Hibernate Data Filters

In a lot of the applications I write, I prefer to use soft deletes rather than hard deletes to ensure that data can easily and quickly be restored if (and when) a user accidentally deletes something. However, trying to implement soft deletes is typically easier said than done. For example, if you wanted a query of all the non-deleted products, your query might look like:

<cfquery name="getProducts">
 select *
 from product
 where isDeleted = 0
</cfquery>

To convert this to ColdFusion 9 ORM, you could write an HQL statement that looks like:

<cfset products = ORMExecuteQuery("from Product where isDeleted = 0") />

Obviously it isn't ideal replacing a simple entityLoad("Product") with HQL, but it becomes even worse when you consider having to recreate that logic across relationships. Yuck.

Introducing Hibernate Filters

"Hibernate3 has the ability to pre-define filter criteria and attach those filters at both a class level and a collection level. A filter criteria allows you to define a restriction clause similar to the existing "where" attribute available on the class and various collection elements. These filter conditions, however, can be parameterized. The application can then decide at runtime whether certain filters should be enabled and what their parameter values should be." Read more.

Long story short, you can define a filter that applies the isDeleted logic to your entities without actually touching your entities.

To accomplish this, I had my Product entity extend a base Entity in order to perform the save() and delete() methods, which are responsible for handling the soft deletes. After that, I updated my Product.hbmxml file to include the filter definition and add it to my Product entity. Finally, I updated Application.onRequestStart() to enable the softDeletes filter, which is disabled by default. Here's the sample code:

Application.cfc

component {
 
 this.name = "sample";
 this.datasource = "sample";
 this.ormEnabled = true;
 this.ormSettings.dbcreate = "update";
 this.ormSettings.saveMapping = true;
 
 public void function onRequestStart() {
  if(structKeyExists(url,"init")) {
   ormReload();
  }
  ORMGetSession().enableFilter("softDeletes");
 }
 
}

Product.cfc

component persistent="true" extends="Entity" {
 
 property id;
 property name;
 
}

Entity.cfc

component accessors="true" {
 
 property isDeleted;
 
 public void function save() {
  setIsDeleted(0);
  entitySave(this);
 }
 
 public void function delete() {
  setIsDeleted(1);
  entitySave(this);
 }
 
}

index.cfm

<cfset products = EntityLoad("Product") />

<cfdump var="#products#" />

Product.hbmxml

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                                   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    
 <class entity-name="Product" lazy="true" name="cfc:sample.Product" table="Product">
         <id name="id" type="int">
              <column length="10" name="id"/>
              <generator class="native"/>
         </id>
         <property name="name" type="string">
              <column name="name"/>
         </property>
         <property name="isDeleted" type="boolean">
              <column name="isDeleted"/>
         </property>
  <filter name="softDeletes" condition="isDeleted = 0" />
 </class>

 <filter-def name="softDeletes" />
 
</hibernate-mapping>

The really nice part about this approach is that I've got soft deletes working without my Product entity being aware, since that logic is hidden in the base class, a config file, and a global template.