1. Chapter 14: Session EJBs and Distributed Transactions
Outline Introduction EJB Overview Remote Interface Home Interface EJB Implementation EJB Container Session Beans Stateful Session EJBs Deploying Session EJBs Stateless Session EJBs EJB Transactions MoneyTransfer EJB Home and Remote Interfaces Bean-Managed Transaction Demarcation Container-Managed Transaction Demarcation MoneyTransfer EJB Client Deploying the MoneyTransfer EJB Internet and World Wide Web Resources

2. Enterprise JavaBeans (EJBs) Session EJBs Distributed Transactions
Introduction
Enterprise JavaBeans (EJBs)
Component model for enterprise application business logic
Session EJBs
Stateful and Stateless
Distributed Transactions
Ensure data integrity across databases and across application servers

3. 14.2 EJB Overview Remote Interface Home Interface Implementation
Declares publicly available methods of EJB
Home Interface
Declares create methods for creating new EJB instances
Declares remove methods for removing EJB instances
Declares finder methods for locating EJB instances
Implementation
Provides implementations for EJB business methods declared in remote interface
Provides implementations for create, remove and finder methods declared in home interface
EJB Container
Runtime environment for managing EJB lifecycle

4. Six roles for enterprise-system implementors
14.2 EJB Overview (cont.)
Six roles for enterprise-system implementors
Enterprise Bean Provider
Implements business logic as EJBs
Application Assembler
Constructs application components from EJBs
Deployer
Deploys application components to a J2EE application server
EJB Server Provider
Implements a J2EE-compliant application server
EJB Container Provider
Implements the application server’s runtime environment for EJBs

5. Remote Interface
Declares business methods that EJB clients can invoke to perform business-logic tasks
Must extend interface javax.ejb.EJBObject
Throw clause for each method must include RemoteException
Throw clause for each method may include application-specific exceptions (e.g., IllegalArgumentException)

6. 14.2.1 Remote Interface (cont.)

7. Home Interface
Declares methods for creating, removing and finding EJB instances
Must extend javax.ejb.EJBHome
Finder methods enable clients to locate particular EJB instances

8. Home Interface (cont.)

9. EJB Implementation
Defines business methods declared in the remote interface
Defines create, remove and finder methods declared in the home interface
Session EJBs must implement interface javax.ejb.SessionBean

10. Manages EJB interactions
EJB Container
Manages EJB interactions
Client interactions
Method invocations
Transactions
Security
Manages EJB lifecycle
Pools EJB instances to enhance performance
Creates new EJB instances
Removes existing EJB instances

11. Perform business logic processing for a particular client
Session Beans
Perform business logic processing for a particular client
Not persistent
Do not represent database-stored data
Instances are lost if EJB container crashes
Two types
Stateful
Stateless

12. Maintain state information between business method invocations
Stateful Session EJBs
Maintain state information between business method invocations
Shopping Cart Stateful Session EJB
Would provide business methods for adding and removing items from the cart
EJB would store state information
Number of items in the cart
Quantity of each item in the cart
Total cost of items in the cart

13. Remote interface must extend interface EJBObject
1 // InterestCalculator.java
2 // InterestCalculator is the remote interface for the
3 // InterestCalculator EJB.
4 package com.deitel.advjhtp1.ejb.session.stateful.ejb; 5
6 // Java core libraries
7 import java.rmi.RemoteException; 8
9 // Java standard extensions
10 import javax.ejb.EJBObject; 11
12 public interface InterestCalculator extends EJBObject { 13
// set principal amount
public void setPrincipal( double amount )
throws RemoteException; 17
// set interest rate
public void setInterestRate( double rate )
throws RemoteException; 21
// set loan length in years
public void setTerm( int years )
throws RemoteException; 25
// get loan balance
public double getBalance() throws RemoteException; 28
// get amount of interest earned
public double getInterestEarned() throws RemoteException;
31 }
Fig InterestCalculator remote interface for calculating simple interest. Line 12 Lines 16, 20, 27 and 30
Remote interface must extend interface EJBObject
throws clause for each business method must include RemoteException

14. Home interface must extend interface EJBHome
1 // InterestCalculatorHome.java
2 // InterestCalculatorHome is the home interface for the
3 // InterestCalculator EJB.
4 package com.deitel.advjhtp1.ejb.session.stateful.ejb; 5
6 // Java core libraries
7 import java.rmi.RemoteException; 8
9 // Java standard extensions
10 import javax.ejb.*; 11
12 public interface InterestCalculatorHome extends EJBHome { 13
// create InterestCalculator EJB
public InterestCalculator create() throws RemoteException,
CreateException;
17 }
Fig InterestCalculatorHome interface for creating InterestCalculator EJBs. Line 12 Lines 15-16
Home interface must extend interface EJBHome
create methods must return the remote interface type (e.g., InterestCalculator)
create method enables clients to create InterestCalculator instances

15. Session EJB implementations must implement interface SessionBean
1 // InterestCalculatorEJB.java
2 // InterestCalculator is a stateful session EJB for calculating
3 // simple interest.
4 package com.deitel.advjhtp1.ejb.session.stateful.ejb; 5
6 // Java core libraries
7 import java.util.*; 8
9 // Java standard extensions
10 import javax.ejb.*; 11
12 public class InterestCalculatorEJB implements SessionBean { 13
private SessionContext sessionContext; 15
// state variables
private double principal;
private double interestRate;
private int term; 20
// set principal amount
public void setPrincipal( double amount ) {
principal = amount; } 26
// set interest rate
public void setInterestRate( double rate ) {
interestRate = rate; } 32
Fig InterestCalculatorEJB implementation of InterestCalculator remote interface. Line 12 Line 14 Lines 17-19
Session EJB implementations must implement interface SessionBean
SessionContext provides access to the EJB container
Member variables maintain state information

16. EJB container invokes setSessionContext after creating the EJB
// set loan length in years
public void setTerm( int years ) {
term = years; } 38
// get loan balance
public double getBalance() {
// calculate simple interest
return principal * Math.pow( interestRate, term ); } 45
// get amount of interest earned
public double getInterestEarned() {
return getBalance() - principal; } 51
// set SessionContext
public void setSessionContext( SessionContext context ) {
sessionContext = context; } 57
// create InterestCalculator instance
public void ejbCreate() {} 60
// remove InterestCalculator instance
public void ejbRemove() {} 63
// passivate InterestCalculator instance
public void ejbPassivate() {} 66
Fig InterestCalculatorEJB implementation of InterestCalculator remote interface. Lines Line 59 Line 62 Line 65
EJB container invokes setSessionContext after creating the EJB
EJB container invokes ejbCreate when a client invokes home interface method create to create a new EJB instance
EJB container invokes ejbRemove when a client invokes home interface method remove to destroy an EJB instance
EJB container invokes ejbPassivate to conserver resources when an EJB has been inactive

