Java Reference
In-Depth Information
One of the more common uses for the request object is to access request parameters. You can
do this by calling the request object's getParameter() method, which is inherited from its
parent javax.servlet.ServletRequest , with the parameter name you are looking for. It will
return a string with the value matching the named parameter. An example of this can be found
in Listing 15.1.
<%@ page errorPage=”errorpage.jsp” %>
// Get the User's Name from the request
out.println(“<b>Hello: “ + request.getParameter(“user”) + “</b>”);
You can see that this JSP calls the request.getParameter() method passing in the parameter
user . This method looks for the key user in the parameter list and returns the value, if it is
found. Enter the following URL into your browser to see the results from this page:
http:// localhost /djs/UseRequest.jsp?user=Bob
After loading this URL, you should see a screen similar to Figure 15.1.
The response Object
The JSP implicit object response represents the javax.servlet.http.HttpServletResponse
object, which defines an object that provides the JSP with the capability to manipulate HTTP-
protocol-specific header information and return data to the client. The response object is
passed into the generated _jspService() method. You can see how it is passed in the follow-
ing code snippet:
public void _jspService(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
The most common use for the response object is writing HTML output back to the client
browser. You would normally call the response.getWriter() method, but the JSP API
abstracts you from this by providing the implicit out object, which will be discussed in a later
section of this chapter.
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