在学习Spring完之后简单的了解了MyBatis。然后进行简单的整合，遇到MyBatista接口映射的Bean无法自动注入的问题；

代码异常：

线程“main”org.springframe .bean .factory中的异常。创建名为“UserController”的bean时出错:通过字段“userdao”表示的不满足的依赖关系;嵌套异常是org.springframe .bean .factory。BeanCreationException:在文件[C:\Users\li rui long\eclipse-workspace\MyBatis_Demo\build\classes\com\mybatis\dao\ userdao]中创建名为“userdao”的bean时出错。类]:在设置bean属性“sqlSessionFactory”时无法解析对bean“sqlSessionFactory”的引用;嵌套异常是org.springframe .bean .factory。BeanCreationException:在类路径资源[ApplicationContext]中定义名称为“sqlSessionFactory”的bean创建错误。:设置bean属性“dataSource”时不能解析对bean“dataSource”的引用;嵌套异常是org.springframe .bean .factory。BeanCreationException:创建名为“dataSource”的bean时出错:查找方法解析失败;嵌套异常是java.lang。IllegalStateException:未能从ClassLoader [jdk.internal.loader.ClassLoader . $AppClassLoader@77a567e1]内检类[org.apache.commons.dbcp2.BasicDataSource]

异常提示，控制器层的Bean无法创建，原因是MyBatis对应的映射接口无法完成映射，无法生成DAO层的Bean；

所以问题应该出现在XML文件里，

测试类，13行报错：

 1 package com.mybatis.test;
 2
 3 import org.springframework.context.ApplicationContext;
 4 import org.springframework.context.support.ClassPathXmlApplicationContext;
 5
 6 import com.mybatis.controller.UserController;
 7
 8
 9 public class Test_Controller {
10
11     public static void main(String[] args) {
12         // TODO Auto-generated method stub
13         ApplicationContext app = new ClassPathXmlApplicationContext("ApplicationContext.xml");
14         UserController coll = (UserController) app.getBean("UserController");
15         coll.test();
16     }
17
18 }

对ApplicationContext.xml配置文件进行一步步排查：

<?xml version="1.0" encoding="UTF-8"?>
<beans  xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/txhttp://www.springframework.org/schema/tx/spring-tx.xsd"><!-- 指定需要扫描的包，使注解生效 --><context:component-scan base-package="com.mybatis.po"/><context:component-scan base-package="com.mybatis.dao"/><context:component-scan base-package="com.mybatis.Controller"/><!-- 配置数据源 -->
<bean id="dataSource" class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close"><property name="driverClassName" value = "com.mysql.jdbc.Driver"/><property name="url" value  ="jdbc:mysql://localhost:3306/Springtest?characterEncoding=utf8"/><property name="username" value = "root"/><property name="password" value ="mysql" /><!--  可同时连接的最大的连接数 --><property name="maxActive" value="60" /><!--  最大的空闲的连接数 --><property name="maxTotal" value="60" /><!--  最小的空闲的连接数，低于这个数量会被创建新的连接，默认为0  --><property name="maxIdle" value="5" />          <!-- 连接池启动时创建的初始化连接数量，默认值为0 -->       <property name="initialSize" value="5" /> </bean>  <!-- 添加事务支持 --><bean id = "txManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager"><property name = "dataSource" ref = "dataSource"/></bean><!-- 开启事务注解 --><tx:annotation-driven transaction-manager ="txManager"/><!-- 配置Mybatis工厂，同时指定数据源，并与MyBatista完美结合 --><bean id="sqlSessionFactory" class = "org.mybatis.spring.SqlSessionFactoryBean"><property name="dataSource" ref ="dataSource"/><!-- configLocation 的属性为Mybatis 的核心配置文件 --><property name = "configLocation" value = "classpath:mybatis-config.xml"></property></bean><!-- Mapper 代理开发，使用Spring自动扫描MyBatista的接口并装配 --><!-- Spring 将指定包中所有的被@Mapper注解标注的接口自动装配为MyBatatis的映射接口 --><bean class = "org.mybatis.spring.mapper.MapperScannerConfigurer"><!-- MyBatis-spring组件的扫描器 --><property name="basePackage" value = "com.mybatis.dao"/><property name="sqlSessionFactoryBeanName" value = "sqlSessionFactory"/> </bean></beans>

1. 检查扫描的包名,是否有写错或者少写的。
2. 确定数据源的配置正常，我的问题就出在这里，修改数据库配置信息(密码等)，看是否会报不一样的错，当还是原来的错，说明配置文件没有加载或者数据源错误。我用的DBCP数据源(需要导入两个包DBCP+连接池包)，修改密码后还是报同样的错误所以我尝试着用Spring自带的数据源，解决了问题，正确代码：

