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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; } }
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原文地址：http://www.cnblogs.com/zhongzheng123/p/5498780.html
