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J2EE Thin-Client Multitiered Application Path and ClassPath Settings

Learn how to set up the path and classpath settings for a J2EE thin-client multitiered application. Includes step-by-step instructions and code examples.

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J2EE Thin-Client Multitiered Application Path and ClassPath Settings

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  1. WritingEnterprise Applications with J2EE(First lesson) Alessio Bechini June 2002 (based on material by Monica Pawlan)

  2. Example Thin-Client Multitiered Application Path and ClassPath Settings J2EE Application Components Create the HTML Page Create the Servlet Create the Session Bean Compile the Session Bean and Servlet Start the J2EE Application Server Start the Deploy Tool Deploy Tool Assemble the J2EE Application Verify and Deploy the J2EE Application Run the J2EE Application Updating Component Code A Simple Session Bean

  3. Thin-Client Multitiered Application

  4. J2EE Download: Contents • The typical download has the J2EE application server, Cloudscape database, a Web server usingsecure socket layer (SSL) also known as HTTP over HTTPS, development and deploymenttools, and the Java APIs for the Enterprise.

  5. PATH and CLASSPATH Path Settings Unix: [..]/J2EE/jdk1.2.2/bin [..]/J2EE/j2sdkee1.2.1/bin Windows:replace / with \ Class Path Settings Unix: [..]/J2EE/j2sdkee1.2.1/lib/j2ee.jar Windows:replace / with \

  6. J2EE Appl. Components The J2EE specification defines the followingapplication components: • Application client components • Enterprise JavaBeans components • Servlets and JavaServer Pages components (also called Web components) • Applets

  7. The session beanexecutes in the J2EE application server. Data flows between the browser and the session bean. Interacting Components

  8. <HTML> <BODY BGCOLOR = "WHITE"> <BLOCKQUOTE> <H3>Bonus Calculation</H3> <FORM METHOD="GET" ACTION="BonusAlias"> <P> Enter social security Number: <P> <INPUT TYPE="TEXT" NAME="SOCSEC"></INPUT> <P> Enter Multiplier: <P> <INPUT TYPE="TEXT" NAME="MULTIPLIER"></INPUT> <P> <INPUT TYPE="SUBMIT" VALUE="Submit"> <INPUT TYPE="RESET"> </FORM> </BLOCKQUOTE> </BODY> </HTML> HTML Code

  9. At run time, the servlet code does the following: Retrieves the user data Looks up the session bean Passes the data to the session bean Upon receiving a value back from the session bean, creates an HTML page to displaythe returned value to the user. Servlet Duties

  10. import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import javax.naming.*; import javax.rmi.PortableRemoteObject; import Beans.*; public class BonusServletextends HttpServlet { CalcHome homecalc; public void init(ServletConfig config)throwsServletException{ //Look up home interface try{ InitialContext ctx=new InitialContext(); Object objref=ctx.lookup("calcs"); homecalc =(CalcHome)PortableRemoteObject.narrow(objref,CalcHome.class); } catch (Exception NamingException) { NamingException.printStackTrace(); } } } Servlet Code (I)

  11. public void doGet ( HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { String socsec = null; int multiplier = 0;double calc = 0.0; PrintWriter out; response.setContentType("text/html"); String title = "EJB Example"; out = response.getWriter(); out.println("<HTML><HEAD><TITLE>"); out.println(title); out.println("</TITLE></HEAD><BODY>"); try{ Calc theCalculation; //Get Multiplier and Soc.Sec. Info StringstrMult=request.getParameter("MULTIPLIER"); Integer integerMult = new Integer(strMult); multiplier = integerMult.intValue(); socsec = request.getParameter("SOCSEC"); //Calculate bonus double bonus = 100.00; theCalculation = homecalc.create(); calc =theCalculation.calcBonus(multiplier, bonus); } catch(Exception CreateException){CreateException.printStackTrace();} Servlet Code (II)

  12. //cont. for public void doGet ( //Display Data out.println("<H1>Bonus Calculation</H1>"); out.println("<P>Soc Sec: " + socsec + "<P>"); out.println("<P>Multiplier: " +multiplier + "<P>"); out.println("<P>Bonus Amount: " + calc + "<P>"); out.println("</BODY></HTML>"); out.close(); } public void destroy() { System.out.println("Destroy"); } } Servlet Code (III)

  13. Interfaces of a EJBean This picture shows how the servlet and session bean application components work as a completeJ2EE application once they are assembled and deployed. The container is the interface between the session bean and the low-level platform-specific functionalitythat supports the session bean. The container is created during deployment.

  14. Creating a session bean A session bean represents a transient conversation with a client. If the server or clientcrashes, the session bean and its data are gone. In contrast, entity beans are persistent andrepresent data in a database. If the server or client crashes, the underlying services ensurethe entity bean data is saved. Because the enterprise bean performs a simplecalculation at the request of BonusServlet,and the calculation can be reinitiated in the event of a crash, it makes sense to use a sessionbean in the current example.

