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EntityBeanLocator(EBL) is a standard framework interface in RSF, that comes with a default implementation which makes writing an OTP space for an entity very easy, given just a standard "DAO-type" API managing the entity. This is a conventional application-scope API with methods such as "findById", "save", "delete", etc. and the EBL does the work of automatically setting up an EL address space for all the managed entities, and managing a request-scope cache so they can be addressed and manipulated quickly and clearly.

Using the framework default implementation#

Assuming the API for the entity is sufficiently "reasonable", this doesn't require writing any code, but simply a Spring definition. This definition is for an application scope bean extending the RSF framework parent entityBeanLocatorParent.

Here is the set of properties supported on this bean and their meaning:

PropertyDescription
fetchMethod(Required) An EL path to a "fetch method" which can fetch entities by their ID - for example, a DAO API bean named BlogDao which had a method called findById which took a single argument, the Id, would be registered with a fetchMethod of BlogDao.findById
newMethodAn EL path to a method which will be used to instantiate "new" (not yet persistent) examples of the entity. Either this property or entityClass must be set.
entityClassA Class object representing the class of the entity that this EBL deals in. If newMethod is not set, the EBL will instantiate new instances of the entity using the default constructor of this class.
saveMethodAn EL path to a "save method" which will save modified entities back to some kind of persistence. This must take a single argument, which is the modified entity to be saved. If this property is not set, the saveAll method of the EBL will not function.
removeMethodAn El path to a "remove method" which will remove an entity from persistence. This method must take one argument, which is the id of the entity to be removed.

A minimal example#

For example, an (minimal)entry for a "Blog" entity might look like this: 
<bean id="Blog" parent="entityBeanLocatorParent">
  <property name="entityClass" value="myPackage.Blog"/>
  <property name="fetchMethod" value="myBlogDao.findById"/>
  <property name="saveMethod" value="myBlogDao.save"/>
</bean>

What you get for your money#

After having set up a definition of the sort just described, what you get done for you is the following:

  • The full OTP pattern supported for your entity - that is, the ability to address in any request scope paths of the form Blog.15 (representing the Blog entity with id 15) or even Blog.new 1 representing a particular, transient Blog entity good for the current request
  • If you supplied a saveMethod, you will get the ability to invoke a saveAll method on the resulting bean. Simply fetch the bean of the name you registered (only at request scope), which will be an implementor of EntityBeanLocator, and invoke saveAll on it at request end.
  • If you supplied a removeMethod, you will get the ability to invoke remove on the resulting bean, with an id argument - as well as the ability to target deletion bindings at the OTP root over the request.
  • Finally, you will get for free to participate in the EntityNameInferrer scheme. This is particularly useful when making selection controls which are meant to select which instance of one entity type is attached to another via the IDDefunnellingReshaper.

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« This page (revision-) was last changed on 28-Jul-2008 14:52 by UnknownAuthor