POJO to JSON : binding and serializing

//see: http://www.cowtowncoder.com/blog/archives/2009/01/entry_137.html
//see: https://github.com/FasterXML/jackson-databind

@Grapes([
/*
  @Grab(
    group='com.fasterxml.jackson.core', module='jackson-core', version='2.2.1'
  ),
  @Grab(
    group='com.fasterxml.jackson.core', module='jackson-annotations', version='2.2.1'
  ),
*/
  @Grab(
    group='com.fasterxml.jackson.core', module='jackson-databind', version='2.2.1'
  )
])
import com.fasterxml.jackson.databind.ObjectMapper

class Abc {
    int id, age
    String person
}

ObjectMapper mapper = new ObjectMapper();
Abc entry = mapper.readValue('{"id": 1, "person": "Steve", "age": "1"}', Abc.class);

assert entry1.id == 1
assert entry1.person == "Steve"
assert entry1.age == 1 //notice the auto type conversion from the JSON!

def entry2 = mapper.readValue('{"id": 1, "person": "Steve", "age": [1, {}, 3]}', LinkedHashMap.class);

assert entry2.id == 1
assert entry2.person == "Steve"
assert entry2.age.size() == 3
assert entry2.age[1].getClass().name == 'java.util.LinkedHashMap'


mapper.writeValue(new File("C:\\result.json"), entry1)  //--> {"id":1,"person":"Steve","age":1}
/*
  public void com.fasterxml.jackson.databind.ObjectMapper#writeValue(java.io.File, java.lang.Object)
  public void com.fasterxml.jackson.databind.ObjectMapper#writeValue(java.io.OutputStream, java.lang.Object)
  public void com.fasterxml.jackson.databind.ObjectMapper#writeValue(java.io.Writer, java.lang.Object)
*/

Simple Timer & TimerTask

public class MyTask extends TimerTask{
    Closure onFinish
    int count, repeat
    
    public MyTask(Closure onFinish = {}, int repeat = 1){
        this.onFinish = onFinish
        this.repeat = repeat
        this.count = 1
    }
    
    private void toDo(){
        println "count-> ${count}"      
    }
    
    private void checkFinished() {
        if (count > repeat) { //this is the condition when you want to stop the task.
            println "DONE-> before ${count}"
            onFinish()
            return
        }
    }
    
    @Override
    public void run() {        
        toDo()
        count++
        checkFinished()
    }
}

public class MyScheduler {
    public static void doIt( Closure then = {} ) {
        Timer timer = new Timer()
        MyTask myTask = new MyTask( repeat:3, 
            onFinish:{ 
                timer.cancel() // stop the timer
                then() // do the callback
            })
        int delayStartMs = 2000
        int intervalMs = 1000
        timer.schedule(myTask, delayStartMs, intervalMs)
    }
}

MyScheduler.doIt( { println "#1 DONE" } )
MyScheduler.doIt( { println "#2 DONE" } )

Run OS command

//windows
String cmd = "ping google.com"

String[] command = ["CMD", "/C", cmd] as String[]
ProcessBuilder builder = new ProcessBuilder(command)
Process process = builder.start()

println process.text

println "*"*5+"DONE"+"*"*5

String padding with zeros

String.metaClass.zeropad = { Integer padding = 0 ->
    return ("0" * Math.max(0, (padding ?: 0) - delegate.size())) + delegate
}
Integer.metaClass.zeropad = { Integer padding = 0 ->
    return delegate.toString().zeropad(padding)
}

assert "123".zeropad()     == "123"
assert "123".zeropad(null) == "123"
assert "123".zeropad(5)    == "00123"
assert "1234".zeropad(5)   == "01234"
assert "12345".zeropad(5)  == "12345"
assert "123456".zeropad(5) == "123456"

assert 123.zeropad()     == "123"
assert 123.zeropad(null) == "123"
assert 123.zeropad(5)    == "00123"
assert 1234.zeropad(5)   == "01234"
assert 12345.zeropad(5)  == "12345"
assert 123456.zeropad(5) == "123456"

@Delegate vs. Extends

// "favor composition over inheritance" ~Effective Java

class Parent {
    def getAll() {
        String resp = ""
        2.times {
            resp += get(it)
        }
        return resp
    }
    
    def get(def i) {
        "get PARENT $i\n"
    }
}

class Child1 extends Parent {
    def get(def i) {
        "get CHILD $i\n" // is used by parent's getAll
    }
}

class Child2 {
    @Delegate Parent p = new Parent() // decorated Parent instance
    
    def get(def i) {
        "get CHILD $i\n" // not used by parent's getAll
    }
}

Parent c1 = new Child1()
assert c1.getAll() == "get CHILD 0\nget CHILD 1\n" // calls child's get()
assert c1.get(0) == "get CHILD 0\n"

//Parent c2 = new Child2() // Child2 is not a Parent!
Child2 c2 = new Child2()
assert c2.getAll() == "get PARENT 0\nget PARENT 1\n" // calls parent's get()
assert c2.get(0) == "get CHILD 0\n"

DNS lookup - timed

int maxTimeout = 30000
int minTimeout = 15000

List domainList = [
    'gmail.com', 'google.co.uk', 'google.com', 'bbc.co.uk', 'cnn.com', 'java.oracle.com',
    'facebook.com', 'twitter.com', 'oracle.com', 'zen.co.uk', 'java.net', 'www.scala-lang.org',
    'plus.google.com', 'guardian.co.uk', 'linkedin.com', 'www.typesafe.com', 'www.yahoo.com',
    'www.ibm.com', 'www.apache.org', 'www.adobe.com', 'www.microsoft.com', 'www.stackoverflow.com',
    'www.apple.com', 'groovy.codehaus.org', 'java.oracle.com', 'www.telegraph.co.uk', 'www.jroller.com',
    'www.dell.com', 'www.samsung.com', 'www.amazon.co.uk', 'docs.oracle.com', 'www.infoq.com',
    'www.devoxx.com', 'www.qconlondon.com', 'www.smashingmagazine.com', 'en.wikipedia.com' ]

int count = 1
while (true) {
    int idx = (int)( Math.random() * domainList.size )    
    println "[$count]  nslookup ${domainList[idx]}"
    def process = "nslookup ${domainList[idx]}".execute()
    println "Found text ${process.text}"
    
    int sleepTime = (int)( minTimeout + Math.random() * ( maxTimeout  - minTimeout))
    Thread.sleep( sleepTime );
    
    ++count
}

Resolve an HTTP Redirect

// source: https://gist.github.com/3899754

def findRealUrl(url) {
    HttpURLConnection conn = url.openConnection()
    conn.followRedirects = false
    conn.requestMethod = 'HEAD'
    if(conn.responseCode in [301,302]) {
        if (conn.headerFields.'Location') {
          return findRealUrl(conn.headerFields.Location.first().toURL())
        } else {
            throw new RuntimeException('Failed to follow redirect')
        }
    }
    return url
}