Thursday, May 28, 2009

seamy photo gallery, writing an authentication filter (part 5)

On the 4th part I used an simple authentication filter, to secure my urls, that come out of the box. It only supported basic & digest authentication. With basic authentication what you get is a ugly browser dependent box which asks the credentials of the user. On IE its like:
Instead of that I wanted the user to use the login page which I created. In order to do that I first removed basic authentication filter component and started coding mine :
@Install(precedence = Install.DEPLOYMENT)
@Filter(within = "org.jboss.seam.web.exceptionFilter")
public class CustomAuthenticationFilter extends AbstractFilter {
protected Log log;

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
ServletException {
if (!(request instanceof HttpServletRequest)) {
throw new ServletException("This filter can only process HttpServletRequest requests");

HttpServletRequest httpRequest = (HttpServletRequest) request;
HttpServletResponse httpResponse = (HttpServletResponse) response;
Context ctx = new SessionContext(new ServletRequestSessionMap(httpRequest));
Identity identity = (Identity) ctx.get(Identity.class);
if (identity.isLoggedIn()) {
chain.doFilter(request, response);
else {
// go login than come back
+ httpRequest.getRequestURL());


public void init(FilterConfig filterConfig) throws ServletException {
Seam handles the creation and order of the filters with the help of @Filter annotation. Instead of adding web.xml entries we annotate our filters and specify where they should be in the filter chain. 
I have extended my filter from the seam AbstractFilter class and on the init method I setted the url pattern which the filter mappes to. 
On the doFilter method first thing to do is try to see if the user is already logged in. We have to access the Identity component but seams injections mechanism does not work with the filters. So instead of injecting you have to create a context (and such) to access the Identity component.
Once we have the Identity component we see if the user is already logged in. If so we proceed with the rest of the chain if not we redirect to our custom login page and pass the original page that the user tried to access with a request parameter that I named serviceUrl.
Once the user successfully logs in we need to redirect the user to original resouce pointed by the serviceUrl. To do that I wrote a Listener class which will fire after the user successfully logs in :
public class LoginRedirectListener {
private String serviceUrl;

public void postAuthentication() throws IOException {
if (serviceUrl != null && serviceUrl.length() > 0) {
The good old observer pattern is implement with annotations on seam. Here using the @Observer annotation we get notified of authentication event end redirect to the serviceUrl if there is one. I have created it as a session bean so that each user will his own serviceUrl. One last thing to do is injecting the serviceUrl parameter to my listener which is done through pages.xml:
<page view-id="/login.xhtml">
<rewrite pattern="/login" />
<param name="serviceUrl" value="#{loginRedirect.serviceUrl}"/>
Thats all there is...

Wednesday, May 27, 2009

seamy photo gallery, resting easier (part 4)

On my previous post I made a restful photo gallery that has a nice little feature where upon a restful request like 'http://.../mygallery/photo/photo/yoda' served the image named 'yoda' to the user. In order to achive that what I did was first I edited the pages.xml so that it could extract the name (id) part from the request url:
<page view-id="/photo/photo.xhtml" login-required="true">
<rewrite pattern="/photo/photo/{fotoId}" />
<param name="fotoId" value="{fotoId}" />
Here the name is extracted into el context as 'fotoId'. Second thing is that I created the photo.xhtml mentioned above:
<s:graphicImage id="imaj" value="#{photoService.getFoto(fotoId)}"
style="border: 1px solid black;" lt="image could not be found">
I used a 's:graphicImage' component which serves the photo using a little service bean using our 'fotoId' parameter. For completeness here is the service bean:
public class PhotoService {
public byte[] getFoto(String fotoId) {
Photo p = getPhoto(fotoId);
if (p == null) {
return null;
return p.getData();
What bugged me on this method was that although I just wanted the serve the image here I was actually serving a html page which linked to the image. 
After looking around I learned that what I wanted, came with the seam & resteasy integration. RESTEasy (jaxrs) comes with annotations where you can use to serve the result of methods & beans directly. Seam package comes with the required jars  (dont go downloading for a resteasy package from for integrating it. You just put them in your classpath. So inorder to serve my 'photoService.getFoto' I can use the @Get, @Path and other annotations :
public class PhotoService {


public byte[] getFoto(@PathParam("fotoId")
String fotoId) {
Rest access is by default configured under '.../seam/resource/rest/'. So by using the path and get annotions I can access the 'photoService.getFoto' method with the '.../seam/resource/rest/foto/yoda' request. ProduceMime annotation tells that we are serving an jpeg image and the PathParam annotation is used so that we can get the 'yoda' out of the request and used it as a parameter to our method.
Now are we done ? No, because we need to secure it!. We dont want Vader to see the comprimising images of the Yoda (hehe) so we need to secure it with the restrict annotation :
@Restrict("#{s:hasRole('user') || s:hasRole('admin')}")
public byte[] getFoto(@PathParam("fotoId")
String fotoId) ...
Now what happens when someone not logged in tries to acces the yoda is we will see a NotLoggedInException on the stacktrace. Of course we need to handle that and give the user the option to log in. Seam has a 'web:authentication-filter' component that supports the http basic or digest authentication which I configured like this on components.xml:
<web:authentication-filter url-pattern="/seam/resource/rest/*"
auth-type="basic" />
Now the yoda is safe I guess and I am sure there will be different authentication types supported in the future. I got few that could be implemented like the oauth which I belive is used by twitter and such.

