Using Spring and Hibernate

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Using Spring and Hibernate

• Dave Elliman

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The overall architecture
3
The enterprise view (Java)
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Revision - What is Dependency Injection?

• DI is all about wiring up objects or plumbing if
  you prefer
• It is about ensuring loose coupling and fits well
  with design patterns
• Design to an interface and then inject the actual
  class at run time
• This is what inheritence is really for

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A Real World Example?
Web App
Authenticator
Stock Quotes
Logger
Error Handler
Database
This example was originally created by Jim
Weirich in Ruby on his blog.
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Remember the old way

• public class WebApp
• public WebApp()
• quotes new StockQuotes()
• authenticator new Authenticator()
• database new Database()
• logger new Logger()
• errorHandler new ErrorHandler()
• // More code here...

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What about the child objects?

• How does the StockQuotes find the Logger?
• How does the Authenticator find the database?
• Suppose you want to use a TestingLogger instead?
  Or a MockDatabase?

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Service Locator Interface

• public interface ILocator
• TObject GetltTObjectgt()

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Service Locator Example

• public class MyLocator ILocator
• protected DictionaryltType, objectgt dict new
  DictionaryltType,objectgt()
• public MyLocator()
• dict.Add(typeof(ILogger), new Logger())
• dict.Add(typeof(IErrorHandler), new
  ErrorHandler(this))
• dict.Add(typeof(IQuotes), new StockQuotes(this))
  
• dict.Add(typeof(IDatabase), new Database(this))
• dict.Add(typeof(IAuthenticator), new
  Authenticator(this))
• dict.Add(typeof(WebApp), new WebApp(this))

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StockQuotes with Locator

• public class StockQuotes
• public StockQuotes(ILocator locator)
• errorHandler locator.GetltIErrorHandlergt()
• logger locator.GetltILoggergt()
• // More code here...

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Good things

• Classes are decoupled from explicit imlementation
  types
• Easy to externalise the configuration

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Dependency Injection Containers

• Gets rid of the dependency on the ILocator
• Object is no longer responsible for finding its
  dependencies
• The container does it for you

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Then what?

• Write your objects the way you want
• Setup the container
• Ask the container for objects
• The container creates objects for you and
  fulfills dependencies

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Setting Up the Container (XML)

• ltDIContainergt
• ltTypeMap fromILogger toLogger /gt
• ltTypeMap fromIDatabase toDatabase /gt
• ltTypeMap fromIErrorHandler toErrorHandler
  /gt
• ltTypeMap fromIQuotes toStockQuotes /gt
• ltTypeMap fromIAuthenticator toAuthenticator
  /gt
• lt/DIContainergt

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Creating Objects

• Test
• public void WebAppTest()
• DIContainer container GetContainer()
• IStockQuotes quotes container.GetltIStockQuotes
  gt()
• IAuthenticator auth container.GetltIAuthenticat
  orgt()
• Assert.IsNotNull( quotes.Logger )
• Assert.IsNotNull( auth.Logger )
• Assert.AreSame( quotes.Logger, auth.Logger )

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Existing Frameworks

• Java
• Pico Container
• Spring Framework
• HiveMind
• Ruby
• Rico
• Copland

• Python
• PyContainer
• .NET
• Pico.NET
• Spring.NET
• pp Object Builder

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Spring with Persistence Layers
Hibernate?
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Spring can act as the Application
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A persistent POJO for Hibernate

• package elc
• public class Tutor
• private String id /// unique identifier
• private String surname
• private String firstname
• private Tutor() /// default constructor
• public Tutor(String id, String surname,
  String firstname)
• this.id id this.surname surname
  this.firstname firstname)
• public String getId() return id
• public String getSurname() return surname
  
• public String getFirstname() return
  firstname
• public void setId(String id)
  this.id id
• public void setSurname(String surname)
  this.surname surname
• public void setLogin(String firstname)
  this.firstname firstname

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The Hibernate Session

• import org.hibernate.Session
• import org.hibernate.SessionFactory
• import org.hibernate.cfg.Configuration
• ... some code
• Session getSessionFactory().openSession()
• Transaction tx session.beginTransaction()
• Tutor davenew Tutor("dge","Elliman","Dave")
• session.save(dave)
• tx.commit()
• session.close()
• ... more code

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Tutor.hbm.xml

• lt?xml version'1.0' encoding'utf-8'?gt
• lt!DOCTYPE hibernate-mapping PUBLIC
• "-//Hibernate/Hibernate Mapping DTD//EN"
• "http//hibernate.sourceforge.net/hibernate-ma
  pping-3.0.dtd"gt
• lthibernate-mappinggt
• ltclass name"elc.Tutor" table"tutor"gt
• ltid name"id" type"String" column"ID" gt
• ltgenerator class"assigned"/gt
• lt/idgt
• ltproperty name"firstName"gt
• ltcolumn name"FIRSTNAME" /gt
• lt/propertygt
• ltproperty name"surname"gt
• ltcolumn name"SURNAME"/gt
• lt/propertygt
• lt/classgt
• lt/hibernate-mappinggt

