spring整合mybatis接口无法注入问题

          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:Usersli rui longeclipse-workspaceMyBatis_Demouildclassescommybatisdao 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：

package com.mybatis.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.mybatis.controller.UserController;


public class Test_Controller {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ApplicationContext app = new ClassPathXmlApplicationContext("ApplicationContext.xml");
        UserController coll = (UserController) app.getBean("UserController");
        coll.test();
    }

}

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/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx
        http://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：

   <?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/beans
           http://www.springframework.org/schema/beans/spring-beans.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context.xsd
           http://www.springframework.org/schema/tx
           http://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.springframework.jdbc.datasource.DriverManagerDataSource">
    <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" />
    </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>

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 configuration
           PUBLIC "-//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 mapper
     PUBLIC "-//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。