今天踩到了一个自己造成的坑，记录一下异常处理的分析过程。

1. 项目是SpringBoot集成mybaits-plus，贴出异常

   org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userPictureController': Unsatisfied dependency expressed through field 'memberService';

   
   nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'qwMemberServiceImpl': Unsatisfied dependency expressed through field 'baseMapper';

   
   nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'qwMemberMapper' defined in file [E:\java\scanner\target\classes\com\sjjd\scanpen\mapper\QwMemberMapper.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 [com/baomidou/mybatisplus/spring/boot/starter/MybatisPlusAutoConfiguration.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 [E:\java\scanner\target\classes\com\sjjd\scanpen\mapper\xml\QwExercisePointMapper.xml]';

   
   nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [E:\java\scanner\target\classes\com\sjjd\scanpen\mapper\xml\QwExercisePointMapper.xml]'.

   
   Cause: org.apache.ibatis.builder.BuilderException: Error resolving class.
   Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'com.sjjd.entity.QwExercisePoint'.  
   Cause: java.lang.ClassNotFoundException: Cannot find class: com.sjjd.entity.QwExercisePoint

2. 分析异常：我们从"Cause:"语句开始找原因,直接定位到最后三行
   1. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class.
      Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'com.sjjd.entity.QwExercisePoint'.  
      Cause: java.lang.ClassNotFoundException: Cannot find class: com.sjjd.entity.QwExercisePoint
   2. 解释：
      1. 第一行：类解析错误，导致项目编译异常;
      2. 第二行：无法解析“com.sjjd.entity.QwExercisePoint”别名，导致ibatis类型异常;
      3. 第三行：找不到com.sjjd.entity.QwExercisePoint的java类的异常;
   3. 结论：xxxxmapper.xml文件中 ‘com.sjjd.entity.QwExercisePoint’ java类找不到导致的一系列异常
3. 代码纠正：
   1. 贴出异常发生所在的xml文件

      <?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.sjjd.scanpen.mapper.QwExercisePointMapper">
      
          <!-- 通用查询映射结果 -->
          <resultMap id="BaseResultMap" type="com.sjjd.entity.QwExercisePoint">
              <id column="id" property="id" />
              <result column="point_key" property="pointKey" />
              <result column="point_value" property="pointValue" />
              <result column="eid" property="eid" />
              <result column="jy_subject_id" property="jySubjectId" />
          </resultMap>
      
      </mapper>

   2. 修改：xml文件中的<resultMap id="BaseResultMap" type="com.sjjd.entity.QwExercisePoint"> 全类名编写错误， 有两种修改方案：
      1. 将全类名改为类名“QwExercisePoint”，让mybaits以别名处理，自己找实体类。（这种方式可以在程序员没有发现实体类全类名错误的时候使用，很少有这样的情况，本次是由于代码迁移产生的问题）
      2. 找到实体类位置，改为正确的全类名  。

         <resultMap id="BaseResultMap" type="com.sjjd.scanpen.entity.QwExercisePoint">

              
      3. 按照第二种方式 修改后的代码

         <?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.sjjd.scanpen.mapper.QwExercisePointMapper">
         
             <!-- 通用查询映射结果 -->
             <resultMap id="BaseResultMap" type="com.sjjd.scanpen.entity.QwExercisePoint">
                 <id column="id" property="id" />
                 <result column="point_key" property="pointKey" />
                 <result column="point_value" property="pointValue" />
                 <result column="eid" property="eid" />
                 <result column="jy_subject_id" property="jySubjectId" />
             </resultMap>
         
         </mapper>

   3. 运行结果：以上两种方式都可以编译通过，成功运行