EJB: Session Beans

EnterpriseJava

v131013 EJB: Session Beans 1

EJB: Session Beans

EnterpriseJava


Needs and JavaSE/EE Implementation Options

EnterpriseJava


Goals

• Be able to deploy business logic to the EJB tier– hosted by the container

• resource management• threading• security• transactions• remote interfaces• async capabilities

– accessed by other local business logic and local web tier– accessed by remote clients

EnterpriseJava


Objectives• Rationale• Stateless Session Bean

– Stateless– Stateful– Singleton

• Enterprise Archives (EARs)• Example Session Bean• Interface Design Issues

– Lazy Load– Pure POJOs– DTO Classes

EnterpriseJavaOverview

• Entity Beans – model business data in system

• Session Beans– model interactions between other beans– Taskflow

• Enterprise Archive (EAR)– Deployment artifact with a specific structure containing

• EJB component(s)• WAR component(s)• Utility jar(s)• …


EnterpriseJava


Associated Design Patterns• Session Façade (covered in Business Logic)• Remote Façade• Data Transfer Objects

EnterpriseJava


Remote Facade• Forces

– core service layer (business logic and its business objects) contains fine grain methods and objects

– a significant number of fine-grain remote calls will not work

• Solution– add a Remote Facade

• a course-grain facade over a service layer • contains no business logic; it calls it• translates course-grain methods and objects into fine-grain

method calls and objects to/from service layer• bulk accessors wrap fine-grain access methods

– service layer does not have a remote interface• fine grain business objects used might not be Serializable

EnterpriseJava


Remote Facade Encapsulates Local Objects

EnterpriseJava


Remote Facade Encapsulates Local Logic

EnterpriseJava


DTO Pattern

• Context– Business Objects represent too much information or

behavior to transfer to remote client• Problem

– Client may get information they don't need– Client may get information they can't handle– Client may get information they are not authorized to use– Client may get too much information/behavior to be

useful (e.g., entire database serialized to client)• Forces

– Some clients are local and can share object references with business logic

– Handling specifics of remote clients outside of core scope of business logic

EnterpriseJava


DTO/Remote Facade Solution

• Layer a Remote Facade over Business Logic• Remote Facade constructs Data Transfer Objects

(DTOs) from Business Objects that are appropriate for remote client view

• Remote Facade uses DTOs to construct or locate Business Objects to communicate with Business Logic

EnterpriseJava


DTO Pattern Roles

• Data Transfer Object– represent a subset of the state of the application at a point

in time– not dependent on Business Objects or server-side

technologies• doing so would require sending Business Objects to client• XML and Web services provide the “ultimate isolation” in

DTO implementation• Remote Facade

– uses Business Logic to perform core business logic– layered on to of Business Logic to translate between

Business Objects and DTOs• Business Logic

– continues to perform core duties as described in DAO Pattern

EnterpriseJava


DTO Pattern Consequences• Clients only get what they need• Clients only get what they understand• Clients only get what they are authorized to use• Remote and Local interfaces to services are different

– makes it harder to provide location transparency

• Lightweight Business Objects can be used as DTOs– Remote Facade must make sure they are “pruned” of

excess related items before transferring to client– Remote Facade must make sure they are “cleaned” of

DAO persistence classes before transferring to client

EnterpriseJava


Use Cases and Session Beans• Session Bean per Use Case too fine grain

– CreateAccountEJB

– DepositEJB

– WithdrawEJB

– TransferEJB

• Group cohesive Use Cases into a larger-grain Session Bean

– TellerEJB• createAccount(), deposit(), withdraw(), transfer()

EnterpriseJava


Use of Session versus Entity Beans• Session Beans

– implementation of a task– interaction between other beans– direct database access

• bulk operations– examples

• TaxDistrict.calcTax(double cost)• Teller.transfer(long fromAccount, long toAccount,

double amount)• Registrar.listStudents(String course)

EnterpriseJava


Use of Session versus Entity Beans (cont.)

