From: Christopher Schultz <[email protected]>
Sent: Friday, November 7, 2025 11:13 AM
To: [email protected]
Subject: Re: Still struggling with getting root causes of exceptions in
tomcat-embed-core in SpringBoot applications
David, On 11/7/25 1: 04 PM, KARR, DAVID wrote: > In the dependency tree of one
of the services that is still not showing the log entry, I see logback-core,
logback-classic, and log4j-to-slf4j. In one service that is showing the log entry,
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David,
On 11/7/25 1:04 PM, KARR, DAVID wrote:
In the dependency tree of one of the services that is still not showing the log
entry, I see logback-core, logback-classic, and log4j-to-slf4j. In one service
that is showing the log entry, it only has logback-classic. The service that
is not showing the log entry is using a NEWER version of springboot than the
one that is showing it, along with a newer patch version of logback.
I also see that “org.apache.juli.logging.Log”, a class in tomcat-juli, is also
present in tomcat-embed-core. Both the “good” and “bad” service use the same
version of tomcat-embed-core.
I remember now that we actually already have a “logging.properties” file in the
classpath of both services, with the following contents:
handlers = java.util.logging.ConsoleHandler
java.util.logging.ConsoleHandler.level = ALL
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter
Can you find a JAR file which contains this class:
org.apache.juli.logging.LogFactory
?
I do see that StandardContext seems to have a big of split-personality
when it comes to logging. Sometimes, it logs to this logger:
org.apache.catalina.core.StandardContext.log
And sometimes it logs to this one:
org.apache.catalina.core.ContainerBase.log
If you have specific configuration to enable DEBUG or TRACE logging for
StandardContext, consider enabling it for both StandardContext and also
ContainerBase.
-chris
From: Christopher Schultz
<[email protected]<mailto:[email protected]>>
Sent: Friday, November 7, 2025 8:40 AM
To: [email protected]<mailto:[email protected]>
Subject: Re: Still struggling with getting root causes of exceptions in
tomcat-embed-core in SpringBoot applications
David, On 11/6/25 1: 51 PM, KARR, DAVID wrote: > We support a large number of
SpringBoot applications using tomcat-embed-core (currently at 10. 1. 41). There are
some configuration issues that result in the service startup failing with a "Tomcat
ZjQcmQRYFpfptBannerEnd
David,
On 11/6/25 1:51 PM, KARR, DAVID wrote:
We support a large number of SpringBoot applications using tomcat-embed-core (currently
at 10.1.41). There are some configuration issues that result in the service startup
failing with a "Tomcat startup" exception, which provides no information about
the actual root cause.
I've spent a lot of time looking at the Tomcat "StandardContext" class for this. The catch clauses
in that typically call "getLogger().error(...". I find that I can set breakpoints at all the
"ok = false" lines, and if the root cause is repeatable on my desktop (pretty rare, actually), I
can set a breakpoint there and inspect the exception in the catch clause, but the log statement doesn't
appear anywhere that I can find.
I've asked related questions about this in the past, and there were times that I thought I had a solution, but I now know I do
not. It appears that since the "bridge" artifact is in use, we can set "logging.level." properties.
However, I have a feeling that only affects the log statements that directly use the "log" instance variable defined
directly in "StandardContext". It doesn't seem to have any effect on the catch clauses that use
"getLogger().error(...".
I now have a simple and repeatable test case for this, so I can experiment with
variations, but I'm still unable to get this to show the actual root cause.
I also note that although our services are mostly on v10.1.41 of
tomcat-embed-core, I see different behavior depending on what version of
SpringBoot they are using. In one service that is not showing the root cause,
I find that it is using version 3.3.11 of SpringBoot, which also results in
version 1.5.18 of logback-core. Another service is using a slightly older
version of SpringBoot, version 3.3.4 (logback-core 1.5.8), and that one IS
showing the root cause.
Over the last few months when I've struggled with this, I've tried other variations like
a "logging.properties" file that sets Catalina-specific properties, but I don't
think that made any difference, although that was before I had this repeatable test case.
I also note that in the service that shows the root cause, I see this in my log:
08:43:14,376 |-INFO in
ch.qos.logback.classic.jul.LevelChangePropagator@4eba373c<mailto:ch.qos.logback.classic.jul.LevelChangePropagator@4eba373c<mailto:ch.qos.logback.classic.jul.LevelChangePropagator@4eba373c%3cmailto:ch.qos.logback.classic.jul.LevelChangePropagator@4eba373c>>
- Propagating DEBUG level on Logger[org.apache.catalina] onto the JUL framework
I do NOT see that in the service that is not showing the root cause.
What other logging-related libraries are being deployed along with your
application. You mentioned logback. Is there anything else? For example,
tomcat-juli.jar?
If tomcat-juli.jar is present, then logging.properties will be used by
java.util.logging to produce logs.
If, however, you (or Spring) have installed some other kind of logging
bridge over to logback, then logging.properties will probably be ignored
in favor of however logback is configured.
-chris
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