I'm trying to report on every HTTP status code returned from my webapp. However the status code does not appear to be accessible via the ServletResponse, or even if I cast it to a HttpServletResponse. Is there a way to get access to this value within a ServletFilter?
7 Answers
First, you need to save the status code in an accessible place. The best to wrap the response with your implementation and keep it there:
public class StatusExposingServletResponse extends HttpServletResponseWrapper {
private int httpStatus;
public StatusExposingServletResponse(HttpServletResponse response) {
super(response);
}
@Override
public void sendError(int sc) throws IOException {
httpStatus = sc;
super.sendError(sc);
}
@Override
public void sendError(int sc, String msg) throws IOException {
httpStatus = sc;
super.sendError(sc, msg);
}
@Override
public void setStatus(int sc) {
httpStatus = sc;
super.setStatus(sc);
}
public int getStatus() {
return httpStatus;
}
}
In order to use this wrapper, you need to add a servlet filter, were you can do your reporting:
public class StatusReportingFilter implements Filter {
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
StatusExposingServletResponse response = new StatusExposingServletResponse((HttpServletResponse)res);
chain.doFilter(req, response);
int status = response.getStatus();
// report
}
public void init(FilterConfig config) throws ServletException {
//empty
}
public void destroy() {
// empty
}
}
Since Servlet 3.0, there's a HttpServletResponse#getStatus()
.
So, if there's room for upgrading, upgrade to Servlet 3.0 (Tomcat 7, Glassfish 3, JBoss AS 6, etc) and you don't need a wrapper.
chain.doFilter(request, response);
int status = ((HttpServletResponse) response).getStatus();
In addition to David's answer, you'll also want to override the reset method:
@Override
public void reset() {
super.reset();
this.httpStatus = SC_OK;
}
... as well as the deprecated setStatus(int, String)
@Override
public void setStatus(int status, String string) {
super.setStatus(status, string);
this.httpStatus = status;
}
If you are stuck with an older container then a alternate solution to David Rabinowitz that uses the actual status code (in case it changes after it is set using the wrapper) is:
public class StatusExposingServletResponse extends HttpServletResponseWrapper {
public StatusExposingServletResponse(HttpServletResponse response) {
super(response);
}
@Override
public void sendError(int sc) throws IOException {
super.sendError(sc);
}
@Override
public void sendError(int sc, String msg) throws IOException {
super.sendError(sc, msg);
}
@Override
public void setStatus(int sc) {
super.setStatus(sc);
}
public int getStatus() {
try {
ServletResponse object = super.getResponse();
// call the private method 'getResponse'
Method method1 = object.getClass().getMethod("getResponse");
Object servletResponse = method1.invoke(object, new Object[] {});
// call the parents private method 'getResponse'
Method method2 = servletResponse.getClass().getMethod("getResponse");
Object parentResponse = method2.invoke(servletResponse, new Object[] {});
// call the parents private method 'getResponse'
Method method3 = parentResponse.getClass().getMethod("getStatus");
int httpStatus = (Integer) method3.invoke(parentResponse, new Object[] {});
return httpStatus;
}
catch (Exception e) {
e.printStackTrace();
return HttpServletResponse.SC_ACCEPTED;
}
}
public String getMessage() {
try {
ServletResponse object = super.getResponse();
// call the private method 'getResponse'
Method method1 = object.getClass().getMethod("getResponse");
Object servletResponse = method1.invoke(object, new Object[] {});
// call the parents private method 'getResponse'
Method method2 = servletResponse.getClass().getMethod("getResponse");
Object parentResponse = method2.invoke(servletResponse, new Object[] {});
// call the parents private method 'getResponse'
Method method3 = parentResponse.getClass().getMethod("getReason");
String httpStatusMessage = (String) method3.invoke(parentResponse, new Object[] {});
if (httpStatusMessage == null) {
int status = getStatus();
java.lang.reflect.Field[] fields = HttpServletResponse.class.getFields();
for (java.lang.reflect.Field field : fields) {
if (status == field.getInt(servletResponse)) {
httpStatusMessage = field.getName();
httpStatusMessage = httpStatusMessage.replace("SC_", "");
if (!"OK".equals(httpStatusMessage)) {
httpStatusMessage = httpStatusMessage.toLowerCase();
httpStatusMessage = httpStatusMessage.replace("_", " ");
httpStatusMessage = capitalizeFirstLetters(httpStatusMessage);
}
break;
}
}
}
return httpStatusMessage;
}
catch (Exception e) {
e.printStackTrace();
return "";
}
}
private static String capitalizeFirstLetters(String s) {
for (int i = 0; i < s.length(); i++) {
if (i == 0) {
// Capitalize the first letter of the string.
s = String.format("%s%s", Character.toUpperCase(s.charAt(0)), s.substring(1));
}
if (!Character.isLetterOrDigit(s.charAt(i))) {
if (i + 1 < s.length()) {
s = String.format("%s%s%s", s.subSequence(0, i + 1),
Character.toUpperCase(s.charAt(i + 1)),
s.substring(i + 2));
}
}
}
return s;
}
@Override
public String toString() {
return this.getMessage() + " " + this.getStatus();
}
}
Warning: lots of assumptions of the class hierarchy when using sneaky reflection and introspection to get to private data values.