• Entity Beans– represent shared data in the database– provide a type-safe, complete view of shared

information– interacts with data generally at the individual

object/row level– examples

• Account, Student• Account.setOwner(String taxId), Account.getOwner()• Account.withdraw(double amount),

Account.deposit(double amount)

EnterpriseJava


Stateless Session Bean• maintains no conversational state

– each method is ignorant of what went before it and what will happen after it

• maintains implementation state– sharable between separate client invocations

• a set of procedures or batch commands that take in a set of parameters and return a result

EnterpriseJava


Stateful Session Bean• maintains conversational state

– object can cache values between calls• ex. iterator

– idle timeout period or client command ends lifetime• maintains implementation state

– not sharable between separate clients/objects• all resources are allocated to perform the work of one

Stateful Session bean instance. That instance is tied to the state of the client

• able to react to transaction states– ex. Publish error message on transaction rollback

EnterpriseJavaSingleton Session Bean

• Stateful session bean with only one instance shared across all clients

• Good for tracking transient state in-memory


EnterpriseJava


Stateless/Stateful/Singleton• Stateless

– can contain cached implementations• JDBC DataSources• JMS Publishers• cached EAI state• all non-visible to calling client

• Stateful– may contain all of the above and add client

conversational state • Singleton

– May contain all of the above except client conversation state would be shared across clients

• e.g., getNextTask()

EnterpriseJava


Stateless/Stateful/Singleton• Stateless

– Cheapest to implement, deploy, scale• Stateful

– should only be used within the scope of a single HttpRequest

– should not be used at HttpSession Scope• multiple threads would access same instance

• Singleton– Newest bean type– More overhead than stateless because of concurrency

management– Extremely efficient when managing in-memory state

EnterpriseJava


Stateless Session Bean Lifecycle

EnterpriseJava


Stateful Session Bean Lifecycle

EnterpriseJava


Singleton Session Bean Lifecycle

EnterpriseJavaJavaEE EARs

• Used for compound deployments– Multiple EJBs

– Multiple WARs

– EJB + WAR

• Optional with new JavaEE 6 “flexible deployment” and the first and last case above

– WAR• EJB(s)


EnterpriseJava


Class Loaders

• Arranged in a parent/child relationship• Requests for a class are first delegated to the parent

class loader• May access classes/resources loaded by local and

parent class loader• Do not have access to classes/resources loaded by

sibling class loaders

Parent Class Loader

Child Class Loader Child Class Loader

EnterpriseJava

27

Application Server Class Loader

EJB AppClass Loader

Web App Class Loader

Web App Class Loader

Separate EJB/WAR Deployment

• Classes loaded by EJB Application Class Loader not seen by Web Application

• Shared implementations must be placed in both applications

– WEB-INF/lib– causes difficulty when passing object between applications

that have loaded the same class

v131013 EJB: Session Beans

EnterpriseJava


J2EE Enterprise Application Deployment

Application Server Class Loader

EAR Class Loader

EJB App Class Loader

EAR Class Loader

Web App 2 Class LoaderWeb App 1 Class Loader Servlets/JSPs and lib.jars

loaded by isolated classloaders

All EJBs are loaded by a single class loader•may also include web dependent classes identified through manifest entries to promote singleton loading of classes across web applications

EJB interfaces and dependent classes identified by EJB manifests loaded by EAR’s classloader

EnterpriseJava


Enterprise Application Archive (EAR)

• WAR(s)

– directory or archive

• EJB(s)


• Client JAR(s)

– client applications

• Utility Classes(s)


– supplies external source utility classes

– referenced through MANIFESTs

• Resource Adapters(s)

– custom resource drivers

WARWARWAR

EJBEJBEJB

EAR

META-INF/application.xml

UtilityClasses

Resource AdapterResource

AdapterResource Adapter

ClientApp

ClientAppClient

App

UtilityClasses

UtilityClasses

EnterpriseJava


Directory and Archive Forms

• Exploded Directory Form– ability to modify static files (html/jsp) without

redeploying

– separate server serves up content in exploded form

– simpler build environment • consistent with build environment of free versions of

IDEs (Forte, JBuilder, etc.)

