java将list对象转换为json字符串数据显示为空的信息_list转jsonarray,保留空字符串

1、首先是一个main 方法

 public static void main(String[] args){
    List l=new ArrayList();
    ImageInfo a=new ImageInfo("images/gonggao_01.jpg","测试1");
    l.add(a);
    l.add(new ImageInfo("slideImages/1.jpg","测试2"));
    l.add(new ImageInfo("images/gonggao_01.jpg","测试3"));
    l.add(new ImageInfo("slideImages/2.jpg","测试4"));
    l.add(new ImageInfo("images/gonggao_01.jpg","测试5"));
    System.out.println(JSONObject.fromObject(a).toString());
    System.out.println(JSONArray.fromObject(l).toString());
    
    List l2=new ArrayList();
    l2.add("a");l2.add("b");l2.add("c");l2.add("d");
    System.out.println(JSONArray.fromObject(l2).toString());
    System.out.println("-------------------------------");
    try {
     System.out.println(JSONUtil.serialize(l).toString());
    } catch (JSONException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
 }
 

2、 然后是ImageInfo的基本信息类

public class ImageInfo{
 String url;
 String newsTitle;
 public ImageInfo(String url,String newTitle){
  this.url=url;
  this.newsTitle=newsTitle;
 }
 public String getUrl() {
  return url;
 }
 public void setUrl(String url) {
  this.url = url;
 }
 public String getNewsTitle() {
  return newsTitle;
 }
 public void setNewsTitle(String newsTitle) {
  this.newsTitle = newsTitle;
 }
 
}
 

打印的时候出现{},{},{},{},{}类似于这种 只有括号但是没有实际数据的时候，是因为基本信息类里面的属性没有添加getset方法，记录下来免得再犯。

 

顺便转载一下json-lib的使用:

json-lib使用，JSONObject和JSONArray 

（转自：http://blog.csdn.net/yangbobo1992/article/details/8350765）

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

 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}]

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

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 }

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

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         }

自定义封装JSON操作的类

 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 }