Category Archives: java

Grails Starter kit

After years of working with Grails, I thought I would put down in one place a few things I tend to use frequently in my Grails projects. These are things I thought might help others getting started with Grails.


I often find that I need to extend the default session timeout(found in the src/templates). All that is needed is

> grails install-templates

You will then need to edit the web.xml contained in the following directory structure that was generated from the above command.

src -> templates -> war -> web.xml

you can now modify the timeout value


Custom Domain Classes

Update your domain class templates to reduce having to type in your company standards for every domain class. One of the environments I worked in had a database standard that required us to label Primary Key column name(PK_column_name) and use oracle’s generator for ids. I addressed this by creating a private company “db standards” Grails plugin.

First I updated the

templates-> artifacts ->DomainClass.groovy file

@artifact.package@class {
    Date lastUpdated
    Date dateCreated
    String createdBy
    String updatedBy

    static constraints = {

    static mapping={
        id generator: 'sequence', params: [sequence: '']
        columns { id column: '' }//prod/test

I then copied and modified a core grails script(see comments in code) that creates domain classes and renamed it create-my-domain(well it was better names then this… but you get the gist :D). See below.
Then I can run

>create-my-domain Book

The following concrete domain class is generated(notice the sequence,id, and generator are all there).

class Book{

  Date lastUpdated
  Date dateCreated
  String createdBy
  String updatedBy
  static mapping = {
    id generator: 'sequence', params: [sequence: 'BOOK_SEQ']
    columns { id column: 'PK_BOOK_ID' }


There are times when I need to query a database that I don’t need/want a Domain Class for.  I tend to create a datasource and inject it into a service that will be handling the connection/query with groovySql

Here is an example datasource in the DataSource.groovy file.

dataSource_salesInfo {
  driverClassName = "oracle.jdbc.driver.OracleDriver"
  url = ""//more on how to configure this later in this blog entry
  username = ""

  password = ""
  dialect = "org.hibernate.dialect.Oracle10gDialect"
  hibernate {
    cache {
      use_second_level_cache = false
      use_query_cache = false

Example service that uses the defined datasource entry.

class AwesomeService{

  def dataSource_salesInfo //Inject it

  def queryDB(){
  def sql = new Sql(dataSource_salesInfo)
  String myQuery ='..'
  sql.rows(myQuery).each { resultSet -> /*do something*/}

Externalize Datasources

One way to externalize your jdbc connection url is to use an system environment variable. Another is to have your operations team generate a properties file based on the tnsnames.ora file and read it into your grails application. I will describe how the properties file based solution would work.
An Example entry might look like the following.


in datasource.groovy file, I add the following to the top of the file.

def props = new Properties()
new File('').withInputStream { stream -> 
props.load(stream) }

then I reference the property in the URL entry for the datasource I am working with 

url = props.get("DATAWAREHOUSE")


Most of my day is spent with Oracle databases. The validation query that I use is


validationQuery = "SELECT sysdate from dual"

here is a complete example.

production {
  dataSource {
    url = props.get("DATAWAREHOUSE")
    username = ""
    password = ""
    properties {
      maxActive = -1
      minEvictableIdleTimeMillis = 1800000
      timeBetweenEvictionRunsMillis = 1800000
      numTestsPerEvictionRun = 3
      testOnBorrow = true
      testWhileIdle = true
      testOnReturn = true
      validationQuery = "SELECT sysdate from dual"


Here are the lines that actually allow you to externalize your config/datasources(Thanks to Burt Beckwith and his book )


production {
grails.config.locations = [
"" //NOTE: don’t leave spaces

I like to have the following in my path

grails.config.locations = [

This forces the file name to have development || production || test and the application name in the configuration file to prevent copy and paste errors(you would never do that right 😉 )

SQL Logging

There are a couple of ways to see what is going on under the hood when your application is querying the database.

The easiest is to add the logSql = true to your datasource

development {
  dataSource {
    url = props.get("DATAWAREHOUSE")
    logSql = true

If you need more information,  Burt Beckwith has the following Logging Hibernate SQL post that you should read. He shows how adding the following lines to your log4j closure will help with understanding what is happening under the hood.

log4j = {
   debug 'org.hibernate.SQL'
   trace 'org.hibernate.type.descriptor.sql.BasicBinder'


A log pattern that works with tomcat(YMMV)

appenders {
console name: 'stdout', threshold: org.apache.log4j.Level.INFO
rollingFile name: 'MyLogs', file: 'logs/MyLog.log', maxSize: 104576, threshold: org.apache.log4j.Level.INFO ,
layout:pattern(conversionPattern: "%d{yyyy-MM-dd HH:mm:ss} [%t] %p %c - %m%n")


Have your war tell you what environment you are deploying to

grails.project.war.file = "target/${appName}-${appVersion}-${System.getProperty('grails.env')[0..3]}.war"

Websites and links to check out


Many of the things I have learned have come from the above links and people. A big Thank You to the gr8 community for all the help over the years.



