Question

I have a global handler for my AJAX calls

$.ajaxSetup({
    error: function(xhr, textStatus, errorThrown) {
             //do something 
    }
});

And in case of an error my servlet filter sends a specifc error

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
        ServletException {

    if(somethingwrong()) {
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "unavailableimage");    
    }
}

Would you recommend to do something like

$.ajaxError({
    error: function(xhr, textStatus, errorThrown) {
        if (xhr.status == 408) {
            //doSomething
        }
        else if xhr.responseText.contains("unavailableimage"){
            //doSomething
        }
    }
}); 

Because I think the responseText is different in every browser.

Answer 1

The response body is available by xhr.responseText.

However, the HttpServletResponse#sendError() ( <– click the link to read the Javadoc yourself) will use the servletcontainer’s default error page template or your custom error page template as you’ve definied in web.xml. This is a HTML document which you thus have to parse yourself.

As per your comment on the other answer, you seem to be using Tomcat and retrieving its default error page; the message is available as first <u> element of the second <p>. So this should do:

var errorMessage = $(xhr.responseText).filter('p:eq(1)').find('u').text();

if (errorMessage == 'unavailableimage') {
    // ...
}

You only need to keep in mind that you’re this way tight coupled to the markup of the (default) error page. Better is to not use HttpServletResponse#sendError(), but just set the status by HttpServletResponse#setStatus() ( <– yes, click it to read javadoc, the answer was in there) and write the error message to the response body yourself:

response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
response.getWriter().write("unavailableimage");

This way the xhr.responseText is exactly unavailableimage.

if (xhr.responseText == 'unavailableimage') {
    // ...
}