Jackson Map与Bean互转
在使用 java 开发中，通常需要把 Map 转成 Bean，或把 Bean 转成 Map，这就用的工具类，在此推荐使用import com.fasterxml.jackson.databind.ObjectMapper;包下的ObjectMapper类，比 JsonObject 效率高
下面就列举了几种使用方法
1、pom.xml
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.6</version>
<scope>compile</scope>
</dependency>2、java 代码
package com.jin.demo.jackson;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.HashMap;
import java.util.Map;
public class JacksonTest {
private static final ObjectMapper mapper = new ObjectMapper();
public static void main(String[] args) throws Exception {
// 测试 将Map转成指定的Bean
Map<String, Object> map = new HashMap<>();
map.put("name", "张三");
Person o = (Person)JacksonTest.mapToBean(map, Person.class);
System.out.println(o);
// 测试 将Bean转成Map
Person person = new Person();
person.setAge(18);
Map map1 = JacksonTest.beanToMap(person);
System.out.println(map1);
}
// 将对象转成字符串
public static String objectToString(Object obj) throws Exception {
return mapper.writeValueAsString(obj);
}
// 将Map转成指定的Bean
public static Object mapToBean(Map map, Class clazz) throws Exception {
return mapper.readValue(objectToString(map), clazz);
}
// 将Bean转成Map
public static Map beanToMap(Object obj) throws Exception {
return mapper.readValue(objectToString(obj), Map.class);
}
}
3、Person 类
package com.jin.demo.jackson;
import java.io.Serializable;
import java.util.Date;
public class Person implements Serializable {
private int age;
private String name;
private Date birthday;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "Person{" +
"age=" + age +
", name='" + name + '\'' +
", birthday=" + birthday +
'}';
}
}
Jackson-ObjectMapper json字符串、bean、map、list互相转换
1、对象转json字符串
ObjectMapper mapper = new ObjectMapper();
User user = new User();
String userJson = mapper.writeValueAsString(user);2、Map转json字符串
ObjectMapper mapper = new ObjectMapper();
Map map = new HashMap();
String json = mapper.writeValueAsString(map);3、数组list转json字符串
ObjectMapper mapper = new ObjectMapper();
User[] uArr = {user1, user2};
String jsonfromArr = mapper.writeValueAsString(uArr);4、json字符串转对象
ObjectMapper mapper = new ObjectMapper();
String expected = "{\"name\":\"ZhangSan\"}";
User user = mapper.readValue(expected, User.class);5、json字符串转Map
ObjectMapper mapper = new ObjectMapper();
String expected = "{\"name\":\"ZhangSan\"}";
Map userMap = mapper.readValue(expected, Map.class);6、json字符串转对象数组List
ObjectMapper mapper = new ObjectMapper();
String expected = "[{\"name\":\"Zhangsan\"},{\"name\":\"Lisi\"}]";
CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, User.class);
List<User> userList = mapper.readValue(expected, listType);7、json字符串转Map数组List<Map<String,Object>>
ObjectMapper mapper = new ObjectMapper();
String expected = "[{\"name\":\"Zhangsan\"},{\"nameEn\":\"Lisi\"}]";
CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, Map.class);
List<Map<String,Object>> userList = mapper.readValue(expected, listType);8、jackson默认将对象转换为LinkedHashMap
ObjectMapper mapper = new ObjectMapper();
String expected = "[{\"name\":\"Zhangsan\"},{\"nameEn\":\"Lisi\"},{\"name\":\"Test\"}]";
ArrayList arrayList = mapper.readValue(expected, ArrayList.class);9、json字符串转对象设置格式
ObjectMapper mapper = new ObjectMapper();
//设置date转换格式
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
mapper.setDateFormat(fmt);
String expected = "{\"name\":\"ZhangSan\",\"bir\":\"2021-04-15 14:00:00\"}";
User user = mapper.readValue(expected, User.class);10、忽略未知字段
ObjectMapper mapper = new ObjectMapper();
//设置忽略未知字段
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
String expected = "{\"name\":\"ZhangSan\",\"job\":\"teacher\"}";
User user = mapper.readValue(expected, User.class);以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
