Controller and Templates in Java Develop Code-39 in Java Controller and Templates

How to generate, print barcode using .NET, Java sdk library control with example project source code free download:
9. using jvm tocompose 3 of 9 for web,windows application Microsoft .NET String option jdk Code 3 of 9 = request.getParameter("option"); try { if (option == null) { rd = getServletContext().getRequestDispatcher("/Main.

jsp"); rd.include(request, response); } else { rd = getServletContext().getRequestDispatcher("/" + option + ".

jsp"); rd.include(request, response); } } catch(IOException ex) { System.err.

println(ex); out.println("<h1>Invalid Option</h1>"); } // the standard footer rd = getServletContext().getRequestDispatcher("/Footer.

jsp"); rd.include(request, response); } catch (Exception ex) { // Error will be displayed using JSP mechanism. if (pageContext != null) { pageContext.

handlePageException(ex); } else { out.println(ex.getMessage()); } } } }.

The servlet is placed directly in the classes directory. The processRequest() method builds up the response for the user starting with the header. Next, it gets the content of the page specified by the option request parameter (or the main page, if that parameter is null), and finally adds the footer.

It uses the RequestDispatcher"s include() method, which inserts the content from the specified URL into the response stream. Note that we set the content type to HTML, because, while Internet Explorer displays HTML pages on the basis of their content, many other browsers (such as Netscape) go by the content type and would display only the source code if it wasn"t set correctly. Both the files, Header.

jsp and Footer.jsp, contain incomplete fragments of JSP pages and are not intended to be opened on their own. For the purposes of this sample, we can create a couple of files containing just the words Header and Footer, so we can see that they have been inserted.

. Controller and Templates To try out Sta rtServlet, you will need to add corresponding <servlet> and <servlet-mapping> elements to web.xml. If you map /StartServlet to the URL pattern, you will be able to access any page by specifying its name in the option parameter like this: http://localhost:8080/StartServlet option=book.

Figure 9.1: StartServlet output StartServlet can be easily exte javabean barcode 3 of 9 nded to add extra functionality. We can conduct a test by calling different pages to make sure that only logged-in users can access the shopping cart. Detailed log messages can be added for debugging, which can be very efficient.

For instance, we could create a special logging method that can be called on demand. Centralized error handling can also be performed in this servlet. Many extensive projects have been implemented using this method and it has been found to be simple, efficient, and easy to control.

But since this book is about Struts, this approach is explained only for the purpose of illumination.. Exercises 1. Enter a non javabean Code 39 Extended existent value for the option parameter for StartServlet and note what happens. How can you improve this outcome There are two options to do this: make changes directly in code or in web.

xml. 2. Create a new JSP with any name and call it through StartServlet.

Delete the JSP and try to call it again (without reloading the context).. 9 . 9.2 Central Controller with Struts ActionServlet provides the "controlle jdk bar code 39 r" in the Model-View-Controller (MVC) design pattern for web applications that is commonly known as "Model 2". This nomenclature originated with a description in the JavaServerPages Specification, version 0.92, and has persisted ever since (in the absence of a better name).

Struts API. Struts offers the so-called ActionServlet for the central control of web application logic. As mentioned previously, you have used ActionServlet already. Create a new shop6 from shop5 and open up the WEB-INF/web.

xml file. Look for the entries matching those shown in Listing 9.2.

Listing 9.2: Definition of ActionServlet in web.xml.

<servlet> javabean barcode code39 ; <servlet-name>action</servlet-name> <servlet-class> org.apache.struts.

action.ActionServlet </servlet-class> <init-param> <param-name>config</param-name> <param-value>/WEB-INF/struts-config.xml</param-value> </init-param> </servlet> .

. . <servlet-mapping> <servlet-name>action</servlet-name> <url-pattern>*.

do</url-pattern> </servlet-mapping>. As you can see , you have a mapping for this class in web.xml (which comes from the blank Struts template folder we copied from when we made our first Struts site). The class itself is contained within the Struts framework JAR file.

It indicates that every call to an Action class (ending in .do, for instance, is mapped through the ActionServlet.

It"s worthwhile looking into the Struts API where the ActionServlet class is documented in detail. It has methods common to all servlets, namely doGet() and doPost(). It also handles the possibility of sub-applications.

Sub-applications divide a project in smaller projects, and are useful only for big projects so we will not discuss them here. It is usually not necessary to extend ActionServlet. You can configure the mapping of beans to forms and classes in struts-config.

xml as we did in previous chapters..
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