• Archive File Format– easy form of distribution

EnterpriseJava


application

icon

small-icon large-icon

display-name description? module+ security-role*

ejb|connector|java|web alt-dd

web-uri context-root

description?

role-name

application.xml

EnterpriseJava


Key Element Definitions

• Modules– ejb – EJBs (Ex. EJB1.jar)– web – web applications– java - client applications– connector – JCA resource adapters

• Web applications– web-uri (ex. webapp1.war)– context-root

• Name of web app’s context• May be empty if only one webapp in the application

EnterpriseJava


application.xml Example

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE application PUBLIC

"-//Sun Microsystems, Inc.//DTD J2EE Application 1.3//EN"

"http://java.sun.com/dtd/application_1_3.dtd">

<application>

<display-name>ejbsessionBankEAR</display-name>

<description>Example Session Bean Bank Application</description>

<module>

<web>

<web-uri>ejbsessionBankWAR.war</web-uri>

<context-root>/ejbsessionBankWAR</context-root>

</web>

</module>

<module>

<ejb>ejbsessionBankEJB-1.0.2007.2-SNAPSHOT.jar</ejb>

</module>

EnterpriseJava


Example: Core ImplementationejbsessionBankImpl/target/classes|-- META-INF| `-- orm.xml`-- ejava `-- examples `-- ejbsessionbank |-- bl | |-- BankException.class | `-- Teller.class |-- blimpl | `-- TellerImpl.class |-- bo | |-- Account.class | |-- Ledger.class | `-- Owner.class |-- dao | |-- AccountDAO.class | |-- DAOException.class | `-- OwnerDAO.class `-- jpa |-- JPAAccountDAO.class `-- JPAOwnerDAO.class

* Note: we are not including a JavaSE persistence.xml in Impl

EnterpriseJava


Example Session Bean: Business Interfacepackage ejava.examples.ejbsessionbank.bl;

import java.util.List;import ejava.examples.ejbsessionbank.bo.Account;import ejava.examples.ejbsessionbank.bo.Ledger;

public interface Teller { Account createAccount(String accNum) throws BankException; Account getAccount(String acctNum) throws BankException; Account closeAccount(String acctNum) throws BankException; void updateAccount(Account account) throws BankException; List<Account> getOverdrawnAccounts(int index, int count) throws BankException; List<Account> getAccounts(int index, int count) throws BankException; Ledger getLedger() throws BankException;}

EnterpriseJava


Example: EJBejbsessionBankEJB/target/classes|-- ejava| `-- examples| `-- ejbsessionbank| |-- dto| | `-- OwnerDTO.class| `-- ejb| |-- Stats.class| |-- StatsEJB.class| |-- StatsLocal.class| |-- StatsRemote.class| |-- TellerEJB.class| |-- TellerLocal.class| `-- TellerRemote.class`-- META-INF |-- ejb-jar.xml `-- persistence.xml

* Note: We are providing a JavaEE persistence.xml in the EJB

EnterpriseJava


Example Session Bean: Local and Remote Interfaces

package ejava.examples.ejbsessionbank.ejb;

import ejava.examples.ejbsessionbank.bl.Teller;

@javax.ejb.Localpublic interface TellerLocal extends Teller {}

package ejava.examples.ejbsessionbank.ejb;

import ejava.examples.ejbsessionbank.bl.Teller;

@javax.ejb.Remotepublic interface TellerRemote extends Teller {} * Warning – although business interfaces can be used

for both local and remote interfaces, this only worksfor simple data models – more later

EnterpriseJava


Example Session Bean: Bean Classpackage ejava.examples.ejbsessionbank.ejb;

import javax.annotation.*;import javax.ejb.*;import javax.persistence.*;...