17. 67 // activate InterestCalculator instance
public void ejbActivate() {}
69 }
EJB container invokes ejbActivate to restore an EJB instance that the container passivated previously
Fig InterestCalculatorEJB implementation of InterestCalculator remote interface. Line 68

18. Remote reference to InterestCalculator EJB instance
1 // InterestCalculatorClient.java
2 // InterestCalculatorClient is a GUI for interacting with the
3 // InterestCalculator EJB.
4 package com.deitel.advjhtp1.ejb.session.stateful.client; 5
6 // Java core libraries
7 import java.awt.*;
8 import java.awt.event.*;
9 import java.rmi.*;
10 import java.text.*;
11 import java.util.*; 12
13 // Java standard extensions
14 import javax.swing.*;
15 import javax.rmi.*;
16 import javax.naming.*;
17 import javax.ejb.*; 18
19 // Deitel libraries
20 import com.deitel.advjhtp1.ejb.session.stateful.ejb.*; 21
22 public class InterestCalculatorClient extends JFrame { 23
// InterestCalculator remote reference
private InterestCalculator calculator; 26
private JTextField principalTextField;
private JTextField rateTextField;
private JTextField termTextField;
private JTextField balanceTextField;
private JTextField interestEarnedTextField; 32
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Line 25 Lines 27-31
Remote reference to InterestCalculator EJB instance
JTextFields for obtaining input values from user

19. 33 // InterestCalculatorClient constructor
public InterestCalculatorClient() {
super( "Stateful Session EJB Example" ); 37
// create InterestCalculator for calculating interest
createInterestCalculator(); 40
// create JTextField for entering principal amount
createPrincipalTextField(); 43
// create JTextField for entering interest rate
createRateTextField(); 46
// create JTextField for entering loan term
createTermTextField(); 49
// create uneditable JTextFields for displaying balance
// and interest earned
balanceTextField = new JTextField( 10 );
balanceTextField.setEditable( false ); 54
interestEarnedTextField = new JTextField( 10 );
interestEarnedTextField.setEditable( false ); 57
// layout components for GUI
layoutGUI(); 60
// add WindowListener to remove EJB instances when user
// closes window
addWindowListener( getWindowListener() ); 64
setSize( 425, 200 );
setVisible( true ); 67
Fig InterestCalculatorClient for interacting with InterestCalculator EJB.

20. Retrieve a reference to the InterestCalculator EJB home interface
} // end InterestCalculatorClient constructor 69
// create InterestCalculator EJB instance
public void createInterestCalculator() {
// lookup InterestCalculatorHome and create
// InterestCalculator EJB
try { 76
InitialContext initialContext = new InitialContext(); 78
// lookup InterestCalculator EJB
Object homeObject =
initialContext.lookup( "InterestCalculator" ); 82
// get InterestCalculatorHome interface
InterestCalculatorHome calculatorHome =
( InterestCalculatorHome )
PortableRemoteObject.narrow( homeObject,
InterestCalculatorHome.class ); 88
// create InterestCalculator EJB instance
calculator = calculatorHome.create(); 91
} // end try 93
// handle exception if InterestCalculator EJB not found
catch ( NamingException namingException ) {
namingException.printStackTrace(); } 98
// handle exception when creating InterestCalculator EJB
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
InitialContext provides access to the JNDI directory for locating the EJB home interface
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Line 77 Lines Lines Line 90 Lines Lines
Retrieve a reference to the InterestCalculator EJB home interface
Cast home interface reference using method PortableRemoteObject.narrow to ensure RMI-IIOP-compatible casting
Invoke home interface create method to create InterestCalculator instance and store remote reference in calculator
InitialContext method lookup throws a NamingException if there is an error locating the home interface
InterestCalculatorHome method create throws a RemoteException if there is an error accessing the remote object

21. Set principal value in InterestCalculator EJB
103
// handle exception when creating InterestCalculator EJB
catch ( CreateException createException ) {
createException.printStackTrace(); }
} // end method createInterestCalculator
109
// create JTextField for entering principal amount
public void createPrincipalTextField() {
principalTextField = new JTextField( 10 );
114
principalTextField.addActionListener(
new ActionListener() {
117
public void actionPerformed( ActionEvent event ) {
// set principal amount in InterestCalculator
try {
double principal = Double.parseDouble(
principalTextField.getText() );
124
calculator.setPrincipal( principal ); }
127
// handle exception setting principal amount
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
132
// handle wrong number format
catch ( NumberFormatException
numberFormatException ) {
numberFormatException.printStackTrace(); }
InterestCalculatorHome method create throws a CreateException if there is an error creating the EJB instance
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Lines Lines Line 125
Set principal value in InterestCalculator EJB
Parse user-entered principal value

22. Set interest rate in InterestCalculator EJB } }
); // end addActionListener
} // end method createPrincipalTextField
142
// create JTextField for entering interest rate
public void createRateTextField() {
rateTextField = new JTextField( 10 );
147
rateTextField.addActionListener(
new ActionListener() {
150
public void actionPerformed( ActionEvent event ) {
// set interest rate in InterestCalculator
try {
double rate = Double.parseDouble(
rateTextField.getText() );
157
// convert from percentage
calculator.setInterestRate( rate / ); }
161
// handle exception when setting interest rate
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); } } }
); // end addActionListener
} // end method createRateTextField
170
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Lines Line 159
Set interest rate in InterestCalculator EJB
Parse user-entered interest rate

23. Parse user-entered term
// create JTextField for entering loan term
public void createTermTextField() {
termTextField = new JTextField( 10 );
175
termTextField.addActionListener(
new ActionListener() {
178
public void actionPerformed( ActionEvent event ) {
// set loan term in InterestCalculator
try {
int term = Integer.parseInt(
termTextField.getText() );
185
calculator.setTerm( term ); }
188
// handle exception when setting loan term
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); } } }
); // end addActionListener
} // end method getTermTextField
197
// get JButton for starting calculation
public JButton getCalculateButton() {
JButton calculateButton = new JButton( "Calculate" );
202
calculateButton.addActionListener(
new ActionListener() {
205
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Lines Line 186
Parse user-entered term
Set number of years interest will accrue in InterestCalculator EJB

