A wrapper for the response is very useful to implement the new features of the response. In our example, we write an implementation that prints the response as a string. To do it, we can implement the javax.servlet.http.HttpServletResponse interface, as follows:

public class ResponseCharacterWrapper extends HttpServletResponseWrapper {
 private CharArrayWriter output;
 public String toString() {
 return output.toString();
 }
public ResponseCharacterWrapper(HttpServletResponse response) {
      super(response);
      output = new CharArrayWriter();
 }
 public PrintWriter getWriter() {
 return new PrintWriter(output);
 }
}

Now, add a servlet mapped with a /filtered/ path:

@WebServlet(urlPatterns = { "/CharacterServlet", "/filtered/CharacterServlet" })
public class CharacterServlet extends HttpServlet {
   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException  
   {
      response.setContentType("text/html;charset=UTF-8");
      try (PrintWriter out = response.getWriter()) {
          out.print("bar");
      }
   }
}

Without filters, if we do a GET HTTP call through the http://localhost:8080/servlets-jsp/filtered/CharacterServlet URL, we should obtain a page with a row bar. As the filter intercepts all the /filtered/ paths, we will obtain a page as illustrated: