ninja tricks for groovy system scripting for javaland 2016
Post on 07-Apr-2017
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01
About me02
Andrey AdamovichBio: Developer, coach, speaker, author
Company: Aestas/IT (http://aestasit.com)
Email: andrey@aestasit.com
Linkedin: http://www.linkedin.com/in/andreyadamovich
Lanyrd: http://lanyrd.com/profile/andreyadamovich
GitHub: https://github.com/aadamovich
SO: http://stackoverflow.com/users/162792/andreyadamovich
Twitter: @codingandrey, @aestasit
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Exposed to operationsMaintenance scripts (backup, cleaning, monitoring)
Scheduled/CRON jobs (transfers, conversions, notifications)
Automation tasks (deployment, packaging, testing)
Web applications (status pages, back doors, dashboards)
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Why Groovy?05
Native system scriptingBash, Dash, Zsh, Fish, Csh etc.
Bat, Cmd and, eventually, PowerShell (PoSH)••
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Arrays in BAT?
07
BASH vs. PoSH
08
Scripting languagesPerl
Python
Ruby
Lua
Javascript
...
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Multiplatformsupport
10
Does it workon Windows?
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Operationalsimplicity
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Maintainablecode
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Stableecosystem14
Richextensionlibrary
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Groovy is just a JAR
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Reuse JVMknowledge17
sdkman.io
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sdkman.iocurl ‐s http://get.sdkman.io | bash
sdk install groovy 2.4.6
sdk default groovy 2.4.6
sdk list groovy
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PoSH GVM> posh‐gvm.psm1 cannot be loaded
> because the execution of scripts
> is disabled on this system.
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Speed up!21
GroovyServ
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Files,directories,and otheranimals23
Readingf = new File('test.txt')
String textContent = f.text
byte[] binaryContent = file.bytes
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Writing If << 'hello, this is a test file'
f.text = new URL('http://server/my_data.json').text
file.bytes = [ 65, 66, 67, 68 ] as byte[]
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Writing IIfile.text = '''What's in a name? That which we call a rose
By any other name would smell as sweet.'''
file << 'What\'s in a name? That which we call a rose\n'
file << 'By any other name would smell as sweet.'
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Writing IIIfile.withWriter { Writer writer ‐>
writer << 'What\'s in a name? That which we call a rose\n'
writer << 'By any other name would smell as sweet.'
}
file.withOutputStream { OutputStream stream ‐>
stream << 'What\'s in a name? That which we call a rose\n'
stream << 'By any other name would smell as sweet.'
}
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Linebylinedef lines = f.readLines()
lines.each { String line ‐>
println line
}
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eachLine and eachBytef.eachLine { String line ‐>
println line
}
file.eachByte { int b ‐>
...
}
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Filtering IoutputFile.withPrintWriter { writer ‐>
inputFile.eachLine { line ‐>
if (!line.startsWith('#')) {
writer.println(line)
}
}
}
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Filtering IIinputFile.filterLine(outputFile.newWriter()) { line ‐>
!line.startsWith('#')
}
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Filtering IIIoutputFile.withWriter { Writer writer ‐>
inputFile.withReader { Reader reader ‐>
reader.transformLine(writer) { String line ‐>
line.replaceAll('\t', ' ')
}
}
}
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Filtering IVinputFile.withReader { reader ‐>
reader.transformLine(outputFile.newWriter()) { line ‐>
line.replaceAll('\t', ' ')
}
}
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Filtering VoutputFile.text = inputFile.text.replaceAll('\t', ' ')01.
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Walking thepath
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eachFile and eachDirf.eachFile { File file ‐>
...
}
f.eachDir { File dir ‐>
...
}
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Recursive walking IcurrentDir.eachFileRecurse { File file ‐>
println file.name
}
currentDir.eachDirRecurse { File dir ‐>
println dir.name
}
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Recursive walking IIcurrentDir.traverse { File file ‐>
if (file.name.endsWith('.groovy')) {
println file.name
}
}
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Recursive walking IIIcurrentDir.traverse(nameFilter: ~/.*\.groovy/) { File file ‐>
println file.name
}
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Recursive walking IVimport static groovy.io.FileType.*
...
currentDir.traverse(
type: FILES,
nameFilter: ~/.*\.groovy/,
excludeNameFilter: ~/^C.*$/) { File file ‐>
println file.name
}
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Extending File IFile.metaClass.safeDelete = {
if (exists()) {
if (isDirectory()) {
if (!deleteDir()) {
def msg = "Unable to delete a directory: ${name}"
throw new IOException(msg)
}
...
