Dynamic Query

Liferay API provides means of accessing the liferay default entities via its liferay API. There would be situations where you need to access a entity with parameters, other than the methods provided by liferay. In which case, dynamic query will be a handy way. It is also a method in the liferay API where you can add the custom query to retrieve the entity that you require.

Here is the sample code

ClassLoader classLoader = PortalClassLoaderUtil.getClassLoader();
or if this service builder method is being called from external portlet better use 

ClassLoader classLoader = PortletClassLoaderUtil.getClassLoader( "<<portlet_id>>" );

DynamicQuery dynamicQuery = DynamicQueryFactoryUtil.forClass(

                           AssetCategoryProperty.class, classLoader).add(

                           PropertyFactoryUtil.forName("categoryId").eq(categoryId));

List<AssetCategoryProperty> liAssetCategoryProperty = AssetCategoryPropertyLocalServiceUtil

                           .dynamicQuery(dynamicQuery);

Here in the above example, I am trying to retrieve the properties that I define on the Asset Category. By default there is no method provided by liferay API (AssetCategoryPropertyLocalServiceUtil) to retrieve the AssetCategoryProperty using the category id. Hence Dynamic Query comes into picture.