Hibernate mapping cheat sheet

Check list

1. Make sure Collections are initialized.
2. Make sure Collections can't be null.
3. Most names and some other fields should not be null.

@Entity
@Table(name = "ar_campus")
public class Campus . . .

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    Long id;

    @Column(name = "xxx")
    @Column(name = "xxx", length = 11, unique = true, nullable = false)
    String someColumn;

Join column name has this rule: "Single same name as property, set name of parent"

Child NO reference back to parent.

class Hand {
    @OneToMany
    @JoinColumn(name = "handid")
    Set<Finger> fingers;

Child HAS reference back to parent.

class Hand {
    @OneToMany(mappedBy = "hand")
    Set<Finger> fingers;
  
class Finger {
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "handid")
    Hand hand;

One to one with join column:

class Organization {
    @OneToOne(optional = false, mappedBy = "organization")
    OrgBoardInfo boardInfo;

class BoardInfo {
    @OneToOne(optional = false)
    @JoinColumn(name = "orgid", unique = true, nullable = false, updatable = false)
    Organization organization;

One to one with shared key:

class User {
    @OneToOne()
    @PrimaryKeyJoinColumn
    public AuxInfo auxInfo;

class AuxInfo {
    //(note must NOT put @GeneratedValue annotation on id)
    @Id
    Long    id;

    @OneToOne()
    @PrimaryKeyJoinColumn
    User    user;

Built in Java classes (String, Date, Long) or custom element.

class Board {
    @Enumerated(EnumType.STRING)
    @Column(name = "type")
    public BoardType type;

class Campus {
    @Column(name = "holiday", nullable = false)
    @CollectionOfElements(targetElement = PersistentLocalDate.class)
    @JoinTable(name = "ar_campus_holiday", joinColumns = { @JoinColumn(name = "cid") })
    Set<LocalDate> holidays;

class User {
    @Column(name = "system", nullable = false)
    @CollectionOfElements
    @Enumerated(EnumType.STRING)
    @JoinTable(name = "user_desired_system", joinColumns = @JoinColumn(name = "user"))
    Set<ExternalSystem> desiredSystems;

class Reservation {
    @ManyToMany
    @JoinTable(name = "rez_sr", joinColumns = { @JoinColumn(name = "rezId") }, inverseJoinColumns = { @JoinColumn(name = "srId") })
    Set<SubReceipt> subReceipts;

Column specs (for postgresql)

    @Column(name = "yearsOfExperience", nullable = false, columnDefinition = "integer default 0")
    int            yearsOfExperience;

    @Column(name = "experience", nullable = false, columnDefinition = "character varying(5000) default ''")
    String        experience;

    @Column(name = "deleted", nullable = false, columnDefinition = "bool default false")
    boolean deleted;

    @Column(name = "reservationId", nullable = false, columnDefinition = "bigint default 0")
    long reservationId;