Tricks of Velocity class loading

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!

22 Comments

Please sign in to comment.

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.

Please sign in to reply.

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))

Please sign in to reply.

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!

Please sign in to reply.

wow cool, velocity java magic! thanks for the lesson

Please sign in to reply.

Neat trick! I'll have to remember that one.

Please sign in to reply.

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

Please sign in to reply.

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.

Please sign in to reply.

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?

Please sign in to reply.

hello ray, how to get value from a field which is characterized by a specific tags on the article?

thanks

Please sign in to reply.

Hey Arya,

Can you clarify a little? I'm not exactly sure what you mean!

Please sign in to reply.

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

Please sign in to reply.

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)

Please sign in to reply.

I don't think that relates to the post. If so, can you explain how?

Please sign in to reply.

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

Please sign in to reply.

We added some security around classloading. You can adjust the settings to your usage. http://docs.liferay.com/portal/6.2/propertiesdoc/portal.properties.html#Velocity%20Engine

Please sign in to reply.

Thank you very much...

Please sign in to reply.

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

Please sign in to reply.

My bad... got it working, wrong constructor invokation

#set ($inetAddressConstructor = $inetAddressClass.getConstructor($stringType))

Please sign in to reply.

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

Please sign in to reply.

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?

Please sign in to reply.

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

Please sign in to reply.

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())

Please sign in to reply.

Menu Display

Blogs

Category Filter

More Blog Entries

Liferay IDE 1.1 Released

Listing Article fragments dynamically using Liferay's WCM Templates