Exploring EJB3 With JBoss Application Server Part 6.3

Transcription

1 By Swaminathan Bhaskar 02/07/2009 Exploring EJB3 With JBoss Application Server Part 6.3 In this part, we will continue to explore Entity Beans Using Java Persistence API (JPA). In the previous part, we had explored the one-to-one and many-to-one entity relationships. In the following paragraphs, we will be looking at one-to-many and many-to-many entity relationships. Let us explore the one-to-many entity relationship. There could be two types of one-to-many relationships Unidirectional or Bidirectional. The relationship between any Team and its Players is one-to-many unidirectional relationship because we look up all the Players in a given Team and not vice versa. The following diagram illustrates the relationship: Before we proceed with the example, we need to setup the two tables in the MySQL database testdb as follows: CREATE TABLE TEAM_TBL ( TEAM_ID INTEGER AUTO_INCREMENT, TEAM_NAME VARCHAR(25) NOT NULL, TEAM_STATE CHAR(2) NOT NULL, PRIMARY KEY PK_TEAM_ID(TEAM_ID) ); CREATE TABLE PLAYER_TBL ( PLAYER_NAME VARCHAR(30) NOT NULL, PLAYER_HEIGHT VARCHAR(8) NOT NULL, TEAM INTEGER, PRIMARY KEY PK_PLAYER_NAME(PLAYER_NAME), CONSTRAINT PLAYER_TEAM_FK FOREIGN KEY (TEAM) REFERENCES TEAM_TBL(TEAM_ID) ); The following code shows the Player Entity Bean: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package teamplay.common;

2 public class Player implements java.io.serializable { private static final long serialversionuid private String private String height; public String getname() { return name; public void setname(string n) { name = n; public String getheight() { return height; public void setheight(string n) { height = n; public String tostring() { StringBuffer sb = new StringBuffer(); sb.append("player name: "); sb.append(name); sb.append(", Player height: "); sb.append(height); return sb.tostring(); The Player entity uses player name as the primary key column (PLAYER_NAME). The following code shows the Team Entity Bean: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package teamplay.common; import java.util.*; public class Team implements java.io.serializable { private static final long serialversionuid = private int id;

3 @Column(name="TEAM_NAME") private String private private Collection<Player> players = new ArrayList<Player>(); public int getid() { return id; public void setid(int n) { id = n; public String getname() { return name; public void setname(string n) { name = n; public String getstate() { return state; public void setstate(string n) { state = n; public Collection<Player> getplayers() { return players; public void setplayers(collection<player> p) { players = p; public String tostring() { StringBuffer sb = new StringBuffer(); sb.append("-> Team Id: "); sb.append(id); sb.append(", Team name: "); sb.append(name); sb.append(", Team state: "); sb.append(state); sb.append("\n"); for (Player p : players) { sb.append("\t-> "); sb.append(p.tostring()); sb.append("\n"); return sb.tostring(); The Team entity uses auto generated primary key column (TEAM_ID). annotation indicates the one-to-many relationship between any Team and its associated Player entities. annotation indicates the foreign key column in the Player entity that references the primary key column in the Team entity. This is what ties the Player to the Team. Since there can be more than one Player per Team, it is represented by a collection data structure in the Team entity Collection<Player>.

4 The following code shows the Remote interface for TeamPlayer: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package teamplay.remote; import javax.ejb.remote; import public interface TeamPlayer { public void addteam(string name, String state); public void addplayer(string team, String name, String height) throws Exception; public void updateplayer(string name, String height) throws Exception; public void removeplayer(string name) throws Exception; public Team getteam(string name) throws Exception; public void removeteam(string name) throws Exception; The TeamPlayer interface allows us to perform various operation on the Player and Team entities. The following shows the code for TeamPlayerBean stateless session bean: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package teamplay.ejb; import teamplay.common.*; import teamplay.remote.teamplayer; import java.util.*; import javax.ejb.stateless; import javax.persistence.entitymanager; import javax.persistence.persistencecontext; import public class TeamPlayerBean implements TeamPlayer private EntityManager _emgr; public void addteam(string name, String state) { Team team = new Team(); team.setname(name);

