Lab1: Stateless Session Bean for Registration Fee Calculation

Transcription

1 Registration Fee Calculation The Lab1 is a Web application of conference registration fee discount calculation. There may be sub-conferences for attendee to select. The registration fee varies for different subconferences. There is a 20% discount for a membership participant and a 50% discount for a student participant. The conference information and regular registration fees are stored in a database table called Conference so that the conference administrator can modify the rates in the database instead of hardcode.

2 A stateless session bean DiscountCalculator accesses the database table and retrieves the conference information there. A method getdiscountedfee() calculates the registration fee based on the attendee s category. The following diagram shows the structure of this Web application.

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4 Step 1. Develop session bean The enterprise bean in this example includes the following code: Remote interface: DiscountCalc.java Home interface: DiscountCalcHome.java Enterprise bean class: DiscountCalcBean.java Helper Classs: ConfDetails The main purpose of a session bean is to run business task for the client. The DiscountCalc remote interface, which extends javax.ejb.ejbobject, defines two business methods: getallconference() returns all conferences and their registration fee and getdiscountedfee() returns discounted registration fee for a specific attendee category. The client invokes business methods on remote object reference that is retuned by create() method.

5 //DiscountCalc.java is a Remote interface of //DiscountCalc session bean package discountcalc; import java.util.*; import javax.ejb.ejbobject; import java.rmi.remoteexception; public interface DiscountCalc extends EJBObject { public ArrayList getallconferences() throws RemoteException; public double getdiscountedfee (double registfee, String attendeetype) throws RemoteException; }

6 The home interface DiscountCalcHome, which extends the javax.ejb.ejbhome interface, has a single method create(). The ejbcreate() method in the bean will be called back when this method is invoked. //DiscountCalcHome.java is a Remote home interface of //DiscountCalc session bean package discountcalc; import java.rmi.remoteexception; import javax.ejb.*; public interface DiscountCalcHome extends EJBHome { } DiscountCalc create() throws RemoteException, CreateException;

7 The discountcalcbean implements the sessionbean interface. The ejbcreate() method specifies some necessary initialization and configuration for the bean. It performs a JNDI lookup to obtain a data source. The bean contains two business methods. The getallconferences() method provides connection to the database. It uses sql code to retrieve data from conference table and returns an ArrayList of confdetails objects. The getdiscountedfee() method implements a business logic of registration fee calculation.

8 //DiscountCalcBean.java is the Stateless Session Bean package discountcalc; import java.util.*; import javax.ejb.*; import javax.naming.*; import java.rmi.remoteexception; import java.math.*; import java.sql.*; import javax.sql.*; public class DiscountCalcBean implements SessionBean { DataSource datasource;

9 public void ejbcreate () { InitialContext ic = null; try { ic = new InitialContext(); datasource = (DataSource)ic.lookup("java:comp/env/jdbc/PointBase"); } catch (NamingException ex) { System.out.println("Naming Exceptions"); } } public ArrayList getallconferences() { ArrayList conflist = new ArrayList(); Connection con = null; PreparedStatement stmt = null; ResultSet rs = null;

10 try { con = datasource.getconnection(); stmt = con.preparestatement ("SELECT * FROM conference "); rs =stmt.executequery(); while (rs.next()) { ConfDetails confdetail = new ConfDetails( rs.getstring(1), rs.getstring(2), rs.getdouble(3)); conflist.add( confdetail ); } rs.close(); stmt.close(); con.close(); } catch (SQLException ex) { System.out.println("SQL Exceptions"); } return conflist; }

11 public double getdiscountedfee (double registfee, String attendeetype) { int discountrate = 0; if (attendeetype.equals ("Member")) discountrate = 20; else if ( attendeetype.equals ("Student") ) discountrate = 50; else discountrate = 0; return (registfee * (1 - (double)discountrate/100 )); } public DiscountCalcBean() {} public void ejbactivate() {} public void ejbpassivate() {} public void ejbremove() {} public void setsessioncontext(sessioncontext sc) {} } // DiscountCalcBean

12 The DiscountCalc session bean has a helper class called confdetails. The serializable confdetails class contains three variables: confid, confname,and registfee, which correspond to the three columns in the conference table respectively. It is particular useful to work with ArrayList to store and retrieve data. Helper classes must reside in the EJB Jar file that contains the enterprise bean class.

13 //ConfDetails class is a helper class package discountcalc; public class ConfDetails implements java.io.serializable { private String confid; private String confname; private double registfee; public ConfDetails (String confid, String confname, double registfee) { this.confid = confid; this.confname = confname; this.registfee = registfee; }

14 public String getconfid() { return confid; } public String getconfname() { return confname; } public double getregistfee() { return registfee; } } // conferencedetails;

15 Step 2. Compiling all source code In c:\ejb\lab1 directory, compile the source files at command prompt. Type >asant build A new directory build is created with four class files.

