Develop > Business logic > Name-value pair command framework > Command types
Controller command programming model
The abstract class and interface are both found in the com.ibm.commerce.command package.
The following diagram illustrates the relationship between the implementation class and interface of a new controller command with the existing abstract implementation class and interface.
A new controller command should extend the abstract controller command class ( com.ibm.commerce.command.ControllerCommandImpl). When writing a new controller command, you should override the following methods from the abstract class:
In the standard WebSphere Commerce implementation there are multiple types of users. These include generic, guest, and registered users. Within the grouping of registered users there are customers and administrators.
The generic user has a common user ID that is used across the entire system. This common user ID supports general browsing on the site in a manner that minimizes system resource usage. It is more efficient to use this common user ID for general browsing, since the Web controller does not need to retrieve a user object for commands that can be invoked by the generic user.
The isGeneric method returns a Boolean value which specifies whether the command can be invoked by the generic user. The isGeneric method of a controller command's superclass sets the value to false (meaning that the invoker must be either a registered customer or a guest customer). If the new controller command can be invoked by generic users, override this method to return true.
You should override this method to return true if the new command does not fetch or create resources associated with a user. An example of a command that can be invoked by a generic user is the ProductDisplay command. It is sensible to allow any user to be able to view products. An example of a command for which a user must be either a guest or registered user (and hence, isGeneric returns false) is the OrderItemAdd command.
When isGeneric returns a value of true, the Web controller does not create a new user object for the current session. As such, commands that can be invoked by the generic user run faster, since the Web controller does not need to retrieve a user object.
The isRetriable method returns a Boolean value which specifies whether the command can be retried on a transaction rollback exception. The isRetriable method of the new controller command's superclass returns a value of false. You should override this method and return a value of true, if the command can be retried on a transaction rollback exception.
An example of a command that should not be retried in the case of a transaction exception is the OrderProcess command. This command invokes the third party payment authorization process. It cannot be retried, since that authorization cannot be reversed. An example of a command that can be retried is the ProductDisplay command.
The setRequestProperties method is invoked by the Web controller to pass all input properties to the controller command. The controller command must parse the input properties and set each individual property explicitly within this method. This explicit setting of properties by the controller command itself promotes the concept of type safe properties.
The validateParameters method is used to do initial parameter checking and any necessary resolution of parameters. For example, it could be used to resolve orderId=*. This method is called before both the getResources and performExecute methods.
This method is used to implement resource-level access control. It returns a vector of resource-action pairs upon which the command intends to act. If nothing is returned, no resource-level access control is performed.
The performExecute method contains the business logic for the command. It should invoke the performExecute method of the command's superclass before any new business logic is executed. At the end, it must return a view name.
- Long-running controller commands
If a controller command takes a long time to execute, you can split the command into two commands. The first command, which is executed as the result of a URL request, simply adds the second command to the Scheduler, so that it runs as a background job.
- Temporary changes to contextual information for URLs
It is possible to override some of the command context information and execute URL commands within the context of another store, or on behalf of another user.
- Format of input properties to views
For Web requests, when controller command completes, it returns the name of a view that should be executed. This view may require that several input properties get passed to it.
- Database commits and rollbacks for controller commands
Throughout the execution of a controller command, data is often created or updated. In many cases, the database must be updated with the new information at the end of the transaction.
- Make controller commands retriable
A retriable command is a controller command that can re-execute itself after encountering a system-level exception during the command execution.
- Create new entity beans
When you have a new attribute that needs to be added to the WebSphere Commerce object model, you can create a new database table with a column for the required attribute. You must then also include this attribute in an enterprise bean, so that WebSphere Commerce commands can access the information. One way to integrate the new attribute into the WebSphere Commerce object model is to create a new CMP enterprise bean. In this bean, you create a field that corresponds to the attribute in the new database table. Since WebSphere Commerce workspace provides a predefined EJB project for the new enterprise beans, you do not need to create an additional EJB project. Your new enterprise beans should be placed into the WebSphereCommerceServerExtensionsData EJB project. Later, when you deploy the customized beans, you create a WebSphereCommerceServerExtensionsData.jar JAR file and replace the existing JAR file in the WebSphere Commerce enterprise application running in WebSphere Application Server. By using this packaging convention, deployment is greatly simplified.
- Deploy custom Java EE assets
You deploy the Java EE assets to WebSphere Application Server.
- Add new EJB projects
Although it is recommended that new enterprise beans be created within the predefined WebSphereCommerceServerExtensionsData project, you may have a requirement to create additional EJB projects.
- Modify existing EJB modules
If modify any of the EJB modules that come with the WebSphere Commerce product, import them into the workspace as projects.
Long-running controller commands
Customize existing controller commands
Configure a Web application