@Statelesspublic class TellerEJB implements TellerLocal, TellerRemote { private static final Log log = ... @Resource protected SessionContext ctx; @PersistenceContext(unitName="ejbsessionbank") protected EntityManager em; @Resource(name="daoClass") protected String daoClassName; protected Teller teller;

Stateless

EnterpriseJava


Example Session Bean: Bean Class@PostConstruct

public void init() {

log.debug("init(), daoClass=" + daoClassName);

teller = new TellerImpl();

try {

AccountDAO dao = (AccountDAO)Thread.currentThread() //just a partial example of resolving

.getContextClassLoader() //a property supplied

.loadClass(daoClassName) //by the container

.newInstance();

((JPAAccountDAO)dao).setEntityManager(em);

((TellerImpl)teller).setAcctDAO(dao);

OwnerDAO ownerDAO = new JPAOwnerDAO();

((JPAOwnerDAO)ownerDAO).setEntityManager(em);

((TellerImpl)teller).setOwnerDAO(ownerDAO); }

catch (Exception ex) {

log.fatal("error loading dao class:" + daoClassName, ex);

throw new EJBException("error loading dao class:" +

daoClassName + ", " + ex);

}

@PreDestroy

public void close() { ... }

EnterpriseJava


Example Session Bean: Bean Class

public Account createAccount(String accountNumber) throws BankException{ try { return teller.createAccount(accountNumber); } catch (AccountDAOException ex) { ctx.setRollbackOnly(); log.fatal("internal error creating account", ex); throw new BankException("internal error creating account:"+ ex); }}

Log details of exception locally on server-side

Provide de-serializable message to client

EnterpriseJava


Example Session Bean: ejb-jar.xml<?xml version="1.0"?><ejb-jar xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_1.xsd" version="3.1">

<enterprise-beans>

<session>

<ejb-name>TellerEJB</ejb-name>

<env-entry>

<env-entry-name>daoClass</env-entry-name>

<env-entry-type>java.lang.String</env-entry-type>

<env-entry-value>ejava.examples.ejbsessionbank.jpa.JPAAccountDAO

</env-entry-value>

</env-entry>

...

</session>

</enterprise-beans>

</ejb-jar>Watch out for <CR>!!!

EnterpriseJava


Example Session Bean: persistence.xml<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">

<persistence-unit name="ejbsessionbank"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source> <jar-file>lib/ejbsessionBankImpl-${project.version}.jar</jar-file> <properties> <property name="hibernate.dialect" value="${hibernate.dialect}"/> </properties> </persistence-unit> </persistence>

EnterpriseJavaExample Singleton Session Bean:

Local and Remote Interfacespackage ejava.examples.ejbsessionbank.ejb;public interface Stats {

void open();void close();int getTotal();int getDelta();void reset();

}

package ejava.examples.ejbsessionbank.ejb;@javax.ejb.Localpublic interface StatsLocal extends Stats {}

package ejava.examples.ejbsessionbank.ejb;@javax.ejb.Remotepublic interface StatsRemote extends Stats {}



Bean Class Setuppackage ejava.examples.ejbsessionbank.ejb;

@[email protected]@javax.ejb.ConcurrencyManagement( javax.ejb.ConcurrencyManagementType.CONTAINER)@javax.ejb.AccessTimeout(value=3000)public class StatsEJB implements StatsLocal, StatsRemote { private static final Log log = ...

private int delta;private int total;

@javax.annotation.PostConstructlog.info("*** StatsEJB ***");

}


(Stateful)


Write/Read Methods@[email protected](

javax.ejb.LockType.WRITE)public void open() {

this.delta += 1;this.total += 1;

}

@Override@Lock(LockType.WRITE)public void close() {

this.delta -= 1;this.total += 1;

}

@Override@Lock(LockType.WRITE)public void reset() {

delta=0;total=0;

}

@Override@Lock(LockType.READ)public int getTotal() {

return total;}

@Override@Lock(LockType.READ)public int getDelta() {

return delta;}


EnterpriseJava


Example: RMI Test

ejbsessionBankTest/target/test-classes|-- ejava| `-- examples| `-- ejbsessionbank| `-- ejbclient… …| |-- TellerEJBClientIT.class| |-- TellerRemotingIT.class| |-- TellerOwnerEJBClientIT.class| `-- TellerOwnerRemotingIT.class|-- jboss-ejb-client.properties|-- jndi.properties`-- log4j.xml

