gretty.gradle

apply plugin: 'war'
apply from: 'https://raw.github.com/akhikhl/gretty/master/pluginScripts/gretty.plugin'

gretty {
    servletContainer = 'tomcat7'
    enableNaming = true
    jvmArgs '-Xmx2048M', '-XX:+CMSClassUnloadingEnabled'
    afterEvaluate {
        clean.dependsOn cleanPrepareArchiveWebApp
        clean.dependsOn cleanPrepareInplaceWebApp
        clean.dependsOn cleanPrepareInplaceWebAppClasses
        clean.dependsOn cleanPrepareInplaceWebAppFolder
    }
}

repositories {
    mavenLocal()
    mavenCentral()
}

dependencies {
    compile 'mysql:mysql-connector-java:5.1.33'
    compile 'postgresql:postgresql:8.3-603.jdbc4'
    compile files("${tomcatHome}/lib/ojdbc5_g.jar")
    compile 'org.apache.tomcat:tomcat-dbcp:7.0.55'
}

clean.dependsOn cleanWar

Getting a whole lot of this:

2014-10-24 14:26:41.339 WARN  - Failed to register in JMX: javax.naming.NamingException: C
ould not create resource factory instance [Root exception is java.lang.ClassNotFoundExcept
ion: org.apache.tomcat.dbcp.dbcp.BasicDataSourceFactory]

First step: change "compile" to "gretty". Files belonging to "compile" configuration are part of webapp. Files belonging to "gretty" configuration are part of server and they are loaded earlier than webapp.