java - How to redirect URLs with trailing slash to the corresponding ones without it?

Question

Spring MVC (3.0) considers URLs with and without trailing slashes as the same URL.

For example:

http://www.example.org/data/something = http://www.example.org/data/something/

I need to redirect the URL with trailing slashes

http://www.example.org/data/something/

to the URL without it:

http://www.example.org/data/something

I need to do this internally the application (so not rewrite rules via Apache, etc).

A way to do it is:

@ResponseStatus(value=HttpStatus.MOVED_PERMANENTLY)
@RequestMapping(value = "/data/something/")
public String dataSomethingRedirect(...) {
    return "redirect:/data/something";
}

but this has generally 2 problems:

1. too many controllers
2. problem with parameters: like wrong encoding

Question

Is there a way to intercept all the URLs and in case they have a trailing slash, redirect them to the relative one without slash?

Answer 1

You could list all the rewrite rules you need in your web configuration

If there aren't many of those, you can configure redirect views like this

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addViewControllers(ViewControllerRegistry registry) {
    registry.addRedirectViewController("/my/path/", "/my/path")
      .setKeepQueryParams(true)
      .setStatusCode(HttpStatus.PERMANENT_REDIRECT); 
}

Or you could create a custom HandlerInterceptor

But interceptors occur before requests are mapped to a specific Controller.action and you've got no way of knowing Controllers and actions in that context.

All you've got is HTTPServlet API and request+response; so you can:

response.sendRedirect("http://example.org/whitout-trailing-slash");

The answer you don't want to read

This behavior (URL with trailing slash = URL without it) is perfectly "valid" when considering HTTP. At least this is the default behavior with Spring, that you can disable with useTrailingSlashMatch (see javadoc).

So using rewrite/redirect rules on the front-end server could a solution; but again, I don't know your constraints (maybe you could elaborate on this and we could figure out other solutions?).