MyBatis3 入门学习--简单CRUD应用

一、简介：什么是MyBatis？
  MyBatis 是支持普通 SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis 消除
了几乎所有的 JDBC 代码和参数的手工设置以及结果集的检索。MyBatis 使用简单的 XML
或注解用于配置和原始映射，将接口和 Java 的POJOs（Plan Old Java Objects，普通的 Java
对象）映射成数据库中的记录。

二、环境介绍
  MyBatis3.0.3 + MySQL5.5.8
  数据库表：student
       

id	name
int	varchar(100)

三、应用开始（我这以学生为例）
1、配置数据库连接配置文件（我的文件放在Classpath下）
Configuration.xml

<?xml version="1.0" encoding="UTF-8" ?> 
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
	<properties resource="init.properties"> 
	</properties> 
	<typeAliases>
		<typeAlias type="com.carvin.mybatis.study01.model.Student" alias="Student"/>
	</typeAliases>
	
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="${driver}" />
				<property name="url" value="${url}" />
				<property name="username" value="${username}" />
				<property name="password" value="${password}" />
			</dataSource>
		</environment>
	</environments>
	
	<mappers>
		<mapper resource="com/carvin/mybatis/study01/config/student.xml" />
	</mappers>
</configuration> 

init.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/mydb?useUnicode=true&characterEncoding=UTF-8
username=root
password=password

2、创建SqlSessionFactory的工具类

public class SqlSessionFactoryUtil {
	private static SqlSessionFactory sqlSessionFactory = null;
	
	static {
		String resource = "Configuration.xml";
		try {
			Reader reader = Resources.getResourceAsReader(resource);
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public static SqlSessionFactory getSqlSessionFactory() {
		return sqlSessionFactory;
	}
	
	public static SqlSession getSqlSession() {
		return sqlSessionFactory.openSession();
	}
	
	public static void closeSession(SqlSession sqlSession) {
		if(sqlSession != null) {
			sqlSession.close();
		}
	}
}

3、创建实体类Student.java

public class Student {
	private int id;
	private String name;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	@Override
	public String toString() {
		return "id : " + id + ", name : " + name;
	}
}

3、创建DAO访问接口IStudentDAO.java

public interface IStudentDAO {
	Student selectStudentById(int id);
	List<Student> selectStudents();
	void insertStudent(Student student);
	void updateStudent(Student student);
	void deleteStudent(int id);
}

4、创建访问SQL语句配置文件student.xml

<?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="com.carvin.mybatis.study01">
	
	<select id="selectStudents" resultType="Student">
		select * from student 
	</select>
	<select id="selectStudentById" resultType="Student" parameterType="int">
		select * from student where id=#{id}
	</select>
	<insert id="insertStudent" parameterType="Student">
		insert student(name) values (#{name})
	</insert>
	<update id="updateStudent" parameterType="Student">
		update student set name=#{name} 
			where id=#{id}
	</update>
	<delete id="deleteStudentById" parameterType="int">
		delete from student where id=#{id}
	</delete>
</mapper>

5、实现数据库访问接口StudentDAOImpl.java

public class StudentDAOImpl implements IStudentDAO {
	
	@Override
	public void insertStudent(Student student) {
		SqlSession session = SqlSessionFactoryUtil.getSqlSession();
		try {
			session.insert("com.carvin.mybatis.study01.insertStudent", student);
		} finally {
			try {
				session.commit();
			} catch (Exception e) {
				session.rollback();
				e.printStackTrace();
			}
			SqlSessionFactoryUtil.closeSession(session);
		}
	}

	@Override
	public void updateStudent(Student student) {
		SqlSession session = SqlSessionFactoryUtil.getSqlSession();
		try {
			session.update("com.carvin.mybatis.study01.updateStudent", student);
		} finally {
			try {
				session.commit();
			} catch (Exception e) {
				session.rollback();
				e.printStackTrace();
			}
			SqlSessionFactoryUtil.closeSession(session);
		}
	}

	@Override
	public void deleteStudent(int id) {
		SqlSession session = SqlSessionFactoryUtil.getSqlSession();
		try {
			session.delete("com.carvin.mybatis.study01.deleteStudentById", id);
		} finally {
			try {
				session.commit();
			} catch (Exception e) {
				session.rollback();
				e.printStackTrace();
			}
			SqlSessionFactoryUtil.closeSession(session);
		}
	}

	@Override
	public List<Student> selectStudents() {
		SqlSession session = SqlSessionFactoryUtil.getSqlSession();
		List<Student> results = null;
		try {
			results = session.selectList("com.carvin.mybatis.study01.selectStudent");
		} finally {
			SqlSessionFactoryUtil.closeSession(session);
		}
		return results;
	}

	@Override
	public Student selectStudentById(int id) {
		SqlSession session = SqlSessionFactoryUtil.getSqlSession();
		Student student = null;
		try {
			student = (Student) session.selectOne("com.carvin.mybatis.study01.selectStudentById", id);
		} finally {
			SqlSessionFactoryUtil.closeSession(session);
		}
		return student;
	}

}

6、创建测试类StudentTest.java

public class StudentTest {
	@Test
	public void testSelectList() {
		IStudentDAO dao = new StudentDAOImpl();
		List<Student> results = dao.selectStudents();
		System.out.println(results.size());
	}
	
	@Test
	public void testSelectOne() {
		IStudentDAO dao = new StudentDAOImpl();
		Student student = dao.selectStudentById(2);
		System.out.println(student);
	}
	
	@Test
	public void testInsert() {
		Student student = new Student();
		student.setName("carvin");
		IStudentDAO dao = new StudentDAOImpl();
		dao.insertStudent(student);
	}
	
	@Test
	public void testUpdate() {
		IStudentDAO dao = new StudentDAOImpl();
		Student student = dao.selectStudentById(2);
		student.setName("oldsmall");
		dao.updateStudent(student);
	}

	@Test
	public void testDelete() {
		IStudentDAO dao = new StudentDAOImpl();
		dao.deleteStudent(2);
	}
}

7、测试

至此，一个简单的MyBatis应用就完成了。