Enterprise JavaBeans™

1. Enterprise JavaBeans™ Trademark of Sun Microsystems, Inc.

2. Agenda • Review • Interfaces • Deployment Descriptors • Using Beans • Homework 5

3. Review • need development and runtime environment • J2EE SDK • development environment from tool vendor like Together, Inprise • runtime environment from Sun, IBM, BEA, Inprise, etc. • beans are server-side components • entity beans model real-world objects • persistent in nature, can be externally manipulated • session beans manage processes or tasks • transient in nature, though have side effects that perist • message-driven beans increase reliability and efficiency • transient in nature, process messages sent to message server

4. Interface Review • remote interface: defines business methods; EJBObject extension • home interface: defines life cycle methods; EJBHome extension • bean class: implements business methods • implements EntityBean or SessionBean • MessageDrivenBean is a different story, left untold • primary key: for entity beans; DB reference

5. Clients and Containers Review • client uses home and remote interfaces • not bean class itself • bean and server/infrastructure interactions managed by "container" • container creates instances, manages storage, etc. • tools support container, doing things like: • mapping between entity beans and DB records • generating code from interfaces • etc.

6. Remote Interface • just the business methods • not used by message-driven beans • import java.rmi.RemoteException; • public interface xxx extends javax.ejb.EJBObject { • public ... throws RemoteException: • } • By convention, xxx is name of business object or process • “…” means any method signature

7. Remote Interface Example package account; import java.rmi.RemoteException; public interface Account extends javax.ejb.EJBObject { public void debit(MoneyAmount amount) throws RemoteException, InsufficientFundsException; public void credit(MoneyAmount amount) throws RemoteException; }

8. Home Interface • life cycle and bean look-up methods • not used by message-driven beans • import java.rmi.RemoteException; • import java.ejb.CreateException; • import java.ejb.FinderException; // BMP entity bean only • public interface xxxHome extends javax.ejb.EJBHome { • public xxx create(...) throws RemoteException, • CreateException; • // BMP entity bean only below • public xxxPK findByPrimaryKey(...) throws • RemoteException, FinderException; • }

9. Home Interface Example package account; import java.rmi.RemoteException; import javax.ejb.CreateException; import javax.ejb.FinderException; public interface AccountHome extends javax.ejb.EJBHome { public Account create(String name, String ssNumber, MoneyAmount initialBalance) throws RemoteException, CreateException; public findByPrimaryKey(AccountPK pk) throws RemoteException, FinderException; }

10. Generic Enterprise Bean Class public class xxxBean implements javax.ejb.zzzBean { // … >>> business methods here <<<… public … ejbCreate(…) {…} public void ejbRemove() {} // context setting public void setzzzContext(javax.ejb.zzzContext ctx) {} // etc. }

11. EntityBean Class public class xxxBean implements javax.ejb.EntityBean { // …>>> public instance variables from persisted storage <<<… // … >>> business methods here <<<… public xxxPK ejbCreate(…some key...) {…; return null;} public void ejbPostCreate(…some key...) {} public void ejbActivate() {} public void ejbPassivate() {} public void ejbRemove() {} public void setEntityContext(javax.ejb.EntityContext ctx) {} public void unsetEntityContext() {} public void ejbLoad() {} public void ejbStore() {} }

12. EntityBean Example, Part 0 // AccountPK.java: package account; public class AccountPK implements java.io.Serializable { public String id; public int hashCode( ){ return // integer hash of id; } public boolean equals(Object obj){ if(obj instanceof AccountPK){ return (id == ((AccountPK)obj).id); } return false; } public String toString(){ return id; } }

13. EntityBean Example, Part 1 // AccountBean.java: package account: public class AccountBean implements javax.ejb.EntityBean { private static int count=0; public String id; public String name; public String ssNumber; public MoneyAmount balance; public void debit(BigDecimal amount) throws RemoteException, InsufficientFundsException { if (balance.compareTo(amount) > 0) balance.Decrement(amount); else raise InsufficientFundsException; } //…continued

