mis minor fixes to doc
This commit is contained in:
parent
289a43c5b5
commit
9ae78dd178
|
@ -95,8 +95,10 @@ The default access type may be specified explicitly using the `@Access` annotati
|
|||
[IMPORTANT]
|
||||
// .Mapping annotations should be placed consistently
|
||||
====
|
||||
Mapping annotations should be placed consistently.
|
||||
If the `@Id` annotation occurs on a field, the other mapping annotations should also be applied to field; or, if the `@Id` annotation occurs on a getter, the other mapping annotations should be applied to getters.
|
||||
Mapping annotations should be placed consistently:
|
||||
|
||||
- if `@Id` annotates a field, the other mapping annotations should also be applied to fields, or,
|
||||
- if `@Id` annotates a getter, the other mapping annotations should be applied to getters.
|
||||
|
||||
It is in principle possible to mix field and property access using explicit `@Access` annotations at the attribute level.
|
||||
We don't recommend doing this.
|
||||
|
@ -211,11 +213,11 @@ JPA defines the following strategies for generating ids, which are enumerated by
|
|||
|===
|
||||
| Strategy | Java type | Implementation
|
||||
|
||||
| `GenerationType.UUID` | `UUID` or `String` | A Java `UUID`.
|
||||
| `GenerationType.IDENTITY` | `Long` or `Integer` | An identity or autoincrement column.
|
||||
| `GenerationType.SEQUENCE` | `Long` or `Integer` | A database sequence.
|
||||
| `GenerationType.TABLE` | `Long` or `Integer` | A database table.
|
||||
| `GenerationType.AUTO` | `Long` or `Integer` | Selects `SEQUENCE`, `TABLE`, or `UUID` based on the identifier type and capabilities of the database.
|
||||
| `GenerationType.UUID` | `UUID` or `String` | A Java `UUID`
|
||||
| `GenerationType.IDENTITY` | `Long` or `Integer` | An identity or autoincrement column
|
||||
| `GenerationType.SEQUENCE` | `Long` or `Integer` | A database sequence
|
||||
| `GenerationType.TABLE` | `Long` or `Integer` | A database table
|
||||
| `GenerationType.AUTO` | `Long` or `Integer` | Selects `SEQUENCE`, `TABLE`, or `UUID` based on the identifier type and capabilities of the database
|
||||
|===
|
||||
|
||||
For example, the following id maps to a SQL `identity`, `auto_increment`, or `bigserial` column:
|
||||
|
@ -243,6 +245,10 @@ Values are generated using a database sequence defined as follows:
|
|||
create sequence seq_book start with 5 increment by 10
|
||||
----
|
||||
|
||||
Notice that Hibernate doesn't have to go to the database every time a new identifier is needed.
|
||||
Instead, a given process obtains a block of ids, of size `allocationSize`, and only needs to hit the database each time the block is exhausted.
|
||||
Of course, the downside is that generated identifiers are not contiguous.
|
||||
|
||||
[CAUTION]
|
||||
// .Check the `initialValue` and `allocationSize`
|
||||
====
|
||||
|
@ -403,7 +409,7 @@ class BookId {
|
|||
|
||||
We'll learn more about <<embeddable-objects>> below.
|
||||
|
||||
Now the entity class may reuse this definition using `@EmbeddedId`:
|
||||
Now the entity class may reuse this definition using `@EmbeddedId`, and the `@IdClass` annotation is no longer required:
|
||||
|
||||
[source,java]
|
||||
----
|
||||
|
@ -1299,7 +1305,7 @@ Alternatively, we could store this array or list in a separate table.
|
|||
[[element-collections]]
|
||||
=== Collections mapped to a separate table
|
||||
|
||||
JPA _does_ define a standard way to map a collection to a table:
|
||||
JPA _does_ define a standard way to map a collection to an auxiliary table:
|
||||
|
||||
[source, java]
|
||||
----
|
||||
|
@ -1314,6 +1320,21 @@ class Event {
|
|||
}
|
||||
----
|
||||
|
||||
Here, each collection elements are stored as separate row of the auxiliary table.
|
||||
By default, this table has the following definition:
|
||||
|
||||
[source,sql]
|
||||
----
|
||||
create table Event_daysOfWeek (
|
||||
Event_id bigint not null,
|
||||
daysOfWeek tinyint check (daysOfWeek between 0 and 6),
|
||||
daysOfWeek_ORDER integer not null,
|
||||
primary key (Event1_id, daysOfWeek_ORDER)
|
||||
)
|
||||
----
|
||||
|
||||
Which is fine, but it's still a mapping we prefer to avoid.
|
||||
|
||||
[WARNING]
|
||||
// .This is not what we would do
|
||||
====
|
||||
|
@ -1330,10 +1351,11 @@ Instead of a surrogate primary key, it has a composite key comprising the foreig
|
|||
|
||||
When—inevitably—we find that we need to add a fourth column to that table, our Java code must change completely.
|
||||
Most likely, we'll realize that we need to add a separate entity after all.
|
||||
|
||||
There's much more we could say about "element collections", but we won't say it, because we don't want to hand you the gun that you'll shoot your foot with.
|
||||
So this mapping isn't very robust in the face of minor changes to our data model.
|
||||
====
|
||||
|
||||
There's much more we could say about "element collections", but we won't say it, because we don't want to hand you the gun you'll shoot your foot with.
|
||||
|
||||
[[entities-summary]]
|
||||
=== Summary of annotations
|
||||
|
||||
|
|
|
@ -497,13 +497,22 @@ This introduction will guide you through the basic tasks involved in developing
|
|||
Naturally, we'll start at the top of this list, with the least-interesting topic: _configuration_.
|
||||
|
||||
<<<
|
||||
|
||||
include::Configuration.adoc[]
|
||||
|
||||
<<<
|
||||
|
||||
include::Entities.adoc[]
|
||||
|
||||
<<<
|
||||
|
||||
include::Mapping.adoc[]
|
||||
|
||||
<<<
|
||||
|
||||
include::Interacting.adoc[]
|
||||
|
||||
<<<
|
||||
|
||||
include::Tuning.adoc[]
|
||||
// include::../userguide/chapters/query/hql/QueryLanguage.adoc[]
|
||||
|
|
|
@ -12,6 +12,13 @@ font:
|
|||
Roboto Light:
|
||||
normal: Roboto-Light.ttf
|
||||
italic: Roboto-LightItalic.ttf
|
||||
Emoji:
|
||||
normal: OpenSansEmoji.ttf
|
||||
bold: OpenSansEmoji.ttf
|
||||
italic: OpenSansEmoji.ttf
|
||||
bold_italic: OpenSansEmoji.ttf
|
||||
fallbacks:
|
||||
- Emoji
|
||||
base:
|
||||
font:
|
||||
color: #151e3d
|
||||
|
|
Loading…
Reference in New Issue