16 Step 3. Packaging the session bean 1. Start J2EE Application Server, PointBase database and deploytool. 2. Creating the J2EE Application In deploytool, select File New Application. Click Browse. In the file chooser, navigate to c:\ejb\lab1. In the File Name field, enter DiscountCalcApp1.ear. Click New Application and OK

17 3. Packaging the EJB To package an enterprise bean, run the New Enterprise Bean wizard of the deploytool utility, which will create the bean s deployment descriptor, package the deployment descriptor and the bean s classes in an EJB JAR file, and Inserts the EJB JAR file into the application s DiscountCalcApp.ear file. To start the New Enterprise Bean wizard, select File New Enterprise Bean. In the EJB JAR General Settings dialog box, select the Create New JAR Module in Application radio button.

18 In the combo box, select DiscountCalcApp. In the JAR Display Name field, enter DiscountCalcJar. Click Edit Contents. In the tree under Available Files, go to c:\ejb\lab1\build directory. Select discountcalc folder from the Available Files tree and click Add. Click OK and Next.

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20 In the Bean General Settings dialog box, select discountcalc.discountcalcbean in the Enterprise Bean Class combo box. Verify DiscountCalcBean in the Enterprise Bean Name field. Under Bean Type, select the Stateless Session radio buttons. Select DiscountCalc.DiscountCalcHome in the Remote Home Interface combo box, select DiscountCalc.DiscountCalc in the Remote Interface combo box, Click Next. In the Expose as Web Service Endpoint dialog box, select the No radio button, click Next and Finish.

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22 4. Specify Resource Reference In the tree select DiscountCalcBean. Click Resource Ref s tab and Add Enter jdbc/pointbase for Coded Name, select javax.sql.datasource for Type, Container for Authentication and Sharable. In the Sun Specific Settings for jdbc/pointbase box enter jdbc/pointbase for JNDI name, pbpublic for User Name and Password

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24 After the packaging process, you can view the deployment descriptor by selecting Tools Descriptor Viewer. <?xml version='1.0' encoding='utf-8'?> <ejb-jar version=" 2.1" xmlns=" xmlns:xsi= " xsi:schemalocation= " "> <display-name> DiscountCalcJar</display-name> <enterprise-beans> <session>

25 <display-name> DiscountCalcBean</display-name> <ejb-name> DiscountCalcBean</ejb-name> <home> discountcalc.discountcalchome</home> <remote> discountcalc.discountcalc</remote> <ejb-class> discountcalc.discountcalcbean</ejb-class> <session-type> Stateless</session-type> <transaction-type> Bean</transaction-type> <resource-ref> <res-ref-name> jdbc/pointbase</res-ref-name> <res-type> javax.sql.datasource</res-type>

26 <res-auth> Container</res-auth> <res-sharing-scope> Shareable</res-sharing-scope> </resource-ref> <security-identity> <use-caller-identity> </use-caller-identity> </security-identity> </session> </enterprise-beans> </ejb-jar>

27 Step 4. Coding the Web component The index.jsp is a Web GUI interface for this application. It uses JSP page and JavaBean component to dynamically construct a HTML page to display conference registration fee lists. By default it displays the registration fee list for a Non-Member attendee (See the page below). The Web page takes the user s inquiry and responds a calculated discounted registration fee list for a specific category request.

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29 The index.jsp source code contains a method jspinit() method which references to the session bean s home interface by a JNDI lookup and create a bean instance. Two business methods (getallconference() and getdiscountedfee()), which are defined in the DiscountCalcBean, are invoked in this page.

30 <%-- Web Client for the EJB: Index.jsp --%> import="javax.naming.*" %> import="javax.rmi.portableremoteobject"%> import="java.rmi.remoteexception"%> import="javax.ejb.*"%> import="java.util.*"%> import="java.text.decimalformat"%> import="discountcalc.*"%> <%! private DiscountCalc discountcalc = null; String attendeetype = null; double registfee = 0.00; ConfDetails confdetail;

31 public void jspinit() { try { InitialContext ic = new InitialContext(); Object objref = ic.lookup("java:comp/env/ejb/simplediscountcalc"); DiscountCalcHome home = (DiscountCalcHome)PortableRemoteObject.narrow (objref, DiscountCalcHome.class); discountcalc = home.create(); } catch (Exception ex) { System.out.println(ex.getMessage()); } } public void jspdestroy() { discountcalc = null; }

