Generic DAO in Hibernate - EmployeeDao.java using GeneticDao.java

Employee.java

package com.bytestree.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

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

	private static final long serialVersionUID = 4910225916550731446L;

	private Long id;
	private String firstname;
	private String lastname;
	private String designation;
	private Integer salary;

	public Employee() {
	}

	public Employee(Long id) {
		this.id = id;
	}

	public Employee(Long id, String firstname, String lastname, String designation, Integer salary) {
		this.id = id;
		this.firstname = firstname;
		this.lastname = lastname;
		this.designation = designation;
		this.salary = salary;
	}

	public Employee(String firstname, String lastname, String designation, Integer salary) {
		this.firstname = firstname;
		this.lastname = lastname;
		this.designation = designation;
		this.salary = salary;
	}

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "id", unique = true, nullable = false)
	public Long getId() {
		return this.id;
	}

	public void setId(Long id) {
		this.id = id;
	}

	@Column(name = "firstname", length = 50)
	public String getFirstname() {
		return this.firstname;
	}

	public void setFirstname(String firstname) {
		this.firstname = firstname;
	}

	@Column(name = "lastname", length = 50)
	public String getLastname() {
		return this.lastname;
	}

	public void setLastname(String lastname) {
		this.lastname = lastname;
	}

	@Column(name = "designation", length = 50)
	public String getDesignation() {
		return this.designation;
	}

	public void setDesignation(String designation) {
		this.designation = designation;
	}

	@Column(name = "salary")
	public Integer getSalary() {
		return this.salary;
	}

	public void setSalary(Integer salary) {
		this.salary = salary;
	}

	@Override
	public String toString() {
		StringBuffer sb = new StringBuffer();
		sb.append("Id: ").append(this.id).append(", firstName: ").append(this.firstname).append(", lastName: ")
				.append(this.lastname).append(", Designation: ").append(this.designation).append(", Salary: ")
				.append(this.salary);
		return sb.toString();
	}

}

EmployeeDao.java

package com.bytestree.dao;

import com.bytestree.model.Employee;

public interface EmployeeDao extends GenericDao<Employee> {
	Integer getMaxSalary();
}

EmployeeDaoImpl.java

package com.bytestree.dao;

import org.hibernate.Criteria;
import org.hibernate.criterion.Projections;
import org.springframework.stereotype.Repository;

import com.bytestree.model.Employee;

@Repository
public class EmployeeDaoImpl extends AbstractGenericDao<Employee> implements EmployeeDao {

	@Override
	public Integer getMaxSalary() {
		Criteria criteria = getSession().createCriteria(Employee.class).setProjection(Projections.max("salary"));
		Integer maxSalary = (Integer) criteria.uniqueResult();
		return maxSalary;
	}

}

EmployeeServiceImpl.java

package com.bytestree.service;

import java.util.List;
import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.bytestree.dao.EmployeeDao;
import com.bytestree.model.Employee;

@Service
@Transactional(readOnly = true)
public class EmployeeServiceImpl implements EmployeeService {

	final static Logger logger = Logger.getLogger(EmployeeServiceImpl.class);

	@Autowired
	EmployeeDao employeeDao;

	public List<Employee> getAllEmployees() {
		logger.debug("Getting all employees...");
		return employeeDao.findAll();
	}

	/**
	 * Add new employee if it in not already exists
	 * 
	 * @param employee: Employee to add
	 */
	@Override
	@Transactional(readOnly = false)
	public void addNewEmployee(Employee employee) {
		Employee emp = new Employee();
		emp.setFirstname(employee.getFirstname());
		emp.setLastname(employee.getLastname());
		List<Employee> emplList = employeeDao.findAllByExample(emp);
		if (emplList == null || emplList.isEmpty()) {
			Long id = (Long) employeeDao.save(employee);
			logger.debug("Id of new Employee " + id);
		} else {
			logger.debug("Employee " + emp + " already exists");
		}
	}

	/**
	 * Return maximum salary given to any employee
	 * 
	 * @return max salary
	 */
	@Override
	public Integer getMaxSalary() {
		return employeeDao.getMaxSalary();
	}

}

Refer Generic DAO in Hibernate for complete example