NetBeans IDE 6.0 Tutorial for Web Applications

Contents Terminology Obtaining the required source files Developing the Application Creating a web project from the provided source files Creating a front controller using a servlet Adding the methods to process requests and to create a cookie Creating the JSP page that receives all the requests Creating the parameter files used to handle user input Using JSTL to handle internationalization Wrapping up Running and Monitoring the Application Enabling the HTTP Monitor Verifying the Context Path Running the application Monitoring requests and sessions Monitoring cookies Monitoring requests for non-existent pages Enabling internationalization Applying What You Have Learned Exploring Further Glossary Next Steps

Installing the Software

Before you begin, you need to install the following software on your computer:

• NetBeans IDE 6.0 Web & Java EE .
• Java Standard Development Kit (JDK™) version 5.0 or version 6.0

Creating a web project from the provided source files

1. Choose File > New Project (Ctrl-Shift-N). Under Categories, select Web. Under Projects, select Web Project with Existing Sources. Click Next.
2. In Location, click Browse to select the web application's document root. The document root is $UNZIPHOME, which is called midnight, if you followed the instructions above. This is the folder to which you unzipped the midnight.zip file. You should see the following:

   

3. In Project Name, notice that midnight has been set. Capitalize the name to "Midnight", just for display purposes, because project name's initial letter is typically capitalized. Change the Project Location to any folder on your computer. From now on, we will refer to this folder as $PROJECTHOME.
4. In Server, select the server.
5. In Java EE Version, make sure that Java EE 5 is selected. Notice that the Context Path is /Midnight. Click Next.
6. In Web Pages Folder, select the document root ($UNZIPHOME). Notice that the $PROJECTHOME/Midnight/WEB-INF/lib and the $PROJECTHOME/Midnight/WEB-INF/classes folders are automatically selected as your lib and sources folders, respectively, as shown here:

   

   Click Finish.

   You are prompted to let the IDE delete your class files, because they will automatically be compiled to your project's build folder when you build the project.

   

   Click Delete to let the IDE do this.

   The IDE imports your sources, deletes the class files, and creates the Midnight project in the IDE. You can view its logical structure in the Projects window and its file structure in the Files window.

   

Creating a front controller using a servlet

A front controller is responsible for routing incoming user requests and can enforce navigation in web applications. A front controller provides a single entry point through which requests for several resources in a web application pass. A front controller can reduce duplication of code in JSP pages, especially in cases where several resources require the same processing. For more information on front controllers, see the J2EE Patterns catalog.

1. Expand the Midnight project node and the Source Packages node.
2. Right-click the com.midnightcookies package node and choose New > Servlet.
3. Enter FrontController in the Class Name text box and make sure that the com.midnightcookies package is selected in the Package drop-down. Click Next.
4. Change the value of the URL Pattern(s) text box to the following:

    /docs/*, /

   

   Note that the "," in the line above is a delimiter between URL mappings. It enables you to create multiple URL mappings for each servlet.

5. Click Finish.

   FrontController.java opens in the Source Editor.

6. Expand the Web Pages node and the WEB-INF node. Double-click the web.xml node. The content of the deployment descriptor file, web.xml, is displayed in the graphical editor. Click Servlets at the top of the editor. Expand the node for the FrontController servlet's entry. Notice the servlet's URL Patterns, which you defined in step 4 above:

   

   The servlet mapping "/docs/*" prevents the FrontController servlet from forwarding pages to itself, while the servlet mapping "/" gives the FrontController servlet a servlet mapping to handle a request such as http://hostname:portnumber/midnight/.

   Click XML at the top of the editor. The content of the deployment descriptor file is shown in XML format. The servlet mappings are as follows:

   

Adding the methods to process requests and to create a cookie

Now you will edit the FrontController.java file to include the logic needed to process the requests received by the web application. You will modify the processRequest method and create a new method called createCookie, which demonstrates how to create a cookie used in a web application.

