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 * to you under the Apache License, Version 2.0 (the
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 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
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 * KIND, either express or implied.  See the License for the
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[[library-uid, UID Library]]
= UID =

[devstatus]
--------------
source=libraries/uid/dev-status.xml
--------------

This library provides Services to easily generate unique identifiers and sequences of numbers.

include::../../build/docs/buildinfo/artifact.txt[]

== Unique Identifiers ==

Assembly is done using the provided Assembler:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=uuid-assembly
----

Usage is quite simple:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=uuid-usage
----


== Sequencing ==

Sequencing is used to automatically generate a sequence of numbers.

The algorithm is that `currentSequenceValue` is the number that was last returned in a `newSequenceValue` call, and will
initially be zero. Persisting Sequencing services defines "initially" as the first run ever, as subsequent starts may
retrieve the `currentSequenceValue` from an EntityStore.


=== Transient Sequences ===

Assembly is done using the provided Assembler:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=seq-assembly
----

Usage is quite simple:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=seq-usage
----

=== Persisted Sequences ===

Assembly is done using the provided Assembler:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=perseq-assembly
----

Usage is quite simple:

[snippet,java]
----
source=libraries/uid/src/test/java/org/qi4j/library/uid/DocumentationSupport.java
tag=seq-usage
----