Example of Java Servlet Web App Facebook App does Authentication followed by Simple Graph API query  and HAS LINK FOR INVITEon user

This uses previous Java based Authentication code -- read there for details of Authentication


RESULTS


RESULTS OF CLICKING ON INVITE LINK --- will send request to users selected  AND THEN GO BACK TO 1st Interface

Servlet class -- invoked by Facebook mapped currently to

       http://puzzle.sci.csueastbay.edu:8080/grewe_FacebookSimpleApp/grewe_FacebookSimpleApp2/

package grewe.FacebookAuthentication;
 import java.io.IOException;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.*;
 import java.net.URL;
 import java.net.URLConnection;
 import java.net.URLEncoder;
 import javax.servlet.RequestDispatcher;
              
 /**
 * Servlet implementation class FacebookSimpleApp
 */
 @WebServlet(name="FacebookSimpleApp" ,urlPatterns={"/grewe_FacebookSimpleApp2/","/FacebookSimpleApp"})
    
 public class FacebookSimpleApp extends HttpServlet {
         private static final long serialVersionUID = 1L;
               
               /**
               * @see HttpServlet#HttpServlet()
               */
         public FacebookSimpleApp() {
               super();
               // TODO Auto-generated constructor stub
 
         }


            /**
             * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
            */
          protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
               // NOTE:  REQUEST (INVITE) CALL CALLBACK is doGet ---the request to send Invite (REQUEST) below in doPost 
               //        will do a GET call back to the deployed webapp real address http://puzzle*  so we have to redirect it to the apps.facebook
               //        which will call the doPost method of this servlet passing again signed_request paramter
               //        The callback to doGet does not include this information and the callback to http://puzzle* takes you
               //        outside the facebook wrapper so must forward it to the https://apps.facebook.com/apid/ url.
               //        You can check the results of whether or not the social call was successful here -- see Social data api to see what returned to callback
               response.sendRedirect("https://apps.facebook.com/296187843796738/");
          }
     
         /**
          * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
          */
          protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           // AUTHENTICATION CODE
               try{
               String signedRequest = (String) request.getParameter("signed_request"); //if authenticated this will be parameter sent to you from Facebook
          
               //create instance of FacebookSignedRequest based on signedRequest parameter retrieved above
               // note even if not authenticated you still get a signedRequest but, the oauth parameter will not be set
               FacebookSignedRequest facebookSignedRequest = FacebookAuthService.getFacebookSignedRequest(signedRequest);
               PrintWriter writer = response.getWriter();

               //if the signedRequest was null, no authentication then the called to getOauth_token() will be null
               //  redirect to authentication URL
               if (facebookSignedRequest.getOauth_token() == null) {
               response.setContentType("text/html");
               writer.print("<script> top.location.href='"	+ FacebookAuthService.getAuthURL() + "'</script>");
               writer.close();
               } else {   //we are authenticated at this point and going to forward the accessToken to your business logic Servlet/JSP
               request.setAttribute("accessToken",	facebookSignedRequest.getOauth_token());


          //Application CODE --- THIS IS WHERE YOUR APPLICATION CODE GOES
               response.setContentType("text/html");
               writer.println("<body bgcolor=\"#ccccff\">");
               //CODE DISPLAYS USER ID
               writer.print("Welcome user ME --  " + facebookSignedRequest.getUser_id() + "<br>");
                
          //CODE FOR LINK TO INVITE -- style the link as you want and fit it in your interface as you want
               //going to create link that uses Facebook request dialog box to ask users to invite their friends to the app
               //which will pop-up a Facebook request dialog box asking for which friends...will return here
               String mess = "Come%20use%20" + FacebookAuthService.getAppName() + "%20with%20me!";
               