1. Open the Navigator (Ctrl-7) and select the FrontController.java node in the Projects window. You now see the class's methods in the Navigator:

   

2. Click the processRequest method's node in the Navigator. The Source Editor displays the processRequest method.
3. Replace the default processRequest method with the following code:

   
    protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
        String id = request.getRequestURI();
        id = id.substring(request.getContextPath().length());
        getServletContext().log
          ("Midnight Cookies FrontController received a request for " + id);
           
        // The page variable holds the path to the page that will be included
        // in the content area of the template page /WEB-INF/docs/main.jsp.
        // It is passed to the template in a request attribute.
        String page;
           
        // If no request is received or if the request received is
        // for the root, serve /WEB-INF/docs/index.jsp
        if (id == null || id.trim().equals("") || id.equals("/")){
            page = "/WEB-INF/docs/index.jsp";
        }
           
        // If a request received is for a file that does not end in
        // .jsp or .html, there was an error. Include the
        // error page (nonesuch.jsp) and set the nonesuch attribute with
        // the path requested.
        else if (!id.endsWith(".jsp") && !id.endsWith(".html")) {
            page = "/WEB-INF/docs/nonesuch.jsp";
            request.setAttribute("nonesuch", id);
        }
        else {
            page = "/WEB-INF".concat(id);
               
            if (id.equals("/docs/cookies/CookieMake.jsp")) {
                Cookie cookie = createCookie(request);
                if (cookie == null) {
                    page = "/WEB-INF/docs/cookies/CookieCutter.jsp";
                }
                else {
                    response.addCookie(cookie);
                    request.setAttribute("cookie", cookie);
                }
            }
        }
           
        request.setAttribute("page", page);
        try {
            request.getRequestDispatcher("/WEB-INF/docs/main.jsp").forward(request, response);
        }
        catch(Throwable t) {
            getServletContext().log(t.getMessage());
        }
    }
           

   Note: After you enter code (either by typing or copying and pasting) into the Source Editor, place the cursor in the Source Editor and press Alt-Shift-F to automatically format the code. To show line numbers, right-click the left margin and choose Show Line Numbers from the contextual menu.

   The line with the call to the createCookie method is underlined and marked as an error, similar to the following illustration. This is because the method does not exist yet.

   Click Alt-Enter in the line with the error and notice that the IDE presents a suggestion of how to solve the error:

   

4. Select the suggestion. The IDE creates the skeleton createCookie method at the end of the file.
5. Fill out the new createCookie method by copying the following code and pasting it in the Source Editor:

     
       private Cookie createCookie(HttpServletRequest request) {
   
           String name = (String)request.getParameter("name");
           if (name == null || name.trim().equals("")) {
               request.setAttribute("noname", "noname");
               request.setAttribute("error", "true");
   	    return null; 
           }
           
           String value = (String)request.getParameter("value");
           if (value == null || value.trim().equals("")) {
               request.setAttribute("novalue", "novalue");
               request.setAttribute("error", "true");
   	    return null; 
           }
           
   	System.out.println(name); 
   	System.out.println(value); 
   
   	Cookie cookie = null; 
   	try { 
   	    cookie = new Cookie(name, value);
   	}
   	catch(IllegalArgumentException ex) { 
   	    // Probably an illegal name
   	    ex.printStackTrace(); 
   	    request.setAttribute("error", "true");
   	    request.setAttribute("noname", "badname");
   	    return null; 
   	}
   
   	String maxage = request.getParameter("maxage");
   	if (maxage != null && !maxage.trim().equals("")) {
   	    try {
   		cookie.setMaxAge(Integer.parseInt(maxage));
   	    }
   	    catch(NumberFormatException nfe) {
   		nfe.printStackTrace(); 
   		request.setAttribute("badnumber", "badnumber");
   		request.setAttribute("error", "true");
   		return null; 
   	    }
   	}
           
   	String domain = request.getParameter("domain");
   	if (domain != null && !domain.trim().equals("")) {
   	    cookie.setDomain(domain);
   	}
           
   	String path = request.getParameter("path");
   	if (path != null && !path.trim().equals("")) {
   	    cookie.setPath(path);
   	}
           
   	String secure = request.getParameter("secure");
   	if (secure != null && secure.equals("on")) {
   	    cookie.setSecure(true);
   	} else {
   	    cookie.setSecure(false);
   	}
           return cookie;
       }
   
               

6. The asterisk in the file's tab at the top of the Source Editor appears whenever there are changes that have not been saved to disk:

   

   Press Ctrl-S to save the document. The asterisk in the file's tab at the top of the Source Editor disappears.

