How to put breakpoint in class without having it's source?

Question

I have a web application where I need to find all classes that accesses the http request object (because one of them is causing a hard to find bug). Therefore I would like to pu

Answer 1

Depending on your luck, you can do this with a decompiler. You'll have to place the breakpoint in the appropriate line (which, alas, might not contain "breakpointable" code)

The better way to do this is to create a ServletResponse wrapper. Incidentally, yesterday I created such a thing (with a slightly different purpose), so here it is:

public class DebugFilter implements Filter {

    public void init(FilterConfig filterConfig) {}

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 
          throws IOException, ServletException {

        chain.doFilter(request, 
              new ResponseWrapper((HttpServletResponse) response));
    }

    public void destroy() {}
}

class ResponseWrapper extends HttpServletResponseWrapper {

    public ResponseWrapper(HttpServletResponse response) {
        super(response);
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        return super.getWriter(); // breakpoint here
    }

    // Override whichever methods you like
}