JPA循环引用GSON

Question

我正在使用JPA，我正在尝试使用GSON将其序列化为JSON。 由于循环引用，我不断得到堆栈溢出。

这是班级

@Entity
@Table(name = "STUDENT")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Student.findAll", query = "SELECT s FROM Student s"),
    @NamedQuery(name = "Student.findById", query = "SELECT s FROM Student s WHERE s.id = :id"),
    @NamedQuery(name = "Student.findByName", query = "SELECT s FROM Student s WHERE s.name = :name"),
    @NamedQuery(name = "Student.findBySurname", query = "SELECT s FROM Student s WHERE s.surname = :surname"),
    @NamedQuery(name = "Student.findByFaculty", query = "SELECT s FROM Student s WHERE s.faculty = :faculty")})
public class Student implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "ID")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "NAME")
    private String name;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "SURNAME")
    private String surname;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "FACULTY")
    private String faculty;
    @JoinColumn(name = "COURSE_ID", referencedColumnName = "ID")
    @ManyToOne(optional = false)
    private Course courseId;

    public Student() {
    }

    public Student(Integer id) {
        this.id = id;
    }

    public Student(Integer id, String name, String surname, String faculty) {
        this.id = id;
        this.name = name;
        this.surname = surname;
        this.faculty = faculty;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSurname() {
        return surname;
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

    public String getFaculty() {
        return faculty;
    }

    public void setFaculty(String faculty) {
        this.faculty = faculty;
    }

    public Course getCourseId() {
        return courseId;
    }

    public void setCourseId(Course courseId) {
        this.courseId = courseId;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Student)) {
            return false;
        }
        Student other = (Student) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "models.Student[ id=" + id + " ]";
    }

}

我尝试使用transient关键字和注释，例如

private transient Course courseId;

或

@Transient
private Course courseId;

但它根本没有帮助。 解决这个问题的方法是什么？

这是课程课程：

@Entity
@Table(name = "COURSE")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Course.findAll", query = "SELECT c FROM Course c"),
    @NamedQuery(name = "Course.findById", query = "SELECT c FROM Course c WHERE c.id = :id"),
    @NamedQuery(name = "Course.findByName", query = "SELECT c FROM Course c WHERE c.name = :name")})
public class Course implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "ID")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 50)
    @Column(name = "NAME")
    private String name;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "courseId")
    private Collection<Student> studentCollection;

    public Course() {
    }

    public Course(Integer id) {
        this.id = id;
    }

    public Course(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @XmlTransient
    public Collection<Student> getStudentCollection() {
        return studentCollection;
    }

    public void setStudentCollection(Collection<Student> studentCollection) {
        this.studentCollection = studentCollection;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Course)) {
            return false;
        }
        Course other = (Course) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "models.Course[ id=" + id + " ]";
    }

}