[[commands-alias]]
= Alias

ifndef::snippets[:snippets: ../../../../src/test/java/org/springframework/shell/docs]

It is possible to define an _alias_ for a command. This is convenient for
cases where you want to create a shorter version of a command or going
through a complete command rename while keeping old one temporarily in
place.

The format of _alias_ is slightly different from a _command_. When _command_
is defined as an array it's concatenated together into a single command.
When _alias_ is defined as an array it's used to create separate aliases.

Aliases with a plain `CommandRegistration` is simple and clear as you
get exactly what you define as there's no "magic" in it.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=builder]
----

Defining alias with `@Command` annotation is a bit more involved as it
can exist on a both class and method levels. Here are examples how it
works.

Alias just on a method gives you _myalias_.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=command1]
----

Or _myalias1_ and _myalias2_ if defined as an array.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=command2]
----

Alias only on a class level does nothing as it's simply an instruction
for annotation on a *method level if defined*.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=command3]
----

Alias on both class and method level combines those two together where
class level works as an prefix and method level as combination of aliases.
Alias on a class level is usually used together with a _command_ prefix
to keep aliases on a same command level.

Here you'd get alias _myalias1 myalias2_.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=command4]
----

On a method level there's a special format, that being an *empty string*
which allows you to create an alias but it only uses prefix from a
class level.

Here you'd get alias _myalias1_.

[source, java, indent=0]
----
include::{snippets}/CommandRegistrationAliasSnippets.java[tag=command5]
----
