Using HTTP Basic-Auth with Google App Engine URLFetch service

Question

How can I specify the username and password for making Basic-Auth requests with App Engine's URLFetch service (in Java)?

It seems I can set HTTP headers:

URL url = new URL("http://www.example.com/comment");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("X-MyApp-Version", "2.7.3");        

What are the appropriate headers for Basic-Auth?

Answer 1

This is a basic auth header over http:

Authorization: Basic base64 encoded(username:password)

eg:

GET /private/index.html HTTP/1.0
Host: myhost.com
Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

You will need to do this:

URL url = new URL("http://www.example.com/comment");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("Authorization",
"Basic "+codec.encodeBase64String(("username:password").getBytes());

And to do that you will want to get a base64 codec api, like the Apache Commons Codec

Answer 2

For those interested in doing this in Python (as I was), the code looks like this:

result = urlfetch.fetch("http://www.example.com/comment",
                        headers={"Authorization": 
                                 "Basic %s" % base64.b64encode("username:pass")})

Answer 3

You set up an Authenticator before you call openConnection() like this,

Authenticator.setDefault(new Authenticator() {
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(username, password.toCharArray());
    }
});

Since there is only one global default authenticator, this doesn't really work well when you have multiple users doing the URLFetch in multiple threads. I would use Apache HttpClient if that's the case.

EDIT: I was wrong. App Engine doesn't allow Authenticator. Even if it's allowed, we would have the multi-thread issue with a global authenticator instance. Even though you can't create threads, your requests may still get served in different threads. So we just add the header manually using this function,

import com.google.appengine.repackaged.com.google.common.util.Base64;
    /**
     * Preemptively set the Authorization header to use Basic Auth.
     * @param connection The HTTP connection
     * @param username Username
     * @param password Password
     */
    public static void setBasicAuth(HttpURLConnection connection,
            String username, String password) {
        StringBuilder buf = new StringBuilder(username);
        buf.append(':');
        buf.append(password);
        byte[] bytes = null;
        try {
            bytes = buf.toString().getBytes("ISO-8859-1");
        } catch (java.io.UnsupportedEncodingException uee) {
            assert false;
        }

        String header = "Basic " + Base64.encode(bytes);
        connection.setRequestProperty("Authorization", header);
    }

Answer 4

Using HttpURLConnection gave me some problems (for some reason the server I was trying to connect to didn't accept auth credentials), and finally I realized that it's actually much easier to do using GAE's low-level URLFetch API (com.google.appengine.api.urlfetch) like so:

URL fetchurl = new URL(url);

String nameAndPassword = credentials.get("name")+":"+credentials.get("password");
String authorizationString = "Basic " + Base64.encode(nameAndPassword.getBytes());

HTTPRequest request = new HTTPRequest(fetchurl);
request.addHeader(new HTTPHeader("Authorization", authorizationString));

HTTPResponse response = URLFetchServiceFactory.getURLFetchService().fetch(request);
System.out.println(new String(response.getContent()));

This worked.

Answer 5

There is a wrapper on Apache HttpClient for App Engine

please go through the post http://esxx.blogspot.com/2009/06/using-apaches-httpclient-on-google-app.html

http://peterkenji.blogspot.com/2009/08/using-apache-httpclient-4-with-google.html