JPA-Ausnahme für optimistische Sperre in Java Development

    4.0.0

    naveen.examples
    jpa
    0.0.1-SNAPSHOT
    jar

    jpa
    http://maven.apache.org

    
        UTF-8
        1.8
        4.3.6.Final
        UTF-8
    

    

        
        
            org.hibernate
            hibernate-entitymanager
            ${hibernate.version}
        

        
        
            org.hibernate
            hibernate-c3p0
            ${hibernate.version}
        

        
        
            mysql
            mysql-connector-java
            5.1.31
        

        
            junit
            junit
            3.8.1
            test
        

    

    
        org.hibernate.jpa.HibernatePersistenceProvider
        
            
            
            
            
            
            
            
            
            
            
            
            
            
            
        
    

// Import statements

@NamedQueries({
    @NamedQuery(name = EmployeeBE.FIND_ALL, query = "SELECT e FROM EmployeeBE e order by e.name "),
})
@Entity
@Table(name = "T_EMP")
public class EmployeeBE implements Serializable{
private static final long serialVersionUID = 1607726899931733607L;

    public static final String FIND_ALL = "naveen.examples.jpa.entity.EmployeeBE.find_all";

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    @Column(name = "NAME")
    private String name;

    @Column(name = "version_num")
    @Version
    private int version;

//  Getters and setters

}

// Interface for CRUD operations.
package naveen.examples.jpa.business;

import java.util.List;

import naveen.examples.jpa.entity.EmployeeBE;

public interface EmployeeCrud {

    List findAllEmployeeBECol();

    EmployeeBE saveEmployee(EmployeeBE employeeBE);

    EmployeeBE updateEmployee(EmployeeBE employeeBE);

    EmployeeBE findById(int id);

}

// Implementatino class for CRUD operations
public class EmployeeCrudImpl implements EmployeeCrud{

    public EmployeeBE saveEmployee(EmployeeBE employeeBE) {
        EntityManager em = EntityManagerUtil.getEntityManager();
        em.getTransaction().begin();
        em.persist(employeeBE);
        em.getTransaction().commit();
        return employeeBE;
    }

    public EmployeeBE updateEmployee(EmployeeBE employeeBE) {
        EntityManager em = EntityManagerUtil.getEntityManager();
        em.getTransaction().begin();
        em.merge(employeeBE);
        em.getTransaction().commit();
        return employeeBE;
    }

    @SuppressWarnings("unchecked")
    public List findAllEmployeeBECol() {
        EntityManager em = EntityManagerUtil.getEntityManager();
        Query query = em.createNamedQuery(EmployeeBE.FIND_ALL);
        return query.getResultList();
    }


    public EmployeeBE findById(int id) {
        EntityManager em = EntityManagerUtil.getEntityManager();
        return em.find(EmployeeBE.class, id);
    }

// Entity Manager
public class EntityManagerUtil {

    private static EntityManager  entityManager;

    private EntityManagerUtil() {
    }

    public static EntityManager getEntityManager() {
        if(entityManager==null){
            EntityManagerFactory emFactory = Persistence.createEntityManagerFactory("jpa-example");
            return emFactory.createEntityManager();
        }
        return entityManager;
    }
}

public class Application {

    public static void main(String args[]) {

        EmployeeCrud employeeCrud = new EmployeeCrudImpl();

        List employeeBEs = employeeCrud.findAllEmployeeBECol();
        if(!employeeBEs.isEmpty()){
            EmployeeBE employeeBE = employeeBEs.get(0);
            employeeBE.setName("Updated");
            employeeCrud.updateEmployee(employeeBE);
            // Here Optimistic lock exception
            employeeCrud.updateEmployee(employeeBE);
        }else{
            EmployeeBE employeeBE = new EmployeeBE();
            employeeBE.setName("Naveen");
            employeeBE = employeeCrud.saveEmployee(employeeBE);
        }
    }