Can't get EntityManager access in JSP/Servlet

Question

Hi all,
our team has started a EJB project (EJBs + JPA configurations)
we managed to access the configured JPA (EntityManager etc) within the EJB instance; however we don't know how to access the EntityManager within JSP/Servlet
Our project's structure:
1 EJB project (EJB classes, EntityBean classes, JPA configuration + eclipselink)
1 Web project (for JSP, Servlets)
the main problem is ... we can't access EntityManager(s) in JSP / Servlets (and we already tried using Struts2.0 to replace servlets/jsp... the problem is the same... so it is not ... the matter of choosing the view technology...)
Jason

Answer 1

Hi Jason,
How i tried to get EntityManager is as following:
Suppose I want to define my Persistence unit like Following:
*<Your-EAR>/APP-INF/classes/MyEmployee.java*
"*MyEmployee.java*"
package entityA;
import java.io.Serializable;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;
import javax.persistence.*;
@Entity()
@Table(name="MYEMPLOYEE")
public class MyEmployee implements Serializable {
     //default serial version id, required for serializable classes.
     private static final long serialVersionUID = 1L;
     private Long empno;
     private String empname;
public MyEmployee() {
     @Id()
     @Column(name="EMPNO", unique=true, nullable=false, precision=22)
     public Long getEmpno() {
          return this.empno;
     public void setEmpno(Long empno) {
          this.empno = empno;
     @Basic()
     @Column(name="EMPNAME", length=15)
     public String getEmpname() {
          return this.empname;
     public void setEmpname(String empname) {
          this.empname = empname;
     public boolean equals(Object other) {
          if (this == other) {
               return true;
          if (!(other instanceof MyEmployee)) {
               return false;
          MyEmployee castOther = (MyEmployee)other;
          return new EqualsBuilder()
               .append(this.getEmpno(), castOther.getEmpno())
               .isEquals();
     public int hashCode() {
          return new HashCodeBuilder()
               .append(getEmpno())
               .toHashCode();
     public String toString() {
          return new ToStringBuilder(this)
               .append("empno", getEmpno())
               .toString();
And I have Placed My "*persistence.xml*" file in *"<Your-EAR>/APP-INF/classes/META-INF/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_1_0.xsd"
     version="1.0">     
     <persistence-unit name="JPA_A_EJB" transaction-type="RESOURCE_LOCAL">
          <provider>org.hibernate.ejb.HibernatePersistence</provider>
          <class>entityA.MyEmployee</class>
          <properties>
               <property name="hibernate.dialect" value="org.hibernate.dialect.OracleDialect"/>
               <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/>
               <property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521:xe"/>
               <property name="hibernate.connection.username" value="jack"/>
               <property name="hibernate.connection.password" value="password"/>
          </properties>
     </persistence-unit>     
</persistence>
***********************************HOW I Access The Above Unit from my EJB mentioned Below*******************************
"*EmployeeSessionBean.java*"
package sfsbA;
import entityA.*;
import javax.ejb.*;
import javax.persistence.*;
@Stateless
public class EmployeeSessionBean implements EmployeeSessionRemoteIntf
*@PersistenceContext*
protected EntityManager entityManager;
*///NOTE: Using the Above Technique You can access the "EntityManager" Object in your Servlets As well...Just write the Above two Lines inside your Servlet*
public void createEmployee(Long empno,String empname) throws Exception{
          System.out.println("\n\tcreateEmployee() called. EntityManager entityManager = "+entityManager);
          MyEmployee employee = new MyEmployee();
