What is wrong with this GET request?

Question

So we are working on this app in Android Studio where we want to make a get request to a website, and when we run this piece of code, we keep getting an error of "null" which I believe to be so because one of the variables in this piece of code is null. Can someone look it over and see any places where you may detect some variable is not being used correctly and therefore providing a null error?

public class SpotAlgo {
String vidLink;
int linkLoc;
String testString = "<title>";
String result;

public String gettheResult(String v) throws Exception{
    String sname = " ";
    vidLink = "https://open.spotify.com/track/43PuMrRfbyyuz4QpZ3oAwN";

    URL obj = new URL(vidLink);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    con.setRequestMethod("GET");
    BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
    String inputLine = "";
    StringBuffer response = new StringBuffer();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();

    result = response.toString();


    linkLoc = result.indexOf(testString) + testString.length();
    for (int i = linkLoc; i < result.indexOf("on Spotify"); i++) {
        sname += result.charAt(i) + "";
    }
    return obj.toString();
}

}

So, what happens if the returned text doesn't contain `"on Spotify"`, such as if the URL returns a 404 error? Please, as mentioned above, supply your LogCat so we can see what the error is. — Ken Y-N, Nov 24 '16 at 01:34
The stacktrace is: Failed to set EGL_SWAP_BEHAVIOR on surface 0xa8d63f60, error=EGL_BAD_MATCH — Programmer87, Nov 24 '16 at 02:01
@enzokie are u referring to the website itself that ive provided? When I run it through postman I am getting a proper response — Programmer87, Nov 24 '16 at 02:03
@Enzokie HEAD request returns 200 for me... Anyways, Programmer87, Volley / OkHttp may be better HTTP libraries for your needs. — OneCricketeer, Nov 24 '16 at 02:08
Yeah it is a 200 request for me now, probably I did use a wrong request. — Enzokie, Nov 24 '16 at 02:09
@cricket_007 point taken. But I would rather use this connection toolset now because I feel more familiar with it — Programmer87, Nov 24 '16 at 02:17
@enzokie what do you mean by that? Sorry I am a bit new to android programming — Programmer87, Nov 24 '16 at 02:19
@Programmer87 [Mainfest permission](http://stackoverflow.com/questions/2169294/how-to-add-manifest-permission-to-android-application#2169311). You also need an AsyncTask to even run this code off the UI Thread. — OneCricketeer, Nov 24 '16 at 02:21
And you are parsing HTML? So, look into JSoup. `indexOf("")` does not seem reliable. — OneCricketeer, Nov 24 '16 at 02:24
@cricket_007 Realized that internet permission wasnt there and I added that... Nothing is being returned now instead of just a null statement — Programmer87, Nov 24 '16 at 02:37
Okay... where is null returned? It is `"null"` (a string), `null` (no object), or NullPointerException, an issue with your exception catching? As Nobody pointed out below, the code seems to work with what you provided, so unless you provide the stacktrace and a [mcve], we cannot help anymore — OneCricketeer, Nov 24 '16 at 02:40
@cricket_007 I think it may actually be an issue with the emulator itself. How would I enable the emulator to have internet access on Windows? — Programmer87, Nov 24 '16 at 03:24
Should have access by default. I use Genymotion, though, so not sure — OneCricketeer, Nov 24 '16 at 03:35

Samuel Yvon · Answer 1 · 2016-11-24T02:03:59.620

0

Nothing, it works fine!

I believe that if you have a null pointer exception, it is related to another part of your code.

However, here are some suggestions to improve it

In this snippet you add text to the sname variable in a loop. When you do that kind of operation a StringBuilder will be more efficient.

for (int i = linkLoc; i < result.indexOf("on Spotify"); i++) {
   sname += result.charAt(i) + "";
}
//Could be replaced b
for (int i = linkLoc; i < result.indexOf("on Spotify"); i++) {
    sb.append(result.charAt(i));
}

You can later use sb.toString() to get the result of the operation.

Also, more importantly, when you do network operation you never know what the result will be. There can be many variables that will inpact the result you will get, and often exceptions will be thrown. It is important that you wrap the network code in a try { } finally {}, and that you close the ressources you open in the finally block (a finally block always execute).

edit Fixed a typo

edit 2

Some people are saying it is throwing a 404 exception, I did not get one when I ran it on my machine, and a 404 would throw an IOException when you do con.getInputStream(), so you would likely see that instead

edited Nov 24 '16 at 02:03

answered Nov 24 '16 at 01:37

Samuel Yvon

416
5
13

It was my mistake, its returning 200 now. – Enzokie Nov 24 '16 at 02:11
@Nobody so are you saying that me assembling the string is what is giving the null error? – Programmer87 Nov 24 '16 at 02:18
No, there is no null error in the code you provided. I am just pointing out a more efficient way of assembling it. – Samuel Yvon Nov 24 '16 at 02:19
@enzokie what are you getting for the value of sname then when you run it? – Programmer87 Nov 24 '16 at 02:20
@Programmer87 I am getting the HTML page text. – Enzokie Nov 24 '16 at 02:21
1

I'm getting "Exchange, a song by Bryson Tiller " when I run your code, directly copy-pasted – Samuel Yvon Nov 24 '16 at 02:22
@Nobody really you are getting that? thats so weird. Thats the value we are trying to get, but it keeps coming up as null – Programmer87 Nov 24 '16 at 02:30
@Nobody one thing that should be noted actually, is that when this code is ran in eclipse, it actually works. But when we move it onto android studio, the null error comes up – Programmer87 Nov 24 '16 at 02:30
When you say null error, you mean a crash or it returns null? Because you return obj.toString and not sname, so it might be from that – Samuel Yvon Nov 24 '16 at 02:36
yea that was just for testing purposes. I changed it to sname and its still returning null – Programmer87 Nov 24 '16 at 02:37
Can you post the console message? – Samuel Yvon Nov 24 '16 at 02:38
@Nobody Are you running my code in android studio or eclipse? – Programmer87 Nov 24 '16 at 03:25

score -1 · Answer 2 · answered Nov 24 '16 at 01:18

-1

You missed actually connecting

con.setRequestMethod("GET");
con.connect();

Your con.getInputStream(); is null since the connection is not made and nothing is returned to con.

answered Nov 24 '16 at 01:18

Luminous_Dev

614
6
14

There is no need for you to explicitly call `con.connect()` because it is implicitly invoked the moment you use `getInputStream` or `getOutputStream()`. For more info see this [post](http://stackoverflow.com/questions/16122999/java-urlconnection-when-do-i-need-to-use-the-connect-method). – Enzokie Nov 24 '16 at 01:44
Alright we added con.connect(), but it is still giving a null. It is not displaying where it is coming from either – Programmer87 Nov 24 '16 at 01:54
what sort of header would I add? – Programmer87 Nov 24 '16 at 02:02
@Programmer87 Are you sure that it returns response?. Try putting Log.w("Error Check------", in ); Just before while loop and see the debug if it print out anything – Luminous_Dev Nov 24 '16 at 02:22

What is wrong with this GET request?

2 Answers2