Java中使用simle json解析器进行JSON解析错误

Question

Let I have a string, json string.

{"cond":{"to_email":"b@b.c"},"ret":"all"}

Now I want to parse it using json simple parser in java.

I am giving the code...

try{
            //String s=request.getParameter("data");
            String s="{\"cond\":{\"to_email\":\"b@b.c\"},\"ret\":\"all\"}";
            JSONParser jsp=new JSONParser();

            if(s == null || s.equals("")){
                //problem
                String json="{\"error\":\"error\",\"message\":\"no json data\"}";
                response.getWriter().println(json);
            }else{              
                JSONObject obj=(JSONObject) jsp.parse(s);   //only object is allowed

                JSONObject condObj=(JSONObject) jsp.parse(""+obj.get("cond"));
                JSONObject returnObj=(JSONObject) jsp.parse(""+obj.get("ret")); 

                System.out.println(condObj);                    
            }

Now the problem is that it's giving error...

Unexpected character (a) at position 0.

But if I remove the "ret" : "all" then it's working well.

Here in the example I printed condObj only but if I print retObj then it's giving null. So, the problem is the the "ret" : "all" part...

But it's a correct json. I checked it. How to get out of this problem??

Answer 1

The thing is very simple! The key "cond" represents an complex JSONObject but the key "ret" just a String. So the parsing fails in this case. I dont know which JSON-libary you are using, but have a look for an JSONObject#getString(String key) method to get the value.

Good luck

UPDATE (with the JSON lib I use)

        try{
        //String s=request.getParameter("data");
        String s="{\"cond\":{\"to_email\":\"b@b.c\"},\"ret\":\"all\"}";

        if(s == null || s.equals("")){
            //problem
            String json="{\"error\":\"error\",\"message\":\"no json data\"}";
        }else{              
            JSONObject obj= new JSONObject(s);

            JSONObject condObj=(JSONObject) obj.getJSONObject("cond");
            String returnObj= obj.getString("ret"); 

            System.out.println(condObj);    
            System.out.println(returnObj);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    }

Answer 2

Just following the above answer ,here is a simple parser.

import java.util.Set;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;


public class ParseJson {

    public static void main(String[] args) throws Exception {
        String s = "{\"cond\":{\"to_email\":\"b@b.c\"},\"ret\":\"all\"}";
        JSONParser jsp = new JSONParser();
        if (s == null || s.equals("")) {
            String json = "{\"error\":\"error\",\"message\":\"no json data\"}";
        } else {
            JSONObject obj = (JSONObject) jsp.parse(s); 
            JSONObject condObj = (JSONObject) jsp.parse("" + obj.get("cond"));
            Set<String> keys = obj.keySet();

            for (String key : keys) {
                System.out.println("Key : " + key);
                System.out.print("Value : " +obj.get(key));
                System.out.println();
            }
        }
    }
}

This prints both the key and value pairs for you. We can add conditionals for specific keys. Key : ret Value : all Key : cond Value : {"to_email":"b@bc"}