JUnit Test Types*Test = unit tests run by surefire plugin*IT = integration tests run by failsafe plugin

EnterpriseJavaRemoting

• JNDI Tree (Internally Accessible)java:global/ejbsessionBankEAR/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerLocal

java:app/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerLocal

java:module/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerLocal

java:global/ejbsessionBankEAR/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote

java:app/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote

java:module/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote

• JNDI Tree (externally Accessible)java:jboss/exported/ejbsessionBankEAR/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote

• jndi.propertiesjava.naming.factory.initial=org.jboss.naming.remote.client.InitialContextFactoryjava.naming.factory.url.pkgs=java.naming.provider.url=remote://127.0.0.1:4447java.naming.security.principal=knownjava.naming.security.credentials=passwordjboss.naming.client.ejb.context=true

• External JNDI NameejbsessionBankEAR/ejbsessionBankEJB/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote


• Generic naming mechanism• Works identical with non-EJB resources• Ignorant of EJB details• Less Efficient• Being deprecated by JBoss in favor of

EJB Client

EnterpriseJavaJUnit Integration Test (IT)

public class TellerRemotingIT { private static final Log log = ... protected Teller teller; @Before public void setUp() throws Exception { InitialContext jndi = new InitialContext(); teller = (TellerRemote)jndi.lookup(jndiName); }

@Test public void testCreateAccount() throws Exception { log.info("*** testCreateAccount ***"); Account account=null; //try with what should be a unique number try { account = teller.createAccount("1234"); log.debug("account created:" + account); } catch (Exception ex) { log.fatal("error creating account:" + ex, ex); fail("error creating account:" + ex); }


JNDI Properties being supplied through jndi.properties file -or-through a Propertiesobject

EnterpriseJavaEJBClient

• jndi.propertiesjava.naming.factory.initial=java.naming.factory.url.pkgs=org.jboss.ejb.client.namingjava.naming.provider.url=java.naming.security.principal=java.naming.security.credentials=

• jboss-ejb-client.properties#top level property listing the names of the connections. There will be a set #of properties for each name listed hereremote.connections=default

#here we define the properties for the server we have called "default"remote.connection.default.host=127.0.0.1remote.connection.default.port=4447remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED=false

• External JNDI Nameejb:(ear)/(module)/(distinctName)/(ejbClass)!(remoteInterface)[?stateful]

ejb:ejbsessionBankEAR/ejbsessionBankEJB/””/TellerEJB!ejava.examples.ejbsessionbank.ejb.TellerRemote


• EJB-specific naming mechanism• Does not work with non-EJB resources• Aware of EJB details• More efficient than Remoting• Non-standard

EnterpriseJava


Lazy Load Issues• EJB

public List<Owner> getOwners(int index, int count) {

return teller.getOwners(index, count);

• RMI Test List<Owner> owners = teller.getOwners(0, 100); assertEquals("unexpected number of owners", 2, owners.size()); for(Owner o : owners) { for (Account a: o.getAccounts()) { //LINE 87 ... } }

• Errororg.hibernate.LazyInitializationException: failed to lazily initialize a

collection of role: ejava.examples.ejbsessionbank.bo.Owner.accounts, no session or session was closed

... org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:86)

at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:249)

at ejava.examples.ejbsessionbank.ejbclient.TellerOwnerRemoteTest.testLazy(TellerOwnerRemoteTest.java:87)

EnterpriseJava


Lazy Load Correction• EJB Remote

@Remotepublic interface TellerRemote extends Teller { List<Owner> getOwnersLoaded(int index, int count) throws BankException;}

• EJB public List<Owner> getOwnersLoaded(int index, int count) throws BankException { List<Owner> owners = getOwners(index, count); for(Owner owner : owners) { for (Account account : owner.getAccounts()) { account.getBalance(); //call a method to get loaded } } return owners; }

• RMI Test List<Owner> owners = teller.getOwnersLoaded(0, 100);

SELECT o FROM Owner o LEFT JOIN FETCH o.accounts

Alt: DAO JPAQL Querypublic class Owner { @OneToMany(fetch=EAGER) private List<Account> accounts;

