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more updates for JPA 3.2 

Signed-off-by: Gavin King <gavin@hibernate.org>
This commit is contained in:
Gavin King 2024-10-23 21:08:06 +02:00
parent 82b20a0e90
commit 6480154cd7
2 changed files with 38 additions and 18 deletions
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40
documentation/src/main/asciidoc/introduction/Entities.adoc
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@ -285,7 +285,7 @@ Any identifier attribute may now make use of the generator named `bookSeq`:
[source,java]
----
@Id
@GeneratedValue(strategy=SEQUENCE, generator="bookSeq") // reference to generator defined elsewhere
@GeneratedValue(generator = "bookSeq") // reference to generator defined elsewhere
Long id;
----
@ -294,18 +294,38 @@ Actually, it's extremely common to place the `@SequenceGenerator` annotation on
[source,java]
----
@Id
@GeneratedValue(strategy=SEQUENCE, generator="bookSeq") // reference to generator defined below
@SequenceGenerator(name="bookSeq", sequenceName="seq_book", initialValue = 5, allocationSize=10)
@GeneratedValue // uses the generator defined below
@SequenceGenerator(sequenceName = "seq_book", initialValue = 5, allocationSize=10)
Long id;
----
[NOTE]
// .JPA id generators may be shared between entities
====
JPA id generators may be shared between entities.
A `@SequenceGenerator` or `@TableGenerator` must have a name, and may be shared between multiple id attributes.
This fits somewhat uncomfortably with the common practice of annotating the `@Id` attribute which makes use of the generator!
====
In this case, the `name` of the `@SequenceGenerator` should not be specified.
We may even place a `@SequenceGenerator` or `@TableGenerator` annotation at the package level:
[source,java]
----
@SequenceGenerator(sequenceName = "id_sequence", initialValue = 5, allocationSize=10)
@TableGenerator(table = "id_table", initialValue = 5, allocationSize=10)
package org.example.entities;
----
Then any entity in this package which specifies `strategy=SEQUENCE` or `strategy=TABLE` without also explicitly specifying a generator `name` will be assigned a generator based on the package-level annotation.
[source,java]
----
@Id
@GeneratedValue(strategy=SEQUENCE) // uses the sequence generator defined at the package level
Long id;
----
// [NOTE]
// // .JPA id generators may be shared between entities
// ====
// JPA id generators may be shared between entities.
// A `@SequenceGenerator` or `@TableGenerator` must have a name, and may be shared between multiple id attributes.
// This fits somewhat uncomfortably with the common practice of annotating the `@Id` attribute which makes use of the generator!
// ====
As you can see, JPA provides quite adequate support for the most common strategies for system-generated ids.
However, the annotations themselves are a bit more intrusive than they should be, and there's no well-defined way to extend this framework to support custom strategies for id generation.

12
documentation/src/main/asciidoc/querylanguage/Expressions.adoc
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@ -316,10 +316,10 @@ The operator precedence is given by this table, from highest to lowest precedenc
[[concatenation]]
==== String concatenation
HQL defines two ways to concatenate strings:
JPQL defines two ways to concatenate strings:
* the SQL-style concatenation operator, `||`, and
* the JPQL-standard `concat()` function.
* the standard `concat()` function.
See <<string-functions, below>> for details of the `concat()` function.
@ -545,7 +545,7 @@ The following special functions make it possible to discover or narrow expressio
| `type()` | The (concrete) entity or embeddable type | `type(e)` | ✔
| `treat()` | Narrow an entity or embeddable type | `treat(e as Entity)` | ✔
| `cast()` | Narrow a basic type | `cast(x as Type)` | ✖
| `cast()` | Narrow a basic type | `cast(x as Type)` | ✔
| `str()` | Cast to a string | `str(x)` | ✖
| `ordinal()` | Get the ordinal value of an enum | `ordinal(x)` | ✖
|===
@ -836,9 +836,9 @@ Naturally, there are a good number of functions for working with strings.
`pad(str with len leading)`, +
`pad(str with len trailing)`, or +
`pad(str with len leading char)` | ✖ / ✖
| `left()` | The leftmost characters of a string | `left(str, len)` | ✖ / ✖
| `right()` | The rightmost characters of a string | `right(str, len)` | ✖ / ✖
| `replace()` | Replace every occurrence of a pattern in a string | `replace(str, patt, rep)` | ✖ / ✖
| `left()` | The leftmost characters of a string | `left(str, len)` | ✔ / ✖
| `right()` | The rightmost characters of a string | `right(str, len)` | ✔ / ✖
| `replace()` | Replace every occurrence of a pattern in a string | `replace(str, patt, rep)` | ✔ / ✖
| `repeat()` | Concatenate a string with itself multiple times | `repeat(str, times)` | ✖ / ✖
| `collate()` | Select a collation | `collate(p.name as collation)` | ✖ / ✖
|===