Mybatis

what is Mybatis

persistence framework with support for custom SQL

A persistence framework assists and automates the storage of program data into databases, especially relational databases. It acts as a layer of abstraction between the application and the database, typically bridging any conceptual differences between the two.

Dao

Java Data Access Object

All database access in the system is made through a DAO to achieve encapsulation.
Each DAO instance is responsible for one primary domain object or entity. If a domain object has an independent lifecycle, it should have its own DAO.
The DAO is responsible for creations, reads (by primary key), updates, and deletions -- that is, CRUD --

The DAO is not responsible for handling transactions, sessions, or connections. These are handled outside the DAO to achieve flexibility.

DAo

@Repository
public interface EmployeeDao {
	public void saveEmployee(Employee employee);

	public Employee getEmployeeById(Integer employeeId);
}

XMl Mapper

 <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="ro.cf.mybatisTutorial.EmployeeDao">

	<insert id="saveEmployee" useGeneratedKeys="true" keyProperty="id">
		INSERT INTO employees (emp_no, birth_date, first_name, last_name,
		gender, hire_date)
		VALUES ( #{emp_no}, #{birth_date}, #{first_name}, #{last_name}, #{gender},
		#{hire_date} );
	</insert>

        <select id="getEmployeeById" resultType="ro.cf.mybatisTutorial.Employee">
		SELECT * from employees WHERE emp_no = #{employeeId};
	</select>

</mapper>

USing dao

using the @AutoWired adnotation

 
  @Autowired
  private EmployeeDao employeeDao;

...
  Employee employee = employeeDao.getEmployeeById(1);