5 team.setstate(state); _emgr.persist(team); public void addplayer(string team, String name, String height) throws Exception { Query qry = _emgr.createquery("select t from Team t where t.name = '" + team + "'"); List<Team> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No team found with name " + team); Team tm = lst.get(0); System.out.println("-> AddPlayer: " + tm); Player player = new Player(); player.setname(name); player.setheight(height); tm.getplayers().add(player); // Uncomment the following if you dont use cascade attribute in OneToMany in Team // _emgr.persist(player); // _emgr.merge(tm); public void updateplayer(string name, String height) throws Exception { Player player = _emgr.find(player.class, name); if (player == null) { throw new Exception("No player found with name " + name); player.setheight(height); public void removeplayer(string name) throws Exception { Player player = _emgr.find(player.class, name); if (player == null) { throw new Exception("No player found with name " + name); _emgr.remove(player); public Team getteam(string name) throws Exception { Query qry = _emgr.createquery("select t from Team t where t.name = '" + name + "'"); List<Team> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No team found with name " + name); Team tm = lst.get(0); System.out.println("-> GetTeam: " + tm); return tm; public void removeteam(string name) throws Exception { Query qry = _emgr.createquery("select t from Team t where t.name = '" + name + "'"); List<Team> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No team found with name " + name); Team tm = lst.get(0); System.out.println("-> RemoveTeam: " + tm); // Uncomment the following if you dont use cascade attribute in OneToMany in Team // for (Player p : tm.getplayers()) { // _emgr.remove(p); // _emgr.remove(tm);

6 The highlighted line in the above code indicates the use of custom Query in JPA. Remember that Team entity uses team id (TEAM_ID) as the primary key. Since we only have the team name and not its team id, we cannot use find method for lookup. The only other option is to use the Query API from JPA. The Query API uses the EJB QL (query language) to query for entities from the database. EJB QL looks and feels like the SQL syntax, which we are all so familiar with. The difference is that EJB QL works with Java entities rather than tables and columns as in SQL. In the above code, we are querying the database using EJB QL for a Team with the specified team name. The following shows the code for a standalone client that is accessing the TeamPlayerBean stateless session bean through the remote interface TeamPlayer: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package teamplay.client; import teamplay.common.*; import teamplay.remote.teamplayer; import java.io.bufferedreader; import java.io.inputstreamreader; import javax.naming.context; import javax.naming.initialcontext; public class TeamPlayerClient { public static void main(string[] args) { BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); Context ctx = new InitialContext(); TeamPlayer tp = (TeamPlayer) ctx.lookup("teamplayer/remote"); boolean exit = false; while (! exit) { System.out.println("1. Add Team"); System.out.println(""); System.out.println(""); System.out.println(""); System.out.println(""); System.out.println(""); System.out.println(""); String choice = input.readline(); if (choice.equals("1")) { System.out.print("Team Name: "); String name = input.readline(); System.out.print("Team State: "); String state = input.readline(); tp.addteam(name, state); System.out.println("-> Added Team, Name: " + name + ", State: " + state); else if (choice.equals("2")) { System.out.print("Player Name: "); String name = input.readline(); System.out.print("Player Height: "); String height = input.readline(); System.out.print("Player Team: "); String team = input.readline(); tp.addplayer(team, name, height);