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Extending File II ...
} else {
if (!delete()) {
def msg = "Unable to delete a file: ${name}"
throw new IOException(msg)
}
}
}
}
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Extending File IIIFile f = new File('test.txt')
f.safeDelete()
File d = new File('test_dir')
d.safeDelete()
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Base script44
Base script IBaseScript.groovy :
abstract class BaseScript extends Script {
static {
File.metaClass.safeDelete = {
if (exists()) {
...
}
}
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Base script IIdelete.groovy :
new File('idonotexist.txt').safeDelete()01.
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Base script IIIgroovy ‐b BaseScript delete.groovy01.
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Externalcommands48
External commands Idef exitValue = "ls ‐l".execute().exitValue()
if (!exitValue) {
println "Command failed with exit code: ${exitValue}"
}
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External commands IIprintln "ls".execute().text()
println "ls".execute().inputStream.eachLine { println it }
"grep abc".execute().waitForOrKill(1000)
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External commands IIIProcess process = "command".execute()
def out = new StringBuffer()
def err = new StringBuffer()
process.waitForProcessOutput(out, err)
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External commands IV"less temp.txt".execute().pipeTo("grep error".execute()).text
def proc1 = "less temp.txt".execute()
def proc2 = "grep error".execute()
proc1 | proc2
println proc2.text
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Arguments53
CliBuilderdef cli = new CliBuilder(usage:'ls')
cli.a('display all files')
cli.l('use a long listing format')
cli.t('sort by modification time')
def options = cli.parse(args)
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Defensivescripting
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Do you likeNPEs?
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Even simple things can cause NPEJava:
System.out.println(user.
getAddress().
getCity())
Groovy:
println user.
address.
city
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Safe navigation operator (?.)println user?.
address?.
city
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Elvis operator (?:)println user?.
address?.
city ?: "No idea"
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Closures forDSLs
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Imaginary DSLtransaction {
request {
id = '2L'
name = 'PUT'
amount = 25
}
request {
...
}
}
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DSL: transaction() methoddef transaction(Closure cl) {
def processor = new RequestProcessor()
try {
processor.init()
cl.delegate = processor
cl()
sendRequests()
} finally {
processor.cleanup()
}}
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DSL: request() methodclass RequestProcessor {
def requests = []
def request(Closure cl) {
def request = new Request()
requests << request
cl.delegate = request
cl()
}
...
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DSL: Request structureclass Request {
String id
String name
String amount
}
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Datamanipulation
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XMLimport groovy.util.XmlSlurper
def xmlSource = new File('shakespeare.xml')
def bibliography = new XmlSlurper().parse(xmlSource)
println bibliography.author
bibliography.play
.findAll { it.year.toInteger() > 1592 }
.each { println it.title }
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JSONimport groovy.json.JsonSlurper
def reader = new FileReader('ui.json')
def ui = new JsonSlurper().parse(reader)
ui.items.each { println it.type }
println ui.items[0]
.axes
.find {
it.fields.contains('y')
}.title
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Grab yourstuff!