24. Invoke getInterestEarned business method to calculate earned interest
public void actionPerformed( ActionEvent event ) {
// use InterestCalculator to calculate interest
try {
210
// get balance and interest earned
double balance = calculator.getBalance();
double interest =
calculator.getInterestEarned();
215
NumberFormat dollarFormatter =
NumberFormat.getCurrencyInstance(
Locale.US );
219
balanceTextField.setText(
dollarFormatter.format( balance ) );
222
interestEarnedTextField.setText(
dollarFormatter.format( interest ) ); }
226
// handle exception when calculating interest
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
} // end method actionPerformed }
); // end addActionListener
234
return calculateButton;
236
} // end method getCalculateButton
238
Invoke getInterestEarned business method to calculate earned interest
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Line 212 Lines
Invoke getBalance business method to calculate balance plus interest

25. 239 // lay out GUI components in JFrame
public void layoutGUI() {
Container contentPane = getContentPane();
243
// layout user interface components
JPanel inputPanel = new JPanel( new GridLayout( 5, 2 ) );
246
inputPanel.add( new JLabel( "Principal" ) );
inputPanel.add( principalTextField );
249
inputPanel.add( new JLabel( "Interest Rate (%)" ) );
inputPanel.add( rateTextField );
252
inputPanel.add( new JLabel( "Term (years)" ) );
inputPanel.add( termTextField );
255
inputPanel.add( new JLabel( "Balance" ) );
inputPanel.add( balanceTextField );
258
inputPanel.add( new JLabel( "Interest Earned" ) );
inputPanel.add( interestEarnedTextField );
261
// add inputPanel to contentPane
contentPane.add( inputPanel, BorderLayout.CENTER );
264
// create JPanel for calculateButton
JPanel controlPanel = new JPanel( new FlowLayout() );
controlPanel.add( getCalculateButton() );
contentPane.add( controlPanel, BorderLayout.SOUTH ); }
270
Fig InterestCalculatorClient for interacting with InterestCalculator EJB.

26. Remove InterestCalculator EJB instance when user closes window
// get WindowListener for exiting application
public WindowListener getWindowListener() {
return new WindowAdapter() {
275
public void windowClosing( WindowEvent event ) {
// check to see if calculator is null
if ( calculator.equals( null ) ) {
System.exit( -1 ); }
282
else {
// remove InterestCalculator instance
try {
calculator.remove(); }
288
// handle exception removing InterestCalculator
catch ( RemoveException removeException ) {
removeException.printStackTrace();
System.exit( -1 ); }
294
// handle exception removing InterestCalculator
catch ( RemoteException remoteException ) {
remoteException.printStackTrace();
System.exit( -1 ); }
300
System.exit( 0 ); } } };
} // end method getWindowListener
Fig InterestCalculatorClient for interacting with InterestCalculator EJB. Line 286
Remove InterestCalculator EJB instance when user closes window

27. 306
// execute the application
public static void main( String[] args ) {
new InterestCalculatorClient(); }
312 }
Fig InterestCalculatorClient for interacting with InterestCalculator EJB.

28. 14.3.2 Deploying Session EJBs
Fig Creating New Application in Application Deployment Tool.

29. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying EAR file for New Application.

30. 14.3.2 Deploying Session EJBs (Cont.)
Fig Creating a New Enterprise Bean.

31. 14.3.2 Deploying Session EJBs (Cont.)
Fig Adding InterestCalculator EJB classes.

32. 14.3.2 Deploying Session EJBs (Cont.)
Fig Selecting InterestCalculator EJB classes to add.

33. 14.3.2 Deploying Session EJBs (Cont.)
Fig Result of adding InterestCalculator EJB classes.

34. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying Enterprise Bean Class for InterestCalculator EJB.

35. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying InterestCalculator EJB classes and Stateful Session Bean Type.

36. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying Container Managed Transactions for InterestCalculator EJB.

37. 14.3.2 Deploying Session EJBs (Cont.)
Fig XML deployment descriptor for InterestCalculator EJB.

38. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying JNDI Name for InterestCalculator EJB.

39. 14.3.2 Deploying Session EJBs (Cont.)
Fig Deploying enterprise application to localhost.

40. 14.3.2 Deploying Session EJBs (Cont.)
Fig Specifying the Application Deployment Tool should Return Client Jar.

41. 14.3.2 Deploying Session EJBs (Cont.)
Fig Successful completion of deployment process.

42. 14.3.3 Stateless Session EJBs
Maintain no state information between business method invocations
Any Stateless Session EJB instance of a particular type can respond to any client request

43. Remote interface must extend interface EJBObject
1 // MathTool.java
2 // MathTool is the remote interface for the MathTool EJB.
3 package com.deitel.advjhtp1.ejb.session.stateless.ejb; 4
5 // Java core libraries
6 import java.rmi.RemoteException; 7
8 // Java standard extensions
9 import javax.ejb.EJBObject; 10
11 public interface MathTool extends EJBObject
12 {
// get Fibonacci series
public int[] getFibonacciSeries( int howMany )
throws RemoteException, IllegalArgumentException; 16
// get factorial of given integer
public int getFactorial( int number )
throws RemoteException, IllegalArgumentException;
20 }
Fig MathTool remote interface for calculating factorias and generating Fibonacci series. Line 11 Lines 15 and 19
Remote interface must extend interface EJBObject
throws clauses of business methods must include RemoteException
throws clauses of business methods can include application-specific exceptions

44. EJB implementation must implement interface SessionBean
1 // MathToolEJB.java
2 // MathToolEJB is a stateless session EJB with methods for
3 // calculating Fibonacci series and factorials.
4 package com.deitel.advjhtp1.ejb.session.stateless.ejb; 5
6 // Java standard extensions
7 import javax.ejb.*; 8
9 public class MathToolEJB implements SessionBean { 10
private SessionContext sessionContext; 12
// get Fibonacci series
public int[] getFibonacciSeries( int howMany )
throws IllegalArgumentException {
// throw IllegalArgumentException if series length
// is less than zero
if ( howMany < 2 )
throw new IllegalArgumentException(
"Cannot generate Fibonacci series of " +
"length less than two." ); 23
// starting points
int startPoint1 = 0;
int startPoint2 = 1; 27
// array to contain Fibonacci sequence
int[] series = new int[ howMany ]; 30
// set base cases
series[ 0 ] = 0;
series[ 1 ] = 1; 34
EJB implementation must implement interface SessionBean
Fig MathToolEJB implementation of MathTool remote interface. Line 9 Line 11
SessionContext provides access to EJB container

