Developing WEB applications with Tomcat and Eclipse

Developing WEB applications with Tomcat and Eclipse

Apache Tomcat & Eclipse Platform is an outstanding WEB development platform

If you integrate Eclipse directly with Apache Tomcat, it will be easier to use it as a WEB development platform. In this article, learn how to set up Eclipse and Apache Tomcat V5.5 to develop the classic Hello world servlet.

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Nathan A. Good, writer and software engineer, Freelance Developer

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Nathan A. Good lives in Twin Cities, Minnesota. Its full-time work is software development, software architecture and system management. While not writing software, he likes to assemble PCs and servers, read and write technical articles, and encourage all his friends to switch to open source software. He authored and collaborated with others on a number of books and articles, including Professional Red Hat Enterprise Linux 3,Regular Expression recipes:a Problem-solution approach,Regular Expression Recipes for Windows developers:a problem-solutionapproach, PHP 5 recipes:a problem-solution approach and the latest masterpiece Foundations of pear:rapid PHP development.

May 25, 2007

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edited Note : This article is a follow-up to the article "using Eclipse as a development environment for Jakarta Tomcat" published in June 2004 by Geoffrey Duck.

Required Components

The Eclipse V3.2 Callisto integrated Development Environment (IDE) includes tools for WEB development and integration with servers. So, in addition to the Software Development Toolkit (SDK), just install Eclipse and Apache Tomcat. The components and versions used in this article are as follows:

Table 1. Components and versions to use

The Eclipse IDE is an open source IDE that serves as the development environment for Java™server Pages (JSP) and Java files. If you install both the Web and Java 2 platform,enterprise Edition (EE) development tools, Eclipse will be great for creating HTML, JSPs, and Servlets.

The Java SDK is required to run the servlet. Finally, Apache Tomcat is also used in the formal reference implementation of Java Servlet and Java Server Page, an open source Web and Servlet container.

Installation

The installation of Eclipse and Tomcat is very similar-you need to unzip the archive file to a folder on your local hard disk. If you want to uninstall any of them, simply delete the folder that contains the extracted files.

Install Eclipse

To install the Eclipse IDE, unzip the compressed file (. zip or. tar.gz) downloaded from the Eclipse Web site, and then put the compressed folder in the appropriate location. I choose the location of the installation based on the conventions of the operating system you are using. If you install Eclipse on the Macintosh, I'll place the Eclipse folder inside the Applications folder. If you are using microsoft™windows™, I will put the unpacked folder into the C:\Program file directory.

Once you've downloaded and installed Eclipse, you're ready to start it. Before you start creating a Web project, you need to install the Java EE and Web development plugins. Fortunately, these plugins are easy to install with the Callisto Discovery site.

Install Web Tools

After the Eclipse IDE is working, select Help > Software Updates > Find and Install. This option allows you to download and install Web tools without having to go to the Web site.

Select Search for New Features to Install, as shown below, and then click next.

Figure 1. Install/Update window

Select Callisto Discovery Site, as shown below, and then click next.

Figure 2. Select Callisto Discovery Site

Under Callisto Discovery Site , select the Web and Java EE development check box. The wizard warns you that a dependency is missing. When you click Select Required, the warning disappears. Some or all of the components in the graphical Editors and frameworks and Models and Model development categories are selected (shown in 3), which are required to install the WEB and Java EE plug-ins.

Figure 3. Select the features to install

Click Next to continue, and the certificate protocol for each of the selected attributes will also appear. If you agree to these certificates, select Accept to continue the wizard's follow-up process. When the IDE finishes installing the plug-in, you will be asked to restart Eclipse so that the changes will take effect. Be sure to restart the IDE before continuing.

When the IDE is restarted, the new features required to begin developing a dynamic WEB project are ready to be completed.

Installing Tomcat

To install Apache Tomcat, unzip the downloaded archive and put it in the directory, and I put it in my C:\apps directory for later search. This is enough for the time being to start Tomcat using the Eclipse shown later.

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To create a new WEB project

From the Eclipse IDE, choose File > New > Project to View the Projects Wizard. In the Wizards box, enter Web , and the New Project window Filters The wizard to show only those items that match. This approach makes it easy to find wizards without having to traverse each item.

Select Dynamic Web Projectfrom the list. We're going to use the standard WEB project Wizard to build a static HTML Web project. Although you can also technically use Tomcat to run a static Web site, Web servers, such as Apache Web server, are more suitable for static content. WEB servers that are designed to serve static pages have less overhead and are specifically tuned for this purpose.

Target the run-the-Library

Under Target runtime , you can see <none>, 4, as you have not yet created the runtime for Apache Tomcat, you need to click New to open New Target Runtime Wizard. Select Apache Tomcat V5.5 from the Apache folder, shown in 5, and click Next.

Figure 4. Create a new dynamic Web project Figure 5. Create a new server runtime

You can now name this runtime, and of course preserve the default name of Apache Tomcat V5.5. Click Browse to locate the basic folder for Apache Tomcat configuration (My is C:\apps\apache-tomcat-5.5.20, 6). For no particular reason, I recommend that you do not change, leaving the Ibm®java Runtime Environment (JRE) version as the default JRE for the workbench. After entering a valid directory, click Finish to create the runtime configuration.

