靴子。在我的系统中，有两个模型命名为主题，课程（表名称主题，课程并通过外键course_id连接）。addSubject 表单中有一个下拉菜单，我们可以在其中选择课程名称。但是当我尝试将其保存在数据库中时（当我单击保存按钮时），我收到错误无法添加或更新子行：外键约束失败（sampledb。主题、约束courseId_fk外键 （course_code） 引用课程（代码）在更新级联上删除级联）。请帮我解决这个问题。
主题控制器
@Entity
@Table(name="subjects")
@EntityListeners(AuditingEntityListener.class)
public class Subject {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String subject_code;
private String name;
private String hall_code;
private String course_code;
public Subject() {
}
public Subject(String subject_code, String name, String hall_code, String course_code) {
this.subject_code = subject_code;
this.name = name;
this.hall_code = hall_code;
this.course_code = course_code;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getSubject_code() {
return subject_code;
}
public void setSubject_code(String subject_code) {
this.subject_code = subject_code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getHall_code() {
return hall_code;
}
public void setHall_code(String hall_code) {
this.hall_code = hall_code;
}
public String getCourse_code() {
return course_code;
}
public void setCourse_code(String course_code) {
this.course_code = course_code;
}
}
课程道
@Service
public class CourseDAO {
@Autowired
CourseRepository courseRepository;
//to save a course
public Course save(Course course){
return courseRepository.save(course);
}
//to search all courses
public List<Course> findAll(){
return courseRepository.findAll();
}
//get a course by id
public Course findById(Long id){
return courseRepository.findById(id).orElse(null);
}
//delete a course
public void delete(Long id){
courseRepository.deleteById(id);
}
}
课程模式
@Entity
@Table(name="courses")
@EntityListeners(AuditingEntityListener.class)
public class Course {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@NotNull
private int code;
private String name;
public Course() {
}
public Course(@NotNull int code, String name) {
this.code = code;
this.name = name;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public int getCode() {
return code;
}
public void setCode(int code) {
this.code = code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
添加主题表单
<!DOCTYPE html>
<html xmlns:th="https://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Adding a Subject</title>
</head>
<body>
<div align="center">
<h1>Add a new Subject</h1>
<br/>
<form action="#" th:action="@{/subject/save}" th:object="${subject}" method="post">
<table border="0" cell[adding="10">
<tr>
<td>Subject code:</td>
<td><input type="text" th:field="*{subject_code}" /></td>
</tr>
<tr>
<td>Subject Name:</td>
<td><input type="text" th:field="*{name}" /></td>
</tr>
<tr>
<td>Course:</td>
<td>
<select th:field="*{course_code}">
<option value="">Choose..</option>
<option th:each="course: ${courses}" th:value="${course.id}" th:text="${course.name}" />
</select>
</td>
</tr>
<tr>
<td colspan="2"><button type="submit">Save</button></td>
</tr>
</table>
</form>
</div>
</body>
</html>
主题模型
@Entity
@Table(name="subjects")
@EntityListeners(AuditingEntityListener.class)
public class Subject {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String subject_code;
private String name;
private String hall_code;
private String course_code;
public Subject() {
}
public Subject(String subject_code, String name, String hall_code, String course_code) {
this.subject_code = subject_code;
this.name = name;
this.hall_code = hall_code;
this.course_code = course_code;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getSubject_code() {
return subject_code;
}
public void setSubject_code(String subject_code) {
this.subject_code = subject_code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getHall_code() {
return hall_code;
}
public void setHall_code(String hall_code) {
this.hall_code = hall_code;
}
public String getCourse_code() {
return course_code;
}
public void setCourse_code(String course_code) {
this.course_code = course_code;
}
}
主题道
@Service
public class SubjectDAO {
@Autowired
SubjectRepository subjectRepository;
//to save a subject
public Subject save(Subject subject){
return subjectRepository.save(subject);
}
//to search all subjects
public List<Subject> findAll(){
return subjectRepository.findAll();
}
//get a subject by id
public Subject findById(Long id){
return subjectRepository.findById(id).orElse(null);
}
//delete a subject
public void delete(Long id){
subjectRepository.deleteById(id);
}
}
错误由以下原因引起：org.springframework.beans.NotReadableProperty异常：Bean 类 [com.project.attendance.model.Subject] 的属性“course”无效：Bean 属性“course”不可读或具有无效的 getter 方法：getter 的返回类型是否与 setter 的参数类型匹配？
我不得不 course.id 更改为 course.code，这是我犯的一个错误。
<tr>
<td>Course:</td>
<td>
<select th:field="*{course_code}">
<option value="">Choose..</option>
<option th:each="course: ${courses}" th:value="${course.code}" th:text="${course.name}" />
</select>
</td>
</tr>