7. In the Projects window, right-click the FrontController.java node and select Compile File (F9) to check that there were no errors introduced in the steps you have completed. The Output window displays messages from the compiler, including any errors. You can double-click the links in the error messages to locate the source of the error. Resolve all errors listed in the Output window before continuing with the tutorial.

Creating the JSP page that receives all the requests

The main.jsp page receives all the requests that the FrontController servlet processes. A dynamic include statement and a LinksHandler are used to create the page.

1. Expand the Midnight project node, the Web Pages node, and the WEB-INF node. Right-click the docs node, choose New > JSP, and name the JavaServer Pages file main. Click Finish.

   Now main.jsp opens in the Source Editor.

2. In the Source Editor, replace the contents of the main.jsp file with the following code:

   
     <%@page contentType="text/html;charset=UTF-8"%>
     <%@page buffer="none"%> 
     <%-- The <midnight:content/> tag which handles the contents section 
     is simplistically implemented to use an include. Hence this page
     cannot be buffered --%>
   		
     <%@taglib prefix="midnight" uri="http://www.midnightcookies.com/midnight"%> 
   
     <html>
       <head><title>The Midnight Cookie Company</title></head>
       <body text="#996633" link="#cc6600" vlink="#993300" alink="#000000">
           <span font-style="sans-serif">
               <TABLE border="0">
   		<tr>
   		    <table border="0">
   			<tr><td width="80" height="100">&nbsp;</td>
   			    <td width="500" height="100" 
   
   				text="#996633" bgcolor="#ffff99"
   				valign="center"halign="center">
   				<jsp:include page="/WEB-INF/docs/header.jsp" 
   					     flush="true"/>
   			    </td>
   		        </tr>
   			<tr><td width="90" height="300" 
   				text="#996633" bgcolor="#ffff99"
   				valign="top">
   				<midnight:links separator="<br>"/>
   			    </td>
   			    <td width="500" height="300" 
   				valign="top"cellpadding="15"
   				cellspacing="15">
   				<midnight:content/>
   			    </td>
   		        </tr>
   		    </table>
   		</tr>
   		<tr><td width="580" height="50" text="#996633" 
   			bgcolor="#ffff99" valign="top">
   			<midnight:links separator="|"/>
   		    </td>
   		</tr>
   	    </TABLE>
           </span>
       </body>
     </html>
   
               

   Note: After you enter code (either by typing or copying and pasting) into the Source Editor, place the cursor in the Source Editor and press Alt-Shift-F to automatically format the code.

3. Press Ctrl-S to save your changes.

Creating the parameter files used to handle user input

The parameter files that you create in this section illustrate the use of tags from tag libraries to handle internationalization. They also show how input is passed through the Request parameters, specifically through the JSP expression language (EL) expression ${param.input}, which is set in the input field of the Input.jsp page.

1. Right-click the docs node and select New > Other from the contextual menu. Under Categories, select Other and under File Types, select Folder. Click Next.
2. In the Name and Location panel, type parameters in the Folder Name text field and click Finish. The new parameters folder appears in the Projects window under the docs node.
3. Right-click the parameters node and choose New > JSP. Type Input in the JSP File Name text field and make sure that WEB-INF/docs/parameters is selected in the Folder text box. Click Finish.

   Now Input.jsp opens in the Source Editor.

