Container and Bean Managed Persistence

1
Entity Beans

• Container and Bean Managed Persistence

2
Topics

• Understanding Entity Beans
• Implementing Entity Beans
• Container Managed Persistence
• Bean Managed Persistence

3
Understanding Entity Beans
4
Enterprise Bean

• Component that can be deployed in any
  EJB-compliant application server
• Component interface for its operations (Remote
  and Local)
• Home Interface for create, find, and remove
  (Remote and Local)
• Bean Implementation
• implements business methods
• implements finder (BMP Entity), home (2.0
  Entity), and Select (2.0 CMP Entity) methods

5
Bean Types

• Entity Beans
• Represents persistent data in a database
• Account and deposit()
• Exists indefinitely
• Bean-managed and Container-managed persistence
• Session Beans
• Represents business logic operations
• Teller and transfer()
• Stateless and Stateful
• Exist for lifetime of client session

6
Bean Types

• Message Beans
• Stateless component invoked using asynchronous
  message (JMS)

7
Container and Beans
create find
JVM
Container
Remote Home
Remote Home Stub
Remote Client
Remote Object
Remote Object Stub
EJB Class
EJB Class
EJB Class
Local Home
Bean Pool
deposit transfer
Local Client
Local Object
8
Entity Bean (from Spec)

• Provides an object view of data in the database
• Allows shared access from multiple users
• Can be long-lived (lives as long as the data in
  the database)
• The entity, its primary key, and its remote
  reference survive the crash of the EJB container

9
Entity Bean Support

• Optional in EJB 1.0
• Required in EJB 1.1
• Revised in EJB 2.0
• Added Abstract Schemas
• Added EJB Query Language which is portable across
  different database technologies (even though it
  is similar to SQL)
• Added Container Managed Relationships
• EJB 1.1 support still a requirement in EJB 2.0
• EJB 2.1
• J2EE 1.4, timers, ELB-QL updates
• EJB 3.0 radical changes (early draft review)
• Annotations for persistence mappings
• No home or component interface
• Hibernate-inspired
• Not an abstract class

10
Entity Bean Lifecycle
11
Entity Bean States

• Does Not Exist
• no instance instantiated
• default state at container startup
• Pooled
• state entered when container offers component
• state re-entered when object disassociated from
  bean
• Ready
• state where business methods can be invoked

12
Entity Bean Transitions

• Does Not Exist -gt Pooled
• methods invoked
• Class.newInstance() (default constructor)
• usually not provided/no behavior
• place all bean initialization code in
  setEntityContext and object initialization in
  ejbCreate/ejbPostCreate
• setEntityContext(EntityContext ctx)
• establish EJBs reference to container (ctx)

13
Entity Bean Transitions

• Pooled -gt Ready (via creation)
• occurs when client invokes a Home.create(ltargsgt)
• object created, bean instance located
• methods invoked
• ejbCreate(ltargsgt)
• may establish properties
• must establish primary key
• object not yet ready to be advertised
• ejbPostCreate(ltargsgt)
• establish relationships (object ready to be
  advertised)

14
Entity Bean Transitions

• Pooled -gt Ready (via query)
• occurs when Home.find (ltargs) or
  this.ejbSelect(ltargsgt) invoked to return objects
• bean selected from pool, associated with object
• methods invoked
• ejbActivate()
• called after object associated with bean instance
• no transaction or security context
• no interaction with database

15
Entity Bean Transitions

• Ready -gt Pooled (passivation)
• occurs after ejbStore() and just prior to
  disassociating object from bean
• bean returned to pool
• methods invoked
• ejbPassivate()
• simply a notification
• no state serialized as in Stateful Session Beans
• no interaction with database

16
Entity Bean Transitions

• Ready -gt Pooled (removal)
• occurs when client invokes object.remove()
• bean returned to pool
• methods invoked
• ejbRemove()
• must release any object-specific resources
  (identical to ejbPassivate())
• may call ejbPassivate() within ejbRemove()
• called prior to database removal in CMP
• called to remove from database in BMP

