JSON数据和Java对象的相互转换
- JSON解析器
- 创建的解析器：Jsonlib，Gson，Fastjson，jackson
JSON转为Java对象
- 使用步骤：
- 导入jackson相关的jar包
- 创建Jackson革新对象 ObjectMapper
- 调用ObjectMapper的相关方法进行转换
- readValue(json字符串，Class)
@Test
public void Test05() throws Exception {
String json = "{\"gender\":\"男\",\"name\":\"张三\",\"age\":19}";
ObjectMapper mapper = new ObjectMapper();
Person person = mapper.readValue(json, Person.class);
System.out.println(person);//Person{name='张三', age=19, gender='男', date=null}
}
Java对象转换JSON
- 使用步骤：
- 导入jackson相关的jar包
- 创建Jackson革新对象 ObjectMapper
- 调用ObjectMapper的相关方法进行转换
package com.ailyt;
import com.ailyt.domain.Person;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;
import java.io.FileWriter;
public class JacksonTest {
//Java对象转为Json字符串
@Test
public void Test01() throws Exception {
//创建Person对象
Person person = new Person();
person.setName("张三");
person.setAge(17);
person.setGender("男");
//创建Jackson的核心对象ObjectMapper
ObjectMapper mapper = new ObjectMapper();
//转换
/**
* 转换方法：
* writerValue(参数1,obj)
* 参数1：
* File：将obj对象转换为json字符串，并保存到指定的文件中
* Writer：将obj对象转换为json字符串，并将json数据填充到字符输出流中
* OutputStream：将obj对象转换为json字符串，并将json数据填充到字节输出流中
* writerValueAsString(obj):将对象转为json字符串
*/
String json = mapper.writeValueAsString(person);
System.out.println(json);//{"name":"张三","age":17,"gender":"男"}
//writeValue 将文件写入到D:\\a.txt
FileWriter fileWriter = new FileWriter("D:\\a.txt");
mapper.writeValue(fileWriter,person);
fileWriter.close();
}
}
- 注解：
- @JsonIgnore：排除属性
- @JsonFormat：属性值得格式化
package com.ailyt.domain;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnore;
import java.util.Date;
public class Person {
private String name;
private int age;
private String gender;
//@JsonIgnore//忽略改属性
@JsonFormat(pattern = "yyyy-MM-dd")//
private Date date;
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
", gender='" + gender + '\'' +
", date=" + date +
'}';
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public Person() {
}
public Person(String name, int age, String gender, Date date) {
this.name = name;
this.age = age;
this.gender = gender;
this.date = date;
}
}
@Test
public void Test02() throws Exception {
//创建Person对象
Person person = new Person();
person.setName("张三");
person.setAge(17);
person.setGender("男");
person.setDate(new Date());
ObjectMapper mapper = new ObjectMapper();
String value = mapper.writeValueAsString(person);
System.out.println(value);//{"name":"张三","age":17,"gender":"男","date":1661051661487}
}
复杂Java对象转换
- List:数组
- Map：对象格式一直
@Test
public void Test03() throws Exception {
//创建Person对象
Person person1 = new Person();
person1.setName("张三");
person1.setAge(17);
person1.setGender("男");
person1.setDate(new Date());
Person person2 = new Person();
person2.setName("李四");
person2.setAge(15);
person2.setGender("女");
person2.setDate(new Date());
Person person3 = new Person();
person3.setName("王五");
person3.setAge(21);
person3.setGender("男");
person3.setDate(new Date());
ArrayList people = new ArrayList<>();
Collections.addAll(people,person1,person2,person3);
ObjectMapper mapper = new ObjectMapper();
String s = mapper.writeValueAsString(people);
System.out.println(s);//[{"name":"张三","age":17,"gender":"男","date":"2022-08-21"},{"name":"李四","age":15,"gender":"女","date":"2022-08-21"},{"name":"王五","age":21,"gender":"男","date":"2022-08-21"}]
}
@Test
public void Test04() throws Exception {
HashMap map = new HashMap<>();
map.put("name","张三");
map.put("age",19);
map.put("gender",'男');
ObjectMapper mapper = new ObjectMapper();
String s = mapper.writeValueAsString(map);
System.out.println(s);//{"gender":"男","name":"张三","age":19}
}
Original: https://www.cnblogs.com/ailhy/p/16609663.html
Author: 我滴妈老弟
Title: JSON数据和Java对象的相互转换
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