45. Fig. 14.22 MathToolEJB implementation of MathTool remote interface.
// generate Fibonacci series
for ( int i = 2; i < howMany; i++ ) { 37
// calculate next number in series
series[ i ] = startPoint1 + startPoint2; 40
// set start points for next iteration
startPoint1 = startPoint2;
startPoint2 = series[ i ]; } 45
return series; 47
} // end method getFibonacciSeries 49
// get factorial of given integer
public int getFactorial( int number )
throws IllegalArgumentException {
// throw IllegalArgumentException if number less than zero
if ( number < 0 )
throw new IllegalArgumentException(
"Cannot calculate factorial of negative numbers." ); 58
// base case for recursion, return 1
if ( number == 0 )
return 1; 62
// call getFactorial recursively to calculate factorial
else
return number * getFactorial( number - 1 ); 66
} // end method getFactorial 68
Fig MathToolEJB implementation of MathTool remote interface.

46. Fig. 14.22 MathToolEJB implementation of MathTool remote interface.
// set SessionContext
public void setSessionContext( SessionContext context ) {
sessionContext = context; } 74
// create new MathTool instance
public void ejbCreate() {} 77
// remove MathTool instance
public void ejbRemove() {} 80
// activate MathTool instance
public void ejbActivate() {} 83
// passivate MathTool instance
public void ejbPassivate() {}
86 }
Fig MathToolEJB implementation of MathTool remote interface.

47. Home interface must extend interface EJBHome
1 // MathToolHome.java
2 // MathToolHome is the home interface for the MathTool EJB.
3 package com.deitel.advjhtp1.ejb.session.stateless.ejb; 4
5 // Java core libraries
6 import java.rmi.RemoteException; 7
8 // Java standard extensions
9 import javax.ejb.EJBHome;
10 import javax.ejb.CreateException; 11
12 public interface MathToolHome extends EJBHome { 13
// create new MathTool EJB
public MathTool create() throws RemoteException,
CreateException;
17 }
Fig MathToolHome interface for creating of MathTool EJBs. Line 12 Line 15
Home interface must extend interface EJBHome
create methods must return the remote interface type (e.g., MathTool)
create method enables clients to create MathTool instances

48. Reference to MathToolHome interface
1 // MathToolClient.java
2 // MathToolClient is a GUI for calculating factorials and
3 // Fibonacci series using the MathTool EJB.
4 package com.deitel.advjhtp1.ejb.session.stateless.client; 5
6 // Java core libraries
7 import java.awt.*;
8 import java.awt.event.*;
9 import java.rmi.*; 10
11 // Java standard extensions
12 import javax.swing.*;
13 import javax.rmi.*;
14 import javax.naming.*;
15 import javax.ejb.*; 16
17 // Deitel libraries
18 import com.deitel.advjhtp1.ejb.session.stateless.ejb.*; 19
20 public class MathToolClient extends JFrame { 21
private MathToolHome mathToolHome;
private MathTool mathTool; 24
private JTextArea resultsTextArea;
private JTextField numberTextField; 27
// MathToolClient constructor
public MathToolClient() {
super( "Stateless Session EJB Example" ); 32
// create MathTool for calculating factorials
// and Fibonacci series
createMathTool();
Fig MathToolClient for interacting with MathTool EJB. Line 22 Line 23
Reference to MathToolHome interface
Remote reference to MathTool EJB

49. Obtain InitialContext for looking up MathToolHome interface36
// create and lay out GUI components
createGUI(); 39
addWindowListener( getWindowListener() ); 41
setSize( 425, 200 );
setVisible( true ); 44
} // end MathToolClient constructor 46
// create MathTool EJB instance
private void createMathTool() {
// lookup MathToolHome and create MathTool EJB
try { 52
InitialContext initialContext = new InitialContext(); 54
// lookup MathTool EJB
Object homeObject =
initialContext.lookup( "MathTool" ); 58
// get MathToolHome interface
mathToolHome = ( MathToolHome )
PortableRemoteObject.narrow( homeObject,
MathToolHome.class ); 63
// create MathTool EJB instance
mathTool = mathToolHome.create(); 66
} // end try 68
Fig MathToolClient for interacting with MathTool EJB. Line 53 Lines Lines Line 65
Obtain InitialContext for looking up MathToolHome interface
Look up MathToolHome interface in JNDI
Cast MathToolHome reference to proper type
Create new MathTool EJB instance for use throughout this program

50. Fig. 14.23 MathToolClient for interacting with MathTool EJB.
// handle exception if MathTool EJB is not found
catch ( NamingException namingException ) {
namingException.printStackTrace(); } 73
// handle exception when creating MathTool EJB
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); } 78
// handle exception when creating MathTool EJB
catch ( CreateException createException ) {
createException.printStackTrace(); }
} // end method createMathTool 84
// create JButton for calculating factorial
private JButton getFactorialButton() {
JButton factorialButton =
new JButton( "Calculate Factorial" ); 90
// add ActionListener for factorial button
factorialButton.addActionListener(
new ActionListener() { 94
public void actionPerformed( ActionEvent event ) {
// use MathTool EJB to calculate factorial
try { 99
int number = Integer.parseInt(
numberTextField.getText() );
102
Fig MathToolClient for interacting with MathTool EJB.

