HttpServletResponse Output Stream

[Abhishek Rath]

Hi

Can I retrieve the HttpServletResponse output to a file in hard disk using JAVA filter.

[Rob Spoor]

Let me see if I understand the problem.

You want, whatever is sent to the client as HTML output, to be saved to a file. Right?

If so, then yes, filters can do that. In the doFilter method, you create an HttpServletResponseWrapper. A quick example:

public void doFilter(ServletRequest request, ServletResponse response,
                     FilterChain chain)
       throws IOException, ServletException
{
    HttpServletResponse httpResponse = (HttpServletResponse)response;
    httpResponse = new HttpServletResponseWrapper(response)
    {
        public ServletOutputStream getOutputStream() throws IOException
        {
            return new TeeOutputStream(super.getOutputStream(), new FileOutputStream("some file"));
        }

        public PrintWriter getWriter() throws IOException
        {
            return new TeeWriter(super.getWriter(), new FileWriter("some file"));
        }
    };
    chain.doFilter(request, response);
}

class TeeWriter extends PrintWriter
{
    private PrintWriter writer;;
    public TeeWriter(PrintWriter writer1, Writer writer2)
    {
        super(writer2);
        writer = writer1;
    }

    public write(int c)
    {
        super.write(c);
        writer.write(c);
    }

    public write(char[] buf, int offset, int len)
    {
        super.write(buf, offset, len);
        writer.write(buf, offset, len);
    }

    public write(String str, int offset, int len)
    {
        super.write(str, offset, len);
        writer.write(str, offset, len);
    }

    public PrintWriter format(String format, Object... args)
    {
        super.format(format, args);
        writer.format(format, args);
        return this;
    }

    public PrintWriter format(Locale locale, String format, Object... args)
    {
        super.format(locale, format, args);
        writer.format(locale, format, args);
        return this;
    }
}

The TeeOutputStream is similar, but it has no backing writer of itself so you'll need to redirect each call to both output streams:

class TeeOutputStream extends ServletOutputStream
{
    private ServletOutputStream output1;
    private PrintStream output2;

    public TeeOutputStream(ServletOutputStream output1, OutputStream output2)
    {
        this.output1 = output1;
        this.output2 = new PrintStream(output2);
    }

    public void write(int b)
    {
        output1.write(b);
        output2.write(b);
    }

    public void print(char c)
    {
        output1.print(c);
        output2.write(c);
    }

    ...
}

[Abhishek Rath]

public PrintWriter format(String format, Object... args)
{
super.format(format, args);
writer.format(format, args);
return this;
}

public PrintWriter format(Locale locale, String format, Object... args)
{
super.format(locale, format, args);
writer.format(locale, format, args);
return this;
}


the format method is no defined.it is not getting compiled.

[Rob Spoor]

Then you're not using Java 5.0 or up, and you can remove those methods completely.