Spring MVC Servlet Mapping, differences between "/xxx" and "/xxx/*"

Question

I am confused with how Spring MVC's url-pattern mapping works.

When 'getServletMappings' returns "/"，I can get the right response with "http://localhost:8080/hello".

but not working if i change it to "/app" and change url to "http://localhost:8080/app/hello", it returns 404 error.

Am I misunderstanding something, I also find that "/app/*" can work(i can understand this), but why cannot "/app"?

Please check my code:

public class AppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    protected String[] getServletMappings() {
        // works with http://localhost:8080/hello
        return new String[] {
                "/"
        };
        // NOT working with http://localhost:8080/app/hello
        // return new String[] {
        //      "/app"
        //};
    }
}



@RestController
public class HTTPMethodsController {
   @RequestMapping("/hello")
   public String hello() {
       return "Hello SpringMVC.";
   }
}

Nazaret K. · Accepted Answer · 2019-10-02T23:35:21.820

According to the Servlet specification Chapter 12.2, the mapping of servlets must use the following syntax:

A string beginning with a ‘/’ character and ending with a ‘/*’ suffix is used for path mapping.

A string beginning with a ‘*.’ prefix is used as an extension mapping.

The empty string ("") is a special URL pattern that exactly maps to the application's context root, i.e., requests of the form application's context root, i.e., requests of the form http://host:port//. In this case the path info is ’/’ and the servlet path and context path is empty string (““).

A string containing only the ’/’ character indicates the "default" servlet of the application. In this case the servlet path is the request URI minus the context path and the path info is null.

All other strings are used for exact matches only.

Therefore, mapping the DispatcherServlet with the URL "/app", causes the servlet container to route requests to it only when there is an exact match, meaning only if you change your url to "http://localhost:8080/app". That leaves no room for adding extra path to target specific Spring Controllers (to be more accurate: you could actually hit your hello() controller method if you mapped it with @RequestMapping("/app") because DispatcherServlet falls back to searching with the entire url, but practically that's not what you want).

So the mapping "/app/*" is correct, or you could also map it as the default servlet with "/" as you noticed.

Spring MVC Servlet Mapping, differences between "/xxx" and "/xxx/*"

1 Answers1