codeconsole commented on code in PR #15757:
URL: https://github.com/apache/grails-core/pull/15757#discussion_r3562672196
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grails-doc/src/en/guide/upgrading/upgrading80x.adoc:
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@@ -1514,3 +1514,60 @@ Both hooks may be used on the same plugin during
migration; when a registrar and
**Bean-definition overriding edge case.** Grails defaults
`spring.main.allow-bean-definition-overriding` to `true`, and under that
default nothing changes: an application bean (from the application class,
`resources.groovy` or `resources.xml`) that uses the same name as a plugin bean
still replaces the plugin's bean. However, because plugin beans now register
earlier and application beans register in a separate, later step, an
application that explicitly sets `spring.main.allow-bean-definition-overriding`
to `false` will see a `BeanDefinitionOverrideException` for an application bean
that shadows a plugin bean — in previous releases the two definitions were
merged before a single registry write, so the shadowing was silent even with
overriding disabled.
**Most applications and plugins need no action.** Behavior only changes where
a plugin bean and a conditional Boot bean competed for the same name or type —
the plugin bean now wins, which is almost always the intended outcome.
+
+==== 34. Zero-Config Logback Logging Is Now Supported
+
+Newly generated Grails 8 applications continue to include a starter
`grails-app/conf/logback-spring.xml` file, but the file is now optional, and
its content has been simplified to match Spring Boot's defaults.
+
+The starter file no longer duplicates Spring Boot's configuration: it composes
Spring Boot's own `defaults.xml` and `console-appender.xml` and sets an `INFO`
root level, while keeping a `<springProfile name="development">` block for
environment-specific logging. Previous Grails releases generated a standalone
configuration with an `ERROR` root level, which suppressed the `WARN` and
`INFO` output — including framework startup warnings — that Spring Boot shows
by default. Existing applications keep whatever configuration they already have.
+
+An application depends on `grails-logging`, which brings in Spring Boot's
logging starter, so if `grails-app/conf/logback-spring.xml` is removed, Logback
and Spring Boot's own default Logback configuration apply automatically. This
matches the Spring Boot convention of needing no logging configuration file
unless one is actually required.
+
+NOTE: A future major release may stop generating
`grails-app/conf/logback-spring.xml` by default in favor of the zero-config
behavior described here. Existing applications that contain the file are
unaffected either way and continue to use it.
+
+With no configuration file present you get Spring Boot's defaults: an `INFO`
root level and a colorized console pattern. Levels and patterns can be tuned
from `application.yml` with no XML:
+
+[source,yaml]
+.application.yml
+----
+logging:
+ level:
+ root: INFO
+ com.example.myapp: DEBUG # your packages
+ org.hibernate.SQL: DEBUG # see the generated SQL
+ pattern:
+ console: "%d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%n"
+ file:
+ name: logs/myapp.log # setting this activates Spring
Boot's file appender
+----
+
+Per-environment logging also needs no XML. Grails environments map to Spring
profiles, so an `environments` block in `application.yml` applies levels to a
single environment — for example, verbose logging for your own packages in
development only:
+
+[source,yaml]
+.application.yml
+----
+environments:
+ development:
+ logging:
+ level:
+ com.example.myapp: DEBUG
+----
+
+A profile-specific `grails-app/conf/application-development.yml` containing
the same `logging.level` entries works as well.
+
+Keep (or re-add) a `logback-spring.xml` file when properties are not enough —
for example custom appenders, structured/JSON output, or per-environment
appender routing. Use the `-spring` variant (not plain `logback.xml`), because
it is processed by Spring Boot and unlocks `<springProfile>` and
`<springProperty>`:
+
+[source,xml]
+.grails-app/conf/logback-spring.xml
+----
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+ <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
Review Comment:
Good catch — you're right, with no appender the example silenced everything
it claimed to enable. Fixed in 2b1902fbc2: the example now matches the
generated starter's shape (`defaults.xml` + `console-appender.xml` includes and
a `<root level="INFO">` with the `CONSOLE` appender-ref), and the surrounding
text now states explicitly that a custom `logback-spring.xml` replaces Spring
Boot's bundled configuration entirely and must declare its own appenders.
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