spring整合mybatis接口無法注入問題

在學習Spring完之後簡單的瞭解了MyBatis。然後進行簡單的整合，遇到MyBatista接口映射的Bean無法自動注入的問題；

代碼異常：

線程“main”org.springframe .bean .factory中的異常。創建名爲“UserController”的bean時出錯:通過字段“userdao”表示的不滿足的依賴關係;嵌套異常是org.springframe .bean .factory。BeanCreationException:在文件[C:\Users\li rui long\eclipse-workspace\MyBatis_Demo\build\classes\com\mybatis\dao\ userdao]中創建名爲“userdao”的bean時出錯。類]:在設置bean屬性“sqlSessionFactory”時無法解析對bean“sqlSessionFactory”的引用;嵌套異常是org.springframe .bean .factory。BeanCreationException:在類路徑資源[ApplicationContext]中定義名稱爲“sqlSessionFactory”的bean創建錯誤。:設置bean屬性“dataSource”時不能解析對bean“dataSource”的引用;嵌套異常是org.springframe .bean .factory。BeanCreationException:創建名爲“dataSource”的bean時出錯:查找方法解析失敗;嵌套異常是java.lang。IllegalStateException:未能從ClassLoader [jdk.internal.loader.ClassLoader . $AppClassLoader@77a567e1]內檢類[org.apache.commons.dbcp2.BasicDataSource]

異常提示，控制器層的Bean無法創建，原因是MyBatis對應的映射接口無法完成映射，無法生成DAO層的Bean；

所以問題應該出現在XML文件裏，

測試類，13行報錯：

 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 }

對ApplicationContext.xml配置文件進行一步步排查：

<?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">
 <!-- 指定需要掃描的包，使註解生效 -->

 <context:component-scan base-package="com.mybatis.po"/>
 <context:component-scan base-package="com.mybatis.dao"/>
 <context:component-scan base-package="com.mybatis.Controller"/>
 <!-- 配置數據源 -->
<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" />
       <!--  可同時連接的最大的連接數 -->
        <property name="maxActive" value="60" />
       <!--  最大的空閒的連接數 -->
        <property name="maxTotal" value="60" />
       <!--  最小的空閒的連接數，低於這個數量會被創建新的連接，默認爲0  -->
        <property name="maxIdle" value="5" />          
        <!-- 連接池啓動時創建的初始化連接數量，默認值爲0 -->       
        <property name="initialSize" value="5" /> 
 </bean>  
 <!-- 添加事務支持 -->
 <bean id = "txManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager">
 <property name = "dataSource" ref = "dataSource"/>
 </bean>
 <!-- 開啓事務註解 -->
 <tx:annotation-driven transaction-manager ="txManager"/>
 <!-- 配置Mybatis工廠，同時指定數據源，並與MyBatista完美結合 -->
 <bean id="sqlSessionFactory" class = "org.mybatis.spring.SqlSessionFactoryBean">
     <property name="dataSource" ref ="dataSource"/>
     <!-- configLocation 的屬性爲Mybatis 的核心配置文件 -->
     <property name = "configLocation" value = "classpath:mybatis-config.xml"></property>
  </bean>
  <!-- Mapper 代理開發，使用Spring自動掃描MyBatista的接口並裝配 -->
  <!-- Spring 將指定包中所有的被@Mapper註解標註的接口自動裝配爲MyBatatis的映射接口 -->
  <bean class = "org.mybatis.spring.mapper.MapperScannerConfigurer">
  <!-- MyBatis-spring組件的掃描器 -->
  <property name="basePackage" value = "com.mybatis.dao"/>
  <property name="sqlSessionFactoryBeanName" value = "sqlSessionFactory"/> 
  </bean>
  
 </beans>

檢查掃描的包名,是否有寫錯或者少寫的。

確定數據源的配置正常，我的問題就出在這裏，修改數據庫配置信息(密碼等)，看是否會報不一樣的錯，當還是原來的錯，說明配置文件沒有加載或者數據源錯誤。我用的DBCP數據源(需要導入兩個包DBCP+連接池包)，修改密碼後還是報同樣的錯誤所以我嘗試着用Spring自帶的數據源，解決了問題，正確代碼：

 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  <!-- 指定需要掃描的包，使註解生效 -->
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  <!-- 配置數據源 -->
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  <!-- 添加事務支持 -->
27  <bean id = "txManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager">
28  <property name = "dataSource" ref = "dataSource"/>
29  </bean>
30  <!-- 開啓事務註解 -->
31  <tx:annotation-driven transaction-manager ="txManager"/>
32  <!-- 配置Mybatis工廠，同時指定數據源，並與MyBatista完美結合 -->
33  <bean id="sqlSessionFactory" class = "org.mybatis.spring.SqlSessionFactoryBean">
34      <property name="dataSource" ref ="dataSource"/>
35      <!-- configLocation 的屬性爲Mybatis 的核心配置文件 -->
36      <property name = "configLocation" value = "classpath:mybatis-config.xml"></property>
37   </bean>
38   <!-- Mapper 代理開發，使用Spring自動掃描MyBatista的接口並裝配 -->
39   <!-- Spring 將指定包中所有的被@Mapper註解標註的接口自動裝配爲MyBatatis的映射接口 -->
40   <bean class = "org.mybatis.spring.mapper.MapperScannerConfigurer">
41   <!-- MyBatis-spring組件的掃描器 -->
42   <property name="basePackage" value = "com.mybatis.dao"/>
43   <property name="sqlSessionFactoryBeanName" value = "sqlSessionFactory"/> 
44   </bean>
45   
46  </beans>

檢查對應的依賴類，配置文件路徑能否Ctrl進去。MyBatis的核心文件和映射文件路徑是否正確。以下是我的代碼：

<?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

<?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">
    <!-- 根據ID查詢用戶信息 -->
    <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>
    添加一個用戶，#{uname}爲com.mybatis.po.MyUser屬性值
    <insert id ="addUser" parameterType = "com.mybatis.po.Myuser">
    INSERT INTO user (uname,usex) VALUES (#{uname},#{usex})
    </insert>
    修改一個用戶
    <update id="updateUser" parameterType = "com.mybatis.po.Myuser">
    UPDATE user SET uname = #{unmae},usex = #{user} where uid = #{uid}
    </update>
    刪除一個用戶
    <delete id = "delectUser" parameterType = "Integer">
    DELECT from user WHERE uid = #{uid}
    </delete> -->
</mapper >

看Dao層的接口和Mapped的映射文件是否是在同一包下。

類似問題的博客：

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

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

嗯嗯，第一次寫這樣的博客，希望會對大家有幫助！！，願我們都被溫柔以待！2019.4.21。

原文出處：https://www.cnblogs.com/liruilong/p/10744962.html

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