Java Server Pages

Sharing Data Between Servlets and JSP Pages

When you use servlets for request processing and JSP pages to render the user interface, you often need a way to let the different components access the same data. The model I recommend is having the servlet create beans and pass them to a JSP page for display.

As I described earlier, the application scope is just a JSP abstraction of javax.servlet.ServletContext attributes. Similarly, the request and session scopes are JSP abstractions for attributes associated with javax.servlet.ServletRequest and javax.servlet.http.HttpSession, respectively. All three classes provide setAttribute( ) , getAttribute( ), and removeAttribute( ) methods. A servlet uses the setAttribute( ) method to make a bean available to a JSP page. For instance, a servlet can create a bean, save it as a request attribute, and then forward control to a JSP page like this:

public void doGet(HttpServletRequest request, 
        HttpServletResponse response) throws ServletException,
        IOException {

        String userName = request.getParameter("userName");
        UserInfoBean userInfo = userReg.getUserInfo(userName);

        request.setAttribute("userInfo", userInfo);
        RequestDispatcher rd = 
            request.getRequestDispatcher("welcome.jsp");
        rd.forward(request, response);
    }

To the JSP page, the bean appears as a request scope variable. It can therefore obtain the bean using the <jsp:useBean> action and then access the properties of the bean as usual, in this case using <jsp:getProperty> :

<h1>Welcome <jsp:useBean ...