Use custom Ant task from Gradle

build.gradle

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'maven'

configurations { taskdef }

repositories { mavenCentral() }

dependencies { taskdef 'java2html:j2h:1.3.1' }

task java2html << {
    def basedir = '.'
    ant.taskdef(name:'java2html'
            ,classpath:configurations.taskdef.asPath
            , classname:"com.java2html.Java2HTMLTask"
            )

    ant.java2html{
        fileset(dir: 'src/main/java'){
            include (name: '*.java')
        }
    }
}