在json转换成对象时，json的key会与java 类的字段一一对应。如果没有映射上的java字段会在该数据类型上填充默认值，如int 0，String null 等。
没有映射的json key在程序结束后会用警告显示出来，告知程序员那个key值没有被映射上
import net.sf.json.JSONObject;
public class MainClass {
public static void main(String[] args) {
TestJsonBean();
}
/**
* java对象与json对象互相转换
*/
private static void TestJsonBean() {
/**
* 创建java对象
*/
Student student = new Student();
student.setId(1);
student.setName("jag");
student.setSex("man");
student.setAge(25);
student.setHobby(new String[]{"篮球","上网","跑步","游戏"});
/**
* java对象转换成json对象，并获取json对象属性
*/
JSONObject jsonStu = JSONObject.fromObject(student);
System.out.println(jsonStu.toString());
System.out.println(jsonStu.getJSONArray("hobby"));
/**
* json对象转换成java对象，并获取java对象属性
*/
Student stu = (Student) JSONObject.toBean(jsonStu, Student.class);
System.out.println(stu.getName());
/**
* 创建json对象
*/
JSONObject jsonObj = new JSONObject();
jsonObj.put("id",1);
jsonObj.put("name","张勇");
jsonObj.put("sex","男");
//jsonObj.put("age",24);
//jsonObj.put("hobby",new String[]{"上网","游戏","跑步","音乐"});
//System.out.println(jsonObj.toString());
/**
* json对象转换成java对象
*/
Student stud = (Student) JSONObject.toBean(jsonObj,Student.class);
System.out.println(stud.getAge());
}
}
运行结果
{"age":25,"hobby":["篮球","上网","跑步","游戏"],"id":1,"name":"jag","sex":"man"}
["篮球","上网","跑步","游戏"]
jag
0
改一下代码
JSONObject jsonObj = new JSONObject();
jsonObj.put("id",1);
jsonObj.put("name","张勇");
jsonObj.put("old","男");//这个是类没有的元素
结果;
{"age":25,"hobby":["篮球","上网","跑步","游戏"],"id":1,"name":"jag","sex":"man"}
["篮球","上网","跑步","游戏"]
jag
0
五月 16, 2016 5:18:22 下午 net.sf.json.JSONObject toBean
警告: Tried to assign property old:java.lang.String to bean of class Student
student 类
import java.io.Serializable;
public class Student implements Serializable {
private long id;
private String name;
private String sex;
private int age;
private String[] hobby;
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 String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String[] getHobby() {
return hobby;
}
public void setHobby(String[] hobby) {
this.hobby = hobby;
}
}