How to handle exceptions thrown while rendering a view in Spring MVC?
You could extends the DispatcherServlet.
In your web.xml replace the generic DispatcherServlet for your own class.
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>com.controller.generic.DispatcherServletHandler</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
Later create your own class DispatcherServletHandler and extends from DispatcherServlet:
public class DispatcherServletHandler extends DispatcherServlet {
private static final String ERROR = "error";
private static final String VIEW_ERROR_PAGE = "/WEB-INF/views/error/view-error.jsp";
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
try{
super.doService(request, response);
} catch(Exception ex) {
request.setAttribute(ERROR, ex);
request.getRequestDispatcher(VIEW_ERROR_PAGE).forward(request, response);
}
}
}
And in that page we only have to show a message to the user.
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);
}