Maven项目中Mybatis的使用

mybatis-config.xml配置文件的注意事项：

1.在Maven项目需要在pom.xml里面配置路径映射,如下代码：

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

资源类一般统一放在resourses目录下，以上配置相当于在src/main/java路径下和src/main/resources路径下配置了.xml和.properteis两种后缀文件的映射，之后把mybatis-config.xml文件放在resources目录下就可以了。

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2.报错：找不到资源配置路径

java.io.IOException: Could not find resource mybatis-config.xml

原因：经查找可能是未缓存pom.xml文件
解决方法：Maven clean清除缓存，然后重新compile即可。

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3.报错：无法获取数据驱动

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver
### The error may exist in src/main/recourses/EmployeeMapper.xml
### The error may involve mybatis.EmployeeMapper.selectEmp
### The error occurred while executing a query
### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.cj.jdbc.Driver

解决方案：
①确保Maven工程成功导入数据库连接的依赖

	<dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.49</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.12</version>
      <scope>compile</scope>
    </dependency>

②确保主配置文件数据库的连接配置无误

<dataSource type="POOLED">
       <property name="driver" value="com.mysql.jdbc.Driver"/>
       <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
       <property name="username" value="root"/>
       <property name="password" value="root"/>
</dataSource>