Enterprise JavaBeans™ Trademark of Sun Microsystems, Inc.

Agenda " Review " Interfaces " Deployment Descriptors " Using Beans " Homework 5

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

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

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.

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

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; }

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; }

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; }

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. }

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() {} }

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; }

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

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 = “ ” + count; // ??? return null; } public void ejbPostCreate(String name, String ssNumber, MoneyAmount initialBalance) {} //…continued

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() {} }

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) {} }

SessionBean Example, Part 0 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, // 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; }

SessionBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, // 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...

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...

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) {} }

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) {} }

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

Deployment Descriptors: EntityBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, This Cabin enterprise bean entity represents a cabin on a cruise ship. CabinBean com.titan.cabin.CabinHome com.titan.cabin.Cabin com.titan.cabin.CabinBean Container com.titan.cabin.CabinPK False id name deckLevel ship bedCount

Deployment Descriptors: EntityBean Example, Part 2 This role represents everyone who is allowed full access to the cabin bean. everyone everyone CabinBean *

Deployment Descriptors: EntityBean Example, Part 3 CabinBean * Required

Deployment Descriptors: SessionBean Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, TravelAgentBean com.titan.travelagent.TravelAgentHome com.titan.travelagent.TravelAgent com.titan.travelagent.TravelAgentBean Stateless Container ejb/CabinHome Entity com.titan.cabin.CabinHome com.titan.cabin.Cabin

Deployment Descriptors: SessionBean Example, Part 2 This role represents everyone who is allowed full access to the cabin bean. everyone everyone TravelAgentBean *

Deployment Descriptors: SessionBean Example, Part 3 TravelAgentBean * Required

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

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

Client Application: Example, Part 1 from: Enterprise JavaBeans, R. Monson-Haefel, O’Reilly, 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...

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...

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(); }

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