51. Fig. 14.23 MathToolClient for interacting with MathTool EJB. Line 104
// get Factorial of number input by user
int result = mathTool.getFactorial( number );
105
// display results in resultsTextArea
resultsTextArea.setText( number + "! = " +
result );
109
} // end try
111
// handle exception calculating factorial
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
} // end method actionPerformed }
); // end addActionListener
119
return factorialButton;
121
} // end method getFactorialButton
123
// create JButton for generating Fibonacci series
private JButton getFibonacciButton() {
JButton fibonacciButton =
new JButton( "Fibonacci Series" );
129
// add ActionListener for generating Fibonacci series
fibonacciButton.addActionListener(
new ActionListener() {
133
public void actionPerformed( ActionEvent event ) {
Invoke getFactorial business method in stateless MathTool EJB to calculate factorial
Fig MathToolClient for interacting with MathTool EJB. Line 104

52. Append each value in Fibonacci sequence to a StringBuffer for display
// generate Fibonacci series using MathTool EJB
try {
138
// get number entered by user
int number = Integer.parseInt(
numberTextField.getText() );
142
// get Fibonacci series
int[] series = mathTool.getFibonacciSeries(
number );
146
// create StringBuffer to store series
StringBuffer buffer =
new StringBuffer( "The first " );
150
buffer.append( number );
152
buffer.append( " Fibonacci number(s): \n" );
154
// append each number in series to buffer
for ( int i = 0; i < series.length; i++ ) {
157
// do not add comma before first number
if ( i != 0 )
buffer.append( ", " );
161
// append next number in series to buffer
buffer.append( String.valueOf(
series[ i ] ) ); }
166
// display series in resultsTextArea
resultsTextArea.setText( buffer.toString() );
169
} // end try
Fig MathToolClient for interacting with MathTool EJB. Lines Lines
Invoke getFibonacciSeries business method in stateless MathTool EJB to calculate Fibonacci sequence
Append each value in Fibonacci sequence to a StringBuffer for display

53. Fig. 14.23 MathToolClient for interacting with MathTool EJB.
171
// handle exception calculating series
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
} // end method actionPerformed }
); // end addActionListener
179
return fibonacciButton;
181
} // end method getFibonacciButton
183
// create lay out GUI components
public void createGUI() {
// create JTextArea to show results
resultsTextArea = new JTextArea();
resultsTextArea.setLineWrap( true );
resultsTextArea.setWrapStyleWord( true );
resultsTextArea.setEditable( false );
192
// create JTextField for user input
numberTextField = new JTextField( 10 );
195
// create JButton for calculating factorial
JButton factorialButton = getFactorialButton();
198
// create JButton for generating Fibonacci series
JButton fibonacciButton = getFibonacciButton();
201
Container contentPane = getContentPane();
203
Fig MathToolClient for interacting with MathTool EJB.

54. Fig. 14.23 MathToolClient for interacting with MathTool EJB.
// put resultsTextArea in a JScrollPane
JScrollPane resultsScrollPane =
new JScrollPane( resultsTextArea );
207
contentPane.add( resultsScrollPane,
BorderLayout.CENTER );
210
// add input components to new JPanel
JPanel inputPanel = new JPanel( new FlowLayout() );
inputPanel.add( new JLabel( "Enter an integer: " ) );
inputPanel.add( numberTextField );
215
// add JButton components to new JPanel
JPanel buttonPanel = new JPanel( new FlowLayout() );
buttonPanel.add( factorialButton );
buttonPanel.add( fibonacciButton );
220
// add inputPanel and buttonPanel to new JPanel
JPanel controlPanel =
new JPanel( new GridLayout( 2, 2 ) );
224
controlPanel.add( inputPanel );
controlPanel.add( buttonPanel );
227
contentPane.add( controlPanel, BorderLayout.NORTH );
229
} // end method createGUI
231
// get WindowListener for exiting application
private WindowListener getWindowListener() {
return new WindowAdapter() {
236
public void windowClosing( WindowEvent event ) {
Fig MathToolClient for interacting with MathTool EJB.

55. Fig. 14.23 MathToolClient for interacting with MathTool EJB. Line 241
// remove MathTool instance
try {
mathTool.remove(); }
243
// handle exception when removing MathTool EJB
catch ( RemoveException removeException ) {
removeException.printStackTrace();
System.exit( -1 ); }
249
// handle exception when removing MathTool EJB
catch ( RemoteException remoteException ) {
remoteException.printStackTrace();
System.exit( -1 ); }
255
System.exit( 0 );
} // end method windowClosing };
} // end method getWindowListener
260
// execute application
public static void main( String[] args ) {
MathToolClient client = new MathToolClient(); }
266 }
Remove MathTool EJB instance when user closes window
Fig MathToolClient for interacting with MathTool EJB. Line 241

56. Fig. 14.23 MathToolClient for interacting with MathTool EJB.

57. EJB Transactions
Distributed transactions include multiple databases and/or multiple application servers
E.g., a transfer of funds from one bank to another
Such a transfer must occur in the context of an atomic transaction, otherwise there is the potential for data loss
Bean-managed transaction demarcation enables bean developers to specify transaction boundaries using the Java Transaction API
Container-managed transaction demarcation enables EJB deployers to specify transaction boundaries declaratively when deploying EJBs

58. 1 // MoneyTransfer.java
2 // MoneyTransfer is the remote interface for the MoneyTransfer
3 // EJB.
4 package com.deitel.advjhtp1.ejb.transactions; 5
6 // Java core libraries
7 import java.rmi.RemoteException; 8
9 // Java standard extensions
10 import javax.ejb.EJBObject; 11
12 public interface MoneyTransfer extends EJBObject { 13
// transfer amount from BankABC to BankXYZ
public void transfer( double amount ) throws RemoteException; 16
// get BankABC account balance
public double getBankABCBalance() throws RemoteException; 19
// get BankXYZ account balance
public double getBankXYZBalance() throws RemoteException;
22 }
Fig MoneyTransfer remote interface for transferring money and getting account balances. Lines 15, 18 and 21
Business methods whose implementations include programmer-defined transaction boundaries

59. 1 // MoneyTransferHome.java
2 // MoneyTransferHome is the home interface for the
3 // MoneyTransferHome EJB.
4 package com.deitel.advjhtp1.ejb.transactions; 5
6 // Java core libraries
7 import java.rmi.RemoteException; 8
9 // Java standard extensions
10 import javax.ejb.*; 11
12 public interface MoneyTransferHome extends EJBHome { 13
// create MoneyTransfer EJB
public MoneyTransfer create() throws RemoteException,
CreateException;
17 }
Fig MoneyTransferHome remote interface for creating MoneyTransfer EJBs.

