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Here we write some random thoughts and articles about software development: Java, Grails, Node.js, iPhone, iPad and more.

Execute Groovy script within Grails context, updated for Grails 1.3.1

Quite often it is needed to execute Groovy script within a Grails application context (including access to domain objects, controllers, services, etc). Unfortunately there is no such built-in functionality in Grails.

However Ted Naleid has written run-script Gant script to do this and published on his blog.

We used it in our project and it worked flawlessly. However it stopped working with upgrade to Grails 1.3.1 and even grabbing the latest version from bitbucket haven’t helped.

So I looked into the sources of built-in Grails scripts, including run-test and hacked run-script a little bit to make it run fine.

You can grab/fork the resulting script on github.

Also, please vote for inclusion of run-script functionality into main Grails distribution in JIRA

Using the script is easy. Just store it in src/scripts/ folder of your Grails app with RunScript.groovy filename.

Then you’ll be able to run your scripts as following:

grails run-script path/to/script1/Script1.groovy path/to/script2/Script2.groovy ...

The script itself is:

import org.codehaus.groovy.grails.commons.GrailsClassUtils as GCU
import org.springframework.orm.hibernate3.SessionFactoryUtils
import org.springframework.orm.hibernate3.SessionHolder

includeTargets << grailsScript("_GrailsBootstrap")
includeTargets << grailsScript("_GrailsRun")
includeTargets << grailsScript("_GrailsSettings")
includeTargets << grailsScript("_GrailsClean")

target('default': "Execute the specified script after starting up the application environment") {
    depends(checkVersion, configureProxy, packageApp, classpath)

target(runScript: "Main implementation that executes the specified script after starting up the application environment") {
    if (argsMap["params"].size() == 0) {
        event("StatusError", ["Required script name parameter is missing"])
        System.exit 1
    argsMap["params"].each { scriptFile ->
        executeScript(scriptFile, classLoader)

def configureHibernateSession() {
    // without this you'll get a lazy initialization exception when using a many-to-many relationship
    def sessionFactory = appCtx.getBean("sessionFactory")
    def session = SessionFactoryUtils.getSession(sessionFactory, true)
    TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(session))

def executeScript(scriptFile, classLoader) {
    File script = new File(scriptFile)
    if (script.exists()) {
        def shell = new GroovyShell(classLoader, new Binding(ctx: appCtx, grailsApplication: grailsApp))
    } else {
        event("StatusError", ["Designated script doesn't exist: $scriptFile"])

Mocking configuration in Grails unit tests

While testing some of the classes in Grails app, I had problem that the tests failed because Grails config (ConfigurationHolder.config) isn’t populated (is null) when unit tests are executed. Some Googling found me issue in JIRA which explained it.

Graeme Rocher commented that there is mockConfig method which allows to specify mocked config to be used for tests. It can be called in setUp method to do necessary initialization.

It is convenient to use it with multi-line strings. Its usage goes as following:

mockConfig ''' = "good"

It is discussed in more details in mrhaki's post.

File uploads using Node.js: once again

I’ve already wrote an article about file uploads in Node.js before. However Node.js is in rapid development and so many things have changed since then.

So, I decided to do an updated version, which accommodates for such changes:

  • events module was removed
  • posix module was replaced by fs
  • various changes into HTTP request/response API
  • multipart module refactored into separate project
  • convenient fs.createWriteStream instead of low-level API

See the code snippet under the cut, or on github. Special thanks goes to Felix Geisendörfer for some useful suggestions.

Please note that you’ll need to install multipart module for the code to work.

To make it clear, Node.js version used was v. 0.1.91.

UPD: Fixed stream.onData handler. It was writing corrupted data (UTF-8 character were translated) because of binary mode not being used. Thanks to Ron Ward for suggesting solution.


Resolving Grails version automatically on Windows

A while ago we showed how it was possible to select automatically version of Grails to run just using a simple bash script. Trouble is, not all users use systems that recognize bash-scripts natively. One of such systems is, apparently, Windows platform. So today I’m going to show how it is possible to accomplish similar tasks on Windows using just the built-in functionality — the batch job processing files.

The bash script we showed earlier, used the knowledge embedded in the Grails-project file called to find out the version of Grails for the current project. Weirdly enough, batch files allow to do this as well (for the syntax used in properties file at least). Here is the snippet of code that does just that:

FOR /F "eol=# tokens=1,2 delims==" %%i IN ( DO (
    IF "%%i" == "app.grails.version" (

CALL %GRAILS_HOME%\bin\grails.bat %*

Design interfaces of iPad apps on paper

If you like drawing UI sketches on paper and plan to design iPad applications, there is a sketchbook for it -

Sketchbook sheets have the layout of iPad in actual size printed on the front. iPad screen is covered with grid which allows to lay out interface elements conveniently. On the back sheets are just covered with simple square grid for comments, various thoughts, design of individual elements, etc.

