java对象与json对象间的相互转换的方法

String json=JSON.toJSONString(user);//关键

1.简单的解析json字符串

首先将json字符串转换为json对象，然后再解析json对象，过程如下。

JSONObject jsonObject = JSONObject.fromObject(jsonStr);

根据json中的键得到它的值

String name = jsonObject.getString("name");
int num = jsonObject.getInt("num");
String sex = jsonObject.getString("sex");
int age = jsonObject.getInt("age");

2.将json字符串转换为java对象

同样先将json字符串转换为json对象，再将json对象转换为java对象，如下所示。

JSONObject obj = new JSONObject().fromObject(jsonStr);
//将json字符串转换为json对象

将json对象转换为java对象

Person jb = (Person)JSONObject.toBean(obj,Person.class);
//将建json对象转换为Person对象

3.将java对象转换为json字符串

先将java对象转换为json对象，在将json对象转换为json字符串

JSONObject json = JSONObject.fromObject(obj);
 
//将java对象转换为json对象
String str = json.toString();//将json对象转换为字符串

完整代码如下：

package baz.parse; 
 
import java.util.ArrayList; 
import java.util.List; 
 
import net.sf.json.JSON; 
import net.sf.json.JSONArray; 
import net.sf.json.JSONObject; 
import net.sf.json.JSONSerializer; 
import baz.bean.Person; 
 
public class ParseJson { 
 
private String jsonStr; 
 
public ParseJson() { 
 
} 
 
public ParseJson(String str){ 
this.jsonStr = str; 
} 
/** 
* 解析json字符串 
*/
public void parse(){ 
JSONObject jsonObject = JSONObject.fromObject(jsonStr); 
String name = jsonObject.getString("name"); 
int num = jsonObject.getInt("num"); 
String sex = jsonObject.getString("sex"); 
int age = jsonObject.getInt("age"); 
 
System.out.println(name + " " + num + " " + sex + " " + age); 
} 
//将json字符串转换为java对象 
public Person JSON2Object(){ 
//接收{}对象，此处接收数组对象会有异常 
if(jsonStr.indexOf("[") != -1){ 
jsonStr = jsonStr.replace("[", ""); 
} 
if(jsonStr.indexOf("]") != -1){ 
jsonStr = jsonStr.replace("]", ""); 
} 
JSONObject obj = new JSONObject().fromObject(jsonStr);//将json字符串转换为json对象 
Person jb = (Person)JSONObject.toBean(obj,Person.class);//将建json对象转换为Person对象 
return jb;//返回一个Person对象 
} 
 
 
} 

package baz.bean; 
 
public class Person { 
 
private String name; 
private int num; 
private String sex; 
private int age; 
 
public Person() { 
// TODO Auto-generated constructor stub 
} 
 
public Person(String name, int num, String sex, int age) { 
super(); 
this.name = name; 
this.num = num; 
this.sex = sex; 
this.age = age; 
} 
 
 
 
public String getName() { 
return name; 
} 
 
public void setName(String name) { 
this.name = name; 
} 
 
public int getNum() { 
return num; 
} 
 
public void setNum(int num) { 
this.num = num; 
} 
 
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; 
} 
 
} package baz.parse; 
 
import java.util.ArrayList; 
import java.util.List; 
 
import net.sf.json.JSON; 
import net.sf.json.JSONArray; 
import net.sf.json.JSONObject; 
import net.sf.json.JSONSerializer; 
import baz.bean.Person; 
 
public class ParseJson { 
 
private String jsonStr; 
 
public ParseJson() { 
 
} 
 
public ParseJson(String str){ 
this.jsonStr = str; 
} 
/** 
* 解析json字符串 
*/
public void parse(){ 
JSONObject jsonObject = JSONObject.fromObject(jsonStr); 
String name = jsonObject.getString("name"); 
int num = jsonObject.getInt("num"); 
String sex = jsonObject.getString("sex"); 
int age = jsonObject.getInt("age"); 
 
System.out.println(name + " " + num + " " + sex + " " + age); 
} 
//将json字符串转换为java对象 
public Person JSON2Object(){ 
//接收{}对象，此处接收数组对象会有异常 
if(jsonStr.indexOf("[") != -1){ 
jsonStr = jsonStr.replace("[", ""); 
} 
if(jsonStr.indexOf("]") != -1){ 
jsonStr = jsonStr.replace("]", ""); 
} 
JSONObject obj = new JSONObject().fromObject(jsonStr);//将json字符串转换为json对象 
Person jb = (Person)JSONObject.toBean(obj,Person.class);//将建json对象转换为Person对象 
return jb;//返回一个Person对象 
} 
 
 
} 

将java对象转换为json字符串

package baz.cons; 
import net.sf.json.JSONObject; 
/** 
* 将java对象转换为json字符串 
* @author Administrator 
* 
*/
public class ConsJson { 
 
public ConsJson() { 
// TODO Auto-generated constructor stub 
} 
 
public String Object2Json(Object obj){ 
JSONObject json = JSONObject.fromObject(obj);//将java对象转换为json对象 
String str = json.toString();//将json对象转换为字符串 
 
return str; 
} 
} 

测试类：

package baz.test; 
 
import java.util.List; 
 
import baz.bean.Person; 
import baz.cons.ConsJson; 
import baz.parse.ParseJson; 
 
 
public class Test { 
public static void main(String[] args) { 
 
//将字符串转换为json对象，然后根据建得到相应的值 
ParseJson pj = new ParseJson("{\"name\":\"gu\",\"num\":123456,\"sex\":\"male\",\"age\":24}"); 
pj.parse(); 
 
//将一个json字符串转换为java对象 
Person p = pj.JSON2Object(); 
System.out.println("Name:" + p.getName()); 
System.out.println("Num:" + p.getNum()); 
System.out.println("Sex:" + p.getSex()); 
System.out.println("age:" + p.getAge()); 
 
//将一个java对象转换为Json字符串 
Person p1 = new Person("gu1",123,"male",23); 
ConsJson cj = new ConsJson(); 
String str1 = cj.Object2Json(p1); 
System.out.println(str1); 
 
} 
 
} 

测试输出如下：

gu 123456 male 24
Name:gu
Num:123456
Sex:male
age:24

{"age":23,"name":"gu1","num":123,"sex":"male"}