7 System.out.println("-> Added Player, Name: " + name + ", Height: " + height + ", Team: " + team); catch (Exception ex) { else if (choice.equals("3")) { System.out.print("Player Name: "); String name = input.readline(); System.out.print("Player Height: "); String height = input.readline(); tp.updateplayer(name, height); System.out.println("-> Updated Player, Name: " + name + ", Height: " + height); catch (Exception ex) { else if (choice.equals("4")) { System.out.print("Player Name: "); String name = input.readline(); tp.removeplayer(name); System.out.println("-> Removed Player, Name: " + name); catch (Exception ex) { else if (choice.equals("5")) { System.out.print("Team Name: "); String name = input.readline(); Team team = null; team = tp.getteam(name); catch (Exception ex) { System.out.println("-> Team " + team); else if (choice.equals("6")) { System.out.print("Team Name: "); String name = input.readline(); tp.removeteam(name); catch (Exception ex) { System.out.println("-> Removed Team Name: " + name); else if (choice.equals("7")) { exit = true; catch (Throwable ex) { Next, we will compile and deploy the EJB jar my_ejb_beans.jar into the JBoss Application Server. Now, open a Terminal window and execute the script TeamPlayer.sh as illustrated below:

8 $./TeamPlayer.sh 1. Add Team 1 Team Name: Team-1 Team State: NJ -> Added Team, Name: Team-1, State: NJ 1. Add Team 1 Team Name: Team-2 Team State: NY -> Added Team, Name: Team-2, State: NY 1. Add Team 2 Player Name: Player-1 Player Height: 5ft 11in Player Team: Team-1 -> Added Player, Name: Player-1, Height: 5ft 11in, Team: Team-1 1. Add Team 2 Player Name: Player-2 Player Height: 6ft 2in Player Team: Team-2 -> Added Player, Name: Player-2, Height: 6ft 2in, Team: Team-2

9 1. Add Team 2 Player Name: Player-3 Player Height: 5ft 10in Player Team: Team-1 -> Added Player, Name: Player-3, Height: 5ft 10in, Team: Team-1 1. Add Team 2 Player Name: Player-4 Player Height: 6ft 3in Player Team: Team-2 -> Added Player, Name: Player-4, Height: 6ft 3in, Team: Team-2 1. Add Team We can verify the data from the database as follows: mysql> select * from TEAM_TBL; TEAM_ID TEAM_NAME TEAM_STATE Team-1 NJ 2 Team-2 NY rows in set (0.00 sec) mysql> select * from PLAYER_TBL; PLAYER_NAME PLAYER_HEIGHT TEAM Player-1 5ft 11in 1 Player-2 6ft 2in 2 Player-3 5ft 10in 1

10 Player-4 6ft 3in rows in set (0.00 sec) 3 Player Name: Player-3 Player Height: 6ft 5in -> Updated Player, Name: Player-3, Height: 6ft 5in 1. Add Team 4 Player Name: Player-3 -> Removed Player, Name: Player-3 1. Add Team 5 Team Name: Team-1 -> Team -> Team Id: 1, Team name: Team-1, Team state: NJ -> Player name: Player-1, Player height: 5ft 11in 1. Add Team 5 Team Name: Team-2 -> Team -> Team Id: 2, Team name: Team-2, Team state: NY -> Player name: Player-2, Player height: 6ft 2in -> Player name: Player-4, Player height: 6ft 3in 1. Add Team

11 6 Team Name: Team-1 -> Removed Team Name: Team-1 1. Add Team We can verify the data from the database as follows: mysql> select * from TEAM_TBL; TEAM_ID TEAM_NAME TEAM_STATE Team-2 NY row in set (0.00 sec) mysql> select * from PLAYER_TBL; PLAYER_NAME PLAYER_HEIGHT TEAM Player-2 6ft 2in 2 Player-4 6ft 3in rows in set (0.00 sec) We have successfully deployed and executed the example depicting the unidirectional one-to-many relationship between any Team and its Players. Next, let us explore the one-to-many bidirectional entity relationship. The relationship between any Person and their Credit-cards is one-to-many bidirectional relationship because we look up all the Credit-cards for a given Person and vice versa. For this example, we will use a join table rather than a join column to make it more interesting. The following diagram illustrates the relationship: Before we proceed with the example, we need to setup the two tables in the MySQL database testdb

