com.oreilly.servlet

Class MultipartResponse

java.lang.Object

com.oreilly.servlet.MultipartResponse

public class MultipartResponse
extends java.lang.Object

A utility class to generate multipart/x-mixed-replace responses, the kind of responses that implement server push. Note that Microsoft Internet Explorer does not understand this sort of response.

To use this class, first construct a new MultipartResponse passing to its constructor the servlet's response parameter. MultipartResponse uses the response object to fetch the servlet's output stream and to set the response's content type.

Then, for each page of content, begin by calling startResponse() passing in the content type for that page. Send the content for the page by writing to the output stream as usual. A call to endResponse() ends the page and flushes the content so the client can see it. At this point a sleep() or other delay can be added until the next page is ready for sending.

The call to endResponse() is optional. The startResponse() method knows whether the last response has been ended, and ends it itself if necessary. However, it's wise to call endResponse() if there's to be a delay between the time one response ends and the next begins. It lets the client display the latest response during the time it waits for the next one.

Finally, after each response page has been sent, a call to the finish() method finishes the multipart response and sends a code telling the client there will be no more responses.

For example:

 MultipartResponse multi = new MultipartResponse(res);
  
 multi.startResponse("text/plain");
 out.println("On your mark");
 multi.endResponse();
  
 try { Thread.sleep(1000); } catch (InterruptedException e) { }
  
 multi.startResponse("text/plain");
 out.println("Get set");
 multi.endResponse();
  
 try { Thread.sleep(1000); } catch (InterruptedException e) { }
  
 multi.startResponse("image/gif");
 ServletUtils.returnFile(req.getRealPath("/images/go.gif"), out);
  
 multi.finish();
 

See Also:

ServletUtils

Constructor Summary

Constructors

Constructor and Description
MultipartResponse(javax.servlet.http.HttpServletResponse response) Constructs a new MultipartResponse to send content to the given servlet response.

Method Summary

Modifier and Type	Method and Description
void	endResponse() Ends a single response.
void	finish() Finishes the multipart response.
void	startResponse(java.lang.String contentType) Begins a single response with the specified content type.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MultipartResponse

public MultipartResponse(javax.servlet.http.HttpServletResponse response)
                  throws java.io.IOException

Constructs a new MultipartResponse to send content to the given servlet response.

Parameters:

response - the servlet response

Throws:

java.io.IOException - if an I/O error occurs

Method Detail

startResponse

public void startResponse(java.lang.String contentType)
                   throws java.io.IOException

Begins a single response with the specified content type. This method knows whether the last response has been ended, and ends it itself if necessary.

Parameters:

contentType - the content type of this response part

Throws:

java.io.IOException - if an I/O error occurs

endResponse

public void endResponse()
                 throws java.io.IOException

Ends a single response. Flushes the output.

Throws:

java.io.IOException - if an I/O error occurs

finish

public void finish()
            throws java.io.IOException

Finishes the multipart response. Sends a code telling the client there will be no more responses and flushes the output.

Throws:

java.io.IOException - if an I/O error occurs