How to search for a person in a datbase using an API

I am writing a HTTP-based RESTful API SMP and I need to write an API that looks up a users with the same handle as the input and returns all the user information, so the entire row. But right now it is not returning anything. I cannot find the problem, any suggestions on what it might be? Thank you for any help!

/api/seeuser        // find a user and give information
// Input: curl -d '{"handle":"@cooldude42", "password":"mysecret!"}' -H "Content-Type: application/json" -X POST http://localhost:9990/api/seeuser/2 (Links to an external site.)
// 2 = Identity.idnum
// Output: {"status":"1", "handle":"@carlos", "fullname":"Carlos Mize", "location":"Kentucky", "email":carlos@notgmail.com", "bdate":"1970-01-26","joined":"2020-04-01"}
// Output: {}. // no match found, could be blocked, user doesn't know. [EDIT: 04/14]
// etc.

API.java

   @GET
   @Path("/seeuser/{idnum}")
   @Produces(MediaType.APPLICATION_JSON)
   public Response seeuser(@PathParam("idnum") String idnum) {
       String responseString = "{\"status_code\":0}";
       StringBuilder crunchifyBuilder = new StringBuilder();
       try {
           String jsonString = crunchifyBuilder.toString();
           Map<String, String> myMap = gson.fromJson(jsonString, mapType);
           String handle = myMap.get("handle");
           Map<String,String> teamMap = Launcher.dbEngine.seeuser(idnum, handle);
           responseString = Launcher.gson.toJson(teamMap);
       } catch (Exception ex) {
           StringWriter sw = new StringWriter();
           ex.printStackTrace(new PrintWriter(sw));
           String exceptionAsString = sw.toString();
           ex.printStackTrace();
           return Response.status(500).entity(exceptionAsString).build();
       }
       return Response.ok(responseString)
               .header("Access-Control-Allow-Origin", "*").build();
   }

DBEngine.java

public Map<String,String> seeuser(String idnum, String handle) {
       Map<String,String> userIdMap = new HashMap<>();

       PreparedStatement stmt = null;
      Integer id = Integer.parseInt(idnum);
       try
       {
           Connection conn = ds.getConnection();
           String queryString = null;
           queryString = "SELECT * FROM Identity WHERE handle = ?";
          stmt = conn.prepareStatement(queryString);
          stmt.setInt(1,id);

           ResultSet rs = stmt.executeQuery();
           while (rs.next()) {
               handle = rs.getString("handle");
               String pass = rs.getString("pass");
               String fullname = rs.getString("fullname");
               String location = rs.getString("location");
               String email = rs.getString("email");
               String bdate = rs.getString("bdate");
               userIdMap.put("handle", handle);
               userIdMap.put("pass", pass);
               userIdMap.put("fullname", fullname);
               userIdMap.put("location", location);
               userIdMap.put("email", email);
               userIdMap.put("bdate", bdate);
           }
           rs.close();
           stmt.close();
           conn.close();
       }
       catch(Exception ex)
       {
           ex.printStackTrace();
       }
       return userIdMap;
   }

I am assuming the handle is being passed as null or empty to the method Launcher.dbEngine.seeuser(idnum, handle).

The variable 'crunchifyBuilder' started as a new StringBuilder() which would be empty. Then the code follows as below

String jsonString = crunchifyBuilder.toString();
Map<String, String> myMap = gson.fromJson(jsonString, mapType);
String handle = myMap.get("handle");

I'm not sure the above code would set the handle to any value, unless I am missing something?