搭建一个简单的Mybatis+Maven项目

Maven依赖

  <!-- 添加log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.16</version>
        </dependency>
        <!-- 添加mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.6</version>
        </dependency>
        <!-- 添加mysql驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.12</version>
        </dependency>
        <!-- 添加junit驱动 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.14.8</version>
        </dependency>

代码

@Data
public class Student {
    private Long id;
    private String name;
}

public interface StudentDao {
        public void insert(Student student);
        public Student findUserById (int id);
        public List<Student> findAllUsers();
}

public class StudentDaoTest {
    @Test
    public void findUserById() {
        SqlSession sqlSession = getSessionFactory().openSession();
        StudentDao userMapper = sqlSession.getMapper(StudentDao.class);
        Student user = userMapper.findUserById(1);
        System.out.println(user.toString());
    }

    //Mybatis 通过SqlSessionFactory获取SqlSession, 然后才能通过SqlSession与数据库进行交互
    private static SqlSessionFactory getSessionFactory() {
        SqlSessionFactory sessionFactory = null;
        String resource = "configuration.xml";
        try {
            sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(resource));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sessionFactory;
    }
}

配置文件

//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>

    <!-- 指定properties配置文件， 我这里面配置的是数据库相关 -->
    <properties resource="dbConfig.properties"></properties>
    <!-- 指定Mybatis使用log4j -->
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/student"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 映射文件，mybatis精髓， 后面才会细讲 -->
    <mappers>
        <mapper resource="userDao-mapping.xml"/>
    </mappers>
</configuration>
//userDao-mapping.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
        "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="com.mybatis.StudentDao">
    <select id="findUserById" resultType="com.mybatis.Student" >
        select * from student where id = #{id}
    </select>
</mapper>   

通过SqlSessionFactory获取SqlSession

执行流程

获取MapperProxy

执行流程

获取Excutor

执行流程