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@Grab: import@Grab('org.apache.httpcomponents:httpclient:4.2.1')
import org.apache.http.impl.client.DefaultHttpClient
import org.apache.http.client.methods.HttpGet
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@Grab: variable@Grab('org.apache.httpcomponents:httpclient:4.2.1')
def httpClient =
new org.apache.http.impl.client.DefaultHttpClient()
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@Grab: method@Grab('org.apache.httpcomponents:httpclient:4.2.1')
def getHttpClient() {
new org.apache.http.impl.client.DefaultHttpClient()
}
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@Grab: class@Grab('org.apache.httpcomponents:httpclient:4.2.1')
class Searcher {
def httpClient
Searcher() {
httpClient =
new org.apache.http.impl.client.DefaultHttpClient()
}
}
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@Grab: multiple@Grapes([
@Grab('org.apache.httpcomponents:httpclient:4.2.1'),
@Grab('org.ccil.cowan.tagsoup:tagsoup:1.2')])
class Searcher { ... }
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@Grab: repository@GrabResolver(name='codehaus',
root='http://repository.codehaus.org/')
class Searcher { ... }
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@Grab: exclude@GrabExclude(group='commons‐codec',
module='commons‐codec')
class Searcher { ... }
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HTTP76
HTTPBuilder: import@Grab(
group='org.codehaus.groovy.modules.http‐builder',
module='http‐builder',
version='0.6'
)
import groovyx.net.http.*
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HTTPBuilder: instantiationdef baseUrl = 'http://api.duckduckgo.com'
def queryString = 'q=groovy&format=json&pretty=1'
def http = new HTTPBuilder(baseUrl)
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HTTPBuilder: requesthttp.request(Method.POST) {
send ContentType.URLENC, queryString
response.success = { response, reader ‐>
println response.statusLine
println reader.text
}
response.failure = { response ‐>
println response.statusLine
}
}
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SQL80
SQL: settingsimport groovy.sql.Sql
def dbSettings = [
url: 'jdbc:hsqldb:hsql://localhost/cookingdb',
driver: 'org.hsqldb.jdbcDriver',
user: 'sa',
password: ''
]
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SQL: querydef sql = Sql.newInstance(dbSettings)
sql.eachRow('SELECT * FROM COOKBOOK') { cookbook ‐>
printf '%‐20s%s\n',
cookbook.id,
cookbook[1]
}
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Groovy as a server (GaaS?)> groovy ‐l 4444 ‐e "println new Date()" &
> telnet localhost 4444
hey groovy give me the date
Wed Feb 04 10:03:23 EET 2015
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Ratpack84
Ratpack: import@Grab("io.ratpack:ratpack‐groovy:1.1.1")
import static ratpack.groovy.Groovy.ratpack
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Ratback: script bodyratpack {
handlers {
get {
response.send "This is the app root (try: /date)"
}
get("date") {
response.send new Date().toString()
}
}
}
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Sshoogr87
Sshoogr: import@Grab(
group='com.aestasit.infrastructure.sshoogr',
module='sshoogr',
version='0.9.16')
import static com.aestasit.ssh.DefaultSsh.*
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Sshoogr: defaultsdefaultUser = 'root'
defaultKeyFile = new File('secret.pem')
execOptions {
verbose = true
showCommand = true
}
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Sshoogr: connectionremoteSession {
url = 'user2:654321@localhost:2222'
exec 'rm ‐rf /tmp/*'
exec 'touch /var/lock/my.pid'
remoteFile('/var/my.conf').text = "enabled=true"
}
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Sshoogr: multiline contentremoteFile('/etc/yum.repos.d/puppet.repo').text = '''
[puppet]
name=Puppet Labs Packages
baseurl=http://yum.puppetlabs.com/el/
enabled=0
gpgcheck=0
'''
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Sshoogr: file copyingremoteSession {
scp {
from { localDir "$buildDir/application" }
into { remoteDir '/var/bea/domain/application' }
}
}
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Sshoogr: command resultdef result = exec(command: '/usr/bin/mycmd',
failOnError: false, showOutput: false)
if (result.exitStatus == 1) {
result.output.eachLine { line ‐>
if (line.contains('WARNING')) {
throw new RuntimeException("First warning: ${line}")
}
}
}
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Sshoogr: shortcutsif (ok('/usr/bin/mycmd')) {
...
}
if (fail('/usr/bin/othercmd')) {
...
}
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Sshoogr: tunnelstunnel('1.2.3.4', 8080) { int localPort ‐>
def url = "http://localhost:${localPort}/flushCache"
def result = new URL(url).text
if (result == 'OK') {
println "Cache is flushed!"
} else {
throw new RuntimeException(result)
}
}
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Sshoogr: prefix/suffixprefix('sudo ') {
exec 'rm ‐rf /var/log/abc.log'
exec 'service abc restart'
}
suffix(' >> output.log') {
exec 'yum ‐y install nginx'
exec 'yum ‐y install mc'
exec 'yum ‐y install links'
}
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Summary97
TakeawaysGroovy scripts are portable.
Groovy scripts are concise.
Groovy scripts are powerful.
Well, the name is groovy as well!
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Danke schön!99
Questions?100
Happyscripting!
101
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