17
Entity Bean Transitions

• Ready State
• occurs when client invokes object.ltbusiness
  methodgt()
• bean activated from pool
• methods invoked
• ejbLoad()
• synchronize cache with database (read from
  database)
• called after db load in CMP command to load in
  BMP
• business method
• ejbStore()
• synchronize cache with database (write to
  database)
• called prior to db store in CMP command to store
  in BMP

18
Implementing CMP Entity Beans
19
Creating a Book CMP Entity Bean

• (Create the Primary Key Class)
• if required
• Create Value Objects
• Create the Local/Remote Object Interface
• Entity Beans should only be accessed by Session
  Facades through their local interfaces
• Create the Local/Remote Home Interface
• Create the Bean Class
• Create the Deployment Descriptors

20
Entity Bean Class
container.BookEJB_Impl ltabstract method
implsgt ltconcrete method interposegt
21
EJBContext
22
PrimaryKey Class

• Uniquely Identifies Object within database
• Two Objects are considered the same if they have
  the same Home and their PrimaryKey objects are
  equal
• Single primary keys can be mapped to java.lang
  classes (e.g. java.lang.String)
• Single primary keys may optionally be implemented
  with a custom Primary Key Class
• Compound primary keys must be implemented with a
  custom Primary Key Class

23
PrimaryKey Classes

• key values
• must be legal RMI-IIOP types
• must match in type and name with declaration in
  the bean class
• must be public
• class must implement a Default Constructor,
  hashCode() and equals() methods
• must be Serializable

24
Create the PrimaryKey Class

• package corej2ee.examples.entitybooks
• import java.io.Serializable
• public class BookPK implements Serializable
• public String id
• public BookPK()
  //this one is required
• public BookPK(String id) this.id id
  //this one is optional
• public String toString() return id
• public int hashCode() return
  id.hashCode()
• public boolean equals(Object rhs)
• try return ((BookPK)rhs).id.equals(id)
• catch (Throwable ex) return false

25
Value Objects

• Used to transfer data between the EJB Tier and
  client-tiers
• Pass-by-Value semantics
• Also called Data Transfer Objects (DTOs)
• Very similar to structs
• Used by bulk accessors
• bulk accessor interfaces usually declared in
  Session Façade Remote

26
Create Book Value Objects

• package corej2ee.examples.entitybooks
• import java.io.Serializable
• public class Book implements Serializable
• private String id_ private String title_
  
• private String author_ private String
  topic_
• public Book()
• public Book(String id, String title, String
  author, String topic)
• id_ id title_ title author_
  author topic_ topic
• public String getId() return id_
  
• public String getTitle() return
  title_
• ...
• public void setTitle(String title) title_
  title
• ...

27
Object Interface

• Defines the business methods to be implemented by
  the Bean that can be invoked by a client
• Arguments and return types must be legal RMI-IIOP
  types
• Local Interface
• fine-grain access from Session Façade
• Remote Interface
• larger-grain bulk accessors

28
Local Object Interface

• Must extend javax.ejb.EJBLocalObject
• Methods may not throw javax.ejb.RemoteException
• package corej2ee.examples.entitybooks.ejb
• public interface BookLocal extends
  javax.ejb.EJBLocalObject
• String getId()
• String getTitle()
• String getAuthor()
• String getTopic()
• void setTitle(String title)
• void setAuthor(String author)
• void setTopic(String topic)

29
Remote Object Interface

• Must extend javax.ejb.EJBObject
• Methods throw java.rmi.RemoteException
• package corej2ee.examples.entitybooks.ejb
• import javax.ejb.EJBObject
• import java.rmi.RemoteException
• public interface BookRemote extends EJBObject
• Book getValues() throws RemoteException
• void setValues(Book values) throws
  RemoteException

