web development helpdesk

When using DWR you sometimes need access to the servlet request or the session.
When you do you can get access to them via the DWR WebContext class as shown in the following example code.

WebContext ctx = WebContextFactory.get();
HttpServletRequest request = ctx.getHttpServletRequest();

written by objects \\ tags: dwr, request, servlet, session

Basically you stream the image to the http response stream. Easier to explain with code so here’s a simple example.

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class ImageServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, 
    		HttpServletResponse response) throws IOException
    {
    	ServletContext application = getServletContext();
    	
    	// Get the path to image we want to return
    	
        String filepath = application.getRealPath("image.gif");
    
        // Get image MIME type
        
        String mimeType = application.getMimeType(filepath);
        if (mimeType == null)
        {
            application.log("Could not get MIME type of "+filepath);
            response.setStatus(
               HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            return;
        }
    
        // Set content type
        
        response.setContentType(mimeType);
    
        // Set content size
        
        File file = new File(filepath);
        response.setContentLength((int)file.length());
        
        // Copy the contents of the file to the responses output stream
        	
        FileInputStream in = new FileInputStream(file);
        OutputStream out = response.getOutputStream();
        byte[] buf = new byte[1024];
        int len = 0;
        while ((len = in.read(buf)) >= 0)
        {
            out.write(buf, 0, len);
        }
        in.close();
        out.close();
    }

}

See also:

• how-to-get-the-path-of-a-file-in-a-web-application
• How-do-i-copy-a-file-using-java
  

  written by objects \\ tags: HttpServletResponse, image, servlet
  

A session can be closed by calling the invalidate() method of the HttpSession class.

session.invalidate();


written by objects \\ tags: close, kill, servlet, session