convert List to json

Question

i use json-lib to convert a java Object to json string,now i define a

List<CustomObject> list=...

i want to convert it to json string,but i got

[{},{},{}]

the CustomObject is defined as:

 class CustomObject{
     int id;
     int num;
 }

is there any way to get a correct string like:

[{'id':1,'num:3'},{'id':2,'num:4'}]

if i use struts2 to do it,it works.but i don`t know how it works,must i use struts2?

Are you using any libraries or something? Because for me with the Gson library, new Gson().toJson(list) works. — Toon Borgers, Mar 04 '15 at 07:56
@ToonBorgers one of the jars is:json-lib-2.2.2-jdk15.jar, my code is :JSONArray.fromObject( list ); — eascape, Mar 04 '15 at 08:16
@ToonBorgers i use Gson library instead of json-lib,it works.thanks — eascape, Mar 04 '15 at 08:31
@ immibis one of the jars is:json-lib-2.2.2-jdk15.jar, my code is :JSONArray.fromObject( list ); the library may call "json-lib" — eascape, Mar 04 '15 at 08:35
some of serializators dont work with fields themselves, they require getters — ametiste, Mar 04 '15 at 08:56

score 0 · Accepted Answer · answered Mar 04 '15 at 09:07

Your class should be somewhat like this:

      public class CustomObject{
     int id;
     int num;


     public int getId() {
        return id;
    }


    public void setId(int id) {
        this.id = id;
    }


    public int getNum() {
        return num;
    }


    public void setNum(int num) {
        this.num = num;
    }


    public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
        List<CustomObject> list=new ArrayList<CustomObject>();
        CustomObject c=new CustomObject();
        c.id=1;
        c.num=1;
        list.add(c);
        System.out.println(new ObjectMapper().writeValueAsString(list)); 
    }
 }

You need to have getters and setters if you want to serialize or deserialize any object. Use jackson to covert to JSON.

convert List to json

1 Answers1