Parse JSON from HttpURLConnection object

Question

I am doing basic http auth with the HttpURLConnection object in Java.

        URL urlUse = new URL(url);         HttpURLConnection conn = null;         conn = (HttpURLConnection) urlUse.openConnection();         conn.setRequestMethod("GET");         conn.setRequestProperty("Content-length", "0");         conn.setUseCaches(false);         conn.setAllowUserInteraction(false);         conn.setConnectTimeout(timeout);         conn.setReadTimeout(timeout);         conn.connect();          if(conn.getResponseCode()==201 || conn.getResponseCode()==200)         {             success = true;         } 

I am expecting a JSON object, or string data in the format of a valid JSON object, or HTML with simple plain text that is valid JSON. How do I access that from the HttpURLConnection after it returns a response?

Answer 1

You can get raw data using below method. BTW, this pattern is for Java 6. If you are using Java 7 or newer, please consider try-with-resources pattern.

public String getJSON(String url, int timeout) {     HttpURLConnection c = null;     try {         URL u = new URL(url);         c = (HttpURLConnection) u.openConnection();         c.setRequestMethod("GET");         c.setRequestProperty("Content-length", "0");         c.setUseCaches(false);         c.setAllowUserInteraction(false);         c.setConnectTimeout(timeout);         c.setReadTimeout(timeout);         c.connect();         int status = c.getResponseCode();          switch (status) {             case 200:             case 201:                 BufferedReader br = new BufferedReader(new InputStreamReader(c.getInputStream()));                 StringBuilder sb = new StringBuilder();                 String line;                 while ((line = br.readLine()) != null) {                     sb.append(line+"\n");                 }                 br.close();                 return sb.toString();         }      } catch (MalformedURLException ex) {         Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);     } catch (IOException ex) {         Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);     } finally {        if (c != null) {           try {               c.disconnect();           } catch (Exception ex) {              Logger.getLogger(getClass().getName()).log(Level.SEVERE, null, ex);           }        }     }     return null; } 

And then you can use returned string with Google Gson to map JSON to object of specified class, like this:

String data = getJSON("http://localhost/authmanager.php"); AuthMsg msg = new Gson().fromJson(data, AuthMsg.class); System.out.println(msg); 

There is a sample of AuthMsg class:

public class AuthMsg {     private int code;     private String message;      public int getCode() {         return code;     }     public void setCode(int code) {         this.code = code;     }      public String getMessage() {         return message;     }     public void setMessage(String message) {         this.message = message;     } } 

JSON returned by http://localhost/authmanager.php must look like this:

{"code":1,"message":"Logged in"} 

Regards

Answer 2

Define the following function (not mine, not sure where I found it long ago):

private static String convertStreamToString(InputStream is) {  BufferedReader reader = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder();  String line = null; try {     while ((line = reader.readLine()) != null) {         sb.append(line + "\n");     } } catch (IOException e) {     e.printStackTrace(); } finally {     try {         is.close();     } catch (IOException e) {         e.printStackTrace();     } } return sb.toString(); 

}

Then:

String jsonReply; if(conn.getResponseCode()==201 || conn.getResponseCode()==200)     {         success = true;         InputStream response = conn.getInputStream();         jsonReply = convertStreamToString(response);          // Do JSON handling here....     }