1.4.3. Review the Quickstart Tutorials
1.4.3.1. Explore the helloworld Quickstart
Summary
The helloworld quickstart shows you how to deploy a simple Servlet to JBoss EAP 6. The business logic is encapsulated in a service which is provided as a CDI (Contexts and Dependency Injection) bean and injected into the Servlet. This quickstart is very simple. All it does is print "Hello World" onto a web page. It is a good starting point to be sure you have configured and started your server properly.
Detailed instructions to build and deploy this quickstart using a command line can be found in the README.html file at the root of the helloworld quickstart directory. Here we show you how to use Red Hat JBoss Developer Studio to run the quickstart. This topic assumes you have installed Red Hat JBoss Developer Studio, configured Maven, and imported and successfully run the
helloworld quickstart.
Prerequisites
- Install Red Hat JBoss Developer Studio following the procedure here: Section 1.3.1.3, “Install Red Hat JBoss Developer Studio 7.1”.
- Configure Maven for use with Red Hat JBoss Developer Studio following the procedure here: Section 2.3.3, “Configure Maven for Use with Red Hat JBoss Developer Studio”.
- Follow the procedures here to import, build, and deploy the
helloworldquickstart in Red Hat JBoss Developer Studio: Section 1.4.2.1, “Run the Quickstarts in Red Hat JBoss Developer Studio” - Verify the
helloworldquickstart was deployed successfully to JBoss EAP by opening a web browser and accessing the application at this URL: http://localhost:8080/jboss-helloworld
Procedure 1.9. Examine the Directory Structure
The code for the helloworld quickstart can be found in the
QUICKSTART_HOME/helloworld directory. The helloworld quickstart is comprised a Servlet and a CDI bean. It also includes an empty beans.xml file which tells JBoss EAP 6 to look for beans in this application and to activate the CDI.
- The
beans.xmlfile is located in theWEB-INF/folder in thesrc/main/webapp/directory of the quickstart. - The
src/main/webapp/directory also includes anindex.htmlfile which uses a simple meta refresh to redirect the user's browser to the Servlet, which is located at http://localhost:8080/jboss-helloworld/HelloWorld. - All the configuration files for this example are located in
WEB-INF/, which can be found in thesrc/main/webapp/directory of the example. - Notice that the quickstart doesn't even need a
web.xmlfile!
Procedure 1.10. Examine the Code
The package declaration and imports have been excluded from these listings. The complete listing is available in the quickstart source code.
Review the HelloWorldServlet code
TheHelloWorldServlet.javafile is located in thesrc/main/java/org/jboss/as/quickstarts/helloworld/directory. This Servlet sends the information to the browser.42. @SuppressWarnings("serial") 43. @WebServlet("/HelloWorld") 44. public class HelloWorldServlet extends HttpServlet { 45. 46. static String PAGE_HEADER = "<html><head><title>helloworld</title></head><body>"; 47. 48. static String PAGE_FOOTER = "</body></html>"; 49. 50. @Inject 51. HelloService helloService; 52. 53. @Override 54. protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 55. resp.setContentType("text/html"); 56. PrintWriter writer = resp.getWriter(); 57. writer.println(PAGE_HEADER); 58. writer.println("<h1>" + helloService.createHelloMessage("World") + "</h1>"); 59. writer.println(PAGE_FOOTER); 60. writer.close(); 61. } 62. 63. }Table 1.1. HelloWorldServlet Details Line Note 43 Before Java EE 6, an XML file was used to register Servlets. It is now much cleaner. All you need to do is add the @WebServletannotation and provide a mapping to a URL used to access the servlet.46-48 Every web page needs correctly formed HTML. This quickstart uses static Strings to write the minimum header and footer output. 50-51 These lines inject the HelloService CDI bean which generates the actual message. As long as we don't alter the API of HelloService, this approach allows us to alter the implementation of HelloService at a later date without changing the view layer. 58 This line calls into the service to generate the message "Hello World", and write it out to the HTTP request. Review the HelloService code
TheHelloService.javafile is located in thesrc/main/java/org/jboss/as/quickstarts/helloworld/directory. This service is very simple. It returns a message. No XML or annotation registration is required.public class HelloService { String createHelloMessage(String name) { return "Hello " + name + "!"; } }
