Alternative to open session in view pattern

[tentacle]

TouchingAfterReturningAdvice offers an alternative to the open session in view pattern in that it touches configurable properties on the return value of method invocations. This advice is available in the Spring Modules sandbox.

If the return value is an instance of java.util.Collection or Object[] all its elements will be touched with the configured properties. If no properties have been specified collections will still be iterated over.

An example:

The service:

public interface CustomerService {
   public Collection findAllCustomers();
}

The domain class:

public class Customer {
   private Collection pendingOrders = null;
   // this property is configured for lazy loading.
   public Collection getPendingOrders() {
      return this.pendingOrders;
   }
   private Collection completedOrders = null;
   // this property is configured for lazy loading.
   public Collection getCompletedOrders() {
      return this.completedOrders;
   }
}

The Spring config:

<bean id="customerService" parent="transactionedBean">
   <property name="target">
      <bean class="....DefaultCustomerService" autowire="byType"/>
   </property>
   <property name="postInterceptors">
      <list>
         <bean class="....NameMatchMethodPointcutAdvisor">
            <property name="mappedNames">
               <value>findAllCustomers</value>
            </property>
            <property name="advice">
               <bean class="org.springmodules.aop.framework.TouchingAfterReturningAdvice">
                  <property name="properties">
                     <list>
                        <value>pendingOrders</value>
                        <map>
                           <entry key="completedOrders">
                              <list>
                                 <value>products</value>
                              </list>
                           </entry>
                        </map>
                     </list>
                  </property>
               </bean>
            </property>
         </bean>
      </list>
   </property>
</bean>

[Rod Johnson]

This makes sense. In fact we were discussing the possibility of this in last week's Core Spring training in London :-)

It might be an idea to try to simplify the configuration through a convenient generic Advisor that, for example, took a set of OGNL expressions.

[Rod Johnson]

One thing to note however: fetch joins may be more efficient if you want to ensure the most efficient database querying. More invasive, however: the declarative touching approach is definitely simpler. It would also work for any ORM tool, so it's not tied to Hibernate, which is a plus.

[tentacle]

I've added support for OGNL expressions and created a convenience class TouchingNameMethodMatchAdvisor. If collections are returned you can use the #returned variable in OGNL expressions:

<bean id="customerService" parent="transactionedBean">
   <property name="target">
      <bean class="....DefaultCustomerService" autowire="byType"/>
   </property>
   <property name="postInterceptors">
      <list>
         <bean class="org.springmodules.aop.framework.TouchingNameMatchMethodAdvisor">
            <property name="mappedNames">
               <value>findAllCustomers</value>
            </property>
            <property name="advice.ognl">
               <list>
                  <value>#returned.&#123;pendingOrders.size&#125;</value>
                  <value>#returned.&#123;completedOrders.&#123;products.size&#125;&#125;</value>
               </list>
            </property>
         </bean>
      </list>
   </property>
</bean>