32 %> <head><center> <title>discountcalc</title> <h4>computing Symposium On-line Registration </h4> <h3>discounted Registration Fee Calculation</h3> </center></head> <% attendeetype = request.getparameter("selectattendeetype"); if (attendeetype == null) attendeetype = "Non-Member"; %> <body><center> <h4><%= attendeetype %> Registration Fee </h4> <table border="1" cellpadding="10"> <tr><th width="220">conference</th> <th width="180">registration Fee</th> </tr>

33 <% List conflist = discountcalc.getallconferences(); Iterator i = conflist.iterator(); while (i.hasnext()) { confdetail = (ConfDetails) i.next(); registfee = discountcalc.getdiscountedfee (confdetail.getregistfee(), attendeetype); DecimalFormat twodigits = new DecimalFormat ("0.00"); %> <tr><td> <%= confdetail.getconfname() %> </td> <td align="right"> <%= twodigits.format(registfee) %></td> </tr> <% } %> </table>

34 <form method="get" action="index.jsp" > <br> <p>please select attendee type: </p> <input type="radio" name="selectattendeetype value="non-member"> </input> Non-Member <input type="radio" name="selectattendeetype" value="member"> </input>member <input type="radio" name="selectattendeetype value="student"> </input>student </p> <br> <input type="submit" name="submit" value="submit" /> </p> <br> </form> </center></body> </html>

35 Step 5. Packaging the Web Client To package a Web client we can first run the New Web Component Wizard which will create a Web application deployment descriptor. Next, add all component files to a war file and add the war file to the application s DiscountCalcApp1.ear file. You build the Web component by the New Web Component wizard, select File New Web Component. See the following dialog boxes. In the WAR File dialog box select Create New WAR Module in Application.

36 Select DiscountCalcApp in the combo box Enter DiscountCalcWar In the WAR Name field Click Edit Contents In the tree under Available Files, go to c:\ejb\lab1\web directory. Select index.jsp and click Add. Click OK and Next. In the Choose Component Type dialog box, select JSP radio button. Click Next In the Component General Properties dialog box select index.jsp in the JSP FileName combo box Click Finish.

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38 Specifying the Web Client's Enterprise Bean Reference: In the tree, select DiscountCalcWar Select the EJB Refs tab Click Add. In the Coded Name field, enter ejb/simplediscountcalc. Select Session in the Type field. Select Remote in the Interfaces field. Type DiscountCalc.DiscountCalcHome in the Home Interface field, type DiscountCalc.DiscountCalc in the Local/Remote Interface field. Select JNDI Name radio button for the Target EJB, enter MyDiscountCalc and click OK.

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40 After the packaging process, you can view the following deployment descriptor by selecting Tools Descriptor Viewer. <?xml version='1.0' encoding='utf-8'?> <web-app version=" 2.4" xmlns=" xmlns:xsi= " xsi:schemalocation= " web-app_2_4.xsd " > <display-name> DiscountCalcWar</display-name>

41 <servlet> <display-name> index</display-name> <servlet-name> index</servlet-name> <jsp-file> /index.jsp</jsp-file> </servlet> <ejb-ref> <ejb-ref-name> ejb/simplediscountcalc</ejb-ref-name> <ejb-ref-type> Session</ejb-ref-type> <home> discountcalc.discountcalchome</home> <remote> discountcalc.discountcalchome</remote> </ejb-ref> </web-app>

42 Step 6. Specifying the JNDI Names and Context Root Follow the following steps to map the enterprise bean references used by the clients to the JNDI name of the bean. In the tree, select DiscountCalcApp. Click Sun-Specific Settings button. Choose JNDI Names for View. To specify a JNDI name for the bean, find the DiscountCalcBean component in the Application table and enter MyDiscountCalc in the JNDI Name column. To map the references, in the References table enter MyDiscountCalc in the JNDI Name.

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44 Specifying the Context Root In the tree, select DiscountCalcWar. Click General tab, enter discountcalc in the Context Root field, so discountcalc becomes the context root in URL. Save the application file.

45 Step 7. Deploying the J2EEApplication At this time, the J2EE application contains all components, it is ready for deployment. Select the DiscountCalcApp application. Select Tools Deploy.. Click OK. Notes: To undeploy an application, you can follow the following steps: Under the Servers in the tree, choose localhost:4848 Select the Deployed Application and click undeploy

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48 Step 8. Running the J2EE Web Client To run the Web client, point your browser at the following URL. You can replace localhost with the name of the host running the J2EE server if your browser is running on different machine. When select the Student and click on the Submit button the registration fees for student would be displayed.

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