[[using-shell-customization-commandnotfound]]
= Command Not Found

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

By default, a missing command is handled via `CommandNotFoundResultHandler`
and outputs a simple message:

[source, text]
----
shell:>missing
No command found for 'missing'
----

Internally, `CommandNotFoundResultHandler` is using `CommandNotFoundMessageProvider`
which is a simple function taking a `ProviderContext` and returning a text
message. Below is an example what a custom message provider might look like.

[source, java, indent=0]
----
include::{snippets}/CommandNotFoundSnippets.java[tag=custom-provider]
----

It's possible to change this implementation by defining it as a bean.

[source, java, indent=0]
----
include::{snippets}/CommandNotFoundSnippets.java[tag=provider-bean-1]
----

`CommandNotFoundResultHandler` is a functional interface so it can
be writter as a lambda.

[source, java, indent=0]
----
include::{snippets}/CommandNotFoundSnippets.java[tag=provider-bean-2]
----