如何将 Java 对象转换为 JSON？_allway2_java object转json

网络投稿 02-07 3124

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StudentPOJO 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：

使用 setter 方法创建Student对象并设置其属性。创建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。调用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 List<String> courses; public Student(Long id, String name, int age, List<String> courses) { 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 List<String> getCourses() { return courses; } public void setCourses(List<String> courses) { this.courses = courses; } }

Maven 依赖项

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://·/artifact/org.json/json --> <dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20211205</version> </dependency>  <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.9.0</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.12.1</version> </dependency> </dependencies> </project>