mybatis学习笔记（四）- MyBatis 映射文件(增删改)

1. MyBatis 映射文件章节的工程目录

映射文件指导着MyBatis如何进行数据库增删改查， 有着非常重要的意义

2. 增删改的使用

2.1. 创建 Employee 类

注意：如果给类创建有参构造器时，一定给它一个无参构造器

package www.xq.mybatis.bean;

import org.apache.ibatis.type.Alias;

public class Employee {

	private Integer id;
	private String lastName;
	private String email;
	private String gender;

	public Employee() {
		super();
	}

	public Employee(Integer id, String lastName, String email, String gender) {
		super();
		this.id = id;
		this.lastName = lastName;
		this.email = email;
		this.gender = gender;
	}

	public Integer getId() {
		return id;
	}

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

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getGender() {
		return gender;
	}

	public void setGender(String gender) {
		this.gender = gender;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]";
	}

}

2.2. 创建 EmployeeMapper 的接口

public interface EmployeeMapper {
    
	public void addEmp(Employee employee);

	public boolean updateEmp(Employee employee);

	public void deleteEmpById(Integer id);
	
}

2.3.创建映射文件 EmployeeMapper.xml

<mapper namespace="www.xq.mybatis.dao.EmployeeMapper">
	
	<!-- public void addEmp(Employee employee); -->
	<!-- parameterType：参数类型，可以省略， 
	获取自增主键的值：
		mysql支持自增主键，自增主键值的获取，mybatis也是利用statement.getGenreatedKeys()；
		useGeneratedKeys="true"；使用自增主键获取主键值策略
		keyProperty；指定对应的主键属性，也就是mybatis获取到主键值以后，将这个值封装给javaBean的哪个属性
	-->
	<insert id="addEmp" parameterType="www.xq.mybatis.bean.Employee"
		useGeneratedKeys="true" keyProperty="id" databaseId="mysql">
		insert into tbl_employee(last_name,email,gender) 
		values(#{lastName},#{email},#{gender})
	</insert>
	
	<!-- public boolean updateEmp(Employee employee);  -->
	<update id="updateEmp">
		update tbl_employee 
		set last_name=#{lastName},email=#{email},gender=#{gender}
		where id=#{id}
	</update>
	
	<!-- public void deleteEmpById(Integer id); -->
	<delete id="deleteEmpById">
		delete from tbl_employee where id=#{id}
	</delete>
</mapper>

2.4. 创建全局配置文件(请参照以前的笔记自行书写)

1. 配置连接数据库相关环境
2. 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到全局配置文件

2.5. 测试(创建单元测试类 MyBatisTest)

public class MyBatisTest {
	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}
	
	/**
	 * 测试增删改
	 * 1、mybatis允许增删改直接定义以下类型返回值
	 * 		Integer、Long、Boolean、void
	 * 2、我们需要手动提交数据
	 * 		sqlSessionFactory.openSession();===》手动提交
	 * 		sqlSessionFactory.openSession(true);===》自动提交
	 * @throws IOException 
	 */
	@Test
	public void test03() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		//1、获取到的SqlSession不会自动提交数据
		SqlSession openSession = sqlSessionFactory.openSession();
		
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			//测试添加
			Employee employee = new Employee(null, "jerry4",null, "1");
			mapper.addEmp(employee);
			//测试是否获取主键值
			System.out.println(employee.getId());
		 	
			//测试修改
			//Employee employee = new Employee(1, "Tom", "[email protected]", "0");
			//boolean updateEmp = mapper.updateEmp(employee);
			//System.out.println(updateEmp);
			//测试删除
			//mapper.deleteEmpById(2);
			//2、手动提交数据
			openSession.commit();
		}finally{
			openSession.close();
		}
		
	}