SpringBoot-SpringData-懒加载

package com.example.SpringData.domain; import java.util.Set; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.ManyToMany; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; import org.hibernate.annotations.NotFound; import org.hibernate.annotations.NotFoundAction; @Entity @Table(name = "course") public class Course implements java.io.Serializable { private static final long serialVersionUID = 6398143635533582335L; private String pid; private String courseName;// 课程名称 private Set<Student> Student; // 选修课程学生 public Course() { } public Course(String pid, String courseName, Set<Student> student) { this.pid = pid; this.courseName = courseName; this.Student = student; } @Id @Column(name = "pid", unique = true, nullable = false, length = 32) // @GeneratedValue(generator = "generator") // @GenericGenerator(name = "generator", strategy = "uuid") public String getPid() { return pid; } @Column(name = "course_name", unique = true, length = 64) public String getCourseName() { return courseName; } //mappedBy : // 表示当前所在表和 Student 的关系是定义在 Student 里面的 course 这个成员上面的， // 他表示此表是一对一关系中的从表，也就是关系是在 Student 表中维护的， // Student 表是关系的维护者，有主导权，它有个外键指向 course (Student 中的 getCourse() ) @ManyToMany(fetch = FetchType.LAZY, mappedBy = "course") //NotFound : 意思是找不到引用的外键数据时忽略，NotFound默认是exception @NotFound(action = NotFoundAction.IGNORE) public Set<Student> getStudent() { return Student; } public void setPid(String pid) { this.pid = pid; } public void setCourseName(String courseName) { this.courseName = courseName; } public void setStudent(Set<Student> student) { Student = student; } }