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Add documentation for `FailureAnalyzer` 

Closes gh-6775
This commit is contained in:
Stephane Nicoll 2016-09-02 13:11:50 +02:00
parent 0e00a49dcc
commit 6f70d53285
2 changed files with 47 additions and 0 deletions
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24
spring-boot-docs/src/main/asciidoc/howto.adoc
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@ -22,6 +22,30 @@ can send us a {github-code}[pull request].
== Spring Boot application == Spring Boot application
[[howto-failure-analyzer]]
=== Create your own FailureAnalyzer
{dc-spring-boot}/diagnostics/FailureAnalyzer.{dc-ext}[[`FailureAnalyzer`] is a great way
to intercept an exception on startup and turn it into a human-readable message, wrapped
into a {dc-spring-boot}/diagnostics/FailureAnalysis.{dc-ext}[[`FailureAnalysis`]. Spring
Boot provides such analyzer for application context related exceptions, JSR-303
validations and more. It is actually very easy to create your own.
`AbstractFailureAnalyzer` is a convenient extension of `FailureAnalyzer` that checks the
presence of a specified exception type in the exception to handle. You can extend from
that so that your implementation gets a chance to handle the exception only when it is
actually present. If for whatever reason you can't handle the exception, return `null`
to let another implementation a chance to handle the exception.
`FailureAnalyzer` implementations are to be registered in a `META-INF/spring.factories`:
the following registers `ProjectConstraintViolationFailureAnalyzer`:
[source,properties,indent=0]
----
org.springframework.boot.diagnostics.FailureAnalyzer=\
com.example.ProjectConstraintViolationFailureAnalyzer
----
[[howto-troubleshoot-auto-configuration]] [[howto-troubleshoot-auto-configuration]]
=== Troubleshoot auto-configuration === Troubleshoot auto-configuration

23
spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc
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@ -46,6 +46,29 @@ When your application starts you should see something similar to the following:
By default `INFO` logging messages will be shown, including some relevant startup details By default `INFO` logging messages will be shown, including some relevant startup details
such as the user that launched the application. such as the user that launched the application.
If your application fails to start, registered `FailureAnalyzers` get a chance to provide
a dedicated error message and a concrete action to fix the problem. For instance if you
start a web application on port `8080` and that port is already in use, you should see
something similar to the following:
[indent=0]
----
***************************
APPLICATION FAILED TO START
***************************
Description:
Embedded servlet container failed to start. Port 8080 was already in use.
Action:
Identify and stop the process that's listening on port 8080 or configure this application to listen on another port.
----
NOTE: Spring Boot provides numerous `FailureAnalyzer` implementations and you can
<<howto.adoc#howto-failure-analyzer,add your own>> very easily.
[[boot-features-banner]] [[boot-features-banner]]
=== Customizing the Banner === Customizing the Banner