Mybatis介绍
MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。
MyBatis是一个优秀的 持久层框架 ，它对jdbc的操作数据库的过程进行封装，使开发者只需要关注 SQL 本身，而不需要花费精力去处理例如注册驱动、创建connection、创建statement、手动设置参数、结果集检索等jdbc繁杂的过程代码。
Mybatis通过xml或注解的方式将要执行的各种statement（statement、preparedStatemnt、CallableStatement）配置起来，并通过java对象和statement中的sql进行映射生成最终执行的sql语句，最后由mybatis框架执行sql并将结果映射成java对象并返回。
Mybatis架构
Mapper动态代理方式
开发规范
- Mapper.xml文件中的namespace与mapper接口的类路径相同。
- Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
- Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同
- Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同
1)UserMapper映射文件
<?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.it.mybatis.mapper.UserMapper">
<!-- 根据id查询user -->
<select id="findById" parameterType="Integer" resultType="com.it.mybatis.pojo.User">
SELECT * FROM user WHERE id = #{id}
</select>
<!-- 根据username模糊查询 -->
<select id="findByLikeName" parameterType="String" resultType="com.it.mybatis.pojo.User">
select * from user where username like "%"#{username}"%"
</select>
<!-- 添加user -->
<insert id="saveUser" parameterType="com.it.mybatis.pojo.User">
<!-- 最后一次插入id -->
<selectKey keyColumn="id" keyProperty="id" order="AFTER" resultType="Integer">
select LAST_INSERT_ID()
</selectKey>
insert into user(username,birthday,sex,address)
values(#{username},#{birthday},#{sex},#{address})
</insert>
<!-- 修改用户 -->
<update id="updateUser" parameterType="com.it.mybatis.pojo.User">
update user set username = #{username},sex = #{sex},address = #{address} where id = #{id}
</update>
<!-- 删除user -->
<delete id="deleteUserById" parameterType="com.it.mybatis.pojo.User">
delete from user where id =#{id}
</delete>
</mapper>2)UserMapper接口文件(注意规范)
public interface UserMapper {
User findById(Integer id);
List<User> findByLikeName(String username);
void saveUser(User user);
void updateUser(User user);
void deleteUserById(Integer id);
}
3)SqlMapConfig.xml文件(加载usermapper.xml文件)
<?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>
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理 -->
<transactionManager type="JDBC" />
<!-- 数据库连接池 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="admin" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/it/mybatis/pojo/User.xml"/>
</mappers>
</configuration>4)测试
public class MapperTest {
//根据ID查询
@Test
public void func1() throws IOException {
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 2. 加载SqlMapConfig.xml配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 3. 创建SqlSessionFactory对象
SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
// 4. 创建SqlSession对象
SqlSession openSession = build.openSession();
UserMapper mapper = openSession.getMapper(UserMapper.class);
User user = mapper.findById(10);
System.out.println(user);
}
//根据username模糊查询
@Test
public void func2() throws IOException {
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 2. 加载SqlMapConfig.xml配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 3. 创建SqlSessionFactory对象
SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
// 4. 创建SqlSession对象
SqlSession openSession = build.openSession();
UserMapper mapper = openSession.getMapper(UserMapper.class);
List<User> user = mapper.findByLikeName("j");
for (User user2 : user) {
System.out.println(user2);
}
}
//插入User
@Test
public void func3() throws IOException {
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 2. 加载SqlMapConfig.xml配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 3. 创建SqlSessionFactory对象
SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
// 4. 创建SqlSession对象
SqlSession openSession = build.openSession();
UserMapper mapper = openSession.getMapper(UserMapper.class);
User user = new User();
user.setAddress("address");
user.setBirthday(new Date());
user.setSex("1");
user.setUsername("jackson");
mapper.saveUser(user);
openSession.commit();
}
//更新
@Test
public void func4() throws IOException {
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 2. 加载SqlMapConfig.xml配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 3. 创建SqlSessionFactory对象
SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
// 4. 创建SqlSession对象
SqlSession openSession = build.openSession();
UserMapper mapper = openSession.getMapper(UserMapper.class);
User user = new User();
user.setId(31);
user.setAddress("address22");
user.setSex("2");
user.setUsername("jackson2222");
mapper.updateUser(user);
openSession.commit();
}
//删除
@Test
public void func5() throws IOException {
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 2. 加载SqlMapConfig.xml配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 3. 创建SqlSessionFactory对象
SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
// 4. 创建SqlSession对象
SqlSession openSession = build.openSession();
UserMapper mapper = openSession.getMapper(UserMapper.class);
mapper.deleteUserById(31);
openSession.commit();
}
}