60. Connections for bank databases
1 // MoneyTransferEJB.java
2 // MoneyTransferEJB is a stateless session EJB for transferring
3 // funds from an Account at BankABC to an Account at BankXYZ
4 // using bean-managed transaction demarcation.
5 package com.deitel.advjhtp1.ejb.transactions.beanmanaged; 6
7 // Java core libraries
8 import java.util.*;
9 import java.sql.*; 10
11 // Java standard extensions
12 import javax.ejb.*;
13 import javax.naming.*;
14 import javax.transaction.*;
15 import javax.sql.*; 16
17 public class MoneyTransferEJB implements SessionBean { 18
private SessionContext sessionContext;
private Connection bankOneConnection;
private Connection bankTwoConnection;
private PreparedStatement withdrawalStatement;
private PreparedStatement depositStatement; 24
// transfer funds from BankABC to BankXYZ
public void transfer( double amount ) throws EJBException {
// create transaction for transferring funds
UserTransaction transaction =
sessionContext.getUserTransaction(); 31
// begin bean-managed transaction demarcation
try {
transaction.begin(); }
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines Lines Lines Line 34
Connections for bank databases
PreparedStatements for withdrawing from, and depositing to, bank accounts
Create UserTransaction for transferring money between accounts
Begin transaction

61. If transaction cannot be started, throw an EJBException36
// catch exception if method begin fails
catch ( Exception exception ) { 39
// throw EJBException indicating transaction failed
throw new EJBException( exception ); } 43
// transfer funds from account in BankABC to account
// in BankXYZ using bean-managed transaction demarcation
try { 47
withdrawalStatement.setDouble( 1, amount ); 49
// withdraw funds from account at BankABC
withdrawalStatement.executeUpdate(); 52
depositStatement.setDouble( 1, amount ); 54
// deposit funds in account at BankXYZ
depositStatement.executeUpdate(); 57
// commit transaction
transaction.commit(); 60
} // end try 62
// handle exceptions when withdrawing, depositing and
// committing transaction
catch ( Exception exception ) { 66
// attempt rollback of transaction
try {
transaction.rollback(); }
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines Lines Line 59 Line 69
If transaction cannot be started, throw an EJBException
Transfer funds between accounts
If database updates are successful, commit the transaction
If there are problems with any of the database updates, rollback the transaction to restore the original data

62. 71
// handle exception when rolling back transaction
catch ( SystemException systemException ) {
throw new EJBException( systemException ); } 76
// throw EJBException indicating transaction failed
throw new EJBException( exception ); } 80
} // end method transfer 82
// get balance of Account at BankABC
public double getBankABCBalance() throws EJBException {
// get balance of Account at BankABC
try { 88
// select balance for Account # 12345
String select = "SELECT balance FROM Account " +
"WHERE accountID = 12345"; 92
PreparedStatement selectStatement =
bankOneConnection.prepareStatement( select ); 95
ResultSet resultSet = selectStatement.executeQuery(); 97
// get first record in ResultSet and return balance
if ( resultSet.next() )
return resultSet.getDouble( "balance" );
else
throw new EJBException( "Account not found" );
103
} // end try
105
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines
Execute simple SQL SELECT statement to retrieve the balances of the accounts at each bank.

63. 106 // handle exception when getting Account balance
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
110
} // end method getBankABCBalance
112
// get balance of Account at BankXYZ
public double getBankXYZBalance() throws EJBException {
// get balance of Account at BankXYZ
try {
118
// select balance for Account # 54321
String select = "SELECT balance FROM Account " +
"WHERE accountID = 54321";
122
PreparedStatement selectStatement =
bankTwoConnection.prepareStatement( select );
125
ResultSet resultSet = selectStatement.executeQuery();
127
// get first record in ResultSet and return balance
if ( resultSet.next() )
return resultSet.getDouble( "balance" );
else
throw new EJBException( "Account not found" );
133
} // end try
135
// handle exception when getting Account balance
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
140
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines
Execute simple SQL SELECT statement to retrieve the balances of the accounts at each bank.

64. 141 } // end method getBankXYZBalance
142
// set SessionContext
public void setSessionContext( SessionContext context )
throws EJBException {
sessionContext = context;
148
openDatabaseResources(); }
151
// create MoneyTransfer instance
public void ejbCreate() {}
154
// remove MoneyTransfer instance
public void ejbRemove() throws EJBException {
closeDatabaseResources(); }
160
// passivate MoneyTransfer instance
public void ejbPassivate() throws EJBException {
closeDatabaseResources(); }
166
// activate MoneyTransfer instance
public void ejbActivate() throws EJBException {
openDatabaseResources(); }
172
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines 149 and Lines 158 and 164
Allocate database Connections when the EJB container provides a SessionContext or activates the EJB
Close database Connections when the container removes or passiavates the EJB

65. Close the Connections and PreparedStatements.
// close database Connections and PreparedStatements
private void closeDatabaseResources() throws EJBException {
// close database resources
try {
178
// close PreparedStatements
depositStatement.close();
depositStatement = null;
182
withdrawalStatement.close();
withdrawalStatement = null;
185
// close database Connections
bankOneConnection.close();
bankOneConnection = null;
189
bankTwoConnection.close();
bankTwoConnection = null; }
193
// handle exception closing database connections
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
198
} // end method closeDatabaseResources
200
// open database Connections and create PreparedStatements
private void openDatabaseResources() throws EJBException {
// look up the BankABC and BankXYZ DataSources and create
// Connections for each
try {
Context initialContext = new InitialContext();
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation. Lines Lines
Create Connections and PreparedStatements for each database for use throughout the lifetime of the MoneyTransfer EJB instance.

66. 208
// get DataSource reference from JNDI directory
DataSource dataSource = ( DataSource )
initialContext.lookup(
"java:comp/env/jdbc/BankABC" );
213
// get Connection from DataSource
bankOneConnection = dataSource.getConnection();
216
dataSource = ( DataSource) initialContext.lookup(
"java:comp/env/jdbc/BankXYZ" );
219
bankTwoConnection = dataSource.getConnection();
221
// prepare withdraw statement for account #12345 at
// BankABC
String withdrawal = "UPDATE Account SET balance = " +
"balance - ? WHERE accountID = 12345";
226
withdrawalStatement =
bankOneConnection.prepareStatement( withdrawal );
229
// prepare deposit statment for account #54321 at
// BankXYZ
String deposit = "UPDATE Account SET balance = " +
"balance + ? WHERE accountID = 54321";
234
depositStatement =
bankTwoConnection.prepareStatement( deposit );
237
} // end try
239
// handle exception if DataSource not found in directory
catch ( NamingException namingException ) {
throw new EJBException( namingException );
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation.

67. }
244
// handle exception getting Connection to DataSource
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
249
} // end method openDatabaseResources
251 }
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using bean-managed transaction demarcation.

