GWT displaying image specified from servlet - gwt

Question

I use a servlet to access a folder outside the web container to load some graphics to web application by using GWT. I use the following snippet in servlet to test the idea:
String s = null;
File inputFile = new File("C:\\Documents and Settings\\User\\My Documents\\My Pictures\\megan-fox.jpg");
FileInputStream fin = null;
try {
fin = new FileInputStream(inputFile);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
byte c[] = new byte[(int) inputFile.length()];
try {
fin.read(c);
} catch (IOException e) {
e.printStackTrace();
}
try {
fin.close();
} catch (IOException e1) {
e1.printStackTrace();
}
String imgFolderPath = getServletContext().getRealPath("/")+"img";
File imgFolder = new File(imgFolderPath);
imgFolder.mkdir();
File newImage = new File("megan-fox.jpg");
FileOutputStream fout = null;
try {
fout = new FileOutputStream(newImage);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
fout.write(c);
} catch (IOException e) {
e.printStackTrace();
}
try {
fout.close();
} catch (IOException e) {
e.printStackTrace();
}
boolean success = newImage.renameTo(new File(imgFolderPath, newImage.getName()));
The code in servlet reads the image file from the specified folder in hard disk, creates a new folder called 'img' in war folder and copies to it the jpg file. Then it returns to the client the path to the image (for now hardcoded as) '/img/megan-fox.jpg'.
The client then uses the Image class in GWT with the returned path-string to display the image, like in the following snippet:
public void onSuccess(String result) {
String myImage = result;
image = new Image(myImage);
RootPanel.get().add(image);
closeButton.setFocus(true);
}
I need to know if there is a way to achieve the same result without using the 'intermediate' step of creating a folder in the web container root (optional) and copying the file there in order to access it with Image GWT class and display it?
updated: The original servlet class.
public class GreetingServiceImpl extends RemoteServiceServlet implements
GreetingService {
// This method is called by the servlet container to process a GET request.
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
// Get the absolute path of the image
ServletContext sc = getServletContext();
// i want to load the image in the specified folder (outside the web container)
String filename = sc.getRealPath("C:\\Documents and Settings\\User\\My Documents\\My Pictures\\megan-fox.jpg");
// Get the MIME type of the image
String mimeType = sc.getMimeType(filename);
if (mimeType == null) {
sc.log("Could not get MIME type of "+filename);
resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
return;
}
// Set content type
resp.setContentType(mimeType);
// Set content size
File file = new File(filename);
resp.setContentLength((int)file.length());
// Open the file and output streams
FileInputStream in = new FileInputStream(file);
OutputStream out = resp.getOutputStream();
// Copy the contents of the file to the output stream
byte[] buf = new byte[1024];
int count = 0;
while ((count = in.read(buf)) >= 0) {
out.write(buf, 0, count);
}
in.close();
out.close();
}
// This is the method that is called from the client using GWT-RPC
public String greetServer(String input) throws IllegalArgumentException {
HttpServletRequest req = this.getThreadLocalRequest();
HttpServletResponse res = this.getThreadLocalResponse();
try {
doGet(req, res);
} catch (IOException e) {
e.printStackTrace();
}
// actually i dont know what that means but i thought i would have to returned something like the image's url?
return res.encodeURL("/img/image0.png");
}
}
I logically misused the method that was proposed to solve my problem. What is the correct way?

Answer 1

Sure, just have your servlet serve the image directly:
Set the Content-Type header to image/jpeg.
Write out image file contents to servlet response writer.
Here is an example.