4. In the Source Editor, replace the contents of the Input.jsp file with the following code:

   
     <%@page contentType="text/html;charset=UTF-8"%>
     <%@taglib prefix="fmt" uri="http://java.sun.com/jstl/fmt" %>
     <%@taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
     <%@taglib prefix="midnight" uri="/WEB-INF/tlds/midnight.tld"%> 
   
     <fmt:setBundle basename="com.midnightcookies.Midnight" var="bundle"
   	       scope="page"/>
   
     <h3><fmt:message key="provide_input" bundle="${bundle}"/></h3>
     <form method="POST" action="Output.jsp">
           <table>
               <tr>
   		<td><fmt:message key="type_input" bundle="${bundle}"/>:<td>
   		<%-- The value of the Input field will be placed in a
   		      request parameter named "input" and it will be
   		      passed to Output.jsp --%> 
   		<td><input type="text" size="20" name="input" value=""></td>
               </tr>
   	    <tr>
   		<td><fmt:message key="submit" bundle="${bundle}" 
   		                 var="buttonLabel" scope="page"/>
                        <midnight:button/>
                   </td>
                   <td></td>
               </tr>
           </table>
     </form>
   
               

5. Press Ctrl-S to save your changes.
6. Create an Output.jsp file in the Parameters folder using the same method that you used to create the Input.jsp file.
7. In the Source Editor, replace the contents of the Output.jsp file with the following code:

   
     <%@page contentType="text/html;charset=UTF-8"%>
     <%@ taglib prefix="fmt" uri="http://java.sun.com/jstl/fmt" %>
     <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
   
     <fmt:setBundle basename="com.midnightcookies.Midnight" var="bundle" scope="page"/>
     <h3><fmt:message key="display_input" bundle="${bundle}"/></h3>
     <fmt:message key="datareceived" bundle="${bundle}"/>: 
   
     <!--The following line gets the value of the request parameter named
     "input". This is a demo application. For security reasons, one should
     never echo user input without parsing first. -->
     <c:out value="${param.input}"/>
   
               

8. Press Ctrl-S to save your changes.

Using JSTL to handle internationalization

The Tray.jsp page that you create in this section illustrates the use of the JSTL, instead of scripting, to internationalize the page. The CookieCutter.jsp file, CookieMaker.jsp file, and resource bundle property files have been provided with the midnight.zip file. You can take a closer look at those files and the Tray.jsp file for examples of how internationalization is handled in this application.

1. Expand the docs node and expand the cookies node.
2. Create a Tray.jsp file in the cookies folder using the same method that you used to create the other JSP files. Make sure that you put it in the cookies folder.
3. In the Source Editor, replace the contents of the Tray.jsp file with the following code:

   
     <%@page contentType="text/html;charset=UTF-8"%>
     <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
     <%@ taglib prefix="fmt" uri="http://java.sun.com/jstl/fmt" %>
   
     <fmt:setBundle basename="com.midnightcookies.Midnight" var="bundle" scope="page"/>
     <h3><fmt:message key="cookies" bundle="${bundle}"/></h3>
       
     <table border="1">
        <tr>
           <th halign="center">#</th>
   	<th align="left">
   	    <fmt:message key="name" bundle="${bundle}"/>
           </th>
           <th align="left">
   	    <fmt:message key="value" bundle="${bundle}"/>
           </th>
        <tr> 
        <%-- We have to use expression to get at an array. 
             If we use ${cookie} then we get a map and 
             the entries are not automatically cast --%>   
        <% request.setAttribute("cookies", request.getCookies()); %>
        <c:set var="i" value="0"/>
        
        <c:forEach var="ck" items="${cookies}">
   	<c:set var="i" value="${i+1}"/>
   	<tr>
   	    <td><c:out value="${i}"/></td>
   	    <td><c:out value="${ck.name}"/></td>
   	    <td><c:out value="${ck.value}"/></td>
           </tr> 
       </c:forEach>
     </table> 
   
               

4. Press Ctrl-S to save your changes.

Wrapping up

Once you have completed the development stage as described above, the views in the Projects window and Files window should look as follows:

         

Note: The application illustrated above deploys to the Tomcat Web Server. If you have registered and selected a different target server instead, you will not have a META-INF/context.xml file. For example, if your server is the Sun Java System Application Server, you will have a WEB-INF/sun-web.xml file as your deployment descriptor.