30
Home Interface

• createltSuffixgt() and createltSuffixgt( args )
• creates row in database
• optional with entity beans
• must have matching ejbCreateltSuffixgt() and
  ejbPostCreateltSuffixgt() methods in bean
  implementation if present
• find()
• findByPrimaryKey(ltprimary key classgt) is
  mandatory
• other finders can be implemented
• ex. findByName(String firstName, String
  lastName)
• ex. findByAddress(String address)
• return types include java.util.Collection and
  java.util.Set
• lthome methodsgt() - work on table as a whole

31
Create Local Home Interface

• package corej2ee.examples.entitybooks.ejb
• import javax.ejb.EJBLocalHome
• import javax.ejb.CreateException
• import javax.ejb.FinderException
• import java.util.Collection
• public interface BookLocalHome extends
  EJBLocalHome
• BookLocal create(String id) throws
  CreateException
• BookLocal create(String id, String title,
  String author, String topic)
• throws CreateException
• BookLocal findByPrimaryKey(String pk) throws
  FinderException
• Collection findAll() throws FinderException

32
Local Creation Example

• InitialContext jndi new InitialContext()
• BookLocalHome bHome (BookLocalHome)jndi.lookup("
  javacomp/env/ejb/BookLocalHome")
• BookLocal bookLocal bHome.create(
• book.getId(), book.getTitle(),
  book.getAuthor(), book.getTopic())

33
Create Remote Home Interface

• package corej2ee.examples.entitybooks.ejb
• import javax.ejb.EJBHome
• import javax.ejb.CreateException
• import javax.ejb.FinderException
• import java.rmi.RemoteException
• import java.util.Collection
• public interface BookRemoteHome extends EJBHome
• BookRemote create(String id) throws
  CreateException, RemoteException
• BookRemote create(Book values)
• throws CreateException, RemoteException
• BookRemote findByPrimaryKey(String pk) throws
  FinderException
• Collection findAll() throws FinderException,
  RemoteException

34
Remote Creation Example

• InitialContext jndi new InitialContext()
• BookRemoteHome bHome (BookRemoteHome)
• PortableObjectRemote.narrow(jndi.lookup("java
  comp/env/ejb/BookRemoteHome"),
• BookRemoteHome.class)
• BookRemote bookRemote bHome.create(book)

35
Create the Bean Class

• package corej2ee.examples.entitybooks.ejb
• import javax.ejb.EntityBean
• import javax.ejb.EntityContext
• public abstract class BookEJB implements
  EntityBean
• / This is our reference into the container.
  /
• private EntityContext ctx_

36
Define the Abstract Accessors

• public abstract void setId(String id)
• public abstract String getId()
• public abstract void setAuthor(String author)
• public abstract String getAuthor()
• public abstract void setTitle(String title)
• public abstract String getTitle()
• public abstract void setTopic(String topic)
• public abstract String getTopic()

37
Implement the Bean Class Business Methods

• public Book getValues()
• return new Book(getId(), getTitle(),
  getAuthor(), getTopic())
• public void setValues(Book values)
• setTitle(values.getTitle())
• setAuthor(values.getAuthor())
• setTopic(values.getTopic())

38
Coordinate Access to Container

• / This method is invoked after the bean
  class is instantiated and just
• prior to being available in the pool. The
  bean should acquire any
• object-neutral resources at this point.
  Note that the bean is not
• associated with an object at this point and
  any calls to the
• context's getPrimaryKey() will result in an
  exception. /
• public void setEntityContext(EntityContext
  ctx) ctx_ ctx
• / This method is invoked just after removing
  the bean from the pool and
• finalizing it. The bean should release any
  object-neural resources at
• this point. Note that the bean is not
  associated with an object at
• this point and any attempt to access the
  primary key or abstract data
• model will result in an error. /
• public void unsetEntityContext() ctx_
  null

