Question

I have a Spring MVC application which uses FreeMarker as View technology (But maybe the view technology doesn’t really matter for my question). I need to intercept all exceptions which may get thrown during a request.

I have implemented a HandlerExceptionResolver but this resolver is only executed when the exception occurs within a controller. But when a controller returns a ModelAndView and the exception occurs while rendering the view (Because a variable was not found or something like this) then the exception resolver is not called and instead I get a stack trace in the browser window.

I also tried using an exception handler method within the controller which returns the view and annotated it with @ExceptionHandler but this also doesn’t work (Most likely again because the exception is not thrown in the controller but in the view).

So is there some Spring mechanism where I can register an exception handler which captures view errors?

Answer 1

A word upfront: if you just need a “static” error page without much logic and model preparation, it should suffice to put a <error-page>-Tag in your web.xml (see below for an example).

Otherwise, there might be better ways to do this, but this works for us:

We use a servlet <filter> in the web.xml that catches all Exceptions and calls our custom ErrorHandler, the same we use inside the Spring HandlerExceptionResolver.

<filter>
   <filter-name>errorHandlerFilter</filter-name>
   <filter-class>org.example.filter.ErrorHandlerFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>errorHandlerFilter</filter-name>
  <url-pattern>/*</url-pattern>
</filter-mapping>

The implementation looks essentially like this:

public class ErrorHandlerFilter implements Filter {

  ErrorHandler errorHandler;

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
    try {
      filterChain.doFilter(request, response);
    } catch (Exception ex) {
      // call ErrorHandler and dispatch to error jsp
      String errorMessage = errorHandler.handle(request, response, ex);
      request.setAttribute("errorMessage", errorMessage);
      request.getRequestDispatcher("/WEB-INF/jsp/error/dispatch-error.jsp").forward(request, response);
    }

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    errorHandler = (ErrorHandler) WebApplicationContextUtils
      .getRequiredWebApplicationContext(filterConfig.getServletContext())
      .getBean("defaultErrorHandler");
  }

  // ...
}

I believe this should work pretty much the same for FreeMarker templates. Of course if your error view throws an error, you’re more or less out of options.

To also catch errors like 404 and prepare the model for it, we use a filter that is mapped to the ERROR dispatcher:

<filter>
   <filter-name>errorDispatcherFilter</filter-name>
   <filter-class>org.example.filter.ErrorDispatcherFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>errorDispatcherFilter</filter-name>
  <url-pattern>/*</url-pattern>
  <dispatcher>ERROR</dispatcher>
</filter-mapping>

<error-page>
  <error-code>404</error-code>
  <location>/WEB-INF/jsp/error/dispatch-error.jsp</location>
</error-page>
<error-page>
  <exception-type>java.lang.Exception</exception-type>
  <location>/WEB-INF/jsp/error/dispatch-error.jsp</location>
</error-page>

The doFilter-Implementation looks like this:

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

  final HttpServletRequest request = (HttpServletRequest) servletRequest;

  // handle code(s)
  final int code = (Integer) request.getAttribute("javax.servlet.error.status_code");
  if (code == 404) {
    final String uri = (String) request.getAttribute("javax.servlet.error.request_uri");
    request.setAttribute("errorMessage", "The requested page '" + uri + "' could not be found.");
  }

  // notify chain
  filterChain.doFilter(servletRequest, servletResponse);
}