Wednesday, May 20, 2009

Moving the keyboard out of the way

After happily doing a little work for iphone, being content for that I was finished with it, I made realize that the text boxes near the bottom of the screen disappeared when the keyboard appeared after saying "hmmmm...", I started searching for a solution. Apples iphone developer library suggest this solution and here I am going to write about how I used it in my project. 
Here is how the problem looks like  in a simple case(a before),
What we are going to do is, we are going to define UIScrollView and put our view inside it and scroll it up when the keyboard shows up. In order to do it in a OO fashion I defined a base class that will handle the scroll details.
#import <UIKit/UIKit.h>

@interface BaseViewController : UIViewController <UITextFieldDelegate> {
bool keyboardShown;

UITextField * activeField;

UIScrollView * scrollView;

UIView * mainView;

@property (nonatomic, retain) IBOutlet UIScrollView * scrollView;
@property (nonatomic, retain) IBOutlet UIView * mainView;

I will bind the mainView with the original view which contains the text field. The scrollView will be inside a proxy view. The implementation;
#import "BaseViewController.h"

@implementation BaseViewController

@synthesize mainView, scrollView;

- (BOOL)textFieldShouldReturn:(UITextField *)theTextField {
return [theTextField resignFirstResponder];

- (void)textFieldDidBeginEditing:(UITextField *)textField {
activeField = textField;

- (void)registerForKeyboardNotifications
[[NSNotificationCenter defaultCenter] addObserver:self
name:UIKeyboardDidShowNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self
name:UIKeyboardDidHideNotification object:nil];

// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
if (keyboardShown)

NSDictionary* info = [aNotification userInfo];

// Get the size of the keyboard.
NSValue* aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];
CGSize keyboardSize = [aValue CGRectValue].size;

// Resize the scroll view (which is the root view of the window)
CGRect viewFrame = [scrollView frame];
viewFrame.size.height -= keyboardSize.height;
scrollView.frame = viewFrame;

// Scroll the active text field into view.
CGRect textFieldRect = [activeField frame];
[scrollView scrollRectToVisible:textFieldRect animated:YES];
keyboardShown = YES;


// Called when the UIKeyboardDidHideNotification is sent
- (void)keyboardWasHidden:(NSNotification*)aNotification
NSDictionary* info = [aNotification userInfo];

// Get the size of the keyboard.
NSValue* aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];
CGSize keyboardSize = [aValue CGRectValue].size;

// Reset the height of the scroll view to its original value
CGRect viewFrame = [scrollView frame];
viewFrame.size.height += keyboardSize.height;
scrollView.frame = viewFrame;
[scrollView scrollRectToVisible:CGRectMake(0, 0, 1, 1) animated:YES];
keyboardShown = NO;

- (void)viewDidLoad {
[super viewDidLoad];
keyboardShown = false;
scrollView.indicatorStyle = UIScrollViewIndicatorStyleWhite;
scrollView.clipsToBounds = YES; // default is NO, we want to restrict drawing within our scrollview
scrollView.scrollEnabled = NO;
scrollView.pagingEnabled = NO;
[scrollView setContentSize:CGSizeMake(320, 480)];
[scrollView addSubview:mainView];
[self registerForKeyboardNotifications];

The example is here under KeyboardLift. And this is the after screenshot;

Monday, May 4, 2009

seamy photo gallery, securing it (part 3)

Previous part was about setting up security so that we have a admin user that could approve photos and an ordinary one. We have done basic authentication on this part we will look at handling authorization exceptions, securing our view and code based on authority.
First thing I did was adding approve and disapprove (delete the photo) methods to my photoService and make them authorized :
public void approvePhoto(Photo p) {"approving :" + p.getName());

public void disapprovePhoto(Photo p) {"disapprovePhoto :" + p.getName());
@Restrict annotation with the specified EL makes sure that user invoking these methods have admin right. Upon unauthorized access an authorization exception thrown which I handled in the pages.xml :
<exception class="">
<message>You don't have permission to do this</message>
By doing so we will have an authorization exception message on our message component. There is a small issue I encountered however ;
Next I added links to pics in the gallery that will invoke these actions. Seam has annatotions just for doing this kind of stuff on datatables. This is what my datatable looked liked : 
<rich:dataGrid value="#{photoService.frontPagePhotos}" var="foto"
columns="3" elements="9">
<s:link id="lnk_foto" view="/photo/photo.xhtml" propagation="none">
<f:param name="fotoId" value="#{}" />
<s:graphicImage id="imaj" value="#{}"
style="border: 1px solid black;" lt="image could not be found">
<s:transformImageSize width="100" maintainRatio="true" />
<h:outputLabel value="#{}" for="imaj" />
<h:commandLink value="Approve"
rendered="#{foto.approved eq null}" />
<h:outputText value="," rendered="#{foto.approved eq null}" />
<h:commandLink value="Delete"
rendered="#{s:hasRole('admin')}" />
Approve and delete buttons must be rendered only with the user with the role admin #{s:hasRole('admin')} EL does that. 
The last thing I did was adding a logout method which is just :
<h:commandButton action="#{identity.logout()}" value="Logout" />

Again I encountered a litte problem with this : . Thats all for now. Keep coding...