Tomcat is not redirecting to 400 bad request custom error page

Question

We have tomcat 9 web server in production. The problem we are facing is we want to show the custom error page for our application if tomcat receives any malformed URL as follows

http://URL/|

or

http://URL/[

I have added error page tag in web.xml of tomcat application server as follows

<error-page>
   <error-code>400</error-code>
   <location>/error.html</location>
 </error-page>
 <error-page>
   <error-code>404</error-code>
   <location>/error.html</location>
 </error-page>

and we have error.html in our application ROOT folder in webapps directory of tomcat.

Whenever the user tries to request any nonexistent webpage he receives error page correctly corresponding to 404 error code as specified above.

Real Problem is tomcat not able to redirect to error.html when the user enters malformed URL in the browser like http://URL/|

Tomcat is showing the default 400 bad request error page instead of the custom error page.

Answer 1

This is not a bug, it is a configuration issue.

Tomcat 9 has improved the error handling so that more errors, particularly those those occur before request processing starts, are passed to the standard error handling mechanism rather than just returning an error code.

In the case of malformed URIs, it is not possible for Tomcat to parse the URI hence the URI cannot be mapped to a web application. Tomcat is, therefore, unable to trigger the application level error handling because it cannot identify an application. In this case, the error is handled by the ErrorReportValve which can be configured in server.xml.

A recent(ish) addition to the ErrorReportValve is the ability to define static web pages (i.e. no Servlets or JSPs, just HTML) per status code and/or Exception type in a similar manner to the per web application error page configuration.

Example Error Report Valve:

<Valve className="org.apache.catalina.valves.ErrorReportValve"
        errorCode.400="webapps/ROOT/error400.html"
        errorCode.0="webapps/ROOT/errorOthers.html"
        showReport="false"
        showServerInfo="false" />