1.从Object到String
要先用Object对象构造一个JSONObject或者JSONArray对象，然后调用它的toString()方法即可

（1）示例一

1 Book book=new Book();
2 book.setName("Java");
3 book.setPrice(52.3f);
4 JSONObject object=JSONObject.fromObject(book);
5 System.out.println(object.toString());

（2）示例二
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1 Book book=new Book();
2 book.setName("Java");
3 book.setPrice(52.3f);
4
5 Book book2=new Book();
6 book2.setName("C");
7 book2.setPrice(42.3f);
8 List list=new ArrayList();
9 list.add(book);
10 list.add(book2);
11 JSONArray arry=JSONArray.fromObject(list);
12 System.out.println(arry.toString());
13 //结果如下：
14 [{"name":"Java","price":52.3},{"name":"C","price":42.3}]

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2.从String到Object
要先用String对象构造一个JSONObject或者JSONArray对象
(1)示例一

1 String json="{name:'Java',price:52.3}";
2 JSONObject object=JSONObject.fromObject(json);
3 System.out.println(object.get("name")+" "+object.get("price"));

(2)示例二
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1 String json="[{name:'Java',price:52.3},{name:'C',price:42.3}]";
2 JSONArray array=JSONArray.fromObject(json);
3 for(int i=0;i<array.size();i++){
4 Map o=(Map)array.get(i);
5 System.out.println(o.get("name")+" "+o.get("price"));
6 }

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3.从String到Bean

(1)单个Bean对象

1 String json="{name:'Java',price:52.3}";
2 JSONObject object=JSONObject.fromObject(json);
3 Product product=(Product)JSONObject.toBean(object,Product.class);
4 System.out.println(product.getName()+" "+product.getPrice());

(2).Bean的数组
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1 String json="[{name:'Java',price:52.3},{name:'C',price:42.3}]";
2 JSONArray array=JSONArray.fromObject(json);
3 Product[] products=(Product[]) JSONArray.toArray(array,Product.class);
4 for(Product p:products){
5 System.out.println(p.getName()+" "+p.getPrice());
6 }

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自定义封装JSON操作的类
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1 package com.util;
2
3 import java.util.List;
4 import java.util.Map;
5
6 import net.sf.json.JSONArray;
7 import net.sf.json.JSONObject;
8
9 public class JsonHelper {
10 //从普通的Bean转换为字符串
11 public static String getJson(Object o){
12 JSONObject jo=JSONObject.fromObject(o);
13 return jo.toString();
14 }
15 //从Java的列表转换为字符串
16 public static String getJson(List list){
17 JSONArray ja=JSONArray.fromObject(list);
18 return ja.toString();
19 }
20 //从Java对象数组转换为字符串
21 public static String getJson(Object[] arry){
22 JSONArray ja=JSONArray.fromObject(arry);
23 return ja.toString();
24 }
25 //从json格式的字符串转换为Map对象
26 public static Map getObject(String s){
27 return JSONObject.fromObject(s);
28 }
29 //从json格式的字符串转换为List数组
30 public static List getArray(String s){
31 return JSONArray.fromObject(s);
32 }
33 //从json格式的字符串转换为某个Bean
34 public static Object getObject(String s,Class cls){
35 JSONObject jo=JSONObject.fromObject(s);
36 return JSONObject.toBean(jo, cls);
37 }
38 //从json格式的字符串转换为某类对象的数组
39 public static Object getArray(String s,Class cls){
40 JSONArray ja=JSONArray.fromObject(s);
41 return JSONArray.toArray(ja, cls);
42 }
43 }