Aim of this article: Add custom velocity by hook.
Use of Custom Velocity Variables: We will be able to use custom velocity variable directly in the VM files.It separates java logic from VM file. Code looks better.
While developing Liferay theme we have used many velocity variables. Some of the common velocity variables widely used in theme are
$processor $request $themeDisplay $company $user $realUser $layout $layouts $plid $layoutTypePortlet $portletGroupId $locale $timeZone $theme $colorScheme $portletDisplay
We know that sometimes we need more than default. Liferay is flexible to add our own custom velocity variables. Below are the step by step guide
Step 1:
Create a hook to override servlet.service.events.pre of portal.properties. In this article I am not going to discuss how to create hook. But all these information will be enough to create the hook. You can use Liferay IDE to create the hook. In my eclipse the project look like as below
CustomVelocityDemo
package com.proliferay.demo;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.liferay.portal.kernel.events.Action;
import com.liferay.portal.kernel.events.ActionException;
import com.liferay.portal.kernel.util.WebKeys;
/**
*
* @author Hamidul Islam
*
*/
public class CustomVelocityDemo extends Action{
@Override
public void run(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ActionException {
/**
* Create and empty map
*/
Map< String, Object > customVelocityVariables = new HashMap<String, Object>();
/**
* For demo we are creating here two velocity variables. One is variable1
* another is variable2
*/
customVelocityVariables.put("variable1", "This is the first variable");
customVelocityVariables.put("variable2", "This is the second variable");
/**
* Keep the customVelocityVariables map in request scope
*
* WebKeys.VM_VARIABLES should be the attribute name
*
* For example in VM put $variable1 you will get the corresponding value
*/
httpServletRequest.setAttribute( WebKeys.VM_VARIABLES, customVelocityVariables );
}
}
portal.properties
servlet.service.events.pre=com.proliferay.demo.CustomVelocityDemo
liferay-hook.xml
<?xml version="1.0"?> <!DOCTYPE hook PUBLIC "-//Liferay//DTD Hook 6.2.0//EN" "http://www.liferay.com/dtd/liferay-hook_6_2_0.dtd"> <hook> <portal-properties>portal.properties</portal-properties> </hook>
Step 2:
Deploy the hook
Step 3:
Use the velocity variable in VM file in your theme like $variable1
I have not explained the code. Instead I have added necessary comment. Read those comments for better understanding.
