksonTset() throws Exception {
ObjectMapper mapper = new ObjectMapper();
/*------- 对象 序列化 Json 字符串 -------*/
DgjTestEntity entity = new DgjTestEntity("dgs",23,"男",new Date(),"dgs@qq.com","");
String jsonObjectToString = mapper.writeValueAsString(entity);
System.out.println(jsonObjectToString);
//{"name":"dgs","age":23,"sex":"男","birthday":1650872520038,"email":"dgs@qq.com","address":""}
DgjTestEntity entity1 = new DgjTestEntity("dgs",23,"男",new Date(),"dgs@qq.com","");
DgjTestEntity entity2 = new DgjTestEntity("dgs",23,"男",new Date(),"dgs@qq.com","");
/*------- Map 序列化 Json 字符串 -------*/
Map map = new HashMap();
map.put("entity1",entity1);
map.put("entity2",entity2);
String jsonMapToString = mapper.writeValueAsString(map);
System.out.println(jsonMapToString);
//{"entity1":{"name":"dgs","age":23,"sex":"男","birthday":1650872840157,"email":"dgs@qq.com","address":""},
// "entity2":{"name":"dgs","age":23,"sex":"男","birthday":1650872840157,"email":"dgs@qq.com","address":""}}
/*------- List 序列化 Json 字符串 -------*/
List list = new ArrayList();
list.add(entity1);
list.add(entity2);
String jsonListToString = mapper.writeValueAsString(list);
System.out.println(jsonListToString);
//[{"name":"dgs","age":23,"sex":"男","birthday":1650872840157,"email":"dgs@qq.com","address":""},
// {"name":"dgs","age":23,"sex":"男","birthday":1650872840157,"email":"dgs@qq.com","address":""}]
/*------- int[] 序列化 Json 字符串 -------*/
int[] intArray = {1,2,3,4,5,6,7,8,9,10};
String intArrayToJson = mapper.writeValueAsString(intArray);
System.out.println(intArrayToJson);
//[1,2,3,4,5,6,7,8,9,10]
/*------- String[] 序列化 Json 字符串 -------*/
String[] stringArray = {"1,2,3,4,5,6,7,8,9,10","DGS"};
String stringArrayToJson = mapper.writeValueAsString(stringArray);
System.out.println(stringArrayToJson);
}public void jacksonTset() throws Exception {
ObjectMapper mapper = new ObjectMapper();
String jsonToOject = "{\"name\":\"dgs\",\"age\":23,\"sex\":\"男\",\"birthday\":1650872520038,\"email\":\"dgs@qq.com\",\"address\":\"\"}";
String jsonToMap = "{\"entity1\":{\"name\":\"dgs\",\"age\":23,\"sex\":\"男\",\"birthday\":1650872840157,\"email\":\"dgs@qq.com\",\"address\":\"\"},\n" +
" \"entity2\":{\"name\":\"dgs\",\"age\":23,\"sex\":\"男\",\"birthday\":1650872840157,\"email\":\"dgs@qq.com\",\"address\":\"\"}}";
String jsonToList = "[{\"name\":\"dgs\",\"age\":23,\"sex\":\"男\",\"birthday\":1650872840157,\"email\":\"dgs@qq.com\",\"address\":\"\"},\n" +
" {\"name\":\"dgs\",\"age\":23,\"sex\":\"男\",\"birthday\":1650872840157,\"email\":\"dgs@qq.com\",\"address\":\"\"}]";
String jsonToIntList = "[1,2,3,4,5,6,7,8,9,10]";
String jsonToStringList = "[\"1,2,3,4,5,6,7,8,9,10\",\"DGS\"]";
DgjTestEntity entity = mapper.readValue(jsonToOject, DgjTestEntity.class);
System.out.println(entity);
//DgjTestEntity(name=dgs, age=23, sex=男, birthday=Mon Apr 25 15:42:00 CST 2022, email=dgs@qq.com, address=)
Map map = mapper.readValue(jsonToMap, new TypeReference>() {});
System.out.println(map);
//{entity1=DgjTestEntity(name=dgs, age=23, sex=男, birthday=Mon Apr 25 15:47:20 CST 2022, email=dgs@qq.com, address=),
// entity2=DgjTestEntity(name=dgs, age=23, sex=男, birthday=Mon Apr 25 15:47:20 CST 2022, email=dgs@qq.com, address=)}
List list = mapper.readValue(jsonToList, new TypeReference>() {});
System.out.println(list);
//[DgjTestEntity(name=dgs, age=23, sex=男, birthday=Mon Apr 25 15:47:20 CST 2022, email=dgs@qq.com, address=),