Alt: relation fetch mode

EnterpriseJava


Non-POJO Class Issues• EJB

public List<Owner> getOwnersLoaded(int index, int count) throws BankException { List<Owner> owners = getOwners(index, count); for(Owner owner : owners) { for (Account account : owner.getAccounts()) { account.getBalance(); //call a method to get loaded } } return owners; }

• RMI Test List<Owner> owners = teller.getOwnersLoaded(0, 100); for(Owner o : owners) { for (Account a: o.getAccounts()) { log.info("account=" + a); } log.debug("addresses=" + o.getAccounts().getClass().getName()); assertTrue("unexpected collection class", o.getAccounts().getClass().getName().contains("hibernate")); }

• Output -account=id=2, acctnum=111, bal=$0.0

-addresses=org.hibernate.collection.PersistentBag

EnterpriseJava


Non-POJO Class Correction• EJB

public List<Owner> getOwnersPOJO(int index, int count) ... List<Owner> ownersPOJO = new ArrayList<Owner>(); for(Owner owner : getOwners(index, count)) { Owner ownerPOJO = new Owner(owner.getId()); ownerPOJO.setFirstName(owner.getFirstName()); ownerPOJO.setLastName(owner.getLastName()); ownerPOJO.setSsn(owner.getSsn()); for (Account account : owner.getAccounts()) { Account accountPOJO = new Account(account.getId()); accountPOJO.setAccountNumber(account.getAccountNumber()); accountPOJO.deposit(account.getBalance()); ownerPOJO.getAccounts().add(accountPOJO); } ownersPOJO.add(ownerPOJO); } return ownersPOJO; }

• RMI Test owners = teller.getOwnersPOJO(0, 100);... log.debug("addresses=" + o.getAccounts().getClass().getName()); assertFalse("unexpected collection class", o.getAccounts().getClass().getName().contains("hibernate"));• Output -account=id=2, acctnum=111, bal=$0.0 -addresses=java.util.ArrayList

EnterpriseJava


BO Complexity Class Issues

• Business Objectpublic class Owner implements Serializable {

private long id;

private String firstName;

private String lastName;

private String ssn;

private Collection<Account> accounts = new ArrayList<Account>();

...

EnterpriseJava


BO Complexity Correction• DTO Class

public class OwnerDTO implements Serializable { private static final long serialVersionUID = 1L; private long id; private String firstName; private String lastName; private int accounts;...

• EJB public List<OwnerDTO> getOwnersDTO(int index, int count) throws BankException { List<OwnerDTO> ownersDTO = new ArrayList<OwnerDTO>(); for(Owner owner : getOwners(index, count)) { OwnerDTO ownerDTO = new OwnerDTO(owner.getId()); ownerDTO.setFirstName(owner.getFirstName()); ownerDTO.setLastName(owner.getLastName()); ownerDTO.setAccounts(owner.getAccounts().size()); ownersDTO.add(ownerDTO); } return ownersDTO; }

• RMI Test List<OwnerDTO> owners = teller.getOwnersDTO(0, 100);

EnterpriseJava


Building EJBswith Maven

EnterpriseJava


Parent Project|-- ejbsessionBankBLImpl|-- ejbsessionBankEAR|-- ejbsessionBankEJB|-- ejbsessionBankTest`-- pom.xml

EnterpriseJava


Parent Project<?xml version="1.0" encoding="UTF-8"?><project> <parent> <groupId>ejava</groupId> <artifactId>ejava-root</artifactId> <version>3.0.2012.2-SNAPSHOT</version> <relativePath/> </parent> <modelVersion>4.0.0</modelVersion>

<groupId>ejava.javaee.ejb</groupId> <artifactId>ejbsessionBank</artifactId> <packaging>pom</packaging>

<name>EJB Session Bean Bank</name> <description> This project is the root project for the core session bean example. </description> <modules> <module>ejbsessionBankImpl</module> <module>ejbsessionBankEJB</module> <module>ejbsessionBankWAR</module> <module>ejbsessionBankEAR</module> <module>ejbsessionBankTest</module> </modules></project>

