Error creating bean with name

最近在學一個東西，要使用SSM新建一個案例，是這樣滴，我有以下

1. DeptDAO
2. DeptService
3. DeptServiceImpl
4. DeptController
5. Dept
6. Mybatis

首先，我不是太清楚有了DAO還要有Service，不過這個不是本文章的重點。

重點是，報以下錯，兩個不一樣的錯誤吧

錯誤1：

2019-04-02 22:09:08.697 ERROR 12080 --- [nio-8001-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.vae.springcloud.dao.DeptDAO.findAll] with root cause

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.vae.springcloud.dao.DeptDAO.findAll

錯誤2：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'deptController': Unsatisfied dependency expressed through field 'deptService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'deptServiceImpl': Unsatisfied dependency expressed through field 'deptDAO'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'deptDAO' defined in file [D:\Java Code\SpringCloud\provider\target\classes\com\vae\springcloud\dao\DeptDAO.class]: Unsatisfied dependency expressed through bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\Java Code\SpringCloud\provider\target\classes\mybatis\mapper\DeptMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\Java Code\SpringCloud\provider\target\classes\mybatis\mapper\DeptMapper.xml]'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.vae.springcloud.dao.DeptDAO.findAll. please check mybatis/mapper/DeptMapper.xml and file [D:\Java Code\SpringCloud\provider\target\classes\mybatis\mapper\DeptMapper.xml]

很奇怪的錯誤，我看錯誤說沒有bean，我在網上搜啊搜，網上的文章要麼是抄襲的，要麼是複製粘貼的，要麼解釋的答案簡單的很，根本沒有上升到我這個層次。我糾結了好幾天，最終發現，錯誤竟然是！！！竟然是Mybatis的配置文件！！

我本身寫的mybatis文章裏面，說道，mybatis加載mapper.xml須要這樣

<!-- 加載映射文件-->
    <mappers>
        <mapper resource="config/Message.xml"/>
    </mappers>

這樣是可行，可是，這就是形成我錯誤的緣由。這種方式，我當時使用的是SqlSession來主動加載Mybatis文件的，如今我想自動的去映射，就不能這麼寫了，須要在yml配置文件裏面寫

mybatis:
  config-location: classpath:mybatis/mybatis.cfg.xml        # mybatis配置文件所在路徑
  type-aliases-package: com.atguigu.springcloud.entities    # 全部Entity別名類所在包
  mapper-locations: classpath:mybatis/mapper/**/*.xml        # mapper映射文件

總之，此次的錯誤，徹底是由於我不熟悉Mybatis形成的，爲此困惑了好多天。

順便一提，我正在學習的這個項目是SpringCloud，學會以後，我會專門去詳細的講SpringCloud。到時再提一提這個由於個人無知而形成的報錯。