PropertiesLauncher working differently with slf4j bindings in newer version of spring boot - spring

Question

I have a spring boot project that uses the PropertiesLauncher to load a bunch of hadoop and hive jars at startup to provide connectivity to hadoop and hive. I am using slf4j with logback in my project and when I load the hive-jdbc jars they bring along log4j classes which cause a conflict. This is not an issue as long as I am using springBootVersion = '1.2.3.RELEASE' in my build.gradle.
I have configured the PropertiesLauncher in my build.gradle file
springBoot { layout = 'ZIP' }
bootRepackage {
mainClass = 'com....Application'
enabled = true
}
And starting up the application using this command
java -Dloader.path=file:///etc/hadoop/conf,file:///etc/hive/conf,jars,
byod-ui-1.0.0.SNAPSHOT.jar -jar byod-ui-1.0.0.SNAPSHOT.jar
When the projects start up, the output looks like this
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/byod/byod-ui-1.0.0.SNAPSHOT.jar!/lib/logback-classic-1.1.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/byod/jars/hive-jdbc-0.14.0.2.2.8.0-3150-standalone.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/byod/jars/hive-jdbc.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]
Notice that my application jar is detected first and then the hive-jdbc jars and I am assuming because my jar is detected first, the final line indicates that the binding selected is ch.qos.logback.classic.util.ContextSelectorStaticBinder which is logback so everything works great.
If I only change the spring boot version (and nothing else in code or configuration or jars/classpath setup) to springBootVersion = '1.3.2.RELEASE' Now the output looks like this
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/byod/jars/hive-jdbc.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/byod/jars/hive-jdbc-0.14.0.2.2.8.0-3150-standalone.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/byod/byod-ui-1.0.0.SNAPSHOT.jar!/lib/logback-classic-1.1.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:53)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext
but Logback is on the classpath. Either remove Logback or the competing implementation
(class org.slf4j.impl.Log4jLoggerFactory loaded from jar:file:/home/aq728y/byod/jars/hive-jdbc.jar!/).
If you are using WebLogic you will need to add 'org.slf4j' to prefer-application-packages in WEB-INF/weblogic.xml Object
of class [org.slf4j.impl.Log4jLoggerFactory] must be an instance of class ch.qos.logback.classic.LoggerContext
Now the order of detected bindings is different. This time, first bindings are detected from the hive-jdbc.jar instead of my application jar and that leads to log4j becoming the "actual binding" at the end. This results in an error and the application start up FAILS.
I wanted to provide these details and post this question to see if there were some changes in the recent version of spring boot that would explain this behavior and possibly help with the resolution. If possible, I would like to continue to use logback and not have to switch to log4j.

Answer 1

In Spring Boot 1.3.x the handling of classpath order has changed.
In 1.2.x, the order was reversed, so specifying
-Dloader.path=file:///etc/hadoop/conf,file:///etc/hive/conf,jars,
byod-ui-1.0.0.SNAPSHOT.jar
produced the following classpath order:
byod-ui-1.0.0.SNAPSHOT.jar
jars
file:///etc/hive/conf
file:///etc/hadoop/conf
In 1.3.x the classpath isn't reverted anymore, so the same commandline options leads to the follwing classpath order:
file:///etc/hadoop/conf
file:///etc/hive/conf
jars
byod-ui-1.0.0.SNAPSHOT.jar
and this causes slf4j to pick the bindings in the hive-jars up first.
So the solution is to simply revert the order on commandline:
-Dloader.path=byod-ui-1.0.0.SNAPSHOT.jar,jars,file:///etc/hive/conf,file:///etc/hadoop/conf
See commit for further informations:
https://github.com/spring-projects/spring-boot/commit/bfa816f2a30dbc188ca563da8f28c22417d907e5