mybatis 主键自增 insert后返回主键

mybatis 主键自增 insert后返回主键 ：

<insert id="insertStudentAutoKey" parameterType="StudentEntity">  
    <selectKey keyProperty="studentID" resultType="String" order="BEFORE">  
            select nextval('student')   
    </selectKey>  
        INSERT INTO STUDENT_TBL (STUDENT_ID,   
                                 STUDENT_NAME,   
                                 STUDENT_SEX,   
                                 STUDENT_BIRTHDAY,   
                                 CLASS_ID)   
              VALUES   (#{studentID},   
                        #{studentName},   
                        #{studentSex},   
                        #{studentBirthday},   
                        #{classEntity.classID})       
</insert>