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An HTTP request URL contains the following parts:
http://[host]:[port][request-path]?[query-string]
The request path is further composed of the following elements:
■ Context path: A concatenation of a forward slash (/) with the context root of the servlet’s
web application.
■ Servlet path: The path section that corresponds to the component alias that activated this
request. This path starts with a forward slash (/).
■ Path info: The part of the request path that is not part of the context path or the servlet path.
If the context path is /catalog and for the aliases listed in Table 4–4, Table 4–5 gives some
examples of how the URL will be parsed.
TABLE 4–4 Aliases
Pattern Servlet
/lawn/* LawnServlet
/*.jsp JSPServlet
TABLE 4–5 Request Path Elements
Request Path Servlet Path Path Info
/catalog/lawn/index.html /lawn /index.html
/catalog/help/feedback.jsp /help/feedback.jsp null
Query strings are composed of a set of parameters and values. Individual parameters are
retrieved from a request by using the getParameter method. There are two ways to generate
query strings:
■ A query string can explicitly appear in a web page. For example, an HTML page generated
by CatalogServlet could contain the link Add
To Cart. CatalogServlet extracts the parameter named Add as follows:
String bookId = request.getParameter("Add");
Writing Service Methods
■ A query string is appended to a URL when a form with a GET HTTP method is submitted. In
the Duke’s Bookstore application, CashierServlet generates a form, then a user name
input to the form is appended to the URL that maps to ReceiptServlet, and finally
ReceiptServlet extracts the user name using the getParameter method.
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