EnterpriseJava


EJB Project

ejbsessionBankEJB/src/`-- main |-- java | `-- ejava | `-- examples | `-- ejbsessionbank | |-- dto | | `-- OwnerDTO.java | `-- ejb | |-- StatsEJB.java | |-- Stats.java | |-- StatsLocal.java | |-- StatsRemote.java | |-- TellerEJB.java | |-- TellerLocal.java | `-- TellerRemote.java `-- resources `-- META-INF |-- ejb-jar.xml |-- persistence.xml `-- (jboss-ejb3.xml)

EnterpriseJava


EJB Project pom.xml: ejb Packaging<project> <parent> <artifactId>ejbsessionBank</artifactId> <groupId>ejava.javaee.ejb</groupId> <version>3.0.2012.2-SNAPSHOT</version> <relativePath>..</relativePath> </parent> <modelVersion>4.0.0</modelVersion>

<artifactId>ejbsessionBankEJB</artifactId> <packaging>ejb</packaging> <name>Session Bank EJB</name> <description> This project provides an example of the core properties of a session bean. </description>

<dependencies> </dependencies>

<build> </build>

<profiles> </profiles></project>

EnterpriseJava


EJB Project: dependencies<dependencies>  <dependency> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> <scope>provided</scope> </dependency> <dependency> <groupId>javax</groupId> <artifactId>javaee-api</artifactId> <scope>provided</scope> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankImpl</artifactId> <version>${project.version}</version> <scope>provided</scope> </dependency></dependencies>

EnterpriseJava


EJB Project: plugins <build>  <resources> <resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> </resources>

<plugins>  <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-ejb-plugin</artifactId> <configuration> <generateClient>true</generateClient> <clientExcludes> <clientExclude>**/ejb/*Local.class</clientExclude> <clientExclude>**/ejb/*EJB.class</clientExclude> </clientExcludes> </configuration> </plugin> </plugins> </build>

EnterpriseJava


EJB Project: profiles <profiles> <profile>  <id>h2db</id> <properties> <jdbc.driver>org.h2.Driver</jdbc.driver> <jdbc.url>jdbc:h2:${basedir}/target/h2db/ejava</jdbc.url> <jdbc.user>sa</jdbc.user> <jdbc.password/>

<hibernate.dialect> org.hibernate.dialect.H2Dialect </hibernate.dialect>

</properties>... </profile> </profiles>

EnterpriseJava


EJB Project: persistence.xml<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">

<persistence-unit name="ejbsessionbank"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source> <properties>

<property name="hibernate.dialect" value="${hibernate.dialect}"/>

<property name="hibernate.show_sql" value="false"/> </properties> </persistence-unit>

•After filtering <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>

EnterpriseJava


EAR ProjectejbsessionBankEAR/`-- pom.xml

• pom.xml<project> <parent> <artifactId>ejbsessionBank</artifactId> <groupId>ejava.javaee.ejb</groupId> <version>3.0.2012.2-SNAPSHOT</version> <relativePath>..</relativePath> </parent> <modelVersion>4.0.0</modelVersion>

<artifactId>ejbsessionBankEAR</artifactId> <packaging>ear</packaging>

<name>Session Bank EAR</name>

<dependencies> </dependencies>

<build> </build>

</project>

EnterpriseJava

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EAR Project (cont.): dependencies <dependencies> <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankEJB</artifactId> <version>${project.version}</version> <type>ejb</type> <exclusions> <exclusion> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankWAR</artifactId> <version>${project.version}</version> <type>war</type> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankImpl</artifactId> <version>${project.version}</version> <exclusions> <exclusion> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> </exclusion> </exclusions> </dependency> </dependencies>

v131013 EJB: Session Beans

EnterpriseJava


EAR Project (cont.): plugins <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-ear-plugin</artifactId> <configuration> <description> Example Session Bean Bank Application </description> <defaultLibBundleDir>lib</defaultLibBundleDir>  <applicationName>${project.artifactId}</applicationName> <modules> <webModule> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankWAR</artifactId> <contextRoot>ejbsessionBank</contextRoot> </webModule>  <ejbModule> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankEJB</artifactId> <bundleFileName>ejbsessionBankEJB.jar</bundleFileName> </ejbModule> </modules> </configuration> </plugin> </plugins> </build>