    1 <?xml version="1.0" encoding="UTF-8"?>
    2 <beans  xmlns="http://www.springframework.org/schema/beans"
    3         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    4         xmlns:context="http://www.springframework.org/schema/context"
    5         xmlns:tx="http://www.springframework.org/schema/tx"
    6         xsi:schemaLocation="
    7         http://www.springframework.org/schema/beans
    8         http://www.springframework.org/schema/beans/spring-beans.xsd
    9         http://www.springframework.org/schema/context
   10         http://www.springframework.org/schema/context/spring-context.xsd
   11         http://www.springframework.org/schema/tx
   12         http://www.springframework.org/schema/tx/spring-tx.xsd">
   13  <!-- 指定需要扫描的包，使注解生效 -->
   14
   15  <context:component-scan base-package="com.mybatis.po"/>
   16  <context:component-scan base-package="com.mybatis.dao"/>
   17  <context:component-scan base-package="com.mybatis.Controller"/>
   18  <!-- 配置数据源 -->
   19 <bean id = "dataSource" class = "org.springframework.jdbc.datasource.DriverManagerDataSource">
   20  <property name="driverClassName" value = "com.mysql.jdbc.Driver"/>
   21  <property name="url" value  ="jdbc:mysql://localhost:3306/Springtest?characterEncoding=utf8"/>
   22  <property name="username" value = "root"/>
   23  <property name="password" value ="mysql" />
   24  </bean>
   25
   26  <!-- 添加事务支持 -->
   27  <bean id = "txManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager">
   28  <property name = "dataSource" ref = "dataSource"/>
   29  </bean>
   30  <!-- 开启事务注解 -->
   31  <tx:annotation-driven transaction-manager ="txManager"/>
   32  <!-- 配置Mybatis工厂，同时指定数据源，并与MyBatista完美结合 -->
   33  <bean id="sqlSessionFactory" class = "org.mybatis.spring.SqlSessionFactoryBean">
   34      <property name="dataSource" ref ="dataSource"/>
   35      <!-- configLocation 的属性为Mybatis 的核心配置文件 -->
   36      <property name = "configLocation" value = "classpath:mybatis-config.xml"></property>
   37   </bean>
   38   <!-- Mapper 代理开发，使用Spring自动扫描MyBatista的接口并装配 -->
   39   <!-- Spring 将指定包中所有的被@Mapper注解标注的接口自动装配为MyBatatis的映射接口 -->
   40   <bean class = "org.mybatis.spring.mapper.MapperScannerConfigurer">
   41   <!-- MyBatis-spring组件的扫描器 -->
   42   <property name="basePackage" value = "com.mybatis.dao"/>
   43   <property name="sqlSessionFactoryBeanName" value = "sqlSessionFactory"/>
   44   </bean>
   45
   46  </beans>

3. 检查对应的依赖类，配置文件路径能否Ctrl进去。MyBatis的核心文件和映射文件路径是否正确。以下是我的代码：

4. <?xml version="1.0" encoding="UTF-8" ?>
   <!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
   <configuration><mappers><!-- 映射文件--><mapper resource = "com/mybatis/dao/UserMapper.xml"/></mappers>
   </configuration

5. <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
   <mapper namespace = "com.mybatis.dao.UserDao"><!-- 根据ID查询用户信息 --><select id="selectUserById" parameterType = "Integer" resultType = "com.mybatis.po.Myuser">SELECT * FROM user WHERE uid = #{uid}</select><!-- <select id="selectAllUser" resultType = "com.mybatis.po.Myuser">SELECT * FROM user</select>添加一个用户，#{uname}为com.mybatis.po.MyUser属性值<insert id ="addUser" parameterType = "com.mybatis.po.Myuser">INSERT INTO user (uname,usex) VALUES (#{uname},#{usex})</insert>修改一个用户<update id="updateUser" parameterType = "com.mybatis.po.Myuser">UPDATE user SET uname = #{unmae},usex = #{user} where uid = #{uid}</update>删除一个用户<delete id = "delectUser" parameterType = "Integer">DELECT from user WHERE uid = #{uid}</delete> -->
   </mapper >

   看Dao层的接口和Mapped的映射文件是否是在同一包下。

类似问题的博客：

https://blog.csdn.net/h363659487/article/details/74275972

https://blog.csdn.net/u012385190/article/details/53186552

         嗯嗯，第一次写这样的博客，希望会对大家有帮助！！，愿我们都被温柔以待！2019.4.21。