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hibernate.cfg.xml
lt?xml version'1.0' encoding'utf-8'?gt lt!DOCTYPE
hibernate-configuration PUBLIC "-//Hibernate/Hiber
nate Configuration DTD//EN" "http//hibernate.sour
ceforge.net/hibernate-configuration-3.0.dtd"gt lthib
ernate-configurationgt ltsession-factorygt
ltproperty name"hibernate.connection.driver_class"
gt com.mysql.jdbc.Driverlt/propertygt
ltproperty name"hibernate.connection.url"gt
jdbcmysql//localhost/hibernatetutoriallt/property
gt ltproperty name"hibernate.connection.usern
ame"gtrootlt/propertygt ltproperty
name"hibernate.connection.password"gtlt/propertygt
ltproperty name"hibernate.connection.pool_siz
e"gt10lt/propertygt ltproperty
name"show_sql"gttruelt/propertygt ltproperty
name"dialect"gtorg.hibernate.dialect.MySQLDialectlt
/propertygt ltproperty name"hibernate.hbm2ddl
.auto"gtupdatelt/propertygt lt!-- Mapping files
--gt ltmapping resource"tutor.hbm.xml"/gt lt/se
ssion-factorygt lt/hibernate-configurationgt
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Using Hibernate with Spring

• One simply creates a Hibernate Session Factory
  bean in Spring
• ltbean idsessionFactory
• classorg.springframework.orm.hibernate3.LocalSe
  ssio nFactoryBeangt
• ltproperty nameconfigurationClass
• value org.bibernate.cfg.Annotation.Configuratio
  n /gt
• ltproperty nameconfigLocation
  valueclasspathhibernate.cfg.xml /gt
• lt/beangt

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An Intereface and a class to define

• public interface TutorDao
• public void createTutor(final Tutor tutor)
• public Tutor getTutor(final String id)
• Also saveTutor() deleteTutor() etc.
• CRUD is now done with single lines of code. No
  SQL needed

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Do you get the CONCEPTS?

• You can look up the detail when you need it
• ELC exam will test the concepts and not the
  detail of xml configuration files of Java code
• You need to know that a configuration file is
  needed and what it does, not the fine detail of
  its formatting

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Any Questions?
Im confused
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JEE and EJBs

• Dave Elliman

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POJOs and POJIs

• Plain Old Java Objects and Interfaces
• In the past EJBs were all rather different and
  special and you could not test them outside a
  container
• Now they are POJ you can

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Annotations

• There has been a revolution in Server-side Java
  and Tiger Jane 1.5 EJB annotations
• These are processed by a new tool called apt
• You can write your own if you like

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Writing EJBs was rather stereotyped

• An ideal situation for annotations.
• No longer need to write a Home interface
• No longer need an XML deployment descriptor
  (deploytool)

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The Concept

• Entity bean
• corresponds to a set of records in a database
• Session bean
• handles business flow (one per client unless
  stateless, when may be shared)

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Enterprise JavaBeans

• Definition from OReillys Enterprise JavaBeans
  book
• An Enterprise Java Bean is a standard server-side
  component model
• Aha! Its a standard for building MIDDLEWARE In
  multi-tiered solutions

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The Context in Which EJBs Are Used
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It All Works by RMI
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A Taxonomy of EJBs
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Differences Between Beans

• Entity Beans
• Represent persistent data
• Long-lived

• Session Beans
• Interact with clients
• Model business Logic
• Short-lived

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Session Bean (Stateful)

• Assigned to 1 client only
• Keeps info about a client
• ie has attributes for clients state
• Assigned to a client for lifetime
• Non-persistent
• Short-lived (client, timeout, server crash)

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Session Bean (Stateless)

• Many clients can access it
• Implements business logic
• One bean can service multiple clients (fast and
  efficient)
• Lifetime controlled by container
• No state across methods
• Each instance identical upon creation
• Short-lived

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Insight Into Session Beans
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Entity EJBs

• Bean managed persistence (BMP)
• developer writes JDBC code and SQL statements
• Container managed persistence (CMP)
• Container generates methods to read and write to
  the database dropped!
• Takes necessary information from the Deployment
  Descriptor

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EJB Architecture Diagram
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A Stateless Session Bean

• import javax.ejb./ A stateless session
  bean requesting that a remote busines
  interface be generated for it./_at_Stateless_at_Remo
  tepublic class HelloWorldBean    public String
  sayHello()       return "Hello World!!!"  
  

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A Stateful Session Bean

• import javax.ejb.
• _at_Stateful
• public class ShoppingCartBean implements
  ShoppingCart
• private String customer
• public void startToShop(String customer)
  this.customer customer
• public void addToCart(Item item)
• System.out.println("Added item to cart... ")
• _at_Remove
• public void finishShopping()
• System.out.println("Shopping Done... ")

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A Entity Java Bean

• import javax.ejb.
• _at_Entity
• public class Order
• private Long id
• private int version
• private int itemId
• private int quantity
• private Customer cust
• _at_Id(generateAUTO)
• public Long getId() return id
• public void setId(Long id) this.id id
• _at_Version
• protected int getVersion() return version
• protected void setVersion(int version)
  this.version version
• _at_Basic
• public int getItemId() return itemId

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SQL and Entity beans

• Queries can be defined through the _at_NamedQuery
  annotation
• _at_NamedQuery (name"findACustomers",queryString"
  SELECT c FROM Customer c WHERE c.name LIKE
  custName")

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End of detour into Java!
Any Questions?