Download 764_7_EJB

CIS 764 Database Systems Engineering
L7. EJB’s
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CIS 764 Database Systems Engineering
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CIS 764 Database Systems Engineering
http://www.zakon.org/robert/internet/timeline/
1945 … V. Bush, concept of hypertext
1961 … Kleinrock paper on packet switching
1966 … Roberts , plan for ARPA net
1967 … hypertext system, Brown Univ
1969 …. ARPA net , 4 nodes
1972 … email
1974 … Cerf , Kahn … TCP paper
1981 … APRA net down , status virus
1982 … CS net
1986 … NSF net
1987 … 10 K nodes
1987 … Apple Hypercard
1988 … CERT
1989 … 100K nodes
1991 … WWW … CGI scripts
(each request is separate process, non-OO)
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http://www.zakon.org/robert/internet/timeline/
1991 …
1992 …
1995
1998
1999
WWW … CGI scripts
1M nodes
… Java
… Google … servlets … JDeveloper
… J2EE, servlets, EJB 1 (RMI remote objects)
JSP 1 (embedded code)
2000 … 20 M web sites
2001 … JDev separate from Borland
2003 … SQL Slammer worm
… EJB 2 (adds QL )
… JSP 2 (tags )
2005 … YouTube
… Java annotations
2006 … Google buys YouTube
… EJB 3 ( annotated POJO’s)
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CIS 764 Database Systems Engineering
EJB specification details how an application server provides:
Persistence
Transaction processing
Concurrency control
Events using Java Message Service
Java Naming and directory services (JNDI)
Security ( Java Cryptography Extension (JCE) and JAAS )
Deployment of software components in an application server
Remote procedure calls using RMI-IIOP.
Exposing business methods as Web Services.
defines the roles played by the EJB container vs the EJBs
From http://en.wikipedia.org/wiki/Enterprise_JavaBean
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CIS 764 Database Systems Engineering
… old EJB 1, 2
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CIS 764 Database Systems Engineering
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CIS 764 Database Systems Engineering
EJB3
POJO + Annotations => EJB
EJB 3.0 Resources
http://www.oracle.com/technology/tech/java/ejb30.html
Introduction:
http://www.oracle.com/technology/tech/java/newto/introejb.htm
or
Java World: (has more code examples)
http://www.javaworld.com/javaworld/jw-08-2004/jw-0809-ejb.html
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CIS 764 Database Systems Engineering
Entity bean … bound to entity data,
with unique key value;
can contain multiple subitems.

where is the concept of a result set ?
Session bean …
 “session beans generally represent actions …” << bad OO !
“process entity” vs “data entity”
Stateless … do not have internal state (  )
… rather: do not keep track of the callers state !
Stateful …..maintains the conversation state across
multiple method invocations
(e.g. a shopping cart)
Beans have an associated deployment descriptor
Beans have own QL … “OO version of sql “
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CIS 764 Database Systems Engineering
EJB annotations
http://www.fnogol.de/archives/2005/05/13/ejb-30-annotations-cheat-sheet/
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CIS 764 Database Systems Engineering
import javax.ejb.Stateless.*;
@Stateless(name="CalculateEJB")
public class CalculateEJBBean
implements CalculateEJB
{
int value = 0;
public String incrementValue()
{ value++;
return "value incremented by 1";
}
}
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CIS 764 Database Systems Engineering
import javax.persistence.*;
import java.util.ArrayList;
import java.util.Collection;
@Entity
@Table(name = "EMPLOYEES")
public class Employee implements java.io.Serializable
{
private int empId;
private String eName;
private double sal;
@Id
@Column(name="EMPNO", primaryKey=true)
/* getters and setters here … see next slide
}
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CIS 764 Database Systems Engineering
public int getEmpId(
) { return empId; }
public void setEmpId(int empId) { this.empId = empId; }
public String getEname(
) { return eName; }
public void setEname(String eName) { this.eName = eName; }
public double getSal(
) { return sal; }
public void setSal(double sal) { this.sal = sal; }
public String toString()
{
StringBuffer buf = new StringBuffer();
buf.append("Class:").append(this.getClass().
getName()).append(" :: ").append(" empId:").append(getEmpId()).
append("
ename:").append(getEname()).append("sal:").append(getSal());
return buf.toString();
}
??? Why the toString method <<<<<<<<<<<<<<<<
??? Why ArrayList and Collection
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CIS 764 Database Systems Engineering
import javax.naming.Context;
import javax.naming.InitialContext;
public class CalculateejbClient
{
public static void main(String [] args)
{ Context context = new InitialContext();
CalculateEJB myejb =
(CalculateEJB)context.lookup("java:comp/env/ejb/CalculateEJB");
myejb.incrementValue();
}
}
??? Where does this “client” run ??
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CIS 764 Database Systems Engineering
An OQL Resources
http://www.oracle.com/technology/sample_code/tutorials/fbs/eql/toc.htm
http://publib.boulder.ibm.com/infocenter/tivihelp/v8r1/index.jsp?topic=/com.ibm.netc
ool_precision.doc/pr35se/xF1118340.html
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CIS 764 Database Systems Engineering
Homework:
Oracle “EJB3 Simple Tutorial”
http://www.oracle.com/technology/obe/obe1013jdev/10131/10131_ejb_30/ejb_
30.htm
Do an “in essence” version for the PO DB.
(e.g. … not the DB in the tutorial,
do not need to implements all of the operations)
Note: This is not a web app.
The client has remote access to the bean.
The client does just text output.
Post snapshots in JDev , running the client , link to code
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CIS 764 Database Systems Engineering
Note: Begin planning for future requirements:
Group project: requirements, design, implementation, doc’s
(weekly during 2ed half of semester)
Contribute some tutorial content … ** “how to”
( more Oracle tutorials or dotNet, Ruby, Eclipse, etc.)
( expend previous tutorials or add new ones )
Submit some technical paper …. **
concepts … not “how to”
( 2 .. 4 pages, w references, related to 764 topics )
Class presentation or either tutorial or paper:
** both require prior approval of topics .
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CIS 764 Database Systems Engineering
end.
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