Reduce log level for message re: missing annotation [SPR-9233]

[spring-projects-issues]

Minas Manthos opened SPR-9233 and commented

Since 3.1.1 the AbstractRecursiveAnnotationVisitor logs a warning when annotation class could not be loaded (see AbstractRecursiveAnnotationVisitor#logNonFatalException). Until 3.1.0 any Exception was catched without any message. I agree to log this but IMO this should be a debug log message. Annotations (even if RetentionPolicy.RUNTIME) may or may not be available at run-time. See also Java Language Specification:

9.6.1.2 Retention

Annotations may be present only in the source code, or they may be present in the binary form of a class or interface. An annotation that is present in the binary may or may not be available at run-time via the reflective libraries of the Java platform.
...

So there is nothing wrong about getting a ClassNotFoundException regarding annotations.

I suggest to change the log level to debug or (IMO better) to catch ClassNotFoundException -> logger.debug(...) because it's legitimate and any other Exception -> logger.warn(...).

Background: We currently use jsr305 with @javax.annotation.Nonnull and @javax.annotation.Nullable doing some code analyses during builds. At run-time these annotations are no longer available/needed and we get tons of warnings ??"Failed to classload type while reading annotation metadata. This is a non-fatal error, but certain annotation metadata may be unavailable."??. Of course, it's not a problem to workaround this: we can include jsr305 or change log level in config of this logger but IMO I should not get a warning when everything is like expected and JLS-compliant.

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Affects: 3.1.1

Sub-tasks:

• Backport "Reduce log level for message re: missing annotation" [SPR-9447] #14082 Backport "Reduce log level for message re: missing annotation"

Issue Links:

• @ComponentScan with includeFilters on @Import-ed context does not work [SPR-9031] #13670 @ComponentScan with includeFilters on @Import-ed context does not work

Referenced from: commits c25a1bc, f55a4a1

6 votes, 7 watchers

[spring-projects-issues]

Chris Beams commented

Good point, thanks. We're working on other logging-related efforts for 3.2 M1 as it is, so this will fit in nicely.

[spring-projects-issues]

Bernd Götz commented

I could live with a warning but what's really cluttering the startup of the application is the output of the stack trace for it.

[spring-projects-issues]

Chris Beams commented

commit 535d31f8d43029ff4a53238c787a52d770f8532c
Author: Chris Beams <cbeams@vmware.com>
Date:   Sun May 27 13:27:39 2012 +0300

    Reduce log level for message re: missing annotation
    
    Previously (since Spring 3.1.1) RecursiveAnnotationAttributesVisitor
    logs at level WARN when ASM parsing encounters an annotation or an (enum
    used within an annotation) that cannot be classloaded. This is not
    necessarily indicative of an error, e.g. JSR-305 annotations such as
    @Nonnull may be used only for static analysis purposes, but because
    these annotations have runtime retention, they remain present in the
    bytecode. Per section 9.6.1.2 of the JLS, "An annotation that is present
    in the binary may or may not be available at run-time via the reflective
    libraries of the Java platform."
    
    This commit lowers the log level of these messages from warn to debug,
    but leaves at warn level other messages dealing with the ability
    reflectively read enum values from within annotations.
    
    Issue: SPR-9233