Unable to use logback.groovy, but logback.xml works

Question

I wanted to configure Logback using Groovy DSL. The file is very simple:

import ch.qos.logback.classic.encoder.PatternLayoutEncoder
import ch.qos.logback.core.ConsoleAppender
import static ch.qos.logback.classic.Level.DEBUG
import static ch.qos.logback.classic.Level.INFO

appender("stdout", ConsoleAppender) {
    encoder(PatternLayoutEncoder) {
        pattern = "%d %p [%c] - <%m>%n"
    }
}

root(INFO, ["stdout"])

I use Gradle to build my application and run it with jettyRun. I get the following error:

Failed to instantiate [ch.qos.logback.classic.LoggerContext]
Reported exception:
org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object 'ch.qos.logback.core.ConsoleAppender[null]' with class 'ch.qos.logback.core.ConsoleAppender' to class 'ch.qos.logback.core.Appender'
    at  org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:360)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.castToType(ScriptBytecodeAdapter.java:599)
at ch.qos.logback.classic.gaffer.ConfigurationDelegate.appender(ConfigurationDelegate.groovy:119)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at org.codehaus.groovy.runtime.metaclass.MixinInstanceMetaMethod.invoke(MixinInstanceMetaMethod.java:53)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoMetaMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:308)
at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:52)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:149)

However, when I switch to equivalent XML configuration, everything works. What am I doing wrong?

Using Logback 1.0.0. Tried with Logback 1.0.3.

Answer 1

I figured the solution out, but some questions remain opened. The problem was that I had no proper Groovy on the classpath. I decided to make an example project to demonstrate this bug. I started with a console application using Gradle's "application" plugin. I didn't include Groovy as dependency.

apply plugin: 'application'

repositories {
    mavenCentral()
}

ext.logbackVersion = '1.0.3'
ext.slf4jVersion = '1.6.4'

dependencies {
    compile "ch.qos.logback:logback-classic:$ext.logbackVersion"
    compile "org.slf4j:jcl-over-slf4j:$ext.slf4jVersion"
    //runtime "org.codehaus.groovy:groovy:1.8.6" // the problem was here
}

mainClassName = "org.test.Main"

This gave me an error, which is quite straighforward.

|-ERROR in ch.qos.logback.classic.LoggerContext[default] - Groovy classes are not available on the class path. ABORTING INITIALIZATION.

OK, cool. The dependency was missing - easy to fix. But why didn't I get the same error when I ran my web application? Adding Groovy dependency solved the initial problem in the web application. I stripped my project down and will create a corresponding JIRA. Perhaps, Groovy on classpath detection is not quite correct.