68. 1 // MoneyTransferEJB.java
2 // MoneyTransferEJB is a stateless session EJB for transferring
3 // funds from an Account at BankABC to an Account at BankXYZ
4 // using container-managed transaction demarcation.
5 package com.deitel.advjhtp1.ejb.transactions.containermanaged; 6
7 // Java core libraries
8 import java.util.*;
9 import java.sql.*; 10
11 // Java standard extensions
12 import javax.ejb.*;
13 import javax.naming.*;
14 import javax.sql.*; 15
16 public class MoneyTransferEJB implements SessionBean { 17
private SessionContext sessionContext;
private Connection bankOneConnection;
private Connection bankTwoConnection;
private PreparedStatement withdrawalStatement;
private PreparedStatement depositStatement; 23
// transfer funds from BankABC to BankXYZ
public void transfer( double amount ) throws EJBException {
// transfer funds from account in BankABC to account in
// BankXYZ using container-managed transaction demarcation
try { 30
withdrawalStatement.setDouble( 1, amount ); 32
// withdraw funds from account at BankABC
withdrawalStatement.executeUpdate(); 35
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

69. 36 depositStatement.setDouble( 1, amount );37
// deposit funds in account at BankXYZ
depositStatement.executeUpdate(); 40
} // end try 42
// handle exception withdrawing and depositing
catch ( SQLException sqlException ) { 45
// throw EJBException to indicate transfer failed
// and roll back container-managed transaction
throw new EJBException( sqlException ); } 50
} // end method transfer 52
// get balance of Account at BankABC
public double getBankABCBalance() throws EJBException {
// get balance of Account at BankABC
try { 58
// select balance for Account # 12345
String select = "SELECT balance FROM Account " +
"WHERE accountID = 12345"; 62
PreparedStatement selectStatement =
bankOneConnection.prepareStatement( select ); 65
ResultSet resultSet = selectStatement.executeQuery(); 67
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation. Line 48
Throws an EJBException in response to any SQLException thrown from lines

70. 68 // get first record in ResultSet and return balance
if ( resultSet.next() )
return resultSet.getDouble( "balance" );
else
throw new EJBException( "Account not found" ); 73
} // end try 75
// handle exception when getting Account balance
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); } 80
} // end method getBankABCBalance 82
// get balance of Account at BankXYZ
public double getBankXYZBalance() throws EJBException {
// get balance of Account at BankXYZ
try { 88
// select balance for Account # 54321
String select = "SELECT balance FROM Account " +
"WHERE accountID = 54321"; 92
PreparedStatement selectStatement =
bankTwoConnection.prepareStatement( select ); 95
ResultSet resultSet = selectStatement.executeQuery(); 97
// get first record in ResultSet and return balance
if ( resultSet.next() )
return resultSet.getDouble( "balance" );
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

71. else
throw new EJBException( "Account not found" );
103
} // end try
105
// handle exception when getting Account balance
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
110
} // end method getBankXYZBalance
112
// set SessionContext
public void setSessionContext( SessionContext context )
throws EJBException {
sessionContext = context;
118
openDatabaseResources(); }
121
// create MoneyTransfer instance
public void ejbCreate() {}
124
// remove MoneyTransfer instance
public void ejbRemove() throws EJBException {
closeDatabaseResources(); }
130
// passivate MoneyTransfer instance
public void ejbPassivate() throws EJBException {
closeDatabaseResources(); }
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

72. 136
// activate MoneyTransfer instance
public void ejbActivate() throws EJBException {
openDatabaseResources(); }
142
// close database Connections and PreparedStatements
private void closeDatabaseResources() throws EJBException {
// close database resources
try {
148
// close PreparedStatements
depositStatement.close();
depositStatement = null;
152
withdrawalStatement.close();
withdrawalStatement = null;
155
// close database Connections
bankOneConnection.close();
bankOneConnection = null;
159
bankTwoConnection.close();
bankTwoConnection = null; }
163
// handle exception closing database connections
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
168
} // end method closeDatabaseConnections
170
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

73. 171 // open database Connections and create PreparedStatements
private void openDatabaseResources() throws EJBException {
// look up the BankABC and BankXYZ DataSources and create
// Connections for each
try {
Context initialContext = new InitialContext();
178
// get DataSource reference from JNDI directory
DataSource dataSource = ( DataSource )
initialContext.lookup(
"java:comp/env/jdbc/BankABC" );
183
// get Connection from DataSource
bankOneConnection = dataSource.getConnection();
186
dataSource = ( DataSource) initialContext.lookup(
"java:comp/env/jdbc/BankXYZ" );
189
bankTwoConnection = dataSource.getConnection();
191
// prepare withdraw statement for account #12345 at
// BankABC
String withdrawal = "UPDATE Account SET balance = " +
"balance - ? WHERE accountID = 12345";
196
withdrawalStatement =
bankOneConnection.prepareStatement( withdrawal );
199
// prepare deposit statment for account #54321 at
// BankXYZ
String deposit = "UPDATE Account SET balance = " +
"balance + ? WHERE accountID = 54321";
204
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

74. depositStatement =
bankTwoConnection.prepareStatement( deposit );
207
} // end try
209
// handle exception if DataSource not found in directory
catch ( NamingException namingException ) {
throw new EJBException( namingException ); }
214
// handle exception getting Connection to DataSource
catch ( SQLException sqlException ) {
throw new EJBException( sqlException ); }
219
} // end method openDatabaseConnections
221 }
Fig MoneyTransferEJB implementation of MoneyTransfer remote interface using container-managed transaction demarcation.

75. 14.4.3 Container-Managed Transaction Demarcation

76. 1 // MoneyTransferEJBClient.java
2 // MoneyTransferEJBClient is a client for interacting with
3 // the MoneyTransfer EJB.
4 package com.deitel.advjhtp1.ejb.transactions.client; 5
6 // Java core libraries
7 import java.awt.*;
8 import java.awt.event.*;
9 import java.rmi.*; 10
11 // Java standard extensions
12 import javax.swing.*;
13 import javax.ejb.*;
14 import javax.rmi.*;
15 import javax.naming.*; 16
17 // Deitel libraries
18 import com.deitel.advjhtp1.ejb.transactions.*; 19
20 public class MoneyTransferEJBClient extends JFrame { 21
private MoneyTransfer moneyTransfer; 23
private JTextField bankABCBalanceTextField;
private JTextField bankXYZBalanceTextField;
private JTextField transferAmountTextField; 27
// MoneyTransferEJBClient constructor
public MoneyTransferEJBClient( String JNDIName ) {
super( "MoneyTransferEJBClient" ); 32
// create MoneyTransfer EJB for transferring money
createMoneyTransfer( JNDIName ); 35
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB. Lines Line 34
Declare JTextFields to display the account balances and accept a user-input transfer amount.
Invokes method createMoneyTransfer to create a new MoneyTransfer EJB instance.