12 as follows: CREATE TABLE PERSON_TBL ( PERSON_ID INTEGER AUTO_INCREMENT, PERSON_NAME VARCHAR(25) NOT NULL, PERSON_ZIP VARCHAR(5) NOT NULL, PRIMARY KEY PK_PERSON_ID(PERSON_ID) ); CREATE TABLE CREDIT_CARD_TBL ( CARD_ID INTEGER AUTO_INCREMENT, CARD_NUMBER VARCHAR(16) NOT NULL, CARD_EXPIRY VARCHAR(5) NOT NULL, PRIMARY KEY PK_CARD_ID(CARD_ID) ); CREATE TABLE PERSON_CARD_TBL ( PID INTEGER NOT NULL, CID INTEGER NOT NULL, CONSTRAINT PERSON_ID_FK FOREIGN KEY (PID) REFERENCES PERSON_TBL(PERSON_ID), CONSTRAINT CARD_ID_FK FOREIGN KEY (CID) REFERENCES CREDIT_CARD_TBL(CARD_ID) ); The following code shows the Person Entity Bean: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package percredit.common; import java.util.*; public class Person implements java.io.serializable { private static final long serialversionuid = private int private String private joincolumns={@joincolumn(name="pid"),

13 ) private Collection<CreditCard> cards = new ArrayList<CreditCard>(); public int getid() { return id; public void setid(int n) { id = n; public String getname() { return name; public void setname(string n) { name = n; public String getzip() { return zip; public void setzip(string s) { zip = s; public Collection<CreditCard> getcards() { return cards; public void setcards(collection<creditcard> c) { cards = c; public String tostring() { StringBuffer sb = new StringBuffer(); sb.append("-> Person Id: "); sb.append(id); sb.append(", Person name: "); sb.append(name); sb.append(", Person zip: "); sb.append(zip); sb.append("\n"); for (CreditCard cc : cards) { sb.append("\t-> "); sb.append(cc.tostring()); sb.append("\n"); return sb.tostring(); The Person entity uses auto generated primary key column (PERSON_ID). Each Person can have zero or more credit cards. annotation indicates this one-to-many relationship with the CreditCard entity. From the diagram above, it is clear that we have used a join table PERSON_CARD_TBL to indicate this one-to-many relationship between PERSON_TBL and CREDIT_CARD_TBL. annotation indicates the use of this join table. The joincolumns attribute indicates the foreign key in the join table (PID) that references the primary key of the Person entity (PERSON_ID). The inversejoincolumns attribute indicates the foreign key in the join table (CID) that references the primary key of the related CreditCard entity (CARD_ID). This is the mapping when we are looking at the relationship from the Person entity.

14 The following code shows the CreditCard Entity Bean: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package percredit.common; public class CreditCard implements java.io.serializable { private static final long serialversionuid = private int private String private joincolumns={@joincolumn(name="cid"), inversejoincolumns={@joincolumn(name="pid") ) private Person person; public int getid() { return id; public void setid(int n) { id = n; public String getnumber() { return number; public void setnumber(string n) { number = n; public String getexpiry() { return expiry; public void setexpiry(string s) { expiry = s; public Person getperson() { return person; public void setperson(person p) { person = p; public String tostring() { StringBuffer sb = new StringBuffer();

15 sb.append("-> Card Id: "); sb.append(id); sb.append(", Card number: "); sb.append(number); sb.append(", Card expiry: "); sb.append(expiry); sb.append(", Person: "); if (person!= null) { sb.append(person.getname()); return sb.tostring(); The CreditCard entity uses auto generated primary key column (CARD_ID). Many CreditCard entities may belong to a Person. annotation indicates this many-to-one relationship with the Person entity. annotation indicates the use of the join table PERSON_CARD_TBL. The joincolumns attribute indicates the foreign key in the join table (CID) that references the primary key of the CreditCard entity (CARD_ID). The inversejoincolumns attribute indicates the foreign key in the join table (PID) that references the primary key of the related Person entity (PERSON_ID). This is the mapping when we are looking at the relationship from the CreditCard entity. The following code shows the Remote interface for PersonCard: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package percredit.remote; import javax.ejb.remote; import public interface PersonCard { public void addperson(string name, String zip); public void removeperson(string name) throws Exception; public Person getperson(string name) throws Exception; public void addcreditcard(string name, String number, String expiry) throws Exception; public void removecreditcard(string number) throws Exception; public CreditCard getcreditcard(string number) throws Exception; The PersonCard interface allows us to perform various operation on the Person and CreditCard entities. The following shows the code for PersonCardBean stateless session bean:

