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要将 Java 对象或 POJO (普通旧 Java 对象)转换为 JSON,我们可以使用JSONObject
将对象作为参数的构造函数之一。在下面的示例中,我们将Student
POJO 转换为 JSON 字符串。Student
类必须提供 getter 方法,JSONObject
通过调用这些方法创建 JSON 字符串。
在此代码段中,我们执行以下操作:
Student
对象并设置其属性。JSONObject
调用object
并将Student
对象用作其构造函数的参数。JSONObject
使用 getter 方法生成 JSON 字符串。object.toString()
方法获取 JSON 字符串。import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.gson.Gson;
import org.json.JSONObject;
import java.util.Arrays;
public class PojoToJSON {
public static void main(String[] args) throws JsonProcessingException {
Student student = new Student();
student.setId(1L);
student.setName("Alice");
student.setAge(20);
student.setCourses(Arrays.asList("Engineering", "Finance", "Chemistry"));
JSONObject object = new JSONObject(student);
String json = object.toString();
System.out.println(json);
System.out.println(new Gson().toJson(student));
// Creating Object of ObjectMapper define in Jackson API
ObjectMapper Obj = new ObjectMapper();
// Converting the Java object into a JSON string
String jsonStr = Obj.writeValueAsString(student);
// Displaying Java object into a JSON string
System.out.println(jsonStr);
}
}
运行此代码会产生以下结果:
{"courses":["Engineering","Finance","Chemistry"],"name":"Alice","id":1,"age":20}
{"id":1,"name":"Alice","age":20,"courses":["Engineering","Finance","Chemistry"]}
{"id":1,"name":"Alice","age":20,"courses":["Engineering","Finance","Chemistry"]}
上面代码中使用的Student
类:
import java.util.List;
public class Student {
private Long id;
private String name;
private int age;
private Listcourses;
public Student(Long id, String name, int age, Listcourses) {
this.id = id;
this.name = name;
this.age = age;
this.courses = courses;
}
Student() {
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
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 ListgetCourses() {
return courses;
}
public void setCourses(Listcourses) {
this.courses = courses;
}
}
Maven 依赖项
4.0.0 com.example.javaobjectjson JavaObjectJSON1.0-SNAPSHOT org.json json20211205 com.google.code.gson gson2.9.0 com.fasterxml.jackson.core jackson-databind2.12.1
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