39
Implement Bean ClassCreate Methods

• /
• This method must set the primary key for the
  object and optionally
• set any of the fields that will get mapped
  into the database. /
• public String ejbCreate(String id) throws
  CreateException
• setId(id)
• return null //container gets primary key
  another way
• /
• This method is where we establish any
  relationships to our object. /
• public void ejbPostCreate(String id)

40
Implement Bean ClassCreate Methods (cont.)

• public String ejbCreate(String id, String title,
  String author, String topic)
• throws CreateException
• setId(id)
• setTitle(title)
• setAuthor(author)
• setTopic(topic)
• return null //container gets primary key
  another way
• public void ejbPostCreate(
• String id, String title, String author, String
  topic)

41
Implement Bean ClassRemove Method

• /
• This method is called just before the row(s)
  representing the
• abstract data model get removed from the
  database.
• /
• public void ejbRemove()
• log("BookEJB.ejbRemove" getId() ""
  getTitle())

42
Implement Bean ClassResource Management Methods

• / This method is invoked just after the bean is
  associated with an
• object. We have a primary key, but out
  abstract data model has not
• yet been synchronized with the database. We
  can allocate any
• object-specific resources (that do not depend
  on the database values)
• at this point. /
• public void ejbActivate()
• / This method is invoked just prior to
  disassociating the object from
• the bean. The state of the abstract data model
  has already been
• synchronized with the database. We should
  release any object-specific
• resources as this point. /
• public void ejbPassivate()

43
Implement Bean ClassDatabase Synchronization
Methods

• /
• This method is called just after the abstract
  data model has been
• restored from the database. This method should
  prepare any transient
• variables for use by the business methods as
  this time. /
• public void ejbLoad()
• /
• This method is called just before the abstract
  data model gets stored
• to the database. This method should prepare
  the abstract data model
• variables for their stored state. /
• public void ejbStore()

44
Create Deployment Descriptor(ejb-jar.xml)

• lt!DOCTYPE ejb-jar PUBLIC '-//Sun Microsystems,
  Inc.//DTD Enterprise JavaBeans 2.0//EN'
  'http//java.sun.com/dtd/ejb-jar_2_0.dtd'gt
• ltejb-jargt
• ltenterprise-beansgt
• ltentitygt
• ltejb-namegtBookCMPlt/ejb-namegt
• ...
• lt/entitygt
• lt/enterprise-beansgt
• ltassembly-descriptorgt
• ltcontainer-transactiongt
• ...
• lt/container-transactiongt
• lt/ejb-jargt

45
Define the Individual Beans

• ltentitygt
• ltejb-namegtBookCMPlt/ejb-namegt
• lthomegtcorej2ee.examples.entitybooks.ejb.Book
  RemoteHomelt/homegt
• ltremotegtcorej2ee.examples.entitybooks.ejb.Bo
  okRemotelt/remotegt
• ltlocal-homegt corej2ee.examples.entitybooks.e
  jb.BookLocalHomelt/local-homegt
• ltlocalgt corej2ee.examples.entitybooks.ejb.
  BookLocallt/localgt
• ltejb-classgtcorej2ee.examples.entitybooks.ejb
  .BookEJBlt/ejb-classgt

46
Define the Primary Key Class

• ltpersistence-typegtContainerlt/persistence-typ
  egt
• ltprim-key-classgtjava.lang.Stringlt/prim-key-c
  lassgt
• ltreentrantgtFalselt/reentrantgt

47
Define the Container ManagedFields (CMP)

• ltabstract-schema-namegtBooklt/abstract-schema-namegt
• ltcmp-fieldgt
• ltfield-namegtauthorlt/field-namegt
• lt/cmp-fieldgt
• ltcmp-fieldgt
• ltfield-namegtidlt/field-namegt
• lt/cmp-fieldgt
• ltcmp-fieldgt
• ltfield-namegttitlelt/field-namegt
• lt/cmp-fieldgt
• ltcmp-fieldgt
• ltfield-namegttopiclt/field-namegt
• lt/cmp-fieldgt
• ltprimkey-fieldgtidlt/primkey-fieldgt