               //Note- the callbacks from this apprequests url is the http://puzzle* the actual webapp location
               //       if you put https://apps.facebook.com/appid/ you get error message saying that this url not owned by app
               //       this http://puzzl* we are supplying will call back to THIS servelet and is a GET request (calls doGet)
               String s;
               s = "http://www.facebook.com/dialog/apprequests?app_id=" + FacebookAuthService.getAPIId() + "&message="+ mess +"&redirect_uri=" + FacebookAuthService.getCanvasURI();
               writer.println("folloing links to " + s + "<br><br>");
               writer.println("<a target=\"_top\" href=\"" + s +"\">" + "Invite Your Friends --</a> <br>");
               writer.println("<br><hr>");
               
               // This next link will only allow friends that do not have app installed yet
               s = "http://www.facebook.com/dialog/apprequests?app_id=" + FacebookAuthService.getAPIId() + "&message=" + mess + "&filters=['app_non_users']&redirect_uri=" + FacebookAuthService.getCanvasURI();
               writer.println("folloing links to " + s + "<br><br>");
               writer.println("<a target=\"_top\" href=\"" + s +"\">" + "Invite Your Friends --not having app installed </a> <br>");
               writer.println("<br><hr>");
               
         //CODE TO GET SOCIAL DATA -- you will need to parse the results of reading in the lines or like in Authentication use Jackson
               //makes a request to the graph URL and displays output and get the JSON back --you need to parse it
               
               s= "https://graph.facebook.com/me?access_token=" + facebookSignedRequest.getOauth_token();
               writer.println(s);
               
               writer.println("<br><br>Graph on me output = " + "<br>");
               InputStream fileSource = new URL(s).openStream();
               URL u = new URL(s);
               
               URLConnection uc = u.openConnection();
               
               BufferedReader in = new BufferedReader(new InputStreamReader( uc.getInputStream()));
               String inputLine;
               while ((inputLine = in.readLine()) != null) 
               writer.println(inputLine);
               in.close();
               
               writer.println("END Graph  output " + "<br><br>");
               
         //POSSIBLE alternative is to forward on the request to another servlet/JSP for completion
             // be careful about where you place these jsps/servlets --see facebook restrictions about forwarding  
               /* RequestDispatcher requestDispatcher = getServletContext().getRequestDispatcher("/figure_out_path"); //you will change the path to map to business logic Servlet/JSP
               s = requestDispatcher.toString();
               writer.println(s + " <br><br>");
               s = getServletContext().toString();
               writer.println(s + " <br>");
               s = requestDispatcher.FORWARD_REQUEST_URI;
               writer.println("forward uri " + s + " <br>");
               s = requestDispatcher.FORWARD_SERVLET_PATH;
               writer.println("forward servlet path is " + s + "<br>");
               
               requestDispatcher.forward(request, response);
               
               */
            }
              
         }catch(Exception e){}
               
   }
}
            

FacebookAuthService.java (class from authentication)   change things in green

package grewe.FacebookAuthentication;

import  org.apache.commons.lang3.StringUtils;
         import org.apache.commons.codec.binary.Base64;
         import com.fasterxml.jackson.databind.ObjectMapper;
       

public class FacebookAuthService {
         private static final String apiKey = "29618XXXXXX" //you will change this
         private static final String appSecret = "875faXXXXX8";  //you will change this
         private static final String appId = "296XXXXXXXXX8";  //you will change this

         private static final String redirect_uri = "http://puzzle.sci.csueastbay.edu:8080/grewe_FacebookSimpleApp/grewe_FacebookSimpleApp2/";  //you will change this
        

         private static final String apps_uri = "https://apps.facebook.com/296187843796738/";  //you will change this
         private static final String canvas_uri = "http://puzzle.sci.csueastbay.edu:8080/grewe_FacebookSimpleApp/grewe_FacebookSimpleApp2/";  //you will change this
         private static final String appName = "Buzz";

         private static final String[] perms = new String[] {"publish_stream", "email"};
         // private static final String[] perms = new String[] { "email"};
       

