JavaServer Pages, 3rd Edition

Redirect Versus Forward

Back to the shopping cart example. When addtocart.jsp page has added the product to the cart, it needs to invoke the catalog.jsp page to show the user the updated cart contents.

There are two ways you can let one page invoke another page: redirecting or forwarding. Forwarding was used in Example 10-2 to display an appropriate page depending on the result of the user input validation. In Example 10-8, redirection is used to display the catalog page after adding a new product to the cart. The <c:redirect> JSTL action, described in Table 10-8, sends a redirect response to the browser with the new location defined by the url attribute. If URL rewriting is used for session tracking, the URL is encoded with the session ID. If the body of this action contains <c:param> actions, described in Table 10-4, each parameter is added to the URL as query string parameters, encoded according to rules in the HTTP specification.

Table 10-8. Attributes for JSTL <c:redirect>

Attribute name	Java type	Dynamic value accepted	Description
url	String	Yes	Mandatory. An absolute URL, or a context- or page-relative path.
context	String	Yes	Optional. The context path for the application, if the resource isn’t part of the current application.

There’s an important difference between a forward and a redirect. When you forward, the target page is invoked through an internal method call by the JSP container; the new page continues to process the same request and the browser isn’t ...