// DgjTestEntity(name=dgs, age=23, sex=男, birthday=Mon Apr 25 15:47:20 CST 2022, email=dgs@qq.com, address=)]
int[] ints = mapper.readValue(jsonToIntList, int[].class);
System.out.println(ints);
String[] strings = mapper.readValue(jsonToStringList, String[].class);
System.out.println(strings.toString());
} 三、@JsonProperty注解
对类的属性使用@JsonProperty注解,可以重新指定与该属性对应的JSON字符串中的名字
public void jacksonTset() throws Exception {
/*实体类
* @JsonProperty("userName")
* private String name;
* */
ObjectMapper mapper = new ObjectMapper();
/*------- 对象 序列化 Json 字符串 -------*/
DgjTestEntity entity = new DgjTestEntity("dgs",23,"男",new Date(),"dgs@qq.com","");
String jsonObjectToString = mapper.writeValueAsString(entity);
System.out.println(jsonObjectToString);
//{"age":23,"sex":"男","birthday":1650874382780,"email":"dgs@qq.com","address":"","userName":"dgs"}
}补充注解：
@JsonIgnore 作用在字段上面，序列化的时候忽略改字段
@JsonIgnoreProperties({"name","age"}) 作用在实体类上面，序列化的时候忽略里面的字段
四、处理对象的Null 属性
方案一：注解@JsonInclude()
public void jacksonTset() throws Exception {
/*实体类
* @JsonInclude(JsonInclude.Include.NON_NULL)
* public class DgjTestEntity {
* private String name;
* private int age;
* private String sex;
* private Date birthday;
* private String email;
* private String address;
* }
* */
ObjectMapper mapper = new ObjectMapper();
DgjTestEntity entity = new DgjTestEntity(null,23,"男",new Date(),"dgs@qq.com",null);
String jsonObjectToString = mapper.writeValueAsString(entity);
System.out.println(jsonObjectToString);
//{"age":23,"sex":"男","birthday":1650875540546,"email":"dgs@qq.com"}
}public void jacksonTset() throws Exception {
/*实体类
* public class DgjTestEntity {
* private String name;
* private int age;
* private String sex;
* private Date birthday;
* private String email;
* private String address;
* }
* */
ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
DgjTestEntity entity = new DgjTestEntity(null,23,"男",new Date(),"dgs@qq.com",null);
String jsonObjectToString = mapper.writeValueAsString(entity);
System.out.println(jsonObjectToString);
//{"age":23,"sex":"男","birthday":1650875540546,"email":"dgs@qq.com"}
}五、格式化Date类型属性
@JsonFormat 注解提供了 pattern 属性用以自定义其字符串格式
public void jacksonTset() throws Exception {
/*实体类
* public class DgjTestEntity {
* private String name;
* private int age;
* private String sex;
* @JsonFormat(pattern = "yyyy-MM-dd")
* private Date birthday;
* private String email;
* private String address;
* }
* */
ObjectMapper mapper = new ObjectMapper();
DgjTestEntity entity = new DgjTestEntity(null,23,"男",new Date(),"dgs@qq.com",null);
String jsonObjectToString = mapper.writeValueAsString(entity);
System.out.println(jsonObjectToString);
//{"name":null,"age":23,"sex":"男","birthday":"2022-04-25","email":"dgs@qq.com","address":null}
}六、其他
Jackson 支持 Json 字符串 和 Map 对象 之间的转换
public void jacksonTset() throws Exception {
ObjectMapper mapper = new ObjectMapper();
Map map = new HashMap<>();
map.put(521,"1314");
map.put("我不信","我也不行");
map.put('A',"好好生活");
map.put(true,new int[]{1,2,3,4});
String mapToJson = mapper.writeValueAsString(map);
System.out.println(mapToJson);
//{"A":"好好生活","521":"1314","我不信":"我也不行","true":[1,2,3,4]}
Map jsonToMap = mapper.readValue(mapToJson, Map.class);
for (Object key : jsonToMap.keySet()){
System.out.print(key+":"+jsonToMap.get(key)+" ");
}
//A:好好生活 521:1314 我不信:我也不行 true:[1, 2, 3, 4]
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