springboot项目中后端处理逻辑的核心代码是在mapper.xml文件中吗？
xml version="1.0" encoding="UTF-8"?>
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<select id="getPage" resultType="com.rainng.studentinformationsystem.model.vo.response.table.StudentCourseItemVO">
SELECT sc_id AS 'id', course_name AS 'courseName', student_name AS 'studentName', class_name AS 'className',
sc_daily_score AS 'dailyScore', sc_exam_score AS 'examScore', sc_score AS 'score'
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_student on sc_student_id = student_id
JOIN rc_class on student_class_id = class_id
<where>
<if test="className != null and className != ''">
AND class_name LIKE CONCAT('%',#{className},'%')
if>
<if test="courseName != null and courseName != ''">
AND course_name LIKE CONCAT('%',#{courseName},'%')
if>
<if test="studentName != null and studentName != ''">
AND student_name LIKE CONCAT('%',#{studentName},'%')
if>
where>
select>
<select id="count" resultType="java.lang.Integer">
SELECT COUNT(*)
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_student on sc_student_id = student_id
JOIN rc_class on student_class_id = class_id
<where>
<if test="className != null and className != ''">
AND class_name LIKE CONCAT('%',#{className},'%')
if>
<if test="courseName != null and courseName != ''">
AND course_name LIKE CONCAT('%',#{courseName},'%')
if>
<if test="studentName != null and studentName != ''">
AND student_name LIKE CONCAT('%',#{studentName},'%')
if>
where>
select>
<select id="listStudentCourseSelected" resultType="com.rainng.studentinformationsystem.model.vo.response.table.StudentCourseSelectedItemVO">
SELECT sc_id AS 'studentCourseId',
course_name AS 'courseName',
teacher_name AS 'teacherName',
course_credit AS 'credit',
sc_daily_score AS 'dailyScore',
sc_exam_score AS 'examScore',
sc_score AS 'score'
FROM rc_student_course
JOIN rc_student on sc_student_id = student_id
JOIN rc_course on sc_course_id = course_id
JOIN rc_teacher on course_teacher_id = teacher_id
WHERE student_id = #{studentId}
select>
<select id="listStudentExam" resultType="com.rainng.studentinformationsystem.model.vo.response.table.StudentExamItemVO">
SELECT sc_id AS 'studentCourseId',
course_name AS 'courseName',
teacher_name AS 'teacherName',
course_exam_date 'examDate',
course_exam_location AS 'examLocation'
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_student on sc_student_id = student_id
JOIN rc_teacher on course_teacher_id = teacher_id
WHERE student_id = #{studentId}
AND course_exam_date IS NOT NULL
AND course_exam_location IS NOT NULL
AND sc_exam_score IS NULL
select>
<select id="countStudentCourseSelectedByTimePart" resultType="java.lang.Integer">
SELECT COUNT(*)
FROM rc_student_course
JOIN rc_student on sc_student_id = student_id
JOIN rc_course on sc_course_id = course_id
WHERE student_id = #{studentId}
AND course_time LIKE CONCAT(#{timePart}, '-%')
select>
<select id="listStudentTimetable" resultType="com.rainng.studentinformationsystem.model.vo.response.table.TimetableItemVO">
SELECT course_time AS 'time',
course_name AS 'courseName',
teacher_name AS 'teacherName',
course_location AS 'location'
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_teacher on course_teacher_id = teacher_id
WHERE sc_student_id = #{studentId}
select>
<select id="getTeacherGradePage" resultType="com.rainng.studentinformationsystem.model.vo.response.table.TeacherGradeItemVO">
SELECT sc_id AS 'studentCourseId', course_name AS 'courseName',
student_name AS 'studentName', sc_daily_score AS 'dailyScore',
sc_exam_score AS 'examScore', sc_score AS 'score'
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_student on sc_student_id = student_id
JOIN rc_teacher on course_teacher_id = teacher_id
<where>
AND teacher_id = #{teacherId}
<if test="courseName != null and courseName != ''">
AND course_name LIKE CONCAT('%',#{courseName},'%')
if>
<if test="studentName != null and studentName != ''">
AND student_name LIKE CONCAT('%',#{studentName},'%')
if>
where>
select>
<select id="countTeacherGrade" resultType="java.lang.Integer">
SELECT COUNT(*)
FROM rc_student_course
JOIN rc_course on sc_course_id = course_id
JOIN rc_student on sc_student_id = student_id
JOIN rc_teacher on course_teacher_id = teacher_id
<where>
AND teacher_id = #{teacherId}
<if test="courseName != null and courseName != ''">
AND course_name LIKE CONCAT('%',#{courseName},'%')
if>
<if test="studentName != null and studentName != ''">
AND student_name LIKE CONCAT('%',#{studentName},'%')
if>
where>
select>
这里都是select语句，为何选课时会有容量超过上限的错误提示，猜测可能与listStudentCourseSelected这个id有关。设计思路是设置一个课程容量，用选一次课程容量减一。当课程容量减为0时，就会提示超过上限。貌似xml文件里只有查询语句，删除和修改以及增加的处理逻辑一般放在哪里？
你有 mapper.xml 这个文件说明你的dao层用的是 mybatis，你的xml里面只有select语句没有插入语句。
如果你不是用的mybatis-plus的话，你的代码就没有更新和插入语句。
你可以将更新和插入逻辑写在你的mapper.xml文件中。
至于你说的选课容量，应该是你的代码逻辑控制的。容量的控制加减明显也不在这个xml里面
Springboot项目的核心代码主要在src目录下，会根据功能的不同分为几个不同的层，如实体层、服务层等。xml文件一般是配置文件。
不知道你这个问题是否已经解决, 如果还没有解决的话:答案:
通常情况下，增加，删除以及修改的处理逻辑不在mapper.xml文件中，而是在对应的service类中实现的。mapper.xml主要负责SQL查询语句的编写。对于设置课程容量以及选课逻辑，可以在对应的service类中实现。具体步骤如下：
在service类中定义一个变量用于存储课程容量，例如int capacity = 30;
编写一个选课方法，用于判断课程容量是否足够，如果足够则进行选课操作，并将课程容量减一；否则提示超过上限。例如：
@Service
public class CourseService {
private int capacity = 30;
public boolean selectCourse(Student student, Course course) {
if (capacity > 0) {
// 课程容量足够，进行选课操作
// TODO: 将选课记录插入数据库中
capacity--;
return true;
} else {
// 课程容量不足，提示超过上限
System.out.println("超过课程容量上限！");
return false;
}
}
}
@RestController
@RequestMapping("/course")
public class CourseController {
@Autowired
private CourseService courseService;
@PostMapping("/select")
public boolean selectCourse(Student student, Course course) {
return courseService.selectCourse(student, course);
}
}
当然，如果需要将选课记录插入数据库，可以在mapper.xml文件中编写对应的insert语句，并在相应的service类中调用mapper提供的insert方法来实现。例如：
<insert id="insertCourseSelection" parameterType="com.example.demo.entity.CourseSelection">
insert into course_selection (student_id, course_id)
values (#{student.id}, #{course.id})
</insert>
@Service
public class CourseService {
@Autowired
private CourseSelectionMapper courseSelectionMapper;
public boolean selectCourse(Student student, Course course) {
// TODO: 判断课程容量是否足够
// 将选课记录插入数据库
CourseSelection courseSelection = new CourseSelection();
courseSelection.setStudent(student);
courseSelection.setCourse(course);
courseSelectionMapper.insertCourseSelection(courseSelection);
// 更新课程容量
// TODO: 更新课程容量
return true;
}
}