14. EntityBean Example, Part 2 public void credit(MoneyAmount amount) throws RemoteException { balance.Increment(amount); } public AccountPK ejbCreate(String name, String ssNumber, MoneyAmount initialBalance) { this.name = name; // check for errors??? this.ssNumber = ssNumber; balance = new MoneyAmount(initialBalance); count += 1; // ??? id = “123456-” + count; // ??? return null; } public void ejbPostCreate(String name, String ssNumber, MoneyAmount initialBalance) {} //…continued

15. EntityBean Example, Part 3 public void ejbActivate() {} public void ejbPassivate() {} public void ejbRemove() {} public void setEntityContext(javax.ejb.EntityContext ctx) {} public void unsetEntityContext() {} public void ejbLoad() {} public void ejbStore() {} }

16. SessionBean Class public class xxxBean implements javax.ejb.SessionBean { // … >>> business methods here <<<… public ... ejbCreate(...) {…; return null;} public void ejbActivate() {} public void ejbPassivate() {} public void ejbRemove() {} public void setSessionContext(javax.ejb.SessionContext ctx) {} }

17. SessionBean Example, Part 0 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 2000. // TravelAgent.java: // imports... public interface TravelAgent extends javax.ejb.EJBObject{ public String [] listCabins(int shipID, int bedCount) throws RemoteException; } // TravelAgent???.java: // imports... public interface TravelAgent??? extends javax.ejb.EJB???{ public TravelAgent create() throws RemoteException, CreateException; }

18. SessionBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 2000. // TravelAgentBean.java // imports... public class TravelAgentBean implements javax.ejb.SessionBean { public String [] listCabins(int shipID, int bedCount) { try { javax.naming.Context jc = new InitialContext(); CabinHome home = (CabinHome) javax.rmi.PortbleRemoteObject.narrow( (Object) jc.lookup(“CabinHome”), CabinHome.class); Vector list = new Vector(); CabinPK pk = new CabinPK(); Cabin cabin; // continued...

19. SessionBean Example, Part 2 for (int i=0; ; i++) pk.id = i; try { cabin = home.findByPrimaryKey(pk); } catch (javax.ejb.FinderException fe) {break;} if (cabin.getShip() == shipID && cabin.getBedCount() == bedCount) { list.addElement((String) i+”, ” +cabin.getName() + “, “ + cabin.getDeckLevel()); } } String [] strings = new String[list.size()]; list.copyInto(strings); return strings; } catch (Exception e) {throw new EJBException(e);} } // continued...

20. SessionBean Example, Part 3 public TravelAgent ejbCreate() {return null;} public void ejbActivate() {} public void ejbPassivate() {} public void ejbRemove() {} public void setSessionContext(javax.ejb.SessionContext ctx) {} }

21. MessageDrivenBean Class public class xxxBean implements javax.ejb.MessageDrivenBean, javax.jms.MessageListener { public void ejbCreate(...) {…} public void ejbRemove() {} public void onMessage(javax.jms.Message message) {…} public void setMessageDrivenContext( javax.ejb.MessageDrivenContext mdc) {} }

22. Deployment Descriptors • as of EJB 1.1, tags in XML files (ejb-jar.xml) • part of a jar file, which defines a bean • declares behavior externally vs. inside code • allows deployer to change way code works by changing environment, including naming • lists dependencies • groups beans

23. Deployment Descriptors:EntityBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 2000. <ejb-jar> <enterprise-beans> <entity> <description>This Cabin enterprise bean entity represents a cabin on a cruise ship.</description> <ejb-name>CabinBean</ejb-name> <home>com.titan.cabin.CabinHome</home> <remote>com.titan.cabin.Cabin</remote> <ejb-class>com.titan.cabin.CabinBean</ejb-class> <persistence-type>Container</persistence-type> <prim-key-class>com.titan.cabin.CabinPK</prim-key-class> <reentrant>False</reentrant> <cmp-field><field-name>id</field-name></cmp-field> <cmp-field><field-name>name</field-name></cmp-field> <cmp-field><field-name>deckLevel</field-name></cmp-field> <cmp-field><field-name>ship</field-name></cmp-field> <cmp-field><field-name>bedCount</field-name></cmp-field> </entity> </enterprise-beans>

24. Deployment Descriptors:EntityBean Example, Part 2 <assembly-descriptor> <security-role> <description> This role represents everyone who is allowed full access to the cabin bean. </description> <role-name>everyone</role-name> </security-role> <method-permission> <role-name>everyone</role-name> <method> <ejb-name>CabinBean</ejb-name> <method-name>*</method-name> </method> </method-permission>