EnterpriseJava


EAR Project (cont.)• Use cargo plugin to undeploy built and deployed EARs <profile> <id>undeploy</id> <build> <plugins> <plugin> <groupId>org.codehaus.cargo</groupId> <artifactId>cargo-maven2-plugin</artifactId> <executions> <execution> <id>undeploy-ear</id> <phase>pre-clean</phase> <goals> <goal>undeploy</goal> </goals> </execution> </executions> </plugin> </plugins> </build> </profile>

EnterpriseJava


EAR Project (cont.)

ejbsessionBankEAR/target/ejbsessionBankEAR-3.0.2012.2-SNAPSHOT|-- ejbsessionBankEJB.jar|-- ejbsessionBankWAR-3.0.2012.2-SNAPSHOT.war|-- lib| |-- ejava-util-3.0.2012.2-SNAPSHOT.jar| `-- ejbsessionBankImpl-3.0.2012.2-SNAPSHOT.jar`-- META-INF `-- application.xml

EnterpriseJava


RMI Test ProjectejbsessionBankTest/|-- pom.xml`-- src |-- main `-- test |-- java | `-- ejava | `-- examples | `-- ejbsessionbank | `-- ejbclient | |-- TellerOwnerRemoteTest.java | `-- TellerRemoteTest.java `-- resources |-- jndi.properties `-- log4j.xml

• pom.xml<project> <parent> <artifactId>ejbsessionBank</artifactId> <groupId>ejava.javaee.ejb</groupId> <version>3.0.2012.2-SNAPSHOT</version> <relativePath>..</relativePath> </parent> <modelVersion>4.0.0</modelVersion>

<artifactId>ejbsessionBankTest</artifactId> <packaging>jar</packaging> <name>Session Bank Test</name>

EnterpriseJava


RMI Test Project (cont.) <dependencies>...  <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankEJB</artifactId> <version>${project.version}</version> <type>ejb-client</type> <scope>test</scope> </dependency>

 <dependency> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankEAR</artifactId> <version>${project.version}</version> <type>ear</type> <scope>compile</scope> </dependency>

<dependency> <groupId>ejava.common</groupId> <artifactId>jboss-rmi-client</artifactId> <version>${project.version}</version> <type>pom</type> <scope>test</scope> </dependency>...

EnterpriseJava


RMI Test Project (cont.): plugins <build> <plugins>  <plugin> <groupId>org.codehaus.cargo</groupId> <artifactId>cargo-maven2-plugin</artifactId> <configuration> <deployables> <deployable> <groupId>${project.groupId}</groupId> <artifactId>ejbsessionBankEAR</artifactId> <type>ear</type> </deployable> </deployables> </configuration> </plugin>

<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-failsafe-plugin</artifactId> <configuration> <systemPropertyVariables> <foo>${foovar}</foo> </systemPropertyVariables> </configuration> </plugin> </plugins> </build>

EnterpriseJava


Summary• Integrates Bean activity (“task script”)• Server-side code for client

– Stateless and Stateful• Server-side cache for client

– Stateful• POJO with minor amount of class metadata

EnterpriseJava


References

• “Enterprise JavaBeans 3.0, 5th Edition”; Burke & Monsen-Haefel; ISBN 0-596-00978-X; O'Reilly

• “Mobile Design Patterns and Architectures”, http://www.titu.jyu.fi/modpa/ (MODPA)

– Remote Facade• http://www.titu.jyu.fi/modpa/Patterns/pattern-RemoteFaca

de.html• “Patterns of Enterprise Archecture, Chapter 15: Remote

Facade”; Martin Fowler– http://www.theserverside.com/tt/articles/content/

FowlerPatterns/Fowler_ch15.pdf

EJB: Session Beans

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