77. Invokes method createGUI to create and lay out GUI components for the application.38
// display current balances at BankABC and BankXYZ
displayBalances(); 41
setSize( 400, 300 );
setVisible( true ); } 45
// create MoneyTransferEJB for transferring money
private void createMoneyTransfer( String JNDIName ) {
// look up MoneyTransfer EJB using given JNDIName
try {
InitialContext context = new InitialContext(); 52
// lookup MoneyTransfer EJB
Object homeObject = context.lookup( JNDIName ); 55
// get MoneyTransfer interface
MoneyTransferHome moneyTransferHome =
( MoneyTransferHome ) PortableRemoteObject.narrow(
homeObject, MoneyTransferHome.class ); 60
// create MathTool EJB instance
moneyTransfer = moneyTransferHome.create(); 63
} // end try 65
// handle exception when looking up MoneyTransfer EJB
catch ( NamingException namingException ) {
namingException.printStackTrace(); } 70
Invokes method displayBalances to display the current account balances at BankABC and BankXYZ.
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB. Line 37 Line 40 Lines Line 51 Lines Line 62
Method createMoneyTransfer uses the MoneyTransferHome interface to create a MoneyTransfer EJB instance.
Creates an InitialContext for locating the MoneyTransfer EJB in the JNDI directory.
Invoke InitialContext method lookup to get a remote reference to the MoneyTransferHome interface.
Creates a new MoneyTransfer EJB instance by invoking MoneyTransferHome method create.

78. 71 // handle exception when looking up MoneyTransfer EJB
catch ( CreateException createException ) {
createException.printStackTrace(); } 75
// handle exception when looking up MoneyTransfer EJB
catch ( RemoteException remoteException ) {
remoteException.printStackTrace(); }
} // end method createMoneyTransfer 81
// display balance in account at BankABC
private void displayBalances() {
try { 86
// get and display BankABC Account balance
double balance = moneyTransfer.getBankABCBalance(); 89
bankABCBalanceTextField.setText(
String.valueOf( balance ) ); 92
// get and display BankXYZ Account balance
balance = moneyTransfer.getBankXYZBalance(); 95
bankXYZBalanceTextField.setText(
String.valueOf( balance ) ); } 99
// handle exception when invoke MoneyTransfer EJB methods
catch ( RemoteException remoteException ) {
JOptionPane.showMessageDialog( this,
remoteException.getMessage() ); }
} // end method displayBalances
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB.

79. 106
// create button to transfer funds between accounts
private JButton getTransferButton() {
JButton transferButton = new JButton( "Transfer" );
111
transferButton.addActionListener(
new ActionListener() {
114
public void actionPerformed( ActionEvent event ) {
try {
118
// get transfer amount from JTextField
double amount = Double.parseDouble(
transferAmountTextField.getText() );
122
// transfer money
moneyTransfer.transfer( amount );
125
// display new balances
displayBalances(); }
129
// handle exception when transferring money
catch ( RemoteException remoteException ) {
JOptionPane.showMessageDialog(
MoneyTransferEJBClient.this,
remoteException.getMessage() ); }
} // end method actionPerformed }
); // end addActionListener
139
return transferButton;
Method getTransferButton creates a JButton to transfer funds from BankABC to BankXYZ.
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB. Lines Lines Line 127
Read the transfer amount from the user and invoke MoneyTransfer method transfer.
Invokes method displayBalances to update the display with the new account balances.

80. 141
} // end method getTransferButton
143
// create and lay out GUI components
private void createGUI() {
// create JTextFields for user input and display
bankABCBalanceTextField = new JTextField( 10 );
bankABCBalanceTextField.setEditable( false );
150
bankXYZBalanceTextField = new JTextField( 10 );
bankXYZBalanceTextField.setEditable( false );
153
transferAmountTextField = new JTextField( 10 );
155
// create button to transfer between accounts
JButton transferButton = getTransferButton();
158
// layout user interface
Container contentPane = getContentPane();
contentPane.setLayout( new GridLayout( 3, 2 ) );
162
contentPane.add( transferButton );
contentPane.add( transferAmountTextField );
165
contentPane.add( new JLabel( "Bank ABC Balance: " ) );
contentPane.add( bankABCBalanceTextField );
168
contentPane.add( new JLabel( "Bank XYZ Balance: " ) );
contentPane.add( bankXYZBalanceTextField );
171
} // end method createGUI
173
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB.

81. 174 // get WindowListener for exiting application
private WindowListener getWindowListener() {
// remove MoneyTransfer EJB when user exits application
return new WindowAdapter() {
179
public void windowClosing( WindowEvent event ) {
181
// remove MoneyTransfer EJB
try {
moneyTransfer.remove(); }
186
// handle exception removing MoneyTransfer EJB
catch ( RemoveException removeException ) {
removeException.printStackTrace();
System.exit( 1 ); }
192
// handle exception removing MoneyTransfer EJB
catch ( RemoteException remoteException ) {
remoteException.printStackTrace();
System.exit( 1 ); }
198
System.exit( 0 );
200
} // end method windowClosing };
} // end method getWindowListener
204
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB.

82. 205 // execute application
public static void main( String[] args ) {
// ensure user provided JNDI name for MoneyTransfer EJB
if ( args.length != 1 )
System.err.println(
"Usage: java MoneyTransferEJBClient <JNDI Name>" );
212
// start application using provided JNDI name
else
new MoneyTransferEJBClient( args[ 0 ] ); }
217 }
Fig MoneyTransferEJBClient for interacting with MoneyTransfer EJB.

83. MoneyTransferEJBClient.java program output

84. 14.4.5 Deploying the MoneyTransfer EJB
Create resource references to the databases
Transaction management

85. 14.4.5 Deploying the MoneyTransfer EJB (Cont.)
Fig Resource References dialog of New Enterprise Bean Wizard.

86. 14.4.5 Deploying the MoneyTransfer EJB (Cont.)
Fig Add Resource Reference for BankABC.

87. 14.4.5 Deploying the MoneyTransfer EJB (Cont.)
Fig Add Resource Reference for BankXYZ.

88. 14.4.5 Deploying the MoneyTransfer EJB (Cont.)
Fig Selecting Bean-Managed Transactions.

89. 14.4.5 Deploying the MoneyTransfer EJB (Cont.)
Fig Selecting Container-Managed Transactions.