Spring MVC Controller: what is the difference between "return forward", "return redirect" and "return jsp file"

Question

I don't understand what I should use. I have two pages - intro.jsp(1) and booksList.jsp(2). For each page I created one Controller Class. The first page has button which opens second page:

<form method="GET" action="/request-list">
        <input type="submit"/>
</form>

The first question is: I am not sure about correctness this button. It works well, but I have question mark after press this button.

The second question is: When I press that button, method with next annotation is called (Controller for the second page):

@RequestMapping(value = "/books")
@Controller
public class BooksListController {

   @RequestMapping
   public String booksList() {
      return "jsp/books/booksList";
   }
}

What should I return by this method? In other words how can I jump from first page to second one?

1. return "redirect:/books"; returns http://localhost:8080/books?
2. return "jsp/books/booksList"; returns http://localhost:8080/request-list?
3. return "forward:/books"; returns http://localhost:8080/request-list?

I see that result is the same: all these Strings gave me the same page (page 2 was opened). In which cases I should use "redirect", "forward", "page.jsp"?

Also I've read Post/Redirect/Get article. Do I have to use "redirect" after POST method handling??

Solution

The first question is: I am not sure about correctness this button. It works well, but I have question mark after press this button.

Ok, it's insert a question mark because you use GET http method. You need to use POST method to pass the data in the request payload.

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return "redirect:/books";

It returns to the client (browser) which interprets the http response and automatically calls the redirect URL

return "jsp/books/booksList";

It process the JSP and send the HTML to the client

return "forward:/books";

It transfer the request and calls the URL direct in the server side.

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To decide which one to use you have to consider some aspects of each approach:

Forward: is faster, the client browser is not involved, the browser displays the original URL, the request is transfered do the forwarded URL.

Redirect: is slower, the client browser is involved, the browser displays the redirected URL, it creates a new request to the redirected URL.