I think I've found the reason, there's something odd happening when the Client is reproducing the Header as a String... odd tokens are pushed in to the mix that makes the string un-parseable. The cheapest way around this right now is avoid using the Processing Client, and use straight Java.
One possibility is the way new data is read from the stream, the entire header isn't guaranteed to be delivered in one piece in the current implementation.

1. import org.json.*;
2. import java.net.URL;
3. import java.net.URLConnection;
4. void setup() {
5.   try {
6.     URL url = new URL("http://www.processing.org");
7.     URLConnection conn = url.openConnection();
8.     StringBuffer sb = new StringBuffer();
9.     for (int i = 0;; i++) {
10.       String name = conn.getHeaderFieldKey(i);
11.       String value = conn.getHeaderField(i);
12.       if (name == null && value == null) {
13.         break;
14.       }
15.       if (name == null) {
16.         sb.append(value).append("\n");
17.       }
18.       else {
19.         sb.append(name).append(":").append(value).append("\n");
20.       }
21.     }
22.     HTTP http = new HTTP();
23.     JSONObject obj = http.toJSONObject(sb.toString());
24.     System.out.println(obj);
25.   }
26.   catch (Exception e) {
27.   }
28. }
29. void draw() {
30. }

Hi a__g,

Thanks for your reply. I've tried your code and it works. But when I try to use it with my URL it doesn't:

URL url = new URL("http://api.sense-os.nl/login?username=name&password=12345");
(The rest of the code is the same as the above, pw and username are fake, of course.) I get the following result:

{"Reason-Phrase":"Method Not Allowed","Status-Code":"405","Access-Control-Allow-Methods":"POST, GET, PUT, OPTIONS, DELETE","Connection":"keep-alive","Access-Control-Allow-Credentials":"true","Server":"nginx/1.0.8","X-Powered-By":"PHP/5.3.10-1~dotdeb.1","Access-Control-Allow-Headers":"X-SESSION_ID, Content-Type","Date":"Sun, 01 Apr 2012 13:57:38 GMT","Transfer-Encoding":"chunked","Access-Control-Allow-Origin":"*","HTTP-Version":"HTTP/1.1","Content-Type":"text/html"}

So I should somehow use POST in my url, is that possible using url.openConnection?

My original code for using a client was as follows:

1. import processing.net.*;
   Client c;
   String dataIn;
   String[] headerData;
   
   void setup(){
     size(200, 200);
     c = new Client(this, "api.sense-os.nl", 80); // Connect to api.sense-os.nl
     c.write("POST /login?username=name&password=12345 HTTP/1.1\n");
     c.write("Host: api.sense-os.nl\n"); // the host to connect to
     c.write("Accept: */*\n\n"); // accept all kinds of output and close the header
   }
   
   void draw() {
     if (c.available() > 0) {
       dataIn = c.readString();
       println(dataIn);
       headerData = split(dataIn, '\n');
       for(int i=0; i<headerData.length; i++){
         print(i);
         print(": ");
         println(headerData[i]);
       }
     }
   }
   

This returns this result:
0: HTTP/1.1 200 OK

1: Server: nginx/1.0.8

2: Date: Sun, 01 Apr 2012 14:27:04 GMT

3: Content-Type: application/json

4: Transfer-Encoding: chunked

5: Connection: keep-alive

6: X-Powered-By: PHP/5.3.10-1~dotdeb.1

7: Access-Control-Allow-Credentials: true

8: Access-Control-Allow-Methods: POST, GET, PUT, OPTIONS, DELETE

9: X-SESSION_ID: 12345

10: Access-Control-Expose-Headers: X-SESSION_ID

11: Access-Control-Allow-Origin: *

12: Access-Control-Allow-Headers: X-SESSION_ID, Content-Type

13: Access-Control-Max-Age: 1728000

14: Set-Cookie: session_id=12345

15:

16: 2c

17: {"session_id":"12345"}

18: 0

19:

20:

But if I try to make the whole header into a JSON object like this:

1. void draw() {
     if (c.available() > 0) {
       dataIn = c.readString();
       println(dataIn);
       JSONObject header = new JSONObject(dataIn.toString());
     }
   }
   

I get all kinds of errors like this one:
A JSONObject text must begin with '{'
JSON Error: Expected a ':' after a key

If I understand your code correctly you make your own JSON string and you do that in setup? I thought the whole idea of using the JSON library was to let it make it's own name value pairs from the header... But maybe I'm missing something?

