Gradle dependencies to setup logstash logback

gistfile1.txt

dependencies {  
    ext {
        logbackVersion = '1.1.6'
        slf4jApiVersion = '1.7.15'
        logStashLogbackEncoderVersion = '4.7'
    }
...
    compile("ch.qos.logback:logback-classic:$logbackVersion")
    compile("ch.qos.logback:logback-core:$logbackVersion")
    compile("ch.qos.logback:logback-access:$logbackVersion")
    compile("org.slf4j:slf4j-api:$slf4jApiVersion")
    compile("org.slf4j:jcl-over-slf4j:$slf4jApiVersion")
    compile("org.slf4j:log4j-over-slf4j:$slf4jApiVersion")
    compile("net.logstash.logback:logstash-logback-encoder:$logStashLogbackEncoderVersion")
...
}