Enabling the HTTP Monitor

The HTTP Monitor is enabled by default for the Tomcat Web Server. However, for other servers, you must manually enable the HTTP Monitor. In addition, the HTTP Server must be started for the HTTP Monitor to work for other servers.

Do the following to prepare to use the HTTP Monitor:

1. Choose Tools > Server Manager from the main window.
2. Select the server.
3. Click Enable HTTP Monitor and then click Close.
4. In the Runtime window, right-click the HTTP Server node and choose Start HTTP Server.

Verifying the Context Path

1. Right-click the Midnight project node and choose Properties.
2. In the Project Properties dialog box, click Run.
3. Make sure that the Context Path is set to /Midnight.

Running the application

1. In the Projects window, right-click the Midnight project node and choose Run Project from the contextual menu.

   A progress monitor window appears as the application is prepared and deployed to the web server.

   The web browser launches with the URL set to http://hostname:port/Midnight. The following example shows the web browser running on a Microsoft Windows platform.

   

2. In the IDE, notice that the HTTP Monitor is displayed.

   The following sections illustrate how you can use the HTTP Monitor to monitor requests, sessions, and cookies.

Monitoring requests and sessions

1. In the HTTP Monitor, select the last entry under the Current Records node.

   The last entry represents the request for the Midnight web application.

2. Select the Request tab and you see information similar to the following.

   

3. Select the Session tab and you see information similar to the following.

   

4. In your web browser, click the Parameters link to display the Input.jsp page.

   Your web browser displays information similar to the following.

   

5. In the Type Input text field, type hello and click Submit data.

   Your web browser displays the contents of the Output.jsp page, similar to the following.

   

6. In the HTTP Monitor, select the last entry under the Current Records and select the Request tab.

   The HTTP Monitor displays information similar to the following.

   

Monitoring cookies

1. In your web browser, click the Cookies link.

   Your web browser displays the CookieCutter.jsp page.

2. In the Name text field, type cookie, and in the Value text field, type chocolate.

   

3. Click "Make me a cookie now!".

   Your web browser displays information similar to the following.

   

4. In the HTTP Monitor, select the last entry under the Current Records node.

   The Cookies tab in the HTTP Monitor displays information similar to the following.

   

5. In your web browser, click Cookie tray, and your web browser displays information similar to the following.

   

6. In the HTTP Monitor, select the last entry under the Current Records node and select the Cookies tab.

   The HTTP Monitor displays information similar to the following.

   

7. Select the Request tab and the HTTP Monitor displays information similar to the following.

   

8. In the HTTP Monitor, right-click the same entry (GET Tray.jsp) under the Current Records node and choose Edit and Replay from the contextual menu. In the Edit and Replay dialog box, click the Cookies tab and click Add Cookie. Set the name to Ingredient and the value to Sugar. Click Send HTTP Request. The browser redisplays the page with the new cookie.

Monitoring requests for non-existent pages

1. In your web browser, type a URL for a page that does not exist to see how the nonesuch.jsp page is used. For example, you might type http://localhost:8084/Midnight/docs/Bake.jsp for the URL and your web browser displays something similar to the following.

   

2. In the HTTP Monitor, select the Request tab and you will see information similar to the following.

   

   Notice that the content of nonesuch.jsp page is displayed in place of the non-existent Bake.jsp page.

Enabling internationalization

1. Modify the language preference used by your web browser to either French or Swedish in order to see the internationalization feature of this Midnight Cookie Company web application.

   Note that you might have to add these two languages to the list of languages currently available to your web browser.

2. Reload or refresh the pages you have viewed in the previous steps.

   Notice how the links in the left navigation bar, the links on the bottom of the pages, and the contents of some of the application's JSP pages have been translated to the language you have chosen.

   The web application uses the resource bundle property files to help translate some of the pages used in this web application. So, the translation is only as extensive as the contents of the resource bundle property files.