25. Deployment Descriptors:EntityBean Example, Part 3 <container-transaction> <method> <ejb-name>CabinBean</ejb-name> <method-name>*</method-name> </method> <trans-attribute>Required</trans-attribute> </container-transaction> </assembly-descriptor> </ejb-jar>

26. Deployment Descriptors:SessionBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 2000. <ejb-jar> <enterprise-beans> <session> <ejb-name>TravelAgentBean</ejb-name> <home>com.titan.travelagent.TravelAgentHome</home> <remote>com.titan.travelagent.TravelAgent</remote> <ejb-class>com.titan.travelagent.TravelAgentBean</ejb-class> <session-type>Stateless</session-type> <transaction-type>Container</transaction-type> <ejb-ref> <ejb-ref-name>ejb/CabinHome</ejb-ref-name> <ejb-ref-type>Entity</ejb-ref-type> <home>com.titan.cabin.CabinHome</home> <remote>com.titan.cabin.Cabin</remote> </ejb-ref> </session> </enterprise-beans>

27. Deployment Descriptors:SessionBean Example, Part 2 <assembly-descriptor> <security-role> <description> This role represents everyone who is allowed full access to the cabin bean. </description> <role-name>everyone</role-name> </security-role> <method-permission> <role-name>everyone</role-name> <method> <ejb-name>TravelAgentBean</ejb-name> <method-name>*</method-name> </method> </method-permission>

28. Deployment Descriptors:SessionBean Example, Part 3 <container-transaction> <method> <ejb-name>TravelAgentBean</ejb-name> <method-name>*</method-name> </method> <trans-attribute>Required</trans-attribute> </container-transaction> </assembly-descriptor> </ejb-jar>

29. Deployment • put all class files and bean descriptors in a jar file • make a folder called META-INF at root of source tree • copy ejb-jar.xml to META-INF • then: jar cf com\titan\com\travelagent\*.class META-INF\ejb-jar.xml • Use the deployment tool provided by the EJB server vendor to configure the environment • For Sun’s J2EE Reference Implementation: • deploytool: generates .ear file which includes server-specific descriptor (sun-j2ee-ri.xml) and application-specific descriptor • Fill in the fields with information pertinent to the bean • deploy to your EJB server host

30. Client Application • uses the bean(s) • via the remote and home interfaces • never via the bean class • steps • find the naming service • find the bean(s) • use home and business methods as desired

31. Client Application:Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 2000. package com.titan.travelagent; import com.titan.cabin.CabinHome; import com.titan.cabin.Cabin; import com.titan.cabin.CabinPK; import javax.naming.InitialContext; import javax.naming.Context; import javax.naming.NamingException; import javax.ejb.CreateException; import java.rmi.RemoteException; import java.util.Properties; // continued...

32. Client Application:Example, Part 2 public class Client_1 { public static int SHIP_ID = 1; public static int BED_COUNT = 3; public static void main(String [] args){ try { Context jndiContext = getInitialContext(); Object obj = jndiContext.lookup("ejb/TravelAgentHome"); TravelAgentHome home = (TravelAgentHome) javax.rmi.PortableRemoteObject.narrow(obj, TravelAgentHome.class); TravelAgent reserve = home.create(); // continued...

33. Client Application:Example, Part 3 // Get a list of all cabins on ship 1 with a bed count of 3. String list [] = reserve.listCabins(SHIP_ID,BED_COUNT); for(int i = 0; i < list.length; i++){ System.out.println(list[i]); } } catch(java.rmi.RemoteException re){re.printStackTrace();} catch(Throwable t){t.printStackTrace();} } static public Context getInitialContext() throws Exception { Properties p = new Properties(); // ... Specify the JNDI properties specific to the vendor. return new InitialContext(); } }

34. Homework 5 • Programming assignment #2 • tasks • implement Account beans for savings and checking accounts; use student id for account number prefix • implement transferMoney bean • implement client to transfer money from one account to another • deploy (don’t create/delete table) & run • use container-managed persistence • use JNDI for databases: jndi/SavingsAccountDB and jndi/CheckingAccountDB