Enterprise Bean (EJB) programming tutorials

Enterprise Beans Tutorial

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Enterprise Beans Tutorial

15 A customized exception is one that you've coded yourself, such as the InsufficentBalanceException thrown by the debit business method of the AccountEJB example. The javax.ejb package includes several predefined exceptions that are designed to handle common problems. For example, an ejbCreate method should throw a CreateException to indicate an
invalid input parameter. When an enterprise bean throws an application exception, the container does not wrap it in another exception. The client should be able to handle any application exception it receives. If a system exception occurs within a transaction, the EJB container rolls back the transaction. However, if an application exception is thrown within a transaction, the container does not roll
back the transaction. The following table summarizes the exceptions of the javax.ejb package. All of these exceptions are application
exceptions, except for the NoSuchEntityException and the EJBException, which are system exceptions. Exceptions Method Name Exception It Throws Reason for Throwing ejbCreate CreateException An input parameter is invalid. ejbFindByPrimaryKey
(and other finder
methods) ObjectNotFoundException
(subclass of
FinderException) The database row for the requested entity bean is
cannot be found. ejbRemove RemoveException The entity bean's row cannot be deleted from the
database. ejbLoad NoSuchEntityException The database row to be loaded cannot be found. ejbStore NoSuchEntityException The database row to be updated cannot be found. (all methods) EJBException A system problem has been encountered. Primary Key Class You specify the primary key class with the Application Deployment Tool.
When deploying the ProductEJB bean, for example, you would specify a java.lang.String as the primary key class. In most cases, your primary key class will be a String or some other class that belongs to the java package. Creating a Primary Key Class For some entity beans, you will need to define your own primary key class.
if a primary key is composed of multiple fields then you must create a primary key class
Primary Class Requirements The access control modifier of the class is public.
All fields are declared as public.
For container-managed persistence, the field names in the primary key clsss must match the corresponding container-managed fields in the entity bean class. The class has a public default constructor.
The class implements the hashCode() and equals(Object other) methods.
The class is serializable. Bean-Managed Persistence and the Primary Key Class With bean-managed persistence, the ejbCreate method returns the primary key class: