Quick & Dirty JSON => CSV converter for http://stats.jenkins.io/plugin-installation-trend/jvms.json

csv-converter.groovy

import groovy.json.*

def slurper = new groovy.json.JsonSlurper()
def result = slurper.parse(new File('jvms.json'))

def vget(def map, def key) {
  map.get(key) ?: "0"
}

final def JVM_VERSIONS = ["1.5", "1.6", "1.7", "1.8", "1.9"]

println 'timestamp,' + JVM_VERSIONS.join(',')

result['jvmStatsPerMonth'].each { month_map ->
  println month_map.key + "," + ( JVM_VERSIONS.collect { vget(month_map.value, it) }.join(',') )
}

println "timestamp,1.7,1.8"
result['jvmStatsPerMonth_2_x'].each { month_map ->
  println month_map.key + "," + ( ["1.7", "1.8"].collect { vget(month_map.value, it) }.join(',') )
}