48
Define Environment Properties

• lt!-- env-entry - lists properties that will be
  placed in the
• bean's environment at run-time.
• --gt
• ltenv-entrygt
• ltdescriptiongtThis is a sample env
  entry.lt/descriptiongt
• ltenv-entry-namegtexamplelt/env-entry-namegt
• ltenv-entry-typegtjava.lang.Stringlt/env-entry-t
  ypegt
• ltenv-entry-valuegtSample Environment
  Valuelt/env-entry-valuegt
• lt/env-entrygt

49
Define EJB References

• ltejb-refgt
• ltejb-ref-namegtlt/ejb-ref-namegt
• ltejb-ref-typegtSession or
  Entitylt/ejb-ref-typegt
• lthomegtlt/homegt
• ltremotegtlt/remotegt
• ltejb-linkgtlt/ejb-linkgt
• lt/ejb-refgt
• ltejb-local-refgt
• ltejb-ref-namegtlt/ejb-ref-namegt
• ltejb-ref-typegtSession or
  Entitylt/ejb-ref-typegt
• ltlocal-homegtlt/local-homegt
• ltlocalgtlt/localgt
• ltejb-linkgtlt/ejb-linkgt
• lt/ejb-local-refgt

50
Define Queries CMP Queries

• ltquerygt
• ltquery-methodgt
• ltmethod-namegtfindAlllt/method-namegt
• lt! declared in BookLocal/RemoteHome?
• ltmethod-paramsgt
• lt/method-paramsgt
• lt/query-methodgt
• ltejb-qlgtSELECT OBJECT(b) FROM Book blt/ejb-qlgt
• lt/querygt

51
Define Client Jar File

• lt!-- ejb-client-jar
• Specifies the jar file that contains
  classes for use by remote
• clients of the component.
• --gt
• ltejb-client-jargtentityBooksEJBClient.jar
  lt/ejb-client-jargt
• lt/ejb-jargt

52
Things We Skipped (coming)

• Defining Security Roles
• Defining Security Access
• Defining Transaction Scope

53
Defining Database-Specific Mapping(weblogic-cmp-r
dbms-jar.xml)

• lt!DOCTYPE weblogic-rdbms-jar PUBLIC '-//BEA
  Systems, Inc.//DTD WebLogic 7.0.0 EJB RDBMS
  Persistence//EN'http//www.bea.com/servers/wls70
  0/dtd/weblogic-rdbms20-persistence-700.dtd'gt
• ltweblogic-rdbms-jargt
• ltweblogic-rdbms-beangt
• ltejb-namegtBookCMPlt/ejb-namegt
• ltdata-source-namegtcorej2ee/jdbc/DSlt/data-sourc
  e-namegt
• lttable-mapgt
• lttable-namegtentityBooks_Booklt/table-namegt
• . . .
• ltfield-mapgt
• lt/field-mapgt
• lt/table-mapgt
• lt/weblogic-rdbms-beangt
• ltcreate-default-dbms-tablesgtTruelt/create-default
  -dbms-tablesgt
• lt/weblogic-rdbms-jargt

54
Map Columns to Fields(weblogic-cmp-rdbms-jar.xml)

• ltfield-mapgt
• ltcmp-fieldgtauthorlt/cmp-fieldgt
• ltdbms-columngtauthorlt/dbms-columngt
• lt/field-mapgt
• ltfield-mapgt
• ltcmp-fieldgtidlt/cmp-fieldgt
• ltdbms-columngtidlt/dbms-columngt
• lt/field-mapgt
• ltfield-mapgt
• ltcmp-fieldgttitlelt/cmp-fieldgt
• ltdbms-columngttitlelt/dbms-columngt
• lt/field-mapgt
• ltfield-mapgt
• ltcmp-fieldgttopiclt/cmp-fieldgt
• ltdbms-columngttopiclt/dbms-columngt
• lt/field-mapgt

