MyBatis：Day 04

框架

1. 依赖：pom.xml

<dependencies>
    <!-- mysql 数据库驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.16</version>
    </dependency>

    <!-- MyBatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.7</version>
    </dependency>

    <!-- junit -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>

    <!-- lombok -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.24</version>
    </dependency>
</dependencies>


<!-- 在 build 中配置 resources，来防止我们资源导出失败的问题 -->
<build>
    <resources>
        <resource>
            <directory>src/main/resources</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>

2. 外部配置文件：db.properties

drive=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/数据库名?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=Asia/Shanghai
username=xxx
password=xxx

3. 核心配置文件：mybatis-config.xml

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- configuration 核心配置文件 -->
<configuration>

    <properties resource="db.properties"/>
    
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <typeAliases>
        <typeAlias type="com.Sun3285.pojo.xxx" alias="xxx"/>
        <!--<package name="com.Sun3285.pojo"/>-->
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${drive}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 每一个 Mapper.xml 都需要在 Mybatis 核心配置文件中注册 -->
    <mappers>
        <mapper resource="com/Sun3285/dao/xxxMapper.xml"/>
        <!--<mapper class="com.Sun3285.dao.xxxMapper"/>-->
        <!--<package name="com.Sun3285.dao"/>-->
    </mappers>
</configuration>

4. 工具类：MybatisUtils.java

public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory = null;
    static {
        try {
            // 第一步：获取 sqlSessionFactory 对象
            String resource = "mybatis-config.xml";
            InputStream is = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 第二步：获取 sqlSession 对象
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession(true);
    }
}

5. 实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class 实体类 implements Serializable {
    private int xxx;
    private String xxx;
}

6. 接口：xxxMapper.java

public interface xxxMapper {
    
    // 方法
    返回值类型 方法名(@Param("xxx") int xxx);
}

7. 实现类：xxxMapper.xml

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.Sun3285.dao.xxxMapper">

    <cache/>

    <select id="方法名" parameterType="参数类型" resultType="返回值类型">
        sql 语句
    </select>

</mapper>

8. 测试

public class Tset01 {
    @Test
    public void test01() {

        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(xxxMapper.class);

        mapper.方法
        xxxxxx
        
        sqlSession.close();
    }
}