4.2.1.2.2. Attribute Annotations

Attribute annotations should be set for the corresponding fields, with the following exception: if there is a need to declare read-only, non-persistent attribute foo, it is sufficient to create getFoo() method and annotate it with @MetaProperty.

@Column

See javax.persistence.Column.

Defines DB column for storing attribute values.

Parameters:

  • name – the column name.

  • length – (optional parameter, 255 by default) – the length of the column. It is also used for metadata generation and ultimately, can limit the maximum length of the input text in visual components bound to this attribute. Add the @Lob annotation to remove restriction on the attribute length.

  • nullable – (optional parameter, true by default) – determines if an attribute can contain null value. When nullable = false JPA ensures that the field has a value when saved. In addition, visual components working with the attribute can request the user to enter a value.

@Composition

Indicates that the relationship is a composition, which is a stronger variant of the association. Essentially this means that the related entity should only exist as a part of the owning entity, i.e. be created and deleted together with it.

For example, a list of items in an order (Order class contains a collection of Item instances):

@OneToMany(mappedBy = "order")
@Composition
protected List<Item> items;

Choosing @Composition annotation as the relationship type enables making use of a special commit mode for datasources in edit screens. In this mode, the changes to related instances are only stored when the master entity is committed. See Editing Composite Entities for details.

@Embedded

See javax.persistence.Embedded.

Defines a reference attribute of embeddable type. The referenced entity should have @Embeddable annotation.

Example:

@Embedded
protected Address address;
@EmbeddedParameters

By default, ORM does not create an instance of embedded entity if all its attributes are null in the database. You can use the @EmbeddedParameters annotation to specify a different behavior when an instance is always non-null, for example:

@Embedded
@EmbeddedParameters(nullAllowed = false)
protected Address address;
@Id

See javax.persistence.Id.

Indicates that the attribute is the entity primary key. Typically, this annotation is set on the field of a base class, such as BaseUuidEntity. Using this annotation for a specific entity class is required only in case of inheritance from the BaseStringIdEntity base class (i.e. creating an entity with a string primary key).

@IgnoreUserTimeZone

Makes the platform to ignore the user’s time zone (if it is set for the current session) for an attribute of the timestamp type (annotated with @javax.persistence.Temporal.TIMESTAMP).

@JoinColumn

See javax.persistence.JoinColumn.

Defines DB column that determines the relationship between entities. Presence of this annotation indicates the owning side of the association.

Parameters:

  • name – the column name

Example:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "CUSTOMER_ID")
protected Customer customer;
@JoinTable

See javax.persistence.JoinTable.

Defines a join table on the owning side of @ManyToMany relationship.

Parameters:

  • name – the join table name

  • joinColumns – @JoinColumn element in the join table corresponding to primary key of the owning side of the relationship (the one containing @JoinTable annotation)

  • inverseJoinColumns – @JoinColumn element in the join table corresponding to primary key of the non-owning side of the relationship.

Example of the customers attribute of the Group class on the owning side of the relationship:

@ManyToMany
@JoinTable(name = "SALES_CUSTOMER_GROUP_LINK",
 joinColumns = @JoinColumn(name = "GROUP_ID"),
 inverseJoinColumns = @JoinColumn(name = "CUSTOMER_ID"))
protected Set<Customer> customers;

Example of the groups attribute of the Customer class on non-owning side of the same relationship:

@ManyToMany(mappedBy = "customers")
protected Set<Group> groups;
@Lob

See javax.persistence.Lob.

Indicates that the attribute does not have any length restrictions. This annotation is used together with the @Column annotation. If @Lob is set, the default or explicitly defined length in @Column is ignored.

Example:

@Column(name = "DESCRIPTION")
@Lob
private String description;
@LocalizedValue

Determines a method for retrieving a localized value for an attribute, using MessageTools`.getLocValue()` method.

Parameters:

  • messagePack – explicit indication of the package, from which a localized message will be taken, for example, com.haulmont.cuba.core.entity.

  • messagePackExpr – expression defining the path to the attribute, containing a package name from which the localized message should be taken (for example, proc.messagesPack). The path starts from the attribute of the current entity.

The annotation in the example below indicates that localized message for the state attribute value should be taken from the package name defined in the messagesPack attribute of the proc entity.

@Column(name = "STATE")
@LocalizedValue(messagePackExpr = "proc.messagesPack")
protected String state;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "PROC_ID")
protected Proc proc;
@ManyToMany

See javax.persistence.ManyToMany.

Defines a collection attribute with many-to-many relationship type.

Many-to-many relationship always has an owning side and can also have inverse, non-owning side. The owning side should be marked with additional @JoinTable annotation, and the non-owning side – with mappedBy parameter.

Parameters:

  • mappedBy – the field of the referenced entity, which owns the relationship. It must only be set on the non-owning side of the relationship.

  • targetEntity – the type of referenced entity. This parameter is optional if the collection is declared using Java generics.

  • fetch – (optional parameter, LAZY by default) – determines whether JPA will eagerly fetch the collection of referenced entities. This parameter should always remain LAZY, since retrieval of referenced entities in CUBA-application is determined dynamically by the views mechanism.

@ManyToOne

See javax.persistence.ManyToOne.

Defines a reference attribute with many-to-one relationship type.

Parameters:

  • fetch – (EAGER by default) parameter that determines whether JPA will eagerly fetch the referenced entity. This parameter should always be set to LAZY, since retrieval of referenced entity in CUBA-application is determined dynamically by the views mechanism.

  • optional – (optional parameter, true by default) – indicates whether the attribute can contain null value. If optional = false JPA ensures the existence of reference when the entity is saved. In addition, the visual components working with this attribute can request the user to enter a value.

For example, several Order instances refer to the same Customer instance. In this case the Order.customer attribute should have the following annotations:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "CUSTOMER_ID")
protected Customer customer;
@MetaProperty

Indicates that metadata should include the annotated attribute. This annotation can be set for a field or for a getter method, if there is no corresponding field.

This annotation is not required for the fields already containing the following annotations from javax.persistence package: @Column, @OneToOne, @OneToMany, @ManyToOne, @ManyToMany, @Embedded. Such fields are included in metadata automatically. Thus, @MetaProperty is mainly used for defining non-persistent attributes of the entities.

Parameters (optional):

  • mandatory - determines whether the attribute can contain null value. If mandatory = true, visual components working with this attribute can request the user to enter a value.

  • datatype - explicitly defines a datatype that overrides a datatype inferred from the attribute Java type.

  • related - defines the array of related persistent attributes to be fetched from the database when this property is included in a view.

Field example:

@Transient
@MetaProperty
protected String token;

Method example:

@MetaProperty
public String getLocValue() {
    if (!StringUtils.isEmpty(messagesPack)) {
        return AppBeans.get(Messsages.class).getMessage(messagesPack, value);
    } else {
        return value;
    }
}
@OnDelete

Determines related entities handling policy in case of soft deletion of the entity, containing the attribute. See Soft Deletion.

Example:

@OneToMany(mappedBy = "group")
@OnDelete(DeletePolicy.CASCADE)
private Set<Constraint> constraints;
@OnDeleteInverse

Determines related entities handling policy in case of soft deletion of the entity from the inverse side of the relationship. See Soft Deletion.

Example:

@ManyToOne
@JoinColumn(name = "DRIVER_ID")
@OnDeleteInverse(DeletePolicy.DENY)
private Driver driver;
@OneToMany

See javax.persistence.OneToMany.

Defines a collection attribute with one-to-many relationship type.

Parameters:

  • mappedBy – the field of the referenced entity, which owns the relationship.

  • targetEntity – the type of referenced entity. This parameter is optional if the collection is declared using Java generics.

  • fetch – (optional parameter, LAZY by default) – determines whether JPA will eagerly fetch the collection of referenced entities. This parameter should always remain LAZY, since retrieval of referenced entities in CUBA-application is determined dynamically by the views mechanism.

For example, several Item instances refer to the same Order instance using @ManyToOne field Item.order. In this case the Order class can contain a collection of Item instances:

@OneToMany(mappedBy = "order")
protected Set<Item> items;
@OneToOne

See javax.persistence.OneToOne.

Defines a reference attribute with one-to-one relationship type.

Parameters:

  • fetch – (EAGER by default) determines whether JPA will eagerly fetch the referenced entity. This parameter should be set to LAZY, since retrieval of referenced entities in CUBA-application is determined dynamically by the views mechanism.

  • mappedBy – the field of the referenced entity, which owns the relationship. It must only be set on the non-owning side of the relationship.

  • optional – (optional parameter, true by default) – indicates whether the attribute can contain null value. If optional = false JPA ensures the existence of reference when the entity is saved. In addition, the visual components working with this attribute can request the user to enter a value.

Example of owning side of the relationship in the Driver class:

@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "CALLSIGN_ID")
protected DriverCallsign callsign;

Example of non-owning side of the relationship in the DriverCallsign class:

@OneToOne(fetch = FetchType.LAZY, mappedBy = "callsign")
protected Driver driver;
@OrderBy

See javax.persistence.OrderBy.

Determines the order of elements in a collection attribute at the point when the association is retrieved from the database. This annotation should be specified for ordered Java collections such as List or LinkedHashSet to get a predictable sequence of elements.

Parameters:

  • value – string, determines the order in the format:

orderby_list::= orderby_item [,orderby_item]*
orderby_item::= property_or_field_name [ASC | DESC]

Example:

@OneToMany(mappedBy = "user")
@OrderBy("createTs")
protected List<UserRole> userRoles;
@Temporal

See javax.persistence.Temporal.

Specifies the type of the stored value for java.util.Date attribute: date, time or date+time.

Parameters:

  • value – the type of the stored value: DATE, TIME, TIMESTAMP

Example:

@Column(name = "START_DATE")
@Temporal(TemporalType.DATE)
protected Date startDate;
@Transient

See javax.persistence.Transient.

Indicates that field is not stored in the database, meaning it is non-persistent.

The fields supported by JPA types (See http://docs.oracle.com/javaee/7/api/javax/persistence/Basic.html) are persistent by default, that is why @Transient annotation is mandatory for non-persistent attribute of such type.

@MetaProperty annotation is required if @Transient attribute should be included in metadata.

@Version

See javax.persistence.Version.

Indicates that the annotated field stores a version for optimistic locking support.

Such field is required when an entity class implements the Versioned interface (StandardEntity base class already contains such field).

Example:

@Version
@Column(name = "VERSION")
private Integer version;