  15. BonusServlet does not work directly with the session bean, but creates an instance of itshome interface. The home interface extends EJBHome and has a create method for creatingthe session bean in its container. CreateException is thrown if the session bean cannot becreated, and RemoteException is thrown if a communications-related exception occurs duringthe execution of a remote method. package Beans; import java.rmi.RemoteException; import javax.ejb.CreateException; import javax.ejb.EJBHome; public interface CalcHome extends EJBHome { Calc create() throws CreateException,RemoteException; } CalcHome

  16. When the home interface is created, the J2EE application server creates the remote interface and session bean. The remote interface extends EJBObject and declares the calcBonus method for calculating the bonus value. This method is required to throw javax.rmi.RemoteException, and is implemented by the CalcBean class. package Beans; import javax.ejb.EJBObject; import java.rmi.RemoteException; public interface Calc extends EJBObject { public double calcBonus(int multiplier,double bonus) throws RemoteException; } Calc

  17. The session bean class implements the SessionBean interface and provides behavior for the calcBonus method. The setSessionContext and ejbCreate methods are called in that order by the container after BonusServlet calls the create method in CalcHome. package Beans; import java.rmi.RemoteException; import javax.ejb.SessionBean; import javax.ejb.SessionContext; public class CalcBean implements SessionBean { public double calcBonus(int multiplier,double bonus) { double calc = (multiplier*bonus); return calc; } //These methods are not described here public void ejbCreate() { } public void setSessionContext(SessionContext ctx) { } public void ejbRemove() { } public void ejbActivate() { } public void ejbPassivate() { } public void ejbLoad() { } public void ejbStore() { } } CalcBean

  18. Session Bean Unix #!/bin/sh cd [..]/J2EE J2EE_HOME=[..]/J2EE/j2sdkee1.3.1 CPATH=.:$J2EE_HOME/lib/j2ee.jar javac -d . -classpath "$CPATH" Beans/CalcBean.javaBeans/CalcHome.javaBeans/Calc.java Windows cd \home\monicap\J2EE Set J2EE_HOME=[..]\J2EE\j2sdkee1.3.1 set CPATH=.;%J2EE_HOME%\lib\j2ee.jar javac -d . -classpath %CPATH% Beans/CalcBean.javaBeans/CalcHome.javaBeans/Calc.java Servlet Unix [..] javac -d . -classpath "$CPATH" BonusServlet.java Windows [..] javac -d . -classpath "$CPATH" BonusServlet.java Compiling Instructions

  19. J2EE Application Server & Deploy Tool • You need to start the J2EE application server to deploy and run the example. type:j2ee -verbose Note: Sometimes the J2EE server will not start if Outlook is running. • To assemble and deploy the J2EE application, you have to start the deploy tool. type:deploytool Note: If a memory access error is encountered when starting deploytool, add anenvironment variable called JAVA_FONTS and set the path to c: \<font directory>, e.g.c:\winnt\fonts.

  20. The Deploy Tool GUI

  21. Assemble the J2EEApplication Assembling a J2EE application involves creating a new application, and adding the applicationcomponents to it, according to the following steps: • Create a new J2EE application (BonusApp.ear). • Create a new enterprise bean(CalcBean.jar). • Create a new web component(Bonus.war). • Specify JNDI name for the enterprise bean (calcs). • Specify the Root Context for the J2EE application (BonusRoot).

  22. J2EE components are assembled into J2EE application Enterprise Archive (EAR) files. From File menu: Select New Application. New Application dialog box: Fill the data about the application file name (BonusApp.ear) and the application display name (BonusApp), specifying the ditectory where you want to place the application EAR file. The GUI looks as shown. Create J2EE Application

  23. Enterprise beans (entity and session beans) are bundled into a Java Archive (JAR) file. File menu: Select New Enterprise Bean. The New Enterprise Bean Wizard starts anddisplays an Introduction dialog box.Click Next. EJB JAR dialog box:Specify the jar display name (CalcJar, within BonusApp), and possibly other ancillary info. Add Files to Contentsdialog box: Calc.class, CalcHome.class, CalcBean.class. The GUI looks as shown. Go to the next step Create Session Bean (I)

  24. In this step, make sure the following information is selected: classname: CalcBean Home interface: Beans.CalcHome Remote interface: Calc Bean type: Session and Stateless Specify the display name (the name that appears when when the JAR file is added toBonusApp in the Local Applications window) Description: e.g.,This JAR file contains the CalcBean session bean. No further info is needed for the bean.. Create Session Bean (II)

  25. Creation of the Session Bean Once the session bean has been created, the GUI looks as shown.

  26. Web components (servlets, or JSPtechnology) are bundled into a WAR file. File menu: Select New Web Component. The New Web Component Wizard starts. Provide the name to be displayed for the WAR, and then add contents: First, bonus.html And then the servlet class,BonusServlet.class The GUI looks as shown. Go to the next step. Create Web Component (I)

  27. Create Web Component (II) At the next step of the wizard, select the BonusServlet as a servlet component. Now, the GUI looks as shown.

  28. Component Aliases At the “component aliases” step of the wizard, type “BonusAlias.” This is the same alias name you put in the ACTION field of the HTML form embedded in the bonus.html file. Now, the GUI looks as shown.

  29. Components’s Deployment: Summary

  30. Specify JNDI Name Before you can deploy the BonusApp application and its components, you have to specify theJNDI name BonusServlet uses to look up the CalcBean session bean.

  31. Specify Root Context

  32. Verify Specification Compliance

  33. Deploy the J2EE Appl.

  34. Run the J2EE Appl. The web server runs on port 8000 by default. To open the bonus.html page point yourbrowser to http://localhost:8000/BonusRoot/bonus.html which is where the Deploytool put the HTML file.

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