To send get request to Web API from Java Servlet

Question

Common question

Is is possible to send get reguest from Java servlet's doGet method ? I need to check some "ticket" against my Web API .NET service, so can I call to this service from my custom servlet in the doGet method ?

public class IdentityProviderServlet extends HttpServlet {
...
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
...
// make request to Web API and save received user name to response
...
}

Details

We have web-app (.NET, MVC5) that is used TIBCO Spotfire 7.0 as engine of analysis reports. To allow our users to see reports inside web-app we use Spotfire WebPlayer (IIS web app) and JavaScript API. We authenticate our users in web app and then they are allowed to get request to WebPlayer leveraging JS API. In order to use already authenticated users we implemented custom authentication at WebPlayer based on keys-tickets as described here. Thus we created .NET assembly that is loaded by Spotfire WebPlayer and calls overridden function. In this function we call Web API service to validate user and get valid spotfire username, then I create IIdentity with received username. When new version of TIBCO Spotfire 7.5 released we discovered that they removed support of custom authentication, because they changed architecture and now they support "external authentication". This approach could be implemented as as Java servlet that is used to authenticate user and then spotfire:

Retrieves the user name from the getUserPrincipal() method of javax.servlet.http.HttpServletRequest

All this forced us to re-write our logic in Java. However we don't want to change overall workflow of our authentication and we want to stick to already working ticketing schema. I'm new to Java servlets, so my goal to implement the same authentication based on servlet. They have example where servlet class has methods doGet and doPost (link to zip with example). My assumption here that I can implement my own doGet and send request to Web API to validate ticket and get back username.

Does it make sense ?

Answer 1

You can use the library Apache HTTP Components

Short example for doGet() (I didn't compile it):

import org.apache.http.*;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.*;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.InputStreamEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
{
   String url="http://your.server.com/path/to/app?par1=yxc&par2=abc");
   HttpGet get=new HttpGet(url);
   httpClient = HttpClients.createDefault();
   // optional configuration
   RequestConfig config=RequestConfig.custom().setSocketTimeout(socketTimeoutSec * 1000).build();
    // more configuration

    get.setConfig(config);

    CloseableHttpResponse internResponse = httpClient.execute(get);

    int internResponseStatus = internResponse.getStatusLine().getStatusCode();

    InputStream respIn = internResponseEntity.getContent();
    String contentType = internResponseEntity.getContentType().getValue();

    // consume the response
}