From e5fbb445cf2b2cf36badbc0f3d9e40b61d1f051b Mon Sep 17 00:00:00 2001
From: lbw <1192299468@qq.com>
Date: Mon, 15 Dec 2025 16:37:42 +0800
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- 新增StudentDOMapper接口方法selectStudentCountByClassId，用于查询班级下学生数量
- 在ClassServiceImpl中注入StudentDOMapper
- 删除班级时先判断班级下是否存在学生，若存在则抛出异常防止删除
- 更新StudentDOMapper.xml，添加对应的SQL查询语句selectStudentCountByClassId
---
 .../enlish/service/domain/mapper/StudentDOMapper.java      | 2 ++
 .../enlish/service/service/classs/ClassServiceImpl.java    | 7 +++++++
 .../src/main/resources/mapper/StudentDOMapper.xml          | 7 +++++++
 3 files changed, 16 insertions(+)

diff --git a/enlish-service/src/main/java/com/yinlihupo/enlish/service/domain/mapper/StudentDOMapper.java b/enlish-service/src/main/java/com/yinlihupo/enlish/service/domain/mapper/StudentDOMapper.java
index 3931254..ce85bcc 100644
--- a/enlish-service/src/main/java/com/yinlihupo/enlish/service/domain/mapper/StudentDOMapper.java
+++ b/enlish-service/src/main/java/com/yinlihupo/enlish/service/domain/mapper/StudentDOMapper.java
@@ -19,4 +19,6 @@ public interface StudentDOMapper {
 
     // 逻辑删除
     void deleteById(Integer id);
+
+    int selectStudentCountByClassId(@Param("classId") Integer classId);
 }
\ No newline at end of file
diff --git a/enlish-service/src/main/java/com/yinlihupo/enlish/service/service/classs/ClassServiceImpl.java b/enlish-service/src/main/java/com/yinlihupo/enlish/service/service/classs/ClassServiceImpl.java
index c7eed27..5e5271f 100644
--- a/enlish-service/src/main/java/com/yinlihupo/enlish/service/service/classs/ClassServiceImpl.java
+++ b/enlish-service/src/main/java/com/yinlihupo/enlish/service/service/classs/ClassServiceImpl.java
@@ -6,6 +6,7 @@ import com.yinlihupo.enlish.service.domain.dataobject.GradeDO;
 import com.yinlihupo.enlish.service.domain.mapper.ClassDOMapper;
 import com.yinlihupo.enlish.service.domain.mapper.GradeClassDOMapper;
 import com.yinlihupo.enlish.service.domain.mapper.GradeDOMapper;
+import com.yinlihupo.enlish.service.domain.mapper.StudentDOMapper;
 import com.yinlihupo.enlish.service.service.ClassService;
 import jakarta.annotation.Resource;
 import org.springframework.stereotype.Service;
@@ -24,6 +25,8 @@ public class ClassServiceImpl implements ClassService {
     private GradeClassDOMapper gradeClassDOMapper;
     @Resource
     private GradeDOMapper gradeDOMapper;
+    @Resource
+    private StudentDOMapper studentDOMapper;
 
     @Override
     public ClassDO findClassById(Integer id) {
@@ -82,6 +85,10 @@ public class ClassServiceImpl implements ClassService {
 
     @Override
     public void deleteClass(Integer classId) {
+        int selectStudentCountByClassId = studentDOMapper.selectStudentCountByClassId(classId);
+        if (selectStudentCountByClassId > 0) {
+            throw new RuntimeException("该班级下有学生，请先删除该班级下的学生");
+        }
         classDOMapper.delete(classId);
     }
 }
diff --git a/enlish-service/src/main/resources/mapper/StudentDOMapper.xml b/enlish-service/src/main/resources/mapper/StudentDOMapper.xml
index f6ad208..8f323fd 100644
--- a/enlish-service/src/main/resources/mapper/StudentDOMapper.xml
+++ b/enlish-service/src/main/resources/mapper/StudentDOMapper.xml
@@ -61,4 +61,11 @@
         set is_deleted = 1
         where id = #{id}
     </update>
+
+    <select id="selectStudentCountByClassId" resultType="java.lang.Integer">
+        select count(1)
+        from student
+        where class_id = #{classId}
+            and is_deleted = 0
+    </select>
 </mapper>
\ No newline at end of file