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This
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application
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will
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take
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you
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through
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the
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basics
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of
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Stateful
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Session
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Bean.
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This
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application
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will
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demonstrate
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how
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annotations
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like
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@Stateful,
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@Resource,
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@PostConstruct,
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@PreDestroy,
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@PrePassivate,
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@PostActivate,
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@Remove
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are
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used
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in
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an
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EJB3
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application.
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Basically
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a
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Stateful
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Session
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EJB
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is
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used
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whenever
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there
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is
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a
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requirement
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to
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maintain
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a
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session.
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The
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example
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is
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a
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user
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registration
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process
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wherein
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the
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registration
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process
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is
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a
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two
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step
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process.
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First
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page
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prompts
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to
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enter
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your
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personal
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credentials
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and
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second
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page
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prompts
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to
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enter
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your
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billing
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and
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credit
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card
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information.
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The
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session
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is
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maintained
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till
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the
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user
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has
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filled
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up
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both
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the
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jsp
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pages.
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Later
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the
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complete
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information
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is
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populated
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on
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to
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a
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database.
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The
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application
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has
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a
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Controller
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servlet
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which
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routes
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the
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call
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received
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from
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the
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jsp
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client
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to
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the
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Bean
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class,
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setter
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methods
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and
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jsp
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pages.
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To
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run
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this
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tutorial,
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as
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a
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minimum
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you
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will
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be
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required
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to
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have
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installed
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the
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following
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prerequisite
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software.
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- Sun
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- JDK
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- 5.0+
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- (J2SE
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- 1.5)
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- Eclipse
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- 3.3.1.1
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- (Eclipse
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- Classic
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- package
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- of
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- Europa
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- distribution),
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- which
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- is
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- platform
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- specific
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- Web
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- Tools
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- Platform
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- (WTP)
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- 2.0.1
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- Data
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- Tools
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- Platform
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- (DTP)
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- 1.5.1
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- Eclipse
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- Modeling
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- Framework
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- (EMF)
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- 2.3.1
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- Graphical
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- Editing
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- Framework
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- (GEF)
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- 3.3.1
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Details
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on
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installing
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eclipse
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are
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provided
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in
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the
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...
...
section.
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This
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tutorial
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is
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organized
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in
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the
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following
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sections:
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Table of Contents |
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Creating a EJB Project
- Right click Under Project Explorer and Select New->EJB Project.
- Name the project as StatefulBean. Select Next.
- Mark the fields as suggested in the screenshot and Select Next.
- Uncheck Generate Deployment Descriptor. This is beacuse we are using annotations is our applications and so deployment descriptors are redundant entity. Select Next.
- On next screen select all default values and Select finish.
This creates a skeleton for the EJB project. Next steps are adding the bean class, bean interface and setter/getter methods. - Right click on ejbModule in StatefulBean project and select New->class.
- Name the class as PersonalInfo and package as ejb.stateful. Select Finish.
- Add the following code to PersonalInfo.java.
Code Block title PersonalInfo.java borderStyle solid package ejb.stateful; public class PersonalInfo implements java.io.Serializable { private static final long serialVersionUID = 1L; private String FirstName; private String LastName; private String UserName; private String Password; private String Nationality; public void setFirstName(String FirstName) { this.FirstName=FirstName; } public void setLastName(String LastName) { this.LastName=LastName; } public void setUserName(String UserName) { this.UserName=UserName; } public void setPassword(String Password) { this.Password=Password; } public void setNationality(String Nationality) { this.Nationality=Nationality; } public String getFirstName() { return FirstName; } public String getLastName() { return LastName; } public String getUserName() { return UserName; } public String getPassword() { return Password; } public String getNationality() { return Nationality; } }
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- Similarly create a class BillingInfo.java
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- and
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- add
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- the
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- following
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- code.
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Code Block title BillingInfo.java
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borderStyle
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solid
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package ejb.stateful; public class BillingInfo implements java.io.Serializable { private static final long serialVersionUID = 1L; private String houseNo; private String street; private String city; private String pincode; private String country; private String bank; private String cardno; public void setBank(String bank) { this.bank=bank; } public void setCardno(String cardno) { this.cardno=cardno; } public void setHouseNo(String houseNo) { this.houseNo=houseNo; } public void setStreet(String street) { this.street=street; } public void setCity(String city) { this.city=city; } public void setPincode(String pincode) { this.pincode=pincode; } public void setCountry(String country) { this.country=country; } public String getBank() { return bank; } public String getCardno() { return cardno; } public String getHouseNo() { return houseNo; } public String getStreet() { return street; } public String getCity() { return city; } public String getPincode() { return pincode; } public String getCountry() { return country; } }
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PersonalInfo.java
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- and
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- BillingInfo.java
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- are
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- classes
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- for
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- setting
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- and
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- getting
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- the
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- user
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- information.
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- Now
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- we
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- will
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- add
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- the
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- Business
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- interface
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- or
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- bean
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- interface.
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- Right
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- click
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- on
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- the
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- package
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- ejb.stateful
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- and
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- Select
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- New->Interface.
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- Name the interface as AccountCreator and Select Finish.
- Add the following code to AccountCreator interface.