Figure 6. Define the server location runtime configuration

If you find yourself needing to change your runtime configuration in the future, you can do this by choosing Window > Preferences . In the Filter box, type the Runtime list to display the installed run-Library configuration settings under the Server category. Select your Apache Tomcat runtime and click Edit To change the name, directory location, or JRE version.

You also need to choose whether you want to convert to the Java EE perspective. I always choose Yes, because this perspective contains some very useful views, such as the Servers view, that can help you to start and stop Tomcat in the future. You can open the Servers view by selecting Window > Show view .

Add Server

The Servers view does not currently contain any content. This view is for applications and WEB servers, which let you control them and monitor their status. To control tomcat directly from the IDE, you can add a reference to Tomcat by selecting New > Server from the context sensitive menu . The New Server Wizard, shown in Figure 7, will default to the Apache Tomcat V5.5 runtime that you just created.

Figure 7. Define a new server

Click Next. The system asks if you want to add items to the server. Select the project that you created in the previous steps, and then click Add.

Figure 8. Add a project to the server

Click Finish to Close the wizard. The Servers view now contains the Tomcat V5.5 Server, and it also contains the project.

Figure 9. The Tomcat server in the Servers view creates a sample page

The easiest way to test the new dynamic Web project and the Tomcat server integration is to create a simple JSP and deploy it to Tomcat. You can create a new JSP file by choosing File > New > other , or you can use a context sensitive menu by right-clicking the project name in Project Explorer view and selecting new > JSP.

Make sure that the parent directory is webcontent and name the file index.jsp. Click Finish to create the page using the default template. If you click Next, you can also select the template you want to use for the new page (such as HTML or XHTML). For this test, you can leave the default options.

The page code shown below shows a simple date, which indicates that the code works correctly.

Listing 1. Index.jsp's Content

<%@ page language= "java" contenttype= "text/html; Charset=iso-8859-1 "    pageencoding=" Iso-8859-1 "%><! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en"     "Http://www.w3.org/TR/html4/loose.dtd" >
Deploy this page
After the test page is complete, you can use Eclipse to redeploy it to Apache Tomcat. In the Servers view, notice that the state has been set to republish. This is because many changes have occurred since the project was last deployed to the server. Right-click the server and select Publish from the menu  . Once the project is deployed to this server, the status becomes Synchronized. 
Having a problem?
Sometimes things go wrong. To see the errors generated from Tomcat, you can use the Console view. The Console captures the output from the server that you set up in the Servers view.
After the project is successfully deployed and the server starts successfully, you can open the browser and navigate to http://localhost:8080/[projectname]/(where [ProjectName] is the name of the dynamic Web project you created). The new Web page that you created appears, and the date should be the current date. If you refresh the page, the date will change as well.
Figure 10. index.jsp output in the browser Hello World servlet
You can add Java Servlets to your project and deploy it. To quickly create a servlet for testing purposes, you can use the servlet Wizard by right-clicking the dynamic WEB project in Project Explorer View and choosing New >Other. Under Web folders, select the  Servlet, and then click  next. 
Add the package name to the Java packages next to the  com.example.servlets      HelloServlet   Class name  . Click  Finish. As an example, you can leave the default values. The Eclipse IDE generates a servlet class. To see this test servlet in the app, you can  doGet() add a line of code to the method to print the message to the Responsewriter. The servlet class should resemble this as shown below. 
Listing 2. Helloservlet.java's Content
Package Com.example.servlets;import Java.io.ioexception;import Javax.servlet.servletexception;import Javax.servlet.http.httpservletrequest;import javax.servlet.http.httpservletresponse;/** * servlet implementation Class for Servlet:helloservlet * * */public class HelloServlet extends Javax.servlet.http.HttpServlet implements Java X.servlet.servlet {/* (non-java-doc) * @see javax.servlet.http.httpservlet#httpservlet () */public HelloServlet () {Supe   R ();} /* (non-java-doc) * @see Javax.servlet.http.httpservlet#doget (httpservletrequest request, HttpServletResponse respons e) */protected void doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioexcepti on {response.getwriter (). Write ("Hello, world!");}/* (non-java-doc) * @see javax.servlet.http.httpservlet#dopost (httpservletrequest request, HttpServletResponse Res ponse) */protected void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioex ception {//TODO auto-generated method stub}}
After you add this servlet, the Eclipse IDE prompts you to change the project. Look again at the Servers view; Restart now appears in the Status column next to the TOMCAT server. To restart this server, right-click the server in the Servers view and select  Restart > Start. Open the browser and navigate to Http://localhost:8080/[projectname]/helloservlet (where [ProjectName] is the name of the dynamic Web project). The text "Hello, world!" will appear in the browser window. You can add dates, add similar code in the index.jsp file to the  doGet() method, and redeploy the servlet using the Eclipse IDE. 

 
  
 
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Conclusion
You can start, stop, and deploy to the server without leaving the IDE, which is a very efficient way to develop JSPs and Servlets. The combination of Eclipse and Apache Tomcat provides a simple integration environment that allows you to accelerate your development.
Excerpt from IBM DeveloperWorks
Developing WEB applications with Tomcat and Eclipse