hibernate-orm/migration-guide.adoc

= 5.3 Migration Guide
:toc:

This guide discusses migration from Hibernate ORM version 5.2 to version 5.3.  For migration from
earlier versions, see any other pertinent migration guides as well.

== Background

Hibernate 5.3 adds support for the JPA 2.2 specification


== Known changes

=== Changes to positional query parameter handling

This really breaks down into 2 related changes:

* Support for JDBC-style parameter declarations in HQL/JPQL queries has been removed.  This feature
    has been deprecated since 4.1 and removing it made implementing the second change, so we decided
    to remove that support.  JDBC-style parameter declaration is still supported in native-queries.
* Since JPA positional parameters really behave more like named parameters (they can be repeated,
    declared in any order, etc.) Hibernate used to treat them as named parameters - it relied on
    Hibernate's JPA wrapper to interpret the JPA setParameter calls and properly handle delegating to
    the named variant.  This is actually a regression in 5.2 as it causes
    `javax.persistence.Parameter#getPosition` to report `null`.

For JDBC-style parameter declarations in native queries, we have also moved to using one-based
instead of zero-based parameter binding to be consistent with JPA.  That can temporarily be
reverted by setting the `hibernate.query.sql.jdbc_style_params_base` setting to `true` which
reverts to expecting zero-based binding.


=== Change in the `@TableGenerator` stored value

In order to be compliant with the JPA specification, the sequence value stored by Hibernate 5.3 in the database table used by the `javax.persistence.TableGenerator`
is the *last* generated value. Previously, Hibernate stored the *next* sequence value.

For backward compatibility, a new setting called `hibernate.id.generator.stored_last_used` was introduced, which gives you the opportunity to fall back to the old Hibernate behavior.

[NOTE]
====
Existing applications migrating to 5.3 and using the `@TableGenerator` have to set the `hibernate.id.generator.stored_last_used` configuration property to `false`.
====


=== Second-level cache provider SPI changes

Hibernate's second-level cache SPI needed to be redesigned to match with expectations between
Hibernate and the various caching providers.  And the SPI did not really clarify the intention.
These mis-matched expectations certainly had the potential to lead to bugs.  Although it was
originally slated for 6.0 to delay the SPI changes, we decided to back-port the work to
5.3 to address a number of bugs that could have been avoided with a clarified SPI.

The changes also allow the caching providers to perform serious optimizations based on
the users configuration of domain data caching in Hibernate.

Details can be seen on the https://hibernate.atlassian.net/browse/HHH-11356[HHH-11356] Jira issue

One potential upgrade concern is any custom `org.hibernate.cache.spi.QueryCacheFactory` implementations.
`org.hibernate.cache.spi.QueryCacheFactory` was meant as a means to allow service providers the
ability to define query result caching, generally with more stale-tolerant query result invalidation handling.
However, the contract also bound it to the old second level cache contracts so they had to be
updated.  Its responsibilities also changed so we also decided to "rename it" to
`org.hibernate.cache.spi.TimestampsCacheFactory`

Another specific change to be aware of is accessing cache entries via `SecondLevelCacheStatistics#getEntries`
and `NaturalIdCacheStatistics#getEntries`.  These methods have been deprecated, however the new
caching SPI does not really require caching providers to support this.  As of 5.3 these methods
inherently return an empty Map (`Collections#emptyMap`).  This has always been something that providers
did not implement "correctly" anyway


=== Statistics changes

The change for HHH-11356 required changes in its consumers.  One such consumer is the Hibernate
Statistics system....


=== Drop hibernate-infinispan module

Support for using Infinispan as a Hibernate 2nd-level cache provider has been moved to the Infinispan project so
the `hibernate-infinispan` module has been dropped.

A relocation pom which is pointing to `org.infinispan:infinispan-hibernate-cache` dependency is still generated,
therefore, avoiding the need of updating any library dependency.

[WARN]
====
The relocation pom may be dropped in a future release.
====


=== EnhancementTask changes

The API of the `org.hibernate.tool.enhance.EnhancementTask` Ant task was changed, specifically
the `#addFileset` method was dropped in favor of `#setBase` and `#setDir`

See details on the https://hibernate.atlassian.net/browse/HHH-11795[HHH-11795] Jira issue.

The main gist is that EnhancementTask was fixed (through a contribution) to actually work with
`Enhancer` from `BytecodeProvider`.  Previously it had not.  And part of fixing that required this
change.


=== Many-to-one association in embeddable collection elements and composite IDs

A bug introduced in 4.3 caused many-to-one associations in embeddable collection elements and
composite IDs to be eagerly fetched, even when explicitly mapped as lazy.

This bug does not affect many-to-one associations that are not in a composite ID or embeddable
collection element.

In 5.3.2, this bug was fixed. As a result, such associations will be fetched as specified
by their mappings.

Many-to-one associations mapped by using native HBM xml are lazy by default. In order to keep
the associations eager in 5.3.2 and later, mappings will need to explicitly specify that
they are non-lazy.

When mapped with annotations, many-to-one associations use `FetchType.EAGER` by default.
Starting in 5.3.2, if an association is mapped with `FetchType.LAZY`, the assocation will
be lazily fetched, as expected.

See details on the https://hibernate.atlassian.net/browse/HHH-12687[HHH-12687] Jira issue.

=== 5.3 -> 6.0 compatibility changes

The original driving force behind these series of changes is an effort to be as proactive as possible
about designing compatibility between 5.3 and 6.0.


==== Type system changes

Use of NavigableRole, back-ported from 6.0 rather than plain String