Why doesn't doFilter work was expected when a .jsp page is accessed?

Question

I'm hoping an expert could point me in the right direction or tell me
          if this is a bug in WebLogic.
          My environment is WebLogic 6.1 (service pack 4), on Windows 2000.
          I need to capture all the response data that comes back from the
          servlet. So, I have a simple filter that wraps the response object,
          and sends the wrapped object into filterChain.doFilter() method.
          I've set up the web.xml so that any servlet access should trigger my
          filter (the <url-pattern> is /*). I've also configured a sample
          web-app called TEST to serve .html/.jsp pages.
          When the browser makes a .html request, everything works as expected.
          After the filterChain.doFilter(), I can take a look at the wrapped
          response object and print the contents of the response.
          However, when I access a .jsp page as part of form data submit, the
          output stream of my wrapper is empty after the filterChain.doFilter()
          completes.
          If I don't wrap the response, then everything seems to work fine. The
          .jsp gets interpreted properly by the servlet container, I can see the
          result page in the browser just fine.
          By inserting debug statements, I can see that if I wrap the responses,
          for a .html request, under the covers, wrapper's getOutputStream()
          gets called. But for a .jsp request, under the covers, wrapper's
          getWriter() gets called. I don't know how significant this is, but
          this is the only difference I see!
          If I don't wrap the response, I am not sure how to get at the response
          data. All I need to do is to take certain actions depending on the
          response. That is why I'm using a wrapper to get at the response data.
          In the JRun AppServer, the code just works fine.
          I've enclosed the source code & the output that demonstrates the
          problem.
          What am I doing wrong? Or, is this a bug in WebLogic? If this is a
          bug, is there a patch available?
          Thanks,
          --Sridhar
          // HeaderFilter.java
          // This is the filter that gets invoked through the web.xml
          configuration
          import javax.servlet.*;
          import javax.servlet.http.*;
          import java.io.*;
          import java.util.*;
          public class HeaderFilter implements Filter {
          public FilterConfig filterConfig;
          public void destroy() {
                    this.filterConfig = null;
               public void init(FilterConfig filterConfig) {
                    this.filterConfig = filterConfig;
          public FilterConfig getFilterConfig() {
          return filterConfig;
          public void setFilterConfig(FilterConfig filterConfig) {
          this.filterConfig = filterConfig;
          public void doFilter(ServletRequest req, ServletResponse resp,
          FilterChain chain)
          throws java.io.IOException, javax.servlet.ServletException {
          ServletContext context = filterConfig.getServletContext();
          HttpServletResponse response = (HttpServletResponse)resp;
          TestResponseWrapper wrapper = new
          TestResponseWrapper(response);
          chain.doFilter(req, wrapper);
          OutputStream out = resp.getOutputStream();
          System.out.println("The content length is :" +
          wrapper.getContentLength());
          if ("text/html".equals(wrapper.getContentType())) {
          byte[] data = wrapper.getData();
          System.out.println("TEXT RESPONSE, length is " +
          data.length);
          System.out.println(new String(data));
          out.write(data);
          // out.close();
          // TestResponseWrapper.java
          // This class wraps the response object so that you could take a look
          at
          // the response contents after the filterConfig.doFilter() method
          import javax.servlet.ServletOutputStream;
          import javax.servlet.http.HttpServletResponse;
          import javax.servlet.http.HttpServletResponseWrapper;
          import java.io.ByteArrayOutputStream;
          import java.io.PrintWriter;
          public class TestResponseWrapper extends HttpServletResponseWrapper{
          private ByteArrayOutputStream output;
          private int contentLength;
          private String contentType;
          public TestResponseWrapper(HttpServletResponse response) {       
          super(response);
          output = new ByteArrayOutputStream();
          public ServletOutputStream getOutputStream() {    
          System.out.println("****** getOutputStream() called *******");
          return new FilterServletOutputStream(output);
          public byte[] getData() {
          return output.toByteArray();
          public PrintWriter getWriter() {   
          System.out.println("****** getWriter() called *******");
          return new PrintWriter(getOutputStream(), false);
          public void setContentType(String type) {       
          System.out.println("**** Wrapper setContentType called ****");
          this.contentType = type;
          super.setContentType(type);
          public String getContentType() {       
          return this.contentType;
          public int getContentLength() {    
          return contentLength;
          public void setContentLength(int length) {       
          System.out.println("**** Wrapper setContentLength called
          this.contentLength=length;
          super.setContentLength(length);
          // FilterServletOutputStream.java
          // This class is used by the wrapper for getOutputStream() method
          // to return a ServletOutputStream object.
          import javax.servlet.ServletOutputStream;
          import java.io.DataOutputStream;
          import java.io.IOException;
          import java.io.OutputStream;
          import java.io.*;
          public class FilterServletOutputStream extends ServletOutputStream {
          private DataOutputStream stream;
          public FilterServletOutputStream(OutputStream output) {       
          stream = new DataOutputStream(output);
          public void write(int b) throws IOException {       
          stream.write(b);
          public void write(byte[] b) throws IOException {       
          stream.write(b);
          public void write(byte[] b, int off, int len) throws IOException {
          stream.write(b, off, len);
          // test.html
          <html>
          <head>
          <meta http-equiv="Content-Type"
          content="text/html; charset=iso-8859-1">
          <title> Web Posting Information </title>
          </head>
          <body>
          <form name="myform" method="POST" action="resource.jsp">
          <input type="TEXT" name="input"></input>
          <br>
          <input type="SUBMIT" value="done"></input>
          </form>
          </body>
          </html>
          // resource.jsp
          // This gets referenced by the test.html file
          <HTML><BODY>
          <head>
          <title>JRun Programming Techniques</title>
          <meta http-equiv="Content-Type" content="text/html;
          charset=iso-8859-1">
          </head>
          <body>
          <H3>Secure Resource Page</H3>
          <p>This is a secure page.</p>
          <BR><B>User: </B>
          <%
          //     out.write(request.getParameter("input"));
          %>
          </BODY></HTML>
          // HERE IS THE OUTPUT
          // HERE IS WHAT I SEE WHEN I ACCESS
          // http://localhost:7001/TEST/test.html
          **** Wrapper setContentType called ****
          **** Wrapper setContentLength called ****
          ****** getOutputStream() called *******
          The content length is :331
          TEXT RESPONSE, length is 331
          <html>
          <head>
          <meta http-equiv="Content-Type"
          content="text/html; charset=iso-8859-1">
          <title> Web Posting Information </title>
          </head>
          <body>
          <form name="myform" method="POST" action="resource.jsp">
          <input type="TEXT" name="input"></input>
          <br>
          <input type="SUBMIT" value="done"></input>
          </form>
          </body>
          </html>
          // HERE IS WHAT I SEE WHEN I enter some value in the "input" field
          // of the form, and click on the "submit" button.
          // Why isn't setContentLength() getting called on the wrapper?
          // It appears as if the wrapper's output stream isn't getting used
          // at all!!!
          **** Wrapper setContentType called ****
          ****** getWriter() called *******
          ****** getOutputStream() called *******
          The content length is :0
          TEXT RESPONSE, length is 0
          

Answer 1

If someone else runs into this, here is how I solved the problem -
          If you create a PrintWriter object with the autoflush option, it
          doesn't flush the underlying buffer till you call println on it. I
          looked through the generated code for the servlet, and it was doing a
          JSPWriter.print() to output information.
          So, I changed the ResponseWrapper to keep a handle to the PrintWriter
          object, and then flush it in the filter, and that works.
          Why the same code behaves differently in JRun & Weblogic, I'm not sure
          --Sridhar