【Mybatis报错】attempted to return null from a method with a primitive return type (int).-CFANZ编程社区

【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