为什么在ManyToOne关系中使用Hibernate的FetchType.EAGER或fetch = FetchType.LAZY会出错？

在我的Spring Boot应用程序中，我正在使用Hibernate。我有一个多对一的关系，如下所示：\n@Entity\n@Table(name = \"STUDENT\")\n@JsonIdentityInfo(\n generator = ObjectIdGenerators.PropertyGenerator.class,\n property = \"id\")\npublic class Student {\n @Id\n @GeneratedValue(strategy = GenerationType.IDENTITY)\n private Long id;\n @Column\n private String name;\n @Column\n private int mobile;\n @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)\n @JoinColumn(name = \"DEPT_ID\", nullable = false)\n private Department department;\n public Long getId() {\n return id;\n }\n public void setId(Long id){\n this.id = id;\n }\n public String getName() {\n return name;\n }\n public void setName(String name) {\n this.name = name;\n }\n public int getMobile() {\n return mobile;\n }\n public void setMobile(int mobile) {\n this.mobile = mobile;\n }\n public Department getDepartment() {\n return department;\n }\n public void setDepartment(Department department) {\n this.department = department;\n }\n @Override\n public String toString() {\n return \"Student{\" +\n \"id=\" + id +\n \", name=\'\" + name + \'\\\'\' +\n \", mobile=\" + mobile +\n \", department=\" + department +\n \'}\';\n }\n}\n和：\n@Entity\n@Table(name = \"DEPARTMENT\")\n@JsonIdentityInfo(\n generator = ObjectIdGenerators.PropertyGenerator.class,\n property = \"id\")\npublic class Department {\n @Id\n @GeneratedValue(strategy = GenerationType.IDENTITY)\n private Long id;\n @Column\n private String name;\n @OneToMany(mappedBy = \"department\", fetch = FetchType.EAGER, cascade = CascadeType.ALL)\n private List studentList=new ArrayList();\n public Long getId() {\n return id;\n }\n public void setId(Long id) {\n this.id = id;\n }\n public String getName() {\n return name;\n }\n public void setName(String name) {\n this.name = name;\n }\n public List getStudentList() {\n return studentList;\n }\n public void setStudentList(List studentList) {\n this.studentList = studentList;\n }\n}\n对于Department的fetch = FetchType.LAZY和fetch = FetchType.EAGER都可以正常工作。\n为了更好地理解，我将Student的@ManyToOne(fetch = FetchType.EAGER)切换为@ManyToOne(fetch = FetchType.LAZY)。当fetch = FetchType.LAZY时，它会出现以下错误：\n\"Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->com.myjavablog.model.Student[\"department\"]->com.myjavablog.model.Department$HibernateProxy$w9HG3Rv0[\"hibernateLazyInitializer\"])\"\n为什么会发生这种情况？为什么我不能对学生使用fetch type lazy？提前感谢！