关于attempted to return null from a method with a primitive return type (int).报错解决方案

使用mybatis返回int类型时

    <select id="queryPerfTarget" resultType="java.lang.Integer" >
        SELECT sum(perf_target) from subject
    select>

项目总是报错

org.apache.ibatis.binding.BindingException: Mapper method 'queryPerfTarget' (interface com.****.workbench.subject.dao.SubjectMapper) attempted to return null from a method with a primitive return type (int).

解决方案：（当查询出来为空时，给赋值一个默认值：MySQL使用函数ifnull()）

<select id="queryPerfTarget" resultType="java.lang.Integer" >
        SELECT IFNULL(sum(perf_target),0) from subject
select>