16 /* * Name: Bhaskar S * * Date: 02/07/2009 */ package percredit.ejb; import percredit.common.*; import percredit.remote.personcard; import java.util.*; import javax.ejb.stateless; import javax.persistence.entitymanager; import javax.persistence.persistencecontext; import public class PersonCardBean implements PersonCard private EntityManager _emgr; public void addperson(string name, String zip) { Person per = new Person(); per.setname(name); per.setzip(zip); _emgr.persist(per); System.out.println("-> Persisted data for person: " + name); public void removeperson(string name) throws Exception { Query qry = _emgr.createquery("select p from Person p where p.name = '" + name + "'"); List<Person> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No person found with name: " + name); Person per = lst.get(0); System.out.println("-> Remove person: " + per); _emgr.remove(per); public Person getperson(string name) throws Exception { Query qry = _emgr.createquery("select p from Person p where p.name = '" + name + "'"); List<Person> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No person found with name: " + name); Person per = lst.get(0); System.out.println("-> Get person: " + per); return per; public void addcreditcard(string name, String number, String expiry) throws Exception { Query qry = _emgr.createquery("select p from Person p where p.name = '" + name + "'"); List<Person> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No person found with name: " + name); Person per = lst.get(0); System.out.println("-> Lookup person <add-card>: " + per); CreditCard card = new CreditCard(); card.setnumber(number); card.setexpiry(expiry);

17 per.getcards().add(card); System.out.println("-> Added credit card: " + number + " for person: " + per); public void removecreditcard(string number) throws Exception { Query qry = _emgr.createquery("select c from CreditCard c where c.number = '" + number + "'"); List<CreditCard> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No credit card found with number: " + number); CreditCard card = lst.get(0); System.out.println("-> Remove credit card for person: " + card.getperson().getname()); _emgr.remove(card); public CreditCard getcreditcard(string number) throws Exception { Query qry = _emgr.createquery("select c from CreditCard c where c.number = '" + number + "'"); List<CreditCard> lst = qry.getresultlist(); if (lst.size() == 0) { throw new Exception("No credit card found with number " + number); CreditCard card = lst.get(0); System.out.println("-> Get credit card : " + card); return card; The following shows the code for a standalone client that is accessing the PersonCardBean stateless session bean through the remote interface PersonCard: /* * Name: Bhaskar S * * Date: 02/07/2009 */ package percredit.client; import percredit.common.*; import percredit.remote.personcard; import java.io.bufferedreader; import java.io.inputstreamreader; import javax.naming.context; import javax.naming.initialcontext; public class PersonCardClient { public static void main(string[] args) { BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); Context ctx = new InitialContext(); PersonCard pc = (PersonCard) ctx.lookup("personcard/remote"); boolean exit = false; while (! exit) { System.out.println("1. Add Person"); System.out.println("2. Remove Person"); System.out.println("3. Get Person Information"); System.out.println("4. Add Credit Card"); System.out.println("5. Remove Credit Card"); System.out.println("6. Get Credit Card Information"); System.out.println("");