Code Block title AccountCreator.java borderStyle solid package ejb.stateful; import javax.ejb.Remote; @Remote public interface AccountCreator { void addPersonalInfo(PersonalInfo personalinfo); void addBillingInfo(BillingInfo billinginfo); void createAccount(); }
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Info title Information Once you enter this code you might see errors like @EJB can be resolved. Currently there are some limitations with the geronimo eclipse plugin which will resolved soon. We will soon suggest you how to get rid of those errors.
- Next step is to add the implementation to the interface. Right click on ejb.stateful interface and select New->class.
- Name the bean class as AccountCreatorBean and Select Finish.
- Add the following code to AccountCreatorBean.
Code Block title AccountCreatorBean.java borderStyle solid package ejb.stateful; import java.sql.Connection; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.annotation.Resource; import javax.ejb.PostActivate; import javax.ejb.PrePassivate; import javax.ejb.Remove; import javax.ejb.Stateful; import javax.sql.DataSource; @Stateful public class AccountCreatorBean implements AccountCreator{ @Resource(name="jdbc/userds") DataSource datasource; Connection connection; PersonalInfo personalinfo=new PersonalInfo(); BillingInfo billinginfo=new BillingInfo(); public AccountCreatorBean() { super(); } @PostConstruct @PostActivate public void openConnection() { try{ connection=datasource.getConnection(); } catch(Exception e) { e.printStackTrace(); } } @PreDestroy @PrePassivate public void closeConnection() { connection=null; } public void addPersonalInfo(PersonalInfo personalinfo) { this.personalinfo=personalinfo; } public void addBillingInfo(BillingInfo billinginfo) { this.billinginfo=billinginfo; } @Remove public void createAccount() { System.out.println("Your request has been successfully processed"); } }
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Once
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- you
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- have
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- added
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- the
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- code
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- you
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- will
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- see
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- lot
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- of
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- errors
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- but
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- this
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- can
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- be
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- resolved
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- easily
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- and
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- is
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- shown
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- in
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- next
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- step.
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- The
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- errors
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- in
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- the
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- code
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- is
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- due
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- to
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- missing
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- classes
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- from
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- our
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- server
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- runtime.
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- This
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- can
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- be
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- resolved
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- as
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- follows.
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Right
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- click
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- on
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- StatefulBean
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- project
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- and
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- select
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- Properties.
- On the next screen select Java Build Path->Libraries->Add
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- External
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- Jars.
- Browse to <GERONIMO_HOME>/repository/org/apache/geronimo/specs/geronimo-ejb_3.0_spec/1.0.1
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- and
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- select
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- geronimo-ejb_3.0_spec-1.0.1.jar
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- .
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- Select
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- Open.
- Similarly browse to <GERONIMO_HOME>/repository/org/apache/geronimo/specs/geronimo-annotation_1.0_spec/1.1.1
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- and
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- add
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- geronimo-annotation_1.0_spec-1.1.1.jar
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- .
- Once done you can see both the jars enlisted. Select Ok.
- Let us walkthrough the EJB bean class code
- @Stateful public class AccountCreatorBean implements AccountCreator- @ Stateful annotation declares the Bean class as Stateful class.
- @Resource(name="jdbc/userds")
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- DataSource
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- datasource;-
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- This
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- is
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- a
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- resource
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- injection
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- into
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- the
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- bean
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- class
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- wherin
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- a
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- datasource
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- is
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- injected
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- using
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- the
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- @Resource
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- annotation.
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- We
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- will
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- shortly
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- see
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- how
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- to
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- create
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- a
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- datasource
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- in
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- geronimo.
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- public
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- AccountCreatorBean(
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- } -
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- This
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- is
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- a
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- constructor
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- for
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- the
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- bean
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- class
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- and
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- it
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- will
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- be
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- used
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- to
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- create
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- a
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- bean
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- instance
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- whenever
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- a
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- request
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- is
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- received
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- from
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- new
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- client
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- connection.
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- @PostConstruct
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- @PostActivate
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- public
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- void
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- openConnection()-
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- @PostConstruct
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- and
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- @PostActivate
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- are
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- annotations
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- which
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- are
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- basically
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- called
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- lifecycle
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- callback
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- annotation.
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- The
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- lifecycle
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- for
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- these
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- annotation
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- is
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- as
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- follows
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- New
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- bean
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- instance
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- is
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- created
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- using
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- the
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- default
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- constructor.
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- Resources
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- are
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- injected
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- Now
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- the
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- PostConstruct
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- method
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- is
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- called
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- which
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- in
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- our
...
- case
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- is
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- to
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- open
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- a
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- database
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- connection.
- PostActivate is called on the bean instances which have been passivated and required to be reactivated. It goes on the same cycle as being followed by PostConstruct.
- @PreDestroy @PrePassivate public void closeConnection()- Again @PreDestroy and @PrePassivate are Lifecycle callback annotation. The lifecycle of these annotation is as follows
- Bean instances in the pool are used and business methods are invoked.
- Once the client is idle for a period of time container passivates the bean instance. The closeConnection function is called just before container passivates the bean.
- If the client does not invoke a passivated bean for a period of time it is destroyed.