         public static String getAPIKey() {
         return apiKey;
         }

         public static String getSecret() {
         return appSecret;
         }
   
         public static String getAPIId() {
         return appId;
         }
   
         public static String getRedirectURI() {
         return redirect_uri;
         }
   
         public static String getAppsURI() {
         return apps_uri;
         }
   
         public static String getCanvasURI() {
         return canvas_uri;
         }

         public static String getAppName() {
         return appName;
         }

         public static String getLoginRedirectURL() {
         return "https://graph.facebook.com/oauth/authorize?client_id=" + appId
         + "&display=page&redirect_uri=" + redirect_uri + "&scope=" + StringUtils.join(perms,',');
         }

         public static String getAuthURL(String authCode) {
         return "https://graph.facebook.com/oauth/access_token?client_id="
         + appId + "&redirect_uri=" + redirect_uri + "&client_secret="
         + appSecret + "&code=" + authCode;
         }

         public static String getAuthURL() {
         return "https://www.facebook.com/dialog/oauth?client_id="
         + appId + "&redirect_uri=" + redirect_uri + "&scope="
         + StringUtils.join(perms,',');
   
         }
       

         //this is the method that creates instance of FacebookSignedRequest using returned Facebook signed_request info
         public static FacebookSignedRequest getFacebookSignedRequest(String signedRequest) throws Exception{

 //parst the json string returned from Authentication and grab the oauth token
         String payLoad = signedRequest.split("[.]", 2)[1];
         payLoad = payLoad.replace("-", "+").replace("_", "/").trim();

 String jsonString = new String(Base64.decodeBase64(payLoad));

 //this maps the returned response from that has the jsonString as the signed_request returned from Facebook
         //to an instance of the FacebookSignedRequest class.
         // uses 3rd party package called Jackson to do mapping of JSON string to an object.
         return new ObjectMapper().readValue(jsonString, FacebookSignedRequest.class);
         }
  }

 

 

 

FacebookAuthentication.java (again class from previous Authentication example used here)

package grewe.FacebookAuthentication;
             

public class FacebookSignedRequest {
               private String algorithm;
               private Long expires;
               private Long issued_at;
               private String oauth_token;
               private Long user_id;
               private FacebookSignedRequestUser user;

 public String getAlgorithm() {
               return algorithm;
               }

 public void setAlgorithm(String algorithm) {
               this.algorithm = algorithm;
               }

 public Long getExpires() {
               return expires;
               }

 public void setExpires(Long expires) {
               this.expires = expires;
               }

 public Long getIssued_at() {
               return issued_at;
               }

 public void setIssued_at(Long issued_at) {
               this.issued_at = issued_at;
               }

 public String getOauth_token() {
               return oauth_token;
               }

 public void setOauth_token(String oauth_token) {
               this.oauth_token = oauth_token;
               }

 public Long getUser_id() {
               return user_id;
               }

 public void setUser_id(Long user_id) {
               this.user_id = user_id;
               }

 public FacebookSignedRequestUser getUser() {
               return user;
               }

 public void setUser(FacebookSignedRequestUser user) {
               this.user = user;
               }

 //inner class used to represent user information
               public static class FacebookSignedRequestUser {
               private String country;
               private String locale;
               private FacebookSignedRequestUserAge age;

 public String getCountry() {
               return country;
               }

 public void setCountry(String country) {
               this.country = country;
               }

 public String getLocale() {
               return locale;
               }

 public void setLocale(String locale) {
               this.locale = locale;
               }

 public FacebookSignedRequestUserAge getAge() {
               return age;
               }

 public void setAge(FacebookSignedRequestUserAge age) {
               this.age = age;
               }
             

 
               public static class FacebookSignedRequestUserAge{
               private int min;
               private int max;
             

 public int getMin() {
               return min;
               }
             

 public void setMin(int min) {
               this.min = min;
               }
             

 public int getMax() {
               return max;
               }
             

 public void setMax(int max) {
               this.max = max;
               }
               }
               }
               }