employee.setEmpno(empno);
employee.setEmpname(empname);
entityManager.persist(employee);
          System.out.println("\n\t Entity Manager has persisted the Employee Information...");
int count = 0;
public EmployeeSessionBean() {
System.out.println("\n\t EmployeeSessionBean--> EmployeeSessionBean() invoked");
@Init("create")
public void initMethod() throws CreateException {
System.out.println("\n\t EmployeeSessionBean--> public void initMethod() invoked");
@Remove(retainIfException=true)
public void removeWithRetain() throws Exception{
System.out.println("\n\t EmployeeSessionBean--> removeWithRetain() invoked");
@Remove
public void removeWithoutRetain() throws Exception{
System.out.println("\n\t EmployeeSessionBean--> removeWithoutRetain() invoked");
public String printRemoteIntf () {
System.out.println("\n\t EmployeeSessionBean ---> public String printRemoteIntf () invoked");
     return "ReplicableSFSRemoteObjectIntf";
public String printLocalIntf () {
System.out.println("\n\t EmployeeSessionBean ---> public String printLocalIntf () invoked");
     return "ReplicableSFSLocalObjectIntf";
public String printBean () {
System.out.println("\n\t EmployeeSessionBean ---> public String printBean () invoked");
     return "EmployeeSessionBean";
public int testIncrement() throws Exception
System.out.println("\n\t EmployeeSessionBean ---> public int testIncrement() invoked");
count=count+5;
return count;
public int testDecrement() throws Exception
System.out.println("\n\t EmployeeSessionBean ---> public int testDecrement() invoked");
count=count-2;
return count;
public int getCount() throws Exception
System.out.println("\n\t EmployeeSessionBean ---> public int getCount() invoked");
return count;
"*EmployeeSessionRemoteIntf.java*"
package sfsbA;
public interface EmployeeSessionRemoteIntf {
public void createEmployee(Long emono,String empname)     throws Exception;
public void removeWithRetain()throws Exception;
public void removeWithoutRetain() throws Exception;
public String printBean ();
public int testIncrement() throws Exception;
public int testDecrement() throws Exception;
public int getCount() throws Exception;
*"ejb-jar.xml"*
<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar version="3.0" 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_0.xsd">
<enterprise-beans>
<session>
<ejb-name>EmployeeSessionBean</ejb-name>
<business-remote>sfsbA.EmployeeSessionRemoteIntf</business-remote>
<ejb-class>sfsbA.EmployeeSessionBean</ejb-class>
<session-type>Stateless</session-type>
</session>
</enterprise-beans>
</ejb-jar>
*"weblogic-ejb-jar.xml"* (I am writing these file Just because i want my Own JNDI Simple name...Not the Container Generated Complex JNDI name)
<weblogic-ejb-jar xmlns="http://www.bea.com/ns/weblogic/90" xmlns:j2ee="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.bea.com/ns/weblogic/90 http://www.bea.com/ns/weblogic/90/weblogic-ejb-jar.xsd">
<weblogic-enterprise-bean>
<ejb-name>EmployeeSessionBean</ejb-name>
<stateless-session-descriptor>
     <business-interface-jndi-name-map>
<business-remote>sfsbA.EmployeeSessionRemoteIntf</business-remote>
<jndi-name>EmployeeSessionBean</jndi-name>
     </business-interface-jndi-name-map>
</stateless-session-descriptor>
</weblogic-enterprise-bean>
</weblogic-ejb-jar>
"*application.xml*"
<!DOCTYPE application PUBLIC '-//Sun Microsystems, Inc.//DTD J2EE Application 1.3//EN' 'http://java.sun.com/dtd/application_1_3.dtd'>
<application>
<display-name>JPAs_Demo_Jason</display-name>
<module>
<ejb>AccessEntityManager.jar</ejb>
</module>
</application>
NOTE: The Jar "" Contains
1). EmployeeSessionBean
2). EmployeeSessionRemoteIntf
3). META-INF/ejb-jar.xml
4). META-INF/weblogic-ejb-jar.xml
Thanks
Jay SenSharma
http://jaysensharma.wordpress.com  (Real WebLogic Stuff...Not less Than a Magic...Here)
Edited by: Jay SenSharma on Dec 16, 2009 10:59 PM
Edited by: Jay SenSharma on Dec 16, 2009 11:00 PM