Mybatis (a)

Development environment to build Mybatis

创建 mybatis01 的工程，工程信息如下：
Groupid:com.itheima
ArtifactId:mybatis01
Packing:jar

Add coordinates of Mybatis3.4.5

在 pom.xml 文件中添加 Mybatis3.4.5 的坐标，如下：
<dependencies>
   <dependency>
     <groupId>org.mybatis</groupId>
     <artifactId>mybatis</artifactId>
     <version>3.4.5</version>
   </dependency>
   <dependency>
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
     <version>4.10</version>
     <scope>test</scope>
   </dependency>
   <dependency>
     <groupId>mysql</groupId>
     <artifactId>mysql-connector-java</artifactId>
     <version>5.1.6</version>
     <scope>runtime</scope>
   </dependency>
   <dependency>
      <groupId>log4j</groupId>
     <artifactId>log4j</artifactId>
     <version>1.2.12</version>
   </dependency>
</dependencies>

Write User entity class

/**
* 
* <p>Title: User</p>
* <p>Description: 用户的实体类</p>
* <p>Company: http://www.itheima.com/ </p>
*/
public class User implements Serializable {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;
    省略getter,setter，toString方法

Write the persistence layer interface IUserDao

IUserDao 接口就是我们的持久层接口（也可以写成 UserDao 或者 UserMapper）,具体代码如下：
/**
* <p>Title: IUserDao</p>
* <p>Description: 用户的持久层操作</p>
* <p>Company: http://www.itheima.com/ </p>
*/
public interface IUserDao {
    /**
    * 查询所有用户
    * @return
    */
    List<User> findAll();
}

Write the persistence layer interface mapping file IUserDao.xml

demo.png

<?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.itheima.dao.IUserDao">
    <!-- 配置查询所有操作 -->
      <select id="findAll" resultType="com.itheima.domain.User">
        select * from user
      </select>
</mapper>

SqlMapConfig.xml profile

<?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>
    <!-- 配置 mybatis 的环境 -->
    <environments default="mysql">
        <!-- 配置 mysql 的环境 -->
        <environment id="mysql">
            <!-- 配置事务的类型 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置连接数据库的信息：用的是数据源(连接池) -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/ee50"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
   </environments>
   <!-- 告知 mybatis 映射配置的位置 -->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>
</configuration>

Write test classes

/**
* 
* <p>Title: MybatisTest</p>
* <p>Description: 测试 mybatis 的环境</p>
* <p>Company: http://www.itheima.com/ </p>
*/
public class MybatisTest {
      public static void main(String[] args)throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建 SqlSessionFactory 的构建者对象
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        //3.使用构建者创建工厂对象 SqlSessionFactory
        SqlSessionFactory factory = builder.build(in);
        //4.使用 SqlSessionFactory 生产 SqlSession 对象
        SqlSession session = factory.openSession();
        //5.使用 SqlSession 创建 dao 接口的代理对象
        IUserDao userDao = session.getMapper(IUserDao.class);
        //6.使用代理对象执行查询所有方法
        List<User> users = userDao.findAll();
        for(User user : users) {
            System.out.println(user);
        }
        //7.释放资源
        session.close();
        in.close();
  }
}

Annotation-based mybatis

Add comment

public interface IUserDao {
/**
* 查询所有用户
* @return
*/
@Select("select * from user")
List<User> findAll();
}

Modify the configuration SqlMapConfig.xml

<!-- 告知 mybatis 映射配置的位置 -->
<mappers>
    <mapper class="com.itheima.dao.IUserDao"/>
</mappers>

Other above: