234 lines
7.4 KiB
Plaintext
234 lines
7.4 KiB
Plaintext
= Hibernate 6.6.0.Final
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Steve Ebersole
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:awestruct-tags: ["Hibernate ORM", "Releases"]
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:awestruct-layout: blog-post
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:family: 6.6
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:docs-url: https://docs.jboss.org/hibernate/orm/{family}
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:javadocs-url: {docs-url}/javadocs
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:migration-guide-url: {docs-url}/migration-guide/migration-guide.html
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:intro-guide-url: {docs-url}/introduction/html_single/Hibernate_Introduction.html
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:user-guide-url: {docs-url}/userguide/html_single/Hibernate_User_Guide.html
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:ql-guide-url: {docs-url}/querylanguage/html_single/Hibernate_Query_Language.html
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[[jakarta-data]]
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== Jakarta Data
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Hibernate 6.6 includes a complete implementation of the current Jakarta Data 1.0 Release Candidate. As https://in.relation.to/2024/04/18/jakarta-data-1/[discussed here], our implementation:
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- is based on compile-time code generation via an annotation processor, enabling unprecedented compile-time type safety, and
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- is backed by Hibernate's `StatelessSession`, which has been enhanced especially to meet the needs of Jakarta Data.
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This implementation already passes the Jakarta Data TCK, and we have a request for certification pending.
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To make use of _Hibernate Data Repositories_, you'll need to depend on:
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- our annotation processor, `hibernate-jpamodelgen`, and
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- the Jakarta Data API, `jakarta.data-api.
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For example, in Gradle:
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[source,groovy]
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----
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implementation 'jakarta.data:jakarta.data-api:1.0.0-RC1'
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implementation 'org.hibernate.orm:hibernate-core:6.6.0.Alpha1'
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annotationProcessor 'org.hibernate.orm:hibernate-jpamodelgen:6.6.0.Alpha1'
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----
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For more information, please see the brand-new _Hibernate Data Repositories_ link:{docs-url}/repositories/html_single/Hibernate_Data_Repositories.html[documentation].
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[[concrete-proxy]]
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== @ConcreteProxy
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6.6 also provides a new `@ConcreteProxy` annotation intended as an improved replacement for the deprecated `@Proxy` and `@LazyToOne` annotations. Indicates that lazy references should be instantiated as the concrete type rather than the referenced type.
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Consider the following model and data
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[source,java]
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----
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@ConcreteProxy
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@Entity
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@Inheritance
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class Payment { ... }
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@Entity
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class CardPayment extends Payment { ... }
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session1.persist( new CardPayment( 1, ... ) );
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----
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As a simple example -
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[source,java]
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----
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Payment loaded = session2.getReference( Payment.class, 1 );
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----
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Historically, Hibernate would create a lazy proxy for `loaded` of type `Payment`. Attempts to cast that reference to `CardPayment` would result in a casting error. `@ConcreteProxy` forces Hibernate to resolve the actual, concrete type and create a proxy of that type instead -
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[source,java]
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----
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CardPayment loaded = (CardPayment) session2.getReference( Payment.class, 1 );
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----
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IMPORTANT: Hibernate will try a number of different ways to determine the concrete type, but may ultimately have to fall back to hitting the database which might have an effect on performance.
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This feature works with both Hibernate's legacy proxy-based laziness and the newer bytecode enhancement laziness.
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[[extended-array]]
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== Extended Array support
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ORM 6.6 adds support for mapping arrays of embeddable aggregate types e.g.
