【Mybatis报错】attempted to return null from a method with a primitive return type (int).

我在做分页查询时报错，场景是这样的:

• mapper.xml 中sql语句如下

   <select id="selectTotalCount" resultMap="brandResultMap">
          select count(*) from tb_brand;
      </select>

• dao层接口如下

  int selectTotalCount();

• Service层

    public PageBean<Brand> SelectByPage(int currentPage, int pageSize) {
          SqlSession sqlSession = factory.openSession();
          BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
          int begin = (currentPage-1)*pageSize;
          int size = pageSize;
          List<Brand> brands = brandMapper.selectByPage(begin, size);
          int totalCount = brandMapper.selectTotalCount();
          PageBean<Brand> pg = new PageBean<>();
          pg.setRows(brands);
          pg.setTotalCount(totalCount);
  
          sqlSession.close();
          return pg;
      }

  报错如下

  Caused by: org.apache.ibatis.binding.BindingException: Mapper method 'com.itheima.mapper.BrandMapper.selectTotalCount attempted to return null from a method with a primitive return type (int).
  	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:102)
  	at org.apache.ibatis.binding.MapperProxy$PlainMethodInvoker.invoke(MapperProxy.java:152)
  	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:85)
  	at com.sun.proxy.$Proxy28.selectTotalCount(Unknown Source)
  	at com.itheima.service_20211015_114634.impl.BrandServiceImpl.SelectByPage(BrandServiceImpl.java:50)
  	at com.itheima.web.servlet.BrandServlet.selectByPage(BrandServlet.java:57)
  	... 25 more

  网上查询后发现必须将dao层的int数值类型改成Integer类型，修改后还是报错，后来又查到要把mapper.java和mapper.xml文件中的所有int类型都要改成Integer，全都修改后，终于运行成功