55
Map Container-Specific Resources(weblogic-ejb-jar
.xml)

• lt!DOCTYPE weblogic-ejb-jar PUBLIC"-//BEA
  Systems, Inc.//DTD WebLogic 7.0.0
  EJB//EN"http//www.bea.com/servers/wls700/dtd/we
  blogic-ejb-jar.dtd" gt
• ltweblogic-ejb-jargt
• ltweblogic-enterprise-beangt
• ltejb-namegtBookCMPlt/ejb-namegt
• ltentity-descriptorgt
• ...
• lt/entity-descriptorgt
• ltlocal-jndi-namegtcorej2ee/examples/entitybooks
  /BookCMPLocalHome
• lt/local-jndi-namegt
• lt/weblogic-enterprise-beangt
• lt/weblogic-ejb-jargt

56
Map Container-Specific Resources(weblogic-ejb-jar
.xml)

• ltentity-descriptorgt
• ltpersistencegt
• ltpersistence-usegt
• lttype-identifiergtWebLogic_CMP_RDBMSlt/typ
  e-identifiergt
• lttype-versiongt6.0lt/type-versiongt
• lttype-storagegtMETA-INF/weblogic-cmp-rdbm
  s-jar.xmllt/type-storagegt
• lt/persistence-usegt
• lt/persistencegt
• lt/entity-descriptorgt

57
JBoss (jbosscmp-jdbc.xml)
ltjbosscmp-jdbcgt ltdefaultsgt
ltdatasourcegtjavacoredev/jdbc/DSlt/datasourcegt
ltdatasource-mappinggtHypersonic
SQLlt/datasource-mappinggt ltcreate-tablegttruelt
/create-tablegt ltremove-tablegttruelt/remove-ta
blegt lt/defaultsgt ltenterprise-beansgt
ltentitygt ltejb-namegtBookCMPlt/ejb-namegt
lttable-namegtentityBooks_Booklt/table-namegt
ltcmp-fieldgt ltfield-namegtidlt/fie
ld-namegt ltcolumn-namegtidlt/column-namegt
lt/cmp-fieldgt ltcmp-fieldgt
ltfield-namegttitlelt/field-namegt
ltcolumn-namegttitlelt/column-namegt
lt/cmp-fieldgt ltcmp-fieldgt
ltfield-namegttopiclt/field-namegt
ltcolumn-namegttopiclt/column-namegt
lt/cmp-fieldgt lt/entitygt
lt/enterprise-beansgt lt/jbosscmp-jdbcgt

58
Database Synchronization

• As with all EJBs, only a single thread can be
  running within a bean instance
• Multiple entity bean instances can be created to
  represent same data in database
• Consistency ?
• ejbLoad() and ejbStore() are called to
  synchronize bean with underlying storage

59
State Management

• State synchronization methods
• ejbLoad
• ejbStore
• Resource Management methods
• ejbActivate
• ejbPassivate

60
Entity Bean Types

• Bean can have total control over loading and
  storing from database
• Bean Managed Persistence (BMP)
• Container can take over this responsibility
• Container Managed Persistence (CMP)
• Specialized Implementations
• Toplink for relational databases
• CICS

61
CMP Summary

• Eliminates a lot of code
• less code means fewer bugs
• Provides support for relationships (covered
  later)
• Provides support for database-generic queries
  (EJB-QL covered later)
• Problems
• abstract model based on Java database
  implementations do not always map Java constructs
  the same

62
Bean Managed Persistence

• BMP

63
Bean Managed Persistence (BMP)

• The BookBMPBean uses BMP
• implemented all database interaction
• create, remove, and find
• Have to do object-relational mapping
• Synchronize bean state with database when
  requested by container

64
Activation and Passivation

• When Passivated, bean should give up any
  resources held on behalf of the data represented
  by the Primary Key
• When Activated, bean can acquire and resources
  specific to the Primary Key

