Echo Servlet
Table of Contents
How to check my application (which has reverse proxy) is working as expected while applying post/get.
Develop an HTTPServlet which can echo the headers and payload.
The below servlet echo the httpservlet with headers and payload as HTML output in the HttpServletResponse. This is very helpful especially if your application is behind a complex infrastructure with reverse proxies.
public class HttpEchoServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String SECURED = "****SECURED****";
private static final String COOKIE_SECURED = "=" + SECURED;
public HttpEchoServlet() {
super();
}
@Override
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String uri = request.getRequestURI();
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.print("<!DOCTYPE html><html><head> ");
out.print("<title> Debug output from ")
out.print(uri);
out.println("</title></head><body><h1>");
out.print(request.getMethod());
out.print(' ');
out.print(uri);
String query = request.getQueryString();
if (query != null) {
out.print('?');
out.print(query);
}
out.println();
out.println("</h1><h2>Headers:</h2><pre>");
printHeaders(request, out);
out.println("</pre><h2>Payload:</h2><pre>");
BufferedReader in = request.getReader();
String line = in.readLine();
if (line == null) {
out.println("no data");
}
while (line != null) {
out.println(line);
line = in.readLine();
}
out.println("</pre></body></html>");
}
private void printHeaders(HttpServletRequest request, PrintWriter out) {
Enumeration<String> headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
String name = headerNames.nextElement();
Enumeration<String> headerValues = request.getHeaders(name);
while (headerValues.hasMoreElements()) {
String value = headerValues.nextElement();
out.print(name);
out.print(": ");
out.print(getSecuredValue(name, value));
out.println();
}
}
}
private String getSecuredValue(String originalHeaderName, String value) {
String nameLowercase = originalHeaderName.toLowerCase(Locale.US);
if ("authorization".equals(nameLowercase)) {
return SECURED;
}
if ("proxy-authorization".equals(nameLowercase)) {
return SECURED;
}
if ("cookie".equals(nameLowercase)) {
if (value != null) {
return value.replaceAll("=[^; ]*", COOKIE_SECURED);
}
}
return value;
}
}In order to use this servlet simply add the following to your spring configuration.
@Bean
public ServletRegistrationBean echoServletRegistration() {
HttpEchoServlet echoServlet = new HttpEchoServlet();
ServletRegistrationBean registration = new ServletRegistrationBean(echoServlet);
registration.addUrlMappings("/debug/echo/*");
return registration;
}While testing the application use the url: http://<domain>/debug/echo/
This documentation is licensed under the Creative Commons License (Attribution-NoDerivatives 4.0 International).