Groovy Invoke Dynamic Support

The release of Groovy 2.1 comes with full Invoke Dynamic Support. Initially I had issues with trying to get a working example up and running as seen by the following message.

>groovy –indy mergesort.groovy
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
General error during class generation: Cannot use invokedynamic, indy module was excluded from this build.

I checked the groovy version to make sure that I had Java 7 loaded as seen here
groovy -version
Groovy Version: 2.1.0 JVM: 1.7.0_11 Vendor: Oracle Corporation OS: Mac OS X

In order to get things working, I read that I needed to get the “indy” jar on my classpath. I added the following to my .bash_profile and restarted my terminal and the error cleared up

export CLASSPATH=$HOME/.gvm/groovy/current/indy/groovy-2.1.0-indy.jar

Hope this helps and a huge thanks to the Groovy Core Team for this latest update!


Simple Groovy project using Gradle

Hello fellow Groovyists 🙂

I have been kicking the tires on using Gradle for my Groovy projects. I had a few stumbles along the way and wanted to share what I came up with for getting a very simple example working.


apply plugin: 'groovy'
version = "1.0-${new Date().format('yyyyMMdd')}"

manifest.mainAttributes("Main-Class" : "com.javazquez.HelloThere")

repositories {
mavenRepo urls: ""
dependencies {
groovy group: 'org.codehaus.groovy', name: 'groovy-all', version: '1.8.4'
groovy group: 'org.mongodb', name: 'mongo-java-driver', version: '2.6.5'
groovy group: 'com.gmongo', name: 'gmongo', version: '0.9.1'
testCompile "org.spockframework:spock-core:0.5-groovy-1.8"

jar {
from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }

below is the the HelloThere.groovy file located src/main/groovy/com/javazquez/HelloThere

package com.javazquez
public class HelloThere {

public static void main(String []args) {
println "Hello coders!"



after running gradle build, I can navigate to the build/libs directory and run java -jar HelloThere-1.0-20111115.jar and get the following ouptut

Hello coders!

Gradle is a fantastic tool and I hope this article helps show the ease of getting a project set up.

POP3 Gmail access with Clojure and JavaMail

I recently had the need to access gmail using Clojure. I used JavaMail to accomplish this via pop3. Below is some code that I wrote to help me get emails. Hope you find it useful Enjoy 🙂

(use '[])
(def props (System/getProperties))
; Get the default Session object.
(def session (javax.mail.Session/getDefaultInstance props))

; Get a Store object that implements the specified protocol.
(def store (.getStore session "pop3s"))

;Connect to the current host using the specified username and password.
(.connect store "" "" "password")

;Create a Folder object corresponding to the given name.
(def folder (. store getFolder "inbox"))

; Open the Folder.
(.open folder (javax.mail.Folder/READ_ONLY ))
; Get the messages from the server
(def messages (.getMessages folder))

(defn getFrom [message](javax.mail.internet.InternetAddress/toString (.getFrom message)))
(defn getReplyTo [message] (javax.mail.internet.InternetAddress/toString (.getReplyTo message)) )
(defn getSubject [message] (.getSubject message))

;print out the body of the message
(for [m messages] (read-lines(.getInputStream m)) )

;;;;;code for sending an email

(def props (System/getProperties))
(. props put "", "")
(. props put "mail.smtp.port", "465")
(. props put "mail.smtp.auth", "true")
(. props put "mail.transport.protocol", "smtps")

(def session (javax.mail.Session/getDefaultInstance props nil))
(def msg (javax.mail.internet.MimeMessage. session))
(. msg setFrom (javax.mail.internet.InternetAddress. ""))
(. msg addRecipients javax.mail.Message$RecipientType/TO

(. msg setSubject "i am the subject")
(. msg setText "I am the body!!!")

(. msg setHeader "X-Mailer", "msgsend")
(. msg setSentDate (java.util.Date.))

; send the email
(def transport (. session getTransport))
(. transport connect "" 465 "" "password")
(. transport sendMessage msg (. msg getRecipients javax.mail.Message$RecipientType/TO))
(. transport close)

Writing a PayPal SOAP client with Java 6

I have always been mystified on the inner workings of SOAP. That was until I learned about the “wsimport” utility that comes with Java 6. It makes the entire process very easy. Below is an example of writing a SOAP client for PayPal’s Sandbox. This code will execute the SetExpressCheckout API call.