Technical specs (better than iPad in many aspects):

  • 42 A4 sheets
  • actual size of iPad
  • convenient grid
  • multitasking support
  • zero-watt consumption

Choose Grails version and configure GRAILS_HOME automatically

We are using Grails actively to develop web applications. So we ended up with different applications using different versions of framework.

Setting up GRAILS_HOME variable to point to different Grails release each time I switched to other application was really unpleasant hassle. So I thought about how to resolve this problem. Grails stores application version in file, I came out to the following Bash script:


# Get required Grails version
GRAILS_VERSION=`sed -n 's/app.grails.version=\(.*\)$/\1/p' <` 

# Set Grails home using configured prefix and determined version

# Run original Grails script
$GRAILS_HOME/bin/grails $@

It just parses the version from the file and appends it to GRAILS_PREFIX environment variable. The resulting value is exported into GRAILS_HOME variable.

To use the aforementioned script you need to set GRAILS_PREFIX variable to a value appropriate for your system. And of course your Grails distributions should be installed side-by-side in one common folder.
For example I have it set to /home/vg/tools/grails- on my Linux box.

You can grab/fork script easily as a Gist on GitHub.

UPD: The script was updated to take some corner cases into account. See updated version of the script.

UPD 2: There is also version for Windows.

Tags: grails java bash

File uploads using Node.js: now for real


Node.js is a very interesting server-side Javascript application framework. It is based on Google’s V8 Javascript engine and implements evented I/O, so it is blazing fast. It looks very promising for certain types of applications, mostly those that require long-running connections. This includes streaming big files, keeping persistent connections used for realtime communication (chat, games), applications using third-party web services (with long call times), etc.

There is good enough API reference available for Node.js, however it is not trivial to start development as event-based approach is quite unusual compared to commonly used thread-based networking. There are some useful blog posts with code samples available in Debuggable blog, e.g. Streaming file uploads with node.js.

However the given examples have problem — they are too far from real world problems. Take file upload as example — the code sample provided has absolutely no info on how to save the uploaded file. It is assumed that it would be trivial for the reader to figure out, however it’s not when we have to follow evented I/O approach.

In this post I’ll show example of how to save the uploaded files with Node.js. For the impatient — just grab source from github repository.

UPD: The code here is obsolete, see new article about file uploads in new Node.js version.


Run long batch processing jobs in Grails without memory leaks

In one of our Grails applications we had to run a number of batch jobs. Nothing unusual and Grails supports it quite well with the excellent Quartz plugin.

But when we deployed application in production, we noticed that after running for some time, it consumed a lot of memory and JVM was spending all the time running garbage collection. The reason for it was that our jobs were quite long-running, taking several hours to complete, and Grails wasn’t really designed for such kind of use case.

First problem is actually well-known and documented — using single Hibernate session for a long time gets a lot of objects being added to cache. It is described for example in this blog post.
This basically goes into flushing and clearing Hibernate session like following:


But while less memory was being leaked after that, the problem still wasn’t resolved. However thankfully to this nice post about Grails memory leak I learned about another more obscure problem and got it fixed.

Main idea is that save() method stores validation errors info in thread-local storage when HttpServletRequest instance is not available. So this info needs to be cleared from time to time, which can be achieved by something like this:


Resolving these two issues solved our problem with memory usage. Hopefully this post prevents you from spending much time resolving the same issues.

Nimble – easy user profiles and security for Grails

Recently found a really nice Grails plugin – Nimble.

It provides a complete solution for user profiles management, flexible authentication (both local and using OpenID) and fine-grained access control. It is based on Apache Shiro, which we used previously for authentication/access control.

I will try to use it in some simple project and then write a blog post describing my experience.

Offtopic: This is verification code for Technorati – QAEYYR9THPUN

Using cryptographically strong random number generator with SecureRandom in Java

There might be a need occasionally to generate sequences of random numbers in your real-world programs. While there is a special class in Java to deal just with that — java.util.Random — it’s not cryptographically strong, and the numbers chosen are not completely random because a definite mathematical algorithm (based on Donald E. Knuth’s subtractive random number generator algorithm) is used to select them. Therefore it is not safe to use this class for tasks that require high level of security, like creating a random password, for example.

Fortunately, there’s another, much more cryptographically strong random number generator provided with every Java Runtime Environment by default. It can be accessed via the class, which is a subclass of class Random mentioned above. That means that you can use it the same way you did when you used the generator implemented by the Random class, it even allows you to set the random seed of your choice if it happens so that you need to repeat the sequence of numbers generated, which is good as for example the .NET equivalent — System.Security.Cryptography.RNGCryptoServiceProvider — does not allow to do that. However, there is one or two issues that, if not addressed, might turn into real problems and cause lots of headaches. But before I describe those, let me talk you into how to start using this strong random number generator.