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[source,java]
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----
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@Entity
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class MyEntity {
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List<MyEmbeddable> embeddableAggregateList;
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}
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@Struct
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@Embeddable
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class MyEmbeddable { ... }
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----
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[[array-syntax-sugar]]
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== Syntax sugar for array functions
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Plenty of syntax sugar for array operations was added:
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|===
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|Function |Syntax sugar |
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|`array(1, 2)`
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|`[1, 2]`
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|Shorthand bracket syntax for array construction
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|`array_slice(array, 1, 2)`
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|`array[1:2]`
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|Shorthand bracket syntax for array slicing
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|`array_length(array)`
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|`length(array)`
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|Overload length function with array_length semantics on array input
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|`array_position(array, element)`
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|`position(element in array)`
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|Overload position function with array_position semantics on array input
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|`array_to_string(array, ',', 'null')`
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|`cast(array as String)`
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|Support casting array to string
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|`array_contains(array, element)`
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|`array contains element` or `element in array`
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|Contains predicate for containment check
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|`array_includes(array, array)`
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|`array includes subArray`
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|Predicate to for subset checking
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|`array_intersects(array, array(1, 2))`
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|`array intersects [1, 2]`
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|Overlaps predicate for overlaps check
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|===
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[[string-syntax-sugar]]
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== Syntax sugar for string functions
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The bracket syntax can now also be used for string typed expressions to select a single character by index,
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or obtain a substring by start and end index.
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`stringPath[2]` is syntax sugar for `substring(stringPath, 2, 1)` and returns a `Character`.
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`stringPath[2:3]` is syntax sugar for `substring(stringPath, 2, 3-2+1)`,
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where `3-2+1` is the expression to determine the desired string length.
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[[embeddable-inheritance]]
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== Embeddable Inheritance
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Another new feature of this version is discriminator-based inheritance for `@Embeddable` types. An `@Embeddable` class
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may be extended by other `@Embeddable` classes, in which case the `@Embedded` properties using that type will
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rely on an additional discriminator column to store information about the composite value's subtype.
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When retrieving the inherited embedded property, Hibernate will read the discriminator value and instantiate the
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correct `@Embeddable` subtype with its corresponding properties.
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For example, a mapping like this:
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[source,java]
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----
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@Embeddable
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@DiscriminatorValue( "parent" )
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@DiscriminatorColumn( name = "embeddable_type" )
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class ParentEmbeddable implements Serializable {
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private String parentProp;
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// ...
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}
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@Embeddable
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@DiscriminatorValue( "child_one" )
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class ChildOneEmbeddable extends ParentEmbeddable {
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private Integer childOneProp;
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// ...
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}
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@Entity
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class TestEntity {
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@Embedded
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private ParentEmbeddable embeddable;
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// ...
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}
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----
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Will result in the following table structure:
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[source,sql]
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----
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create table TestEntity (
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-- ...
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embeddable_type varchar(31) not null,
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parentProp varchar(255),
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childOneProp integer,
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-- ...
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)
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----
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For more detailed information please refer to the link:{user-guide-url}#embeddable-inheritance[Embeddable inheritance] user guide chapter.
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[[oracle-vector]]
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== Oracle Vector support
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Oracle engineers contributed the support for vector data types and functions to the `hibernate-vector` module
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to use with Oracle database version 23.4 and newer.
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For further information about vectors, consult the link:https://docs.oracle.com/en/database/oracle/oracle-database/23/vecse/overview-node.html[Oracle documentation].
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[[one-to-many-mapped-by-any]]
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== `@OneToMany(mappedBy)` support for `@Any`
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So far, the target of `@OneToMany` had to be a `@ManyToOne`. To map a `@OneToMany` based on an any association,
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it was necessary to spell out a custom `@SQLRestriction` and specify the join columns.
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Targeting an `@Any` association is now supported and will default to the appropriate join columns,
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as well as add a `@SQLRestriction` to the `@OneToMany` automatically.
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[[apply-filter-to-load-by-key]]
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== `@Filter` support for load by key
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Filters can opt in to be applicable also to find by key operations
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like `Session.find()`, lazy initialization and to-one association fetching,
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by setting `@FilterDef(applyToLoadByKey = true)`.
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If the target row of an association is filtered by such a load by key enabled filter,
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Hibernate ORM will throw a `EntityFilterException` to prevent potential data loss
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that can happen when flushing an entity that owns such an association.
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Also, the `@TenantId` filter was changed to apply to load by key operations by default.
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