我的第一个Mybatis程序——Maven项目

1、MyBatis第一个程序

1.1、首先创建Mybatis-config.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">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis/useSSL=true&amp;userUnicode=code&amp;characterEncoding=UTF-8"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>

</configuration>
</>

1.2 编写工具类

//编写工具类
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource="mybatis.config.xml";
        try {
            //使用Mybatis第一步获取配置文件
            InputStream inputStream= Resources.getResourceAsStream(resource);
            SqlSessionFactory factory=new  SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
                e.printStackTrace();
        }
    }
    public static SqlSession gerSqlSession(){
        return sqlSessionFactory.openSession();
       

    }
}

然后需要创建Mapper（Dao）层接口

public interface UserMapper{
List<User> getAllUsers();

}

当然还需要创建实体类

public class User{
int id;
String name;
String pwd;
// 各种setter getter方法 有参构造无参构造
}

我们之前使用mvc分层需要创建Dao层的实现类，但是在Mybatis中实现类改为xml配置文件代替

//将原来的实现类 通过xml文件实现
<?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.MouseFour.Dao">
    <select id="getUserList">
        select * from mybatis.user
    </select>
</mapper>

重点  ：因为mapper文件实在java目录下，可能遇到不会导出的情况，所以需要在pom添加以下配置收手动导出

<build>
        <resources>
            <resource>
                <directory>src/main/resource</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

在Mybatis注册文件中注册Mapper路径 

......
<mappers>
<mapper resource="org/mybatis/example/BlogMapper.xml"/>
</mappers>
......

测试

public class UserDaoTest {
    @Test
    public void test(){
        //第一步获取sqlsession对象
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(new Gson().toJson(user));
        }
        sqlSession.close();

    }
}