Improved Hibernate dialect for Microsoft SQL Server

In one of our Grails projects we had to use Microsoft SQL Server as a database. Hibernate has support for it and works good enough, however the schema generated by it is not ideal, at least from our point of view. In particular, properties of boolean type were stored in columns of type INT, while both SQL Server 2000 and 2005 support special type just for booleans — BIT; all Ids, which usually have type long, had to be squeezed into columns of type INT (again this stupid integer!); such SQL types as TEXT and IMAGE were used, instead of (preferred for SQL Server) VARCHAR(max) and VARBINARY(max) respectively; and finally (for me — the most annoying thing) strings were stored in non-Unicode sequences. The very last point is also very unhandy, since strings in Java are stored in Unicode, and having to deal with encodings explicitly when storing or reading strings or entire texts from the database is a bit against the simplicity we expect from Hibernate when we use it.

So I decided to develop customized Hibernate dialect for MS SQL Server. To do this, I started digging the source code of Hibernate (the dialect classes to be precise), and soon I found out that Hibernate’s SQLServerDialect extends from SybaseDialect, which is responsible for most of the “sins” outlined in the paragraph above. Don’t know why they haven’t overridden any of that in a subclass, probably they had a good reason not to do so, but for our company this reasoning was certainly not working out. Just extending the standard implementation was fairly enough to solve the problem, actually it was sufficient just to register appropriate column types in the constructor. The end result looks like this:

public class SQLServerDialect extends org.hibernate.dialect.SQLServerDialect {
    * Initializes a new instance of the {@link SQLServerDialect} class.
    public SQLServerDialect() {
        registerColumnType(Types.BIGINT, "bigint");
        registerColumnType(Types.BIT, "bit");
        registerColumnType(Types.CHAR, "nchar(1)");
        registerColumnType(Types.VARCHAR, 4000, "nvarchar($l)");
        registerColumnType(Types.VARCHAR, "nvarchar(max)");
        registerColumnType(Types.VARBINARY, 4000, "varbinary($1)");
        registerColumnType(Types.VARBINARY, "varbinary(max)");
        registerColumnType(Types.BLOB, "varbinary(max)");
        registerColumnType(Types.CLOB, "nvarchar(max)");

Obviously, similar technique can be used with any custom Hibernate dialect, not just for MS SQL. Feel free to use it with any other DB engine, etc. If you find it useful, you can fork our code snippet at Github:

Interesting error in Grails with multiple-classes in the same source file

Recently we have got strange error in one of our projects when we upgraded it from Grails 1.2 M2 to Grails 1.2 M4.
After we did the upgrade we started getting java.lang.MissingMethodException for the domain class method calls.

Then it was determined by playing with grails console that the problem was limited to a single domain class. The source code file for it (say, MyDomainClass.groovy) looked like this:

class MyUtilityClass {
      // Some code here

class MyDomainClass {
      // Some code here

Well, it may be not the best idea to have two classes in the same source file, but that is a different question. Interesting thing is that it for some reason prevented Grails from adding the methods to MyDomainClass. And to resolve this issue very simple thing can be done — MyUtilityClass can be put in source file after MyDomainClass. That resolved problem for us.

Hopefully this post would be useful to someone with similar problem.

Setup Vim to work with Terminator terminal emulator

When I tried to use excellent terminal emulator Terminator to edit a file with Vim on remote server, I got strange errors.
Vim wouldn’t use syntax highlighting, had other glitches and output warning message at start-up:

E558: Terminal entry not found in terminfo
'terminator' not known. Available builtin terminals are:
defaulting to 'ansi'

After googling a bit I found a solution in the FAQ of Terminator.

To cut a long story short, here’s how to fix it (just copy your .terminfo to remote machine):

scp -r ~/.terminfo remote_username@remote_hostname:~/

After doing that, all the problems should be gone.

Tags: console vim

Twitter and Google Maps mashup in 20 minutes with Grails


For many developers Java is often a synonym for totally non-sexy enterprise applications development. It is associated with numerous XML configuration files, boilerplate code, etc. So they instead use dynamic languages like Ruby, Python, PHP to develop their projects, especially when these are own simple utilities, mash-ups, etc.

However the Java field has changed much in the recent few years. There are multiple frameworks which relieve developer from “enterprise” burden. Grails is probably one of the best. It is based on Groovy, which is a dynamic language running on Java platform designed specially for Java programmers. It uses well known robust and efficient Java libraries to do all the heavy lifting (Spring, Hibernate, etc.). There is also a plugin system and plugins exist for almost every widely used Java library.

In this article we’ll show how to make a mash-up of Twitter and Google Maps in around 20 minutes. The end result will look similar to this:


In the beginning of the long road

Finally we’ve launched our own blog. We’ll try to write interesting things about Java, Grails, iPhone or about anything else related to our work.

BTW, this blog is powered by Grails, same as other parts of our website.

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