65
BMP Summary

• Have to handle all database interaction
• except transactions
• ejbLoad() and ejbStore() called when bean
  instance state must be synchronized with database
• ejbActivate() and ejbPassivate() called when bean
  is moved between the ready state and pooled state

66
Implement a BMP Entity Bean

• package corej2ee.examples.entitybooks.ejb
• import javax.ejb.EntityBean
• import javax.ejb.EntityContext
• public class BookBMP extends BookEJB
• private DataSource dataSource_
• private EntityContext ctx_

67
Implement the Abstract Data Model

• private String id_
• private String title_
• private String author_
• private String topic_
• public void setId(String id)
  id_ id
• public String getId()
  return id_
• public void setAuthor(String author)
  author_ author
• public String getAuthor()
  return author_
• public void setTitle(String title)
  title_ title
• public String getTitle()
  return title_
• public void setTopic(String topic)
  topic_ topic
• public String getTopic()
  return topic_

68
Locate the Database

• public void setEntityContext(EntityContext ctx)
• super.setEntityContext(ctx)
• ctx_ ctx
• InitialContext jndi null
• try
• jndi new InitialContext()
• dataSource_ (DataSource)jndi.lookup("java
  comp/env/jdbc/mydb")
• catch (NamingException ex)
• throw new EJBException(ex)
• finally
• try if (jndi!null) jndi.close() catch
  (Exception e)

69
Implement DB Insertion

• public String ejbCreate(String id, String title,
  String author, String topic)
• super.ejbCreate(id, title, author, topic)
• Connection conn null
  PreparedStatement pstatement null
• try
• conn dataSource_.getConnection()
• pstatementconn.prepareStatement("insert
  into Book (id, title, author, topic)"
• values (?, ?, ?, ?)")
• pstatement.setString(1,id_)
  pstatement.setString(2,title_)
• pstatement.setString(3,author_)
  pstatement.setString(4,topic_)
• pstatement.execute()
  return id_
• catch(SQLException ex) throw new
  EJBException(ex)
• finally

70
Implement PostCreate

• public void ejbPostCreate(
• String id, String title, String author, String
  topic)
• super.ejbPostCreate(id, title, author, topic)

71
Implement DB Load

• public void ejbLoad()
• Connection conn null
• PreparedStatement pstatement null
• ResultSet rs null
• try
• conn dataSource_.getConnection()
• pstatement conn.prepareStatement(
• "select id, title, author, topic from
  Book " "where id ?")
• pstatement.setString(1, (String)ctx_.getPrim
  aryKey())
• rs pstatement.executeQuery()
• if (rs.next())
• ...

72
Implement DB Load (cont.)

• if (rs.next())
• id_ rs.getString("id") title_
  rs.getString("title")
• author_ rs.getString("author")
  topic_ rs.getString("topic")
• super.ejbLoad()
• else
• throw new EJBException("unable to locate
  row")
• catch(SQLException ex)
• throw new EJBException(getText(ex))
• finally

73
Implement DB Store

• public void ejbStore()
• Connection conn null PreparedStatement
  pstatement null
• try
• super.ejbStore()
• conn dataSource_.getConnection()
• pstatement conn.prepareStatement(
• "update Book set title?, author?,
  topic? " "where id ?")
• pstatement.setString(1,title_)
  pstatement.setString(2,author_)
• pstatement.setString(3,topic_)
  pstatement.setString(4,id_)
• pstatement.executeUpdate()
• catch(SQLException ex) throw new
  EJBException(getText(ex))
• finally

74
Implement DB Remove

• public void ejbRemove()
• Connection conn null
• PreparedStatement pstatement null
• try
• super.ejbRemove()
• conn dataSource_.getConnection()
• pstatement conn.prepareStatement("delete
  from Book " "where id ?")
• pstatement.setString(1, (String)ctx_.getPrim
  aryKey())
• pstatement.executeUpdate()
• catch(SQLException ex) throw new
  EJBException(getText(ex))
• finally

