MyBatis的实际应用案例分析

MyBatis是一个优秀的持久层框架，它支持自定义SQL、存储过程以及高级映射。以下是一个简单的MyBatis使用案例，展示了如何配置MyBatis和使用它来查询数据库。

1. 添加MyBatis依赖到项目的pom.xml文件中：

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.6</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.23</version>
</dependency>

2. 创建一个MyBatis配置文件mybatis-config.xml：

<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mydatabase"/>
                <property name="username" value="root"/>
                <property name="password" value="password"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/myapp/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

3. 创建一个映射器接口UserMapper.java：

package org.myapp.mapper;
 
public interface UserMapper {
    User selectUserById(int id);
}

4. 创建映射器接口的XML文件UserMapper.xml：

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.myapp.mapper.UserMapper">
    <select id="selectUserById" resultType="org.myapp.model.User">
        SELECT * FROM users WHERE id = #{id}
    </select>
</mapper>

5. 创建一个实体类User.java：

package org.myapp.model;
 
public class User {
    private int id;
    private String name;
    // getters and setters
}

6. 使用MyBatis来查询数据库：

String resource = "org/myapp/mybatis-config.xml";
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resource);
 
try (SqlSession session = sqlSessionFactory.openSession()) {
    UserMapper mapper = session.getMapper(UserMapper