Add an Exit link that takes the user to a page that says "Goodbye" in the appropriate language

1. Right-click the com/midnightcookies/Midnight.properties file and choose Open from the contextual menu. Add the following keywords and values.

   Keyword	Default	French	Swedish
   exit	Exit	Sortie	Utgång
   closingRemark	Goodbye	Au revoir	Hej då

   Use å to display the å character.

2. Add an Exit.jsp content file. Use the message tag from the fmt tag library to display the message for the closingRemark keyword (Hint: look at Output.jsp). Don't forget to add a taglib directive for the fmt tag library.
3. Open the com/midnightcookies/taghandlers/LinksHandler.java file in the Source Editor and add a link to the Exit.jsp file. Use the exit keyword to get the link text from the properties bundle. Compile the class.
4. Execute the web application.

Below are some other web application features that you might want to explore.

Examining the Midnight tag library

Expand the tlds/Midnight node to see the list of tags in the library. Look at the the Links tag in the Source Editor and at its Attributes to see that it takes a separator attribute.

Debugging web applications

Open the docs/main.jsp file in the Source Editor and set a breakpoint by clicking in the margin at approximately line 32 (the line that invokes midnight:content). Right-click the project node in the Projects or Files window and choose Debug Project from the contextual menu. The web application will stop at the breakpoint that you set. Press F7 to step into the code. Whenever a dialog appears because of missing source, press OK to select the default of stopping at the first line with source. Continue pressing F7 until you enter the otherDoStartTagOperations() function in the ContentHandler class. Set a breakpoint at line 50 (request.getRequestDispatcher(page).include(request, response)) and press Ctrl-F5 (continue). Place the cursor over "page", "request", and "response" to see the values. You can also see the values in the Local Variables tab. Note that the Call Stack tab shows the relationship between the JSP code and the generated servlet methods. Try setting other breakpoints. Right-click a variable and choose New Watch from the contextual menu. Click the Watches tab to see the values change as you execute the various pages in the web application. Choose Debug > Finish Session to quit the debugging session.

Testing JSP files

To run a public JSP file (one that is not under the WEB-INF folder), you simply right-click the file's node and choose Execute from the contextual menu. If a page is loaded, clicking the Browser's reload button will display any modifications that you have made. Private JSP files, like the ones in this tutorial, are a little harder to execute. One way to test a modified private JSP file without having to restart the web application and navigate to that page is to use the HTTP Monitor's replay action. Modify the docs/cookies/Tray.jsp file by setting the table's border to 10 and save your changes. In the HTTP Monitor, right-click a GET Tray.jsp record and choose Replay from the contextual menu. The Tray.jsp page should appear in the browser with a larger table border.

Below are explanations of some of the terms used in this tutorial.

Composite View

A design pattern that is used to present information in JSP pages. This design pattern creates an aggregate view from component views. Component views might include dynamic and modular portions of the page. The Composite View design pattern pertains to web application design when you are creating a view from numerous subviews. Complex web pages frequently consist of content derived from various resources. The layout of the page is managed independently of the content of its subviews. For instance, a view might have subviews such as Navigation, Search, Feature Story, and Headline.

When creating a composite view, you can include static content and dynamic content. Static content might consist of an HTML file. Dynamic content is a fragment of a JSP page. The specific content can be determined at either JSP translation time or at runtime.

Front Controller

Front controllers are responsible for routing incoming requests and enforcing navigation in web applications. For more information on the use of the Front Controller design pattern, see the J2EE Patterns catalog.

JSP page

Pages that are used in web applications to present information to end users and to enable data from end users to flow back to the server. JSP pages must be placed within a web application in order for the JSP pages to be executable within the IDE.

Servlet

Servlets are Java classes that execute within a servlet container, which is typically running within a web server. Servlets are used to do the following:

• Generate dynamic content.
• Extend the capabilities of web servers and web-enabled application servers.
• Interact with web clients (typically a browser application such as Netscape or Internet Explorer) using a request-response paradigm