[TINKERPOP-3014] Dependencny jcl-over-slf4j in gremlin-core is declared but unused due to dependency conflict.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.7.0
• Fix Version/s: 3.7.1
• Component/s: process
• Labels: dependency
• Flags: Patch
• Assignee: Cole Greer
• Reporter: Wei Zhao
• Created: 10/Nov/23 13:36
• Updated: 16/Nov/23 21:28
• Resolved: 16/Nov/23 21:28

Description

Problem Description

"gremlin-core" declares "jcl-over-slf4j" as its dependency. However, it seems that the dependency is actually unused due to a dependency conflict.

There is another dependency "commons-logging:commons-logging" in the dependency tree as listed below:

org.apache.tinkerpop:gremlin-core:jar:3.7.0-SNAPSHOT
\- org.apache.commons:commons-configuration2:jar:2.9.0:compile
   \- commons-logging:commons-logging:jar:1.2:compile
\- org.slf4j:jcl-over-slf4j:jar:1.7.33:compile

The classes in "jcl-over-slf4j" are also in "commons-logging" as listed below:

[INFO] org.apache.commons.logging.impl.NoOpLog
[INFO] org.apache.commons.logging.impl.SimpleLog$1
[INFO] org.apache.commons.logging.impl.SimpleLog
[INFO] org.apache.commons.logging.impl.SLF4JLocationAwareLog
[INFO] org.apache.commons.logging.impl.SLF4JLog
[INFO] org.apache.commons.logging.impl.SLF4JLogFactory
[INFO] org.apache.commons.logging.Log
[INFO] org.apache.commons.logging.LogConfigurationException
[INFO] org.apache.commons.logging.LogFactory

The problem is that "commons-logging" is ahead of "jcl-over-slf4j" in the dependency tree, thus ahead of "jcl-over-slf4j" in the classpath. When multiple JAR files contain the same class, the class loader will load the first occurrence it finds based on the classpath order. This means the classloader will select classes in "commons-logging" instead of "jcl-over-slf4j".

So despite "jcl-over-slf4j" being declared directly, it's actually unused. "commons-logging" is the actual used dependency, causing confusion.

Possible Solution

Change the order of "jcl-over-slf4j" and "commons-logging" so that "jcl-over-slf4j" appears ahead of "commons-logging" in the classpath. In this way, "jcl-over-slf4j" is used as intended.