CODEWITHSUNDEEP
javaservlets
skaffman
skaffman

Reputation: 403581

Looking for a capturing impl of HttpServletResponseWrapper

The JavaEE API comes with the HttpServletResponseWrapper which, to quote the javadoc, "provides a convenient implementation of the HttpServletResponse interface that can be subclassed by developers wishing to adapt the response from a Servlet." Without subclassing, this class just passes all calls through to the wrapped response object. There's a similar wrapper for requests.

Can anyone point me at any utility libraries that provide useful subclass implementations of these classes? Particularly, I'm looking for a subclass of the response wrapper that captures the written response (as a String, byte[], whatever's appropriate) and exposes it via an API method.

I've written a rather half-baked version myself, but frankly, I shouldn't have to, and I'd rather throw it away and use one off the shelf.

Upvotes: 4

Views: 6860

Answers (2)

David Rabinowitz
David Rabinowitz

Reputation: 30448

I am not aware of any implementation, even though the gzip example can be adapted easily by just writing to a ByteArrayOutputStream. You can also take ideas by looking at other response wrapper implementations at:

Original answer:

There is the classic article in JavaWorld Filter code with Servlet 2.3 model. You can find examples for wrapped request and response:

  • Compression the response

    public class CompressionResponseWrapper extends HttpServletResponseWrapper {
  protected ServletOutputStream stream = null;
  protected PrintWriter writer = null;
  protected int threshold = 0;
  protected HttpServletResponse origResponse = null;
  public CompressionResponseWrapper(HttpServletResponse response) {
super(response);
origResponse = response;
  }
  public void setCompressionThreshold(int threshold) {
this.threshold = threshold;
  }
  public ServletOutputStream createOutputStream() throws IOException {
return (new CompressionResponseStream(origResponse));
  }
  public ServletOutputStream getOutputStream() throws IOException {
if (writer != null) {
  throw new IllegalStateException("getWriter() has already been " +
                                  "called for this response");
}
if (stream == null) {
  stream = createOutputStream();
}
((CompressionResponseStream) stream).setCommit(true);
((CompressionResponseStream) stream).setBuffer(threshold);
return stream;
  }
  public PrintWriter getWriter() throws IOException {
if (writer != null) {
  return writer;
}
if (stream != null) {
  throw new IllegalStateException("getOutputStream() has already " +
                                  "been called for this response");
}
stream = createOutputStream();
((CompressionResponseStream) stream).setCommit(true);
((CompressionResponseStream) stream).setBuffer(threshold);
writer = new PrintWriter(stream);
return writer;
  }
}

  • Handling file upload

    public class MultipartWrapper extends HttpServletRequestWrapper {
  MultipartRequest mreq = null;
  public MultipartWrapper(HttpServletRequest req, String dir)
                                 throws IOException {
super(req);
mreq = new MultipartRequest(req, dir);
  }
  // Methods to replace HSR methods
  public Enumeration getParameterNames() {
return mreq.getParameterNames();
  }
  public String getParameter(String name) {
return mreq.getParameter(name);
  }
  public String[] getParameterValues(String name) {
return mreq.getParameterValues(name);
  }
  public Map getParameterMap() {
Map map = new HashMap();
Enumeration enum = getParameterNames();
while (enum.hasMoreElements()) {
  String name = (String) enum.nextElement();
  map.put(name, mreq.getParameterValues(name));
}
return map;
  }
  // Methods only in MultipartRequest
  public Enumeration getFileNames() {
return mreq.getFileNames();
  }
  public String getFilesystemName(String name) {
return mreq.getFilesystemName(name);
  }
  public String getContentType(String name) {
return mreq.getContentType(name);
  }
  public File getFile(String name) {
return mreq.getFile(name);
  }
}

The code is a bit old (june 2001!), but it demonstrate the usage well.

Upvotes: 4

sillydino
sillydino

Reputation: 11

In the past I've used the objects provide in the spring framework. In particular, this should work: http://static.springsource.org/spring/docs/2.0.x/api/org/springframework/mock/web/MockHttpServletRequest.html

Upvotes: 1

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