How is it possible (if at all) to get the HTTP status code from a java.io.IOException in java
?
I'm assuming this is about an IOException thrown by a URLConnection.
Three possibilities to handle this, depending on your restrictions.
1) Cast your URLConnection to a HttpURLConnection and call getResponseCode
If you have access to the connection object, you can get the status code using this code:
int statusCode = (HttpURLConnection)theConnection).getResponseCode();
2) Use a HttpURLConnection instead of an URLConnection in the first place
If you can do this, it would be the best solution, because an URLConnection doesn't throw on error status codes. You can just call getResponseCode and check the status without getting any exception first.
3) Parse the exception message itself
The IOException's message usually looks like this:
Server returned HTTP response code: 403 for URL: http://something
So you can just use a regex (or simple string manipulation) to get the response code out of there.
Note that for status 404, the message doesn't look like this and a FileNotFoundException is thrown. I'm not sure if there are any other status codes throwing "special" exceptions like this, but watch out for this.
Example code demonstrating methods 2 & 3:
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
public class HelloWorld {
public static void testUrl(String urlString) throws MalformedURLException {
URLConnection conn = null;
System.out.println("Testing URL " + urlString);
try {
URL url = new URL(urlString);
conn = url.openConnection();
// Just to make the exception happen
conn.getInputStream();
System.out.println("Success!");
} catch(IOException ex) {
System.out.println("Error!");
System.out.println();
// Method 2 with access to the URLConnection object
// (Method 1 would have been having the connection as HttpURLConnection from the beginning.)
int responseCode = 0;
System.out.println("Trying method 2 to get status code");
try {
if(conn != null) {
// Casting to HttpURLConnection allows calling getResponseCode
responseCode = ((HttpURLConnection)conn).getResponseCode();
} else {
System.out.println("conn variable not set");
}
} catch(IOException ex2) {
System.out.println("getResponseCode threw: " + ex2);
}
System.out.println("Status code from calling getResponseCode: " + responseCode);
System.out.println();
// Method 3 without access to the URLConnection object
responseCode = 0;
System.out.println("Trying method 3 to get status code");
// First we try parsing the exception message to see if it contains the response code
Matcher exMsgStatusCodeMatcher = Pattern.compile("^Server returned HTTP response code: (\\d+)").matcher(ex.getMessage());
if(exMsgStatusCodeMatcher.find()) {
responseCode = Integer.parseInt(exMsgStatusCodeMatcher.group(1));
} else if(ex.getClass().getSimpleName().equals("FileNotFoundException")) {
// 404 is a special case because it will throw a FileNotFoundException instead of having "404" in the message
System.out.println("Got a FileNotFoundException");
responseCode = 404;
} else {
// There can be other types of exceptions not handled here
System.out.println("Exception (" + ex.getClass().getSimpleName() + ") doesn't contain status code: " + ex);
}
System.out.println("Status code from parsing exception message: " + responseCode);
System.out.println();
}
System.out.println("-------");
System.out.println();
}
public static void main(String []args) throws MalformedURLException {
testUrl("https://httpbin.org/status/200");
testUrl("https://httpbin.org/status/404");
testUrl("https://httpbin.org/status/403");
testUrl("http://nonexistingsite1111111.com");
}
}
Output of the example code:
Testing URL https://httpbin.org/status/200
Success!
-------
Testing URL https://httpbin.org/status/404
Error!
Trying method 2 to get status code
Status code from calling getResponseCode: 404
Trying method 3 to get status code
Got a FileNotFoundException
Status code from parsing exception message: 404
-------
Testing URL https://httpbin.org/status/403
Error!
Trying method 2 to get status code
Status code from calling getResponseCode: 403
Trying method 3 to get status code
Status code from parsing exception message: 403
-------
Testing URL http://nonexistingsite1111111.com
Error!
Trying method 2 to get status code
getResponseCode threw: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from calling getResponseCode: 0
Trying method 3 to get status code
Exception (UnknownHostException) doesn't contain status code: java.net.UnknownHostException: nonexistingsite1111111.com
Status code from parsing exception message: 0
-------