Tricks of Velocity class loading

Ray Augé
Ray Augé
Less Than a Minute Read

Recently I was asked to solve a WCM dynamic Template problem which involved listing articles using the business logic of the template.

One of the first problems I encountered was of course doing a search for the Articles via the JournalArticleLocalService which, in the case of the searchs which return List<JournalArticle>, require an OrderByComparator. Since there is no way to directly instantiate classes in Velocity I wondered how I was going to handle this issue.

Luckily my colleague Thiago was working with a community member (Sabrina Schürhaus Locks) who had already solved the problem in a rather interesting and simple way:

 

#set ($obc = $portal.getClass().forName("com.liferay.portlet.journal.util.comparator.ArticleDisplayDateComparator").newInstance())

 

It's so simple I feel silly that I never thought of this myself.

Kudos Sabrina!

Page Comments
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Amos Fong
15 Years Ago
I ran into this issue as well and found this same solution. However, you can't pass any parameters so you can't do ascending obc's.
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Ray Augé Amos Fong
15 Years Ago
Ah, but you can my friend!


#set ($obcClass = $portal.getClass().forName("com.liferay.portlet.journal.util.comparator.ArticleDisplayDateComparator"))
#set ($booleanType = $portal.getClass().forName('java.lang.Boolean'))
#set ($obcConstructor = $obcClass.getConstructor($booleanType.getField('TYPE').staticValue))

#set ($obc = $obcConstructor.newInstance(true))
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Ray Augé Ray Augé
15 Years Ago
Note, this is complicated by the fact that it's a constructor having primitive args, on top of which you can't directly reference static fields in velocity, so getting the primitive type of a class required more reflection tricks. But this example demonstrates all of that!
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jelmer kuperus
15 Years Ago
I posted something similar to the forums a while back that was even hackier (due to the difficulty of getting to int.class)

http://www.liferay.com/community/forums/-/message_boards/message/5514892

these are pretty dirty tricks tho
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Ian White jelmer kuperus
14 Years Ago
Until recently (I just did a svn update of the portal trunk) the velocity hook approach was working well, whereby you simply defined your java interface + impl pair in an applicationContext.xml file. See Ray's test-velotool-hook sample.

Alas, with the latest trunk code, your beans are not able to be loaded. Fingers crossed this is just a bug and not a decision to stop supporting velocity hooks.
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Ray Augé Ian White
14 Years Ago
Hey Ian,

I tried this with the same old test velo hook:

#set ($myTool = $utilLocator.findUtil('test-velotool-hook','com.mytool.MyTool'))

$myTool
<br />
$myTool.operationOne()
<br/>
$myTool.operationTwo($text.data)

and got back:
com.mytool.MyToolImpl@5741bf0e
Hello out there!
Hello Ray!

Is it still not working?
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oscar caro puerto
13 Years Ago
Hello!
I also tried Ray's test-velotool-hook sample in liferay 6.0.6 and is working fine, but I recently downloaded liferay-portal-6.1.0-ce-ga1 bundled with tomcat, deployed the hook, and tested from a velocity template, but in this version I'm getting:
NoSuchBeanDefinitionException: No bean named 'com.mytool.MyTool' is defined
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Mehdi Khan
13 Years Ago
Hi, I am facing on problem with the Caroussel ,(1)when i refresh the page Caroussel loading slowly some time its take more than 5 minutes to load the message Caroussel.
(2).Sometimes when I log on, the caroussel is just blank. It takes around 2 - 5 minutes till the caroussel loads on the page.
And its happening only on Ineternet Explorer(IE)
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Matej Dolanc
11 Years Ago
Hello!

I've tried velocity class loading in LIferay 6.2 (liferay-portal-6.2.0-ce-ga1) and it doesn't work for me. It works fine in LIferay 6.1.

Example:
#set ($obc = $portal.getClass().forName("com.liferay.portlet.journal.util.comparator.ArticleDisplayDateComparator").newInstance())
$obc

I get the following warning message ( LIferay 6.2):

21:44:52,996 WARN [RuntimePageImpl-3][velocity:145] Cannot retrieve method forName from object of class java.lang.Class due to security restrictions.
21:44:52,997 DEBUG [RuntimePageImpl-3][velocity:155] RHS of #set statement is null. Context will not be modified. 10157#10197#11456[line 1, column 1]

Does anyone know where could be the issue?

Thanks
Matej
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Nasir Hussain
10 Years Ago
Hi Ray,

Somehow this is not working in 6.1+ Java 6 for this particular class

#set ($inetAddressClass = $portal.getClass().forName("javax.mail.internet.InternetAddress"))
#set ($stringType = $portal.getClass().forName('java.lang.String'))
#set ($inetAddressConstructor = $inetAddressClass.getConstructor($stringType.getField('TYPE').staticValue))
#set ($toAddress = $inetAddressConstructor.newInstance("abc@gmail.com"))
$toAddress, $inetAddressConstructor, $inetAddressClass

here the $toAddress is not working other variables are fine
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Nasir Hussain Nasir Hussain
10 Years Ago
My bad... got it working, wrong constructor invokation

#set ($inetAddressConstructor = $inetAddressClass.getConstructor($stringType))
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Dave Weitzel
10 Years Ago
Any idea how to create the obc to be driven by a custom Date field in the structure of the articles?
Seems expensive to get alist here, create another list wioth data from the xml content and then resort that list and then get more data for each article when listing the now correctly sorted list
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André Fabbro
8 Years Ago
Great post! Thanks!
However, it doesn't work in Liferay 7, right? I tried:

#set ($mbMessageClass = $portal.getClass().forName("com.liferay.message.boards.kernel.model.MBMessage"))

and got:

ERROR [http-nio-8080-exec-6][LiferayMethodExceptionEventHandler:54] Unable to execute method forName {exception=java.lang.ClassNotFoundException: com.liferay.message.boards.kernel.model.MBMessage cannot be found by com.liferay.portal.template.velocity_2.0.17, className=java.lang.Class}
java.lang.ClassNotFoundException: com.liferay.message.boards.kernel.model.MBMessage cannot be found by com.liferay.portal.template.velocity_2.0.17

Do you know if is there some workaround for use it on Liferay 7?
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David Weitzel André Fabbro
8 Years Ago
In liferay 7 all the old portlets ar enow stand alone "apps" Messaeg boards part fo the collaboration package. the right class would be :
com.liferay.portlet.messageboards.model.MBMessageModel
the new APIs are all linked from https://dev.liferay.com/develop/reference but harder to find as there are now 8 or more javadocs to check
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André Fabbro David Weitzel
8 Years Ago
Also tried that, didn't work though...

I've found a workaround which is the following:

#* @vtlvariable name="mbMessageObj" type="com.liferay.message.boards.kernel.model.MBMessageModel" *#
#set ($mbMessageClass = $mbMessageObj.getClass())
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