Just enter the following on your command line to generate the com.javazquez package

wsimport -keep -XadditionalHeaders -Xnocompile -p com.javazquez

open your favorite java editor(I used eclipse) and add the package(“com.javazquez”..created in the above command) to your new project

next, write some code to test out the APIs

package com.javazquez;

public class TestEC {

public static void main(String[] args) {
SetExpressCheckoutReq req = new SetExpressCheckoutReq();
SetExpressCheckoutRequestType reqType = new SetExpressCheckoutRequestType();
SetExpressCheckoutRequestDetailsType details = new SetExpressCheckoutRequestDetailsType();
AddressType addr = new AddressType();
addr.cityName = "omaha";
addr.street1 = "123 main"; = CountryCodeType.US; = "joe tester";

details.address = addr;
details.orderTotal = new BasicAmountType();
details.orderTotal.currencyID = CurrencyCodeType.USD;
details.orderTotal.value = "1.00";
details.cancelURL = "";
details.returnURL = "";


reqType.setExpressCheckoutRequestDetails = details;

UserIdPasswordType user = new UserIdPasswordType();
user.username = "XXX";
user.password = "XXXX";
user.signature = "XXXX";

PayPalAPIInterfaceService pp = new PayPalAPIInterfaceService();
PayPalAPIAAInterface pinterface = pp.getPayPalAPIAA();
Holder security = new Holder(new CustomSecurityHeaderType());
SetExpressCheckoutResponseType resp = pinterface.setExpressCheckout(req, security);
for(ErrorType msg: resp.errors){
catch(Exception ex){



(def Bonjour-Clojure “Welcome to functional programming”)

After the briefest of introductions to functional programming in college(a la Lisp) and dabbling with Scala, I took the functional plunge and started using Clojure recently. At this point, I have only written a couple of small programs and haven’t formed much of an opinion on where it stacks against my current favorite language at the moment(Groovy). This post will follow my usual getting started with a language snippets. I plan to write more entries as I get more familiar with the language. On to the code!

user=> (def Bonjour-Clojure “Welcome to functional programming”)
user=> Bonjour-Clojure
“Welcome to functional programming”

;items in a list can be seperated via a comma or white space..
user=> (= [ 1 2 3] [1,2,3])

;count the number of consonants in a string
(defn count-consonants [string] (count ( re-seq #”[^aeiouAEIOU\s]” string )))
user=> (count-consonants “writing code is fun”)

;count the number of vowels in a string
(defn count-vowels [string] (count ( re-seq #”[aeiouAEIOU\s]” string )))
user=> (count-vowels “lukaskiewicz”)

;read a file into a list.. any suggestions on other ways are welcome 🙂
;usage (file-lines “string_path_to_file”) or to read a webpage ((file-lines “”)
(defn file-lines [file] (with-open [rdr ( file)] ( set ( line-seq rdr))))

;view objects class
user=>(class “Im a string”)

;length of string
user=>(count “I am 18 chars long”)

user=>(range 1 9)
(1 2 3 4 5 6 7 8 )

;repeat a digit
user=>(repeat 4 3)
(3 3 3 3)

;list comprehension
user=>(for [fruit [“apple” “orange” “grape”] ] (str fruit))
(“apple” “orange” “grape”)

;use map to create a new list… #() is a shortcut for an anonymous
user=>(map #(* 2 %1) [1 2 3 4])
(2 4 6 8 )

; also an anonymous function
user=> (map (fn [item](* 2 item)) [1 2 3 4])
(2 4 6 8 )

;simple fiter example on a list using odd?
user=> (filter odd? [1, 2,3,4,5])
(1 3 5)

;factorial using reduce
user=> (reduce * [1 2 3])

;if statement
user=> (if true (str “i am true”)(str “i am false”))
“i am true”

Windows GUI File Parser using Groovy

I find myself doing a lot of file parsing on my Windows XP machine lately. I decide to write a quick utility that would allow me to drag and drop files and search for the key words that I have identified. The utility doesn’t have the logic for searching using regex’s yet, but it should be really easy to add this functionality.

I hacked some Groovy Code with some Java Code and came up with the following script. Hope it is useful.


As the title suggests, I have only been able to get this to work on my Windows XP machine, OS X didn’t like the javax.swing.TransferHandler and it appears some other operating systems have a hard time with this also.

