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<html:errors property="myError" /> generate, create uss code 39 none in java projects ASP.NET Web Form Project Or you can get all messag barcode 3 of 9 for Java es like this:. <html:errors /> Exceptions Exercise Implement error handling with a common error message for all errors in struts-config.xml. Summary. In this chapter we compar j2ee Code 3 of 9 ed different error handling mechanisms. We looked at both general error handling in Java with exception classes and also techniques specifically designed for web projects. Struts offers extended possibilities in this area.

. Controller and Templates At this point, the shop l j2ee Code-39 acks the structure for well-regulated navigation through the site. Individual JSP pages are connected to each other, but they can be accessed only if you know their names. This chapter will bring order to all this chaos.

A central servlet takes on the role of captain. We will also implement menus and a consistent page layout with the help of Struts templates, known as Tiles..

9.1 Consistent Layout without Struts Let"s start by creating a applet Code-39 new context shop5, as a copy of shop4. First, we will develop our own controller servlet and then look at possibilities offered by Struts. This will give us a thorough understanding of the controller"s function and will highlight particular problems such as having to restart the context after each modification in the configuration file.

You should view the first part as the theoretical background (despite the purely practical approach) that precedes the actual work in the second part.. 9.1.1 Why Central Control This is the first questio 39 barcode for Java n we should consider. It is definitely possible to create a main menu, perhaps with HTML frames, that allows all JSP pages to be accessed via direct links. We can also connect individual pages with each other directly, for instance, in the way BookView.

jsp follows Book.jsp. This approach is certainly simple and sensible for small and straightforward pages, but for large projects, it could easily lead to chaos.

As it happens, you have already been working with a central servlet throughout the book: org.apache.struts.

action.ActionServlet. We will go over this in detail a little later.

We now introduce a very simple but effective method for implementing the Model 2 paradigm. The pages are controlled by a central servlet, where new pages can be accessed without reloading the context and old ones are either deleted or renamed. So why should we use a servlet and not a JSP JSPs are responsible for presentation, while the central controller performs logic tasks.

Indeed, a JSP can perform all the same. Controller and Templates processes that a servlet servlet Code 3/9 can handle, so there is no actual technical reason to distinguish JSPs and servlets. As you may know, JSPs are themselves compiled into servlets (using Jasper) before they can be accessed by users. The distinction between JSPs and servlets is really a question of good style and adherence to the recommended guidelines.

We will create a servlet called as shown in Listing 9.1.

All links point to this servlet, which assembles the response from the standard header (defined in header.jsp). This is followed by the content of the requested page as determined by the option parameter (or Main.

jsp if that parameter is null) and then the standard footer (from footer.jsp). If the option parameter has an invalid value that is, one that doesn"t correspond to a valid page then an empty page containing just the header and footer will be returned.

Listing 9.1:

import import import impo rt import*; javax.

servlet.*; javax.servlet.

http.*; java.sql.

SQLException; javax.servlet.jsp.

*;. public class StartServlet Code 39 Extended for Java extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } public void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); PageContext pageContext = null; try { JspFactory jspxFactory = JspFactory.

getDefaultFactory(); pageContext = jspxFactory.getPageContext(this, request, response, "Error.jsp", true, 8192, true); // Standard header RequestDispatcher rd = getServletContext() .

getRequestDispatcher("/Header.jsp"); rd.include(request, response);.

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