18 String choice = input.readline(); if (choice.equals("1")) { System.out.print("Person Name: "); String name = input.readline(); System.out.print("Person zip: "); String zip = input.readline(); pc.addperson(name, zip); System.out.println("-> Added Person, Name: " + name + ", Zip: " + zip); else if (choice.equals("2")) { System.out.print("Person Name: "); String name = input.readline(); pc.removeperson(name); System.out.println("-> Removed person, Name: " + name); catch (Exception ex) { else if (choice.equals("3")) { System.out.print("Person Name: "); String name = input.readline(); Person per = null; per = pc.getperson(name); catch (Exception ex) { System.out.println("-> Person: " + per); else if (choice.equals("4")) { System.out.print("Credit Card Owner: "); String name = input.readline(); System.out.print("Credit Card Number: "); String number = input.readline(); System.out.print("Credit Card Expiry: "); String expiry = input.readline(); pc.addcreditcard(name, number, expiry); System.out.println("-> Added Credit Card for Name: " + name); catch (Exception ex) { else if (choice.equals("5")) { System.out.print("Credit Card Number: "); String number = input.readline(); pc.removecreditcard(number); catch (Exception ex) { System.out.println("-> Removed Credit Card with Number: " + number); else if (choice.equals("6")) { System.out.print("Credit Card Number: "); String number = input.readline(); CreditCard card = null; card = pc.getcreditcard(number); catch (Exception ex) { System.out.println("-> Credit Card: " + card); else if (choice.equals("7")) { exit = true;

19 catch (Throwable ex) { Next, we will compile and deploy the EJB jar my_ejb_beans.jar into the JBoss Application Server. Now, open a Terminal window and execute the script PersonCard.sh as illustrated below: $./PersonCard.sh 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 1 Person Name: Swaminathan Bhaskar Person zip: > Added Person, Name: Swaminathan Bhaskar, Zip: Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 1 Person Name: Bill Gates Person zip: > Added Person, Name: Bill Gates, Zip: Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 4 Credit Card Owner: Swaminathan Bhaskar Credit Card Number: Credit Card Expiry: 10/10 -> Added Credit Card for Name: Swaminathan Bhaskar 1. Add Person

20 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 4 Credit Card Owner: Bill Gates Credit Card Number: Credit Card Expiry: 11/11 -> Added Credit Card for Name: Bill Gates 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 4 Credit Card Owner: Bill Gates Credit Card Number: Credit Card Expiry: 12/12 -> Added Credit Card for Name: Bill Gates 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 3 Person Name: Bill Gates -> Person: -> Person Id: 2, Person name: Bill Gates, Person zip: > -> Card Id: 2, Card number: , Card expiry: 11/11, Person: Bill Gates -> -> Card Id: 3, Card number: , Card expiry: 12/12, Person: Bill Gates We can verify the data from the database as follows: mysql> select * from PERSON_TBL; PERSON_ID PERSON_NAME PERSON_ZIP Swaminathan Bhaskar Bill Gates rows in set (0.00 sec) mysql> select * from CREDIT_CARD_TBL; CARD_ID CARD_NUMBER CARD_EXPIRY

21 / / / rows in set (0.00 sec) mysql> select * from PERSON_CARD_TBL; PID CID rows in set (0.00 sec) 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 2 Person Name: Bill Gates -> Removed person, Name: Bill Gates 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 3 Person Name: Swaminathan Bhaskar -> Person: -> Person Id: 1, Person name: Swaminathan Bhaskar, Person zip: > -> Card Id: 1, Card number: , Card expiry: 10/10, Person: Swaminathan Bhaskar We can verify the data from the database as follows: mysql> select * from PERSON_TBL; PERSON_ID PERSON_NAME PERSON_ZIP Swaminathan Bhaskar row in set (0.00 sec) mysql> select * from CREDIT_CARD_TBL;

22 CARD_ID CARD_NUMBER CARD_EXPIRY / row in set (0.00 sec) mysql> select * from PERSON_CARD_TBL; PID CID row in set (0.01 sec) 1. Add Person 2. Remove Person 3. Get Person Information 4. Add Credit Card 5. Remove Credit Card 6. Get Credit Card Information 7 We have successfully deployed and executed the example depicting the bidirectional one-to-many relationship using a join table between a Person and their CreditCards. We will continue to explore EJB Entity Beans Using Java Persistence in Part-6.4 of this series.