Hibernate - Rollback: org.hibernate.MappingException: Unknown entity

Question

I have written few codes for inserting data into my SQL database. Actually, I am trying to learn Struts 2 with Hibernate. But, unfortunately I am facing a problem after submitting my form.

I could not find the reason for this error message. My try & catch block throws error like:

Exception in saveOrUpdate() Rollback  :org.hibernate.MappingException: Unknown entity: v.esoft.pojos.Employee

Pojo(Employee.java):

@Entity
@Table(name = "employee", catalog = "eventusdb")
public class Employee implements java.io.Serializable {

    private Integer empId;
    private String name;
    private String website;

    public Employee() {
    }

    public Employee(String name, String website) {
        this.name = name;
        this.website = website;
    }

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "emp_id", unique = true, nullable = false)
    public Integer getEmpId() {
        return this.empId;
    }

    public void setEmpId(Integer empId) {
        this.empId = empId;
    }

    @Column(name = "name", nullable = false)
    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Column(name = "website", nullable = false, length = 65535)
    public String getWebsite() {
        return this.website;
    }

    public void setWebsite(String website) {
        this.website = website;
    }

}

also having Employee.hbm.xml:

    <?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Sep 10, 2013 4:29:04 PM by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
    <class name="v.esoft.pojos.Employee" table="employee" catalog="eventusdb">
        <id name="empId" type="java.lang.Integer">
            <column name="emp_id" />
            <generator class="identity" />
        </id>
        <property name="name" type="string">
            <column name="name" not-null="true" />
        </property>
        <property name="website" type="string">
            <column name="website" length="65535" not-null="true" />
        </property>
    </class>
</hibernate-mapping>

Answer 1

If the entity isn't mapped, you should inspect the hibernate configuration. Hibernate is ORM framework used to map pojos (entities) to the database schema objects. You didn't configure or hibernate couldn't find mapping for the object Employee. The configuration file is hibernate.cfg.xml should contain the mapping to the resource Employee.hbm.xml. Suppose this file is in the same folder as Employee class. Then the mapping will be

<mapping resource="v/esoft/pojos/Employee.hbm.xml"/>

Another approach if you used an annotation based configuration, then you should use class attribute to map to the pojo that contains Hibernate/JPA annotations.

<mapping class="v.esoft.pojos.Employee"/>

Note, annotation based Configuration might be different depending on version of Hibernate and may require additional libraries.