Thanks in advance for your help, best, d

Try this one.

You're partially correct, what I had to do (there's probably a better way around it...) is make sure the format was parse'able. I didn't research it in depth, but if you can find a prettier solution that would be great.

1. import org.json.*;
2. import java.net.URL;
3. import java.net.URLConnection;
4. 
   
5. URL url;
6. URLConnection conn;
7. 
   
8. void setup() {
9.   // Unfortunately there's a problem in the Processing Client implementation
10.   // that forces us to use straight Java.
11.   try {
12.     url = new URL("http://api.sense-os.nl/login");
13.     conn = url.openConnection();
14.     conn.setDoOutput(true);
15.   }
16.   catch( Exception e) {
17.   }
18.   try {
19.     // Add the POST params.
20.     String data = URLEncoder.encode("name", "UTF-8") + "=" + URLEncoder.encode("username", "UTF-8");
21.     data += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode("password", "UTF-8");
22.     OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
23.     wr.write(data);
24.     wr.flush();
25.   }
26.   catch(Exception e) {
27.     println( e.getMessage() );
28.   }
29.   // We will manually add the entire HTTP reponse to this StringBuffer
30.   // and create the JSONObject using it.
31.   StringBuffer sb = new StringBuffer();
32.   // Construct the String object using the URLConnection.
33.   for (int i = 0;; i++) {
34.     String name = conn.getHeaderFieldKey(i);
35.     String value = conn.getHeaderField(i);
36.     if (name == null && value == null) {
37.       break;
38.     }
39.     if (name == null) {
40.       // Add the value, if there is no key-value pair.
41.       sb.append(value).append("\n");
42.     }
43.     else {
44.       // Add the key-value pair.
45.       sb.append(name).append(":").append(value).append("\n");
46.     }
47.   }
48.   // Create the JSON HTTP instance
49.   HTTP http = new HTTP();
50.   // Create the JSONObject using the HTTP instance
51.   JSONObject obj = http.toJSONObject(sb.toString());
52.   // Print the JSONObject
53.   System.out.println(obj);
54. }
55. 
    
56. void draw() {
57. }

Hi a__g,

Thanks for the quick response and you code. It works fine, except that I had to catch the errors on the JSONObject creation. I can now finally read out the session_id using obj.get("X-SESSION_ID"); I have a few remarks:

1. What I find puzzling is that the actual JSON string at the bottom of the header has disappeared from the header you've build...
2. Isn't there an easy way to just use only the JSON string from the header, line 17: {"session_id":"12345"} in my previous post.
3. And lastly, for my application I will need a client as I will be sending and reading data every 500 milliseconds...

So I'm not quite there with this problem. Any further help would be greatly appreciated, best, danielle.

Hi a__g,

I've asked the developers of the api and they came up with this code:

1. import org.json.*;
   import java.net.URL;
   import java.net.URLConnection;
   
   URL url;
   URLConnection conn;
   InputStream input;
   String sessionId;
   
   void setup() {
     // Unfortunately there's a problem in the Processing Client implementation
     // that forces us to use straight Java.
     try {
       url = new URL("http://api.sense-os.nl/login");
       conn = url.openConnection();
       conn.setDoOutput(true);
     }
     catch( Exception e) {
     }
     try {
       // Add the POST params.
       String data = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode("name", "UTF-8");
       data += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode("12345", "UTF-8");
       OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
       wr.write(data);
       wr.flush();
     }
     catch(Exception e) {
       println( e.getMessage() );
     }
     try{
       input = conn.getInputStream();
       String inputString = "";
       while(input.available() != 0) {
         inputString += (char)input.read();
       }
       println(inputString); // this prints the session_id JSON string
       JSONObject obj = new JSONObject(inputString);
       sessionId = obj.getString("session_id"); // this works!
     }
     catch(Exception e){
       println(e);
     }
   }
   
   void draw() {
   }

Apparently the string I needed for the JSON object is in the body and not in the header. So you should use conn.getInputStream(); instead of conn.getHeaderField();

HTH, best, danielle.

Excellent.