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.util.List;
import java.awt.BorderLayout;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.TransferHandler.*;

class FileDropHandler extends TransferHandler {

private static final long serialVersionUID = 1L;

def wordsToFind =[]
JTextArea output
private JLabel errorMsg;
private String fileText = "";
private boolean test = false;
private boolean same = true;

public boolean canImport(TransferSupport supp) {
/* for the demo, we'll only support drops (not clipboard paste) */
if (!supp.isDrop()) {
return false;

/* return false if the drop doesn't contain a list of files */
if (!supp.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
return false;

boolean copySupported = (COPY & supp.getSourceDropActions()) == COPY;

if (copySupported) {
return true;

return false;

public boolean importData(TransferSupport supp) {
if (!canImport(supp)) {
return false;

/* get the Transferable */
Transferable t = supp.getTransferable();

try {

Object data = t.getTransferData(DataFlavor.javaFileListFlavor);

List fileList = (List) data;

for (int j = 0; j < fileList.size(); j++) { File file = (File) fileList.get(j); //file.getAbsolutePath() def tmpfh = new File("FileParser.txt") println wordsToFind.inspect() new File(file.getAbsolutePath()).eachLine{line->
wordsToFind.each{ if(line =~ "${it}" ){
println "${line}"
}//end for


} catch (UnsupportedFlavorException e) {
return false;
} catch (IOException e) {
return false;
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block

return true;

public void setOutput(JTextArea jta) {
this.output = jta;

public void setOutput(JLabel jta) {
errorMsg = jta;

public String getText() {
return fileText;

public void clearAll() {
fileText = "";
test = false;
same = true;


class AL implements ActionListener{
public JTextField jtf
public FileDropHandler dh
public AL(JTextField jtf,FileDropHandler dh){
this.jtf = jtf
this.dh =dh
public void actionPerformed(ActionEvent actionEvent){
println "${this.jtf.getText()}"
dh.wordsToFind= this.jtf.getText().split(' ')

JTextArea dTextArea = new JTextArea("Drop on me");
FileDropHandler dh = new FileDropHandler()
JTextField jta = new JTextField("Enter words seperated by spaces")
dh.wordsToFind= jta.getText().split(' ')
JButton jb =new JButton("Update Word List")
jb.addActionListener( new AL(jta ,dh ))


JPanel p =new JPanel(new BorderLayout());
JFrame f = new JFrame()
p.add(jta, BorderLayout.NORTH)
p.add(dTextArea, BorderLayout.CENTER)
p.add(jb, BorderLayout.SOUTH)


A Groovy Flickr API

A long time ago I wanted to write a desktop GUI interface for Flickr. At the time I had just learned Java and thought it would be really cool to write it using swing. Little did I know how not cool working with swing would be 🙁

About halfway through the project I heard about a cool new dynamic way to write Java code called Groovy. From that day on Groovy has been making my life a whole lot easier. I didn’t need all the functionality in the flickrj library, so I decide to write a few methods for my app using Groovy. The hardest part of the whole thing was figuring out how to post images to Flickr, for that, I used the flickrj code as a reference. If that source code was not available, I don’t think I would have ever figured it out. So a big thanks to all the folks working on that project!

This is not a complete API for Flickr, but should provide enough to get started.
Link to my GitHub Repo

Rotating Java Images

I am working on a swing flickr app and thought I would share some code to help those that are new to java gui programming( like me) and get them on their way to making their killer application.

I’ll start off with my first problem,  “How do I show an Image?” After looking through Java forums and going through my Java books, I settled on using Image Icons in JLabels. The next thing I wanted to do was rotate the image 90 degrees. I used Java’s Graphics class to accomplish this. The following groovy code loads 100 JLabels containing a JPEG of Pixar’s Wall-e that I had in the same directory rotated 90 degrees.

import java.awt.image.BufferedImage
import javax.swing.*
import java.awt.*;
import java.util.*;
import java.awt.image.AffineTransformOp
import java.awt.geom.AffineTransform

class ImageButton extends JLabel{
	ImageIcon picture

public ImageButton(ImageIcon icon){
	this.setPreferredSize(new Dimension(120,100))

public void rotateImage( int angle) {
	int w = this.picture.getImage().getWidth()
	int h = this.picture.getImage().getHeight()
	BufferedImage bi = new BufferedImage(w,h,
	Graphics bg = bi.createGraphics();
	bg.rotate(Math.toRadians(angle), w/2, h/2);
	bg.drawImage(this.picture.getImage(),0,0,w, h,
			0,0,w, h, null);

	bg.dispose()//cleans up resources
	this.setIcon(new ImageIcon(bi))
	this.setPreferredSize(new Dimension(this.picture.getIconHeight(),

JFrame f= new JFrame()
JPanel panel=new JPanel();
def img= new ImageIcon("walle.jpg")
	def btn=new ImageButton(new ImageIcon(img.getImage()
	btn.rotateImage(90)//rotate the image now
	println i




My first few attempts at the code gave me out of memory Heap errors. I unknowingly had BufferedImage references hanging around.  Once I realized this, I cleaned up my code and remembered to call dispose() on the graphics bg object and everything came together quite nicely.