Receive parameter from AJAX call in Liferay

One very important thing you should noted is set these property in portlet definition (in liferay-portlet.xml) at the end of <portlet> tag:

<add-default-resource>true</add-default-resource>

and

<requires-namespaced-parameters>false</requires-namespaced-parameters>

under <icon> tag.

If not, you can not get parameter's value out in  Portlet Implementation.