75
Implement Finders

• public String ejbFindByPrimaryKey(String pk)
  throws FinderException
• Connection conn null
  PreparedStatement pstatement null
• ResultSet rs null
• try
• conn dataSource_.getConnection()
• pstatement conn.prepareStatement("select
  id from Book " "where id ?")
• pstatement.setString(1, pk)
• rs pstatement.executeQuery()
• if (rs.next()) return rs.getString("id")
  
• else throw new ObjectNotFoundException(pk
  " no found")
• catch(SQLException ex) throw new
  EJBException(getText(ex))
• finally ...

76
Implement Finders (cont.)

• public Collection ejbFindAll() throws
  FinderException
• Connection conn null
• PreparedStatement pstatement null
• ResultSet rs null
• try
• Vector pKeys new Vector()
• conn dataSource_.getConnection()
• pstatement conn.prepareStatement("select
  id from Book ")
• rs pstatement.executeQuery()
• while (rs.next())
  pKeys.add(rs.getString("id"))
• return pKeys
• catch(SQLException ex) throw new
  EJBException(getText(ex))
• finally ...

77
Configure Deployment Descriptors(ejb-jar.xml)

• ltentitygt
• ltejb-namegtBookBMPlt/ejb-namegt
• ltlocal-homegtcorej2ee.examples.entitybooks.ejb
  .BookLocalHomelt/local-homegt
• ltlocalgtcorej2ee.examples.entitybooks.ejb.Book
  Locallt/localgt
• ltejb-classgtcorej2ee.examples.entitybooks.ejb.
  BookBMPlt/ejb-classgt
• ltpersistence-typegtBeanlt/persistence-typegt
• ltprim-key-classgtjava.lang.Stringlt/prim-key-cl
  assgt
• ltreentrantgtFalselt/reentrantgt
• ltresource-refgt
• ltres-ref-namegtjdbc/mydblt/res-ref-namegt
• ltres-typegtjavax.sql.DataSourcelt/res-typegt
• ltres-authgtContainerlt/res-authgt
• lt/resource-refgt
• lt/entitygt

78
Configure Deployment Descriptors(weblogic-ejb-jar
.xml)

• ltweblogic-enterprise-beangt
• ltejb-namegtBookBMPlt/ejb-namegt
• ltreference-descriptorgt
• ltresource-descriptiongt
• ltres-ref-namegtjdbc/mydblt/res-ref-namegt
• ltjndi-namegtcorej2ee/jdbc/DSlt/jndi-namegt
• lt/resource-descriptiongt
• lt/reference-descriptorgt
• ltlocal-jndi-namegtcorej2ee/examples/entitybooks
  /BookBMPLocalHome
• lt/local-jndi-namegt
• lt/weblogic-enterprise-beangt

79
jboss.xml
ltentitygt ltejb-namegtBookBMPlt/ejb-namegt
ltlocal-jndi-namegt corej2ee/examples/entity
books/BookBMPLocalHome lt/local-jndi-namegt
ltresource-refgt ltres-ref-namegtjdbc/mydblt/r
es-ref-namegt ltjndi-namegtjavacoredev/jdbc/
DSlt/jndi-namegt lt/resource-refgt lt/entitygt
80
Entity Bean Performance Issues
81
Performance Issues

• When could Entity Beans be expensive
• CMP performs eager database synchronization on
  each transaction (EJB 2.0 abstract schema much
  better)
• BMP allows for lazy database synchronization
• Who should call the Entity Beans Remote methods
  ?
• Should you utilize entity beans at all ?
• Performance hit - all calls go through the
  container via the EJBObject
• Higher performance going directly to the
  databases vs. functionality of container

82
Entity Bean Summary

• Models persistent state in database
• Facilitates declarative persistence
• BMP vs. CMP
• Performance implications
• wrap calls to entity beans with session beans