This happens also with 6.0.38.

Downgrading zabbix-java-gateway to 6.0.37 solves it ...

We thought we fixed this issue, but on our test system "jboss-client.jar" was not present, therefore the problem did not occur.

We had the same issue. We were able to fix it by replacing "slf4j-api-2.0.16.jar" with "slf4j-api-2.0.17.jar".

The warning about loading the class no longer shows up during startup and the logfile is written as before.

We also tested the update from 6.0.39 to 6.0.40. This will provide again "slf4j-api-2.0.16.jar", but it still works. Both libraries can be loaded at the same time and it seems the newer one is used. So it's enough to just add the jar file to the folder "zabbix-java-gateway/lib/"

This was tested with the following versions:

6.0.38
6.0.39
6.0.40

We got the slf4j-api jar file from:

https://mvnrepository.com/artifact/org.slf4j/slf4j-api/2.0.17

We also tested logback 1.5.18: It only works with "slf4j-api-2.0.17.jar"

So it seems the issue is in slf4j-api-2.0.16.jar. 

https://mvnrepository.com/artifact/ch.qos.logback/logback-core/1.5.18
https://mvnrepository.com/artifact/ch.qos.logback/logback-classic/1.5.18

Replacing the logback jars is not required to fix the issue. It was just an additional test.

We found the following workaround, but later also a final solution. I post this workaround in case it's usefull for somebody. See the next comment for a final solution.

It seems the order of loaded jar files matters in this case. The jboss-client.jar needs to be loaded last from the lib directory. The startup script automatically loads all jar files in alphabetical order. By renaming the jar file it's possible to manipulate the order in which the jars are loaded. 

We renamed "jboss-client.jar" to "zzzjboss-client.jar."  So we added "zzz" in front of the file name. This way the file is the last in alphabetical order.

We changed the log level from "info" to "debug" in the file "/etc/zabbix/zabbix_java_gateway_logback.xml", in order to see more details.

As the file is not provided by the zabbix-java-gateway package, It also works after an update. 

This was tested with the following versions:

6.0.38
6.0.39
6.0.40

There is an easy fix which is obvious in hindsight: Just update the jboss-client.jar

Get the latest version of the jboss-client from:

https://www.wildfly.org/downloads/

(The link is also in the zabbix documentation about the java gateway)

You have to download the zip or tar for "WildFly Distribution". Unpack the archiv and find the jar file under "bin/client/ jboss-client.jar". Replace the file under "/usr/share/zabbix-java-gateway/lib" with this new file.

We had version 7.3 of jboss-client.jar (myabe it was from JBoss EAP or it's very very old). With the new version it works without any problems.

You can check the version of the jar like this:

our old version:

#> unzip -p jboss-client.jar META-INF/MANIFEST.MF
Manifest-Version: 1.0
Implementation-Title: WildFly: EJB and JMS client combined jar
Implementation-Version: 7.3.3.GA-redhat-00004
Java-Version: 1.8.0_121
Built-By: PNC-Builder-0.4.0
Scm-Connection: scm:git:[email protected]:wildfly/wildfly.git/client/wild fly-client-all
Specification-Vendor: JBoss by Red Hat
Os-Arch: amd64
Specification-Title: WildFly: EJB and JMS client combined jar
Implementation-Vendor-Id: org.jboss.eap
JBossAS-Release-Version: 7.3.3.GA-redhat-00004
Java-Vendor: Oracle Corporation
Os-Name: Linux
Scm-Url: https://github.com/wildfly/wildfly
Implementation-Vendor: JBoss by Red Hat
Os-Version: 3.10.0-1127.19.1.el7.x86_64
Scm-Revision: 0a22160f2b73feb9785fe8c201ad5202b5158ede
Multi-Release: true
JBossAS-Release-Codename: N/A
Created-By: Apache Maven 3.3.9
Build-Jdk: 1.8.0_121
Specification-Version: 7.3
Implementation-URL: http://www.jboss.org/jboss-eap-parent/client/wildfly-client-all
 

the newest version:

#> unzip -p jboss-client_wildfly-36.0.0.jar META-INF/MANIFEST.MF 
Manifest-Version: 1.0
Created-By: Maven JAR Plugin 3.4.2
Build-Jdk-Spec: 17
Specification-Title: Galleon shading of WildFly: Jakarta Enterprise Beans and Jakarta Messaging client combined jar
Specification-Version: 36.0
Specification-Vendor: JBoss by Red Hat
Implementation-Title: Galleon shading of WildFly: Jakarta Enterprise Beans and Jakarta Messaging client combined jar
Implementation-Version: Unknown
Implementation-Vendor: JBoss by Red Hat
Implementation-URL: http://www.jboss.org
JBossAS-Release-Codename: N/A
JBossAS-Release-Version: 36.0.0.Final
Java-Version: 17.0.14
Scm-Connection: scm:git:[email protected]:wildfly/wildfly.git
Scm-Revision: b6f8e1f589ba3f560b08282cad1cd8e3f9581b4e
Scm-Url: https://github.com/wildfly/wildfly
Export-Package: *
Bundle-ManifestVersion: 2
Bundle-SymbolicName: org.jboss.client
Bundle-Version: 1.0
Bundle-Name: Jakarta Enterprise Beans and Jakarta Messaging client library
Fragment-Host: org.openjdk.jmc.rjmx
Automatic-Module-Name: org.jboss.client
Multi-Release: true 

We renamed our new file, so that we know the version without checking in the future.

As the file is not provided by the zabbix-java-gateway package, It also works after an update. 

This was tested with the following versions:

6.0.38
6.0.39
6.0.40

HI Marco W. 

Thanks a lot for your notes and results of tests.

Closing this for now, if you have any more questions, feel free to reopen this ticket!