//construct json and output it

public String jsonTest() throws JSONException{

    JSONObject json=new JSONObject();

    JSONArray jsonMembers = new JSONArray();

    JSONObject member1 = new JSONObject();

    member1.put("loginname", "zhangfan");

    member1.put("password", "userpass");

    member1.put("email","10371443@qq.com");

    member1.put("sign_date", "2007-06-12");

    jsonMembers.put(member1);  

    JSONObject member2 = new JSONObject();

    member2.put("loginname", "zf");

    member2.put("password", "userpass");

    member2.put("email","8223939@qq.com");

    member2.put("sign_date", "2008-07-16");

    jsonMembers.put(member2);

    json.put("users", jsonMembers);  

    return json.toString();

}

//construct json from String and resolve it.

public String jsonTest2() throws JSONException{

    String jsonString="{\"users\":[{\"loginname\":\"zhangfan\",\"password\":\"userpass\",\"email\":\"10371443@qq.com\"},{\"loginname\":\"zf\",\"password\":\"userpass\",\"email\":\"822393@qq.com\"}]}";

    JSONObject json= new JSONObject(jsonString);

    JSONArray jsonArray=json.getJSONArray("users");

    String loginNames="loginname list:";

    for(int i=0;i<jsonArray.length();i++){

        JSONObject user=(JSONObject) jsonArray.get(i);

        String userName=(String) user.get("loginname");

        if(i==jsonArray.length()-1){

            loginNames+=userName;

        }else{

            loginNames+=userName+",";

        }

    }

    return loginNames;

}