Handlebars-proto and logstash-logback-encoder slf4j conflict - json

Question

My project uses handlebars-proto to bind templates to json. Also i am trying to use logstash-logback-encoder to log in form of Json for logstash. Below are my compile dependencies ( along with other dependencies)
compile 'net.logstash.logback:logstash-logback-encoder:4.6'
compile 'com.github.jknack:handlebars-proto:4.0.5'
If I remove handlebars dependency logging works fine. If handlebars is present I get the below warning :
SLF4J: Class path contains multiple SLF4J bindings. SLF4J: Found
binding in
[jar:file:/C:/Users/manish/.gradle/caches/modules-2/files-2.1/com.github.jknack/handlebars-proto/4.0.5/5979737344d99e0d8b482e828f247ae86fd0113/handlebars-proto-4.0.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in
[jar:file:/C:/Users/manish/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-classic/1.1.6/665e3de72f19ec66ac67d82612d7b8e6b3de3cd0/logback-classic-1.1.6.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an
explanation.
followed by error :
Failed to instantiate [ch.qos.logback.classic.LoggerContext] Reported
exception:
java.lang.NoSuchMethodError: ch.qos.logback.core.spi.ContextAwareBase.(Lch/qos/logback/core/spi/ContextAware;)V
at
net.logstash.logback.composite.CompositeJsonFormatter.(CompositeJsonFormatter.java:106)
at
net.logstash.logback.composite.loggingevent.LoggingEventCompositeJsonFormatter.(LoggingEventCompositeJsonFormatter.java:28)
at
net.logstash.logback.LogstashFormatter.(LogstashFormatter.java:122)
at
net.logstash.logback.LogstashFormatter.(LogstashFormatter.java:118)
at
net.logstash.logback.LogstashFormatter.(LogstashFormatter.java:114)
at
net.logstash.logback.encoder.LogstashEncoder.createFormatter(LogstashEncoder.java:31)
at
net.logstash.logback.encoder.CompositeJsonEncoder.(CompositeJsonEncoder.java:48)
at
net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder.(LoggingEventCompositeJsonEncoder.java:23)
at
net.logstash.logback.encoder.LogstashEncoder.(LogstashEncoder.java:27)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native
Method) at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at java.lang.Class.newInstance(Class.java:379) at
ch.qos.logback.core.joran.action.NestedComplexPropertyIA.begin(NestedComplexPropertyIA.java:122)
at
ch.qos.logback.core.joran.spi.Interpreter.callBeginAction(Interpreter.java:276)
at
ch.qos.logback.core.joran.spi.Interpreter.startElement(Interpreter.java:148)
at
ch.qos.logback.core.joran.spi.Interpreter.startElement(Interpreter.java:130)
at
ch.qos.logback.core.joran.spi.EventPlayer.play(EventPlayer.java:50)
I tried excluding slf4j as transitive dependency from handlebars but
it did not help.
compile
('com.github.jknack:handlebars-proto:4.0.5'){
exclude module: 'slf4j-api'
}
Thanks in advance for help. Let me know if more details are required.

Answer 1

The error message is because the handlebars-proto jar contains an implementation of org.slf4j.impl.StaticLoggerBinder, which means that it has a logging implementation. You are also trying to add your own logging implementation of Logback, and since SLF4J can't use two logging systems at once, it's complaining.
I'm not familiar with the handlebars project, but I'm guessing that the library you have there is a full application that includes a logging system, and not really designed to be used as a dependency by another project. Perhaps there's a different version available that is just the library, and that doesn't try to include its own logging implementation?