Once we have defined the remote interface of the Cabin EJB, we have defined the remote view of this simple entity bean. Here is a complete definition of the CabinHomeRemote home interface:. The CabinHomeRemote interface extends the javax.
These methods create and locate remote references to Cabin EJBs. Remove methods for deleting enterprise beans are defined in the javax. The CabinBean class is an entity bean that uses container-managed persistence, so its definition will be fairly simple. In addition to the callback methods discussed in Chapter 2 and Chapter 3 , we must also define accessor methods for the CabinRemote interface and an implementation of the create method defined in the CabinHomeRemote interface.
Throughout this book we will show both the EJB 2. In many cases the component interfaces are the same, but the bean class code and XML deployment descriptors will be different. EJB 2. The CabinBean defines several abstract accessor methods that appear in pairs.
For example, setName and getName are a pair of abstract accessor methods. When the bean is deployed, the EJB container automatically implements all the abstract accessor methods so that the bean state can be synchronized with the database. These implementations map the abstract accessor methods to fields in the database.
They will be mapped to the database at deployment time. Unlike the matching methods in the remote interface, the abstract accessor methods do not throw RemoteException s. There is no requirement that CMP fields must be exposed. The id field is another container-managed field, but its abstract accessor methods are not exposed to the client through the CabinRemote interface. Declared fields in a bean class can be persistent fields or property fields. These categories are not mutually exclusive.
Persistent field declarations describe the fields that will be mapped to the database. A persistent field is often a property in the JavaBeans sense : any attribute that is available using public set and get methods. Of course, a bean can have any fields that it needs; they need not all be persistent, or properties.
In CabinBean , all the fields are persistent. The id field is persistent, but it is not a property. In other words, id is mapped to the database but cannot be accessed through the remote interface. The name , deckLevel , shipId , and bedCount fields are also persistent fields. These fields are also properties, because they are publicly available through the remote interface.
In the case of the Cabin EJB, there was only one create method, so there is only one corresponding ejbCreate method and one ejbPostCreate method. When a client invokes the create method on the remote home interface, it is delegated to a matching ejbCreate method on the entity bean instance.
The ejbCreate method initializes the fields; in the case of the CabinBean , it sets the name field. The ejbCreate method always returns the primary key type; with container-managed persistence, this method returns the null value. Why does it return null? Simply put, this convention makes it easier for a bean-managed enterprise bean i. Bean-managed persistence beans, which are covered in Chapter 10 , always return the primary key type. Once the ejbCreate method has executed, the ejbPostCreate method is called to perform any follow-up operations.
The ejbPostCreate method is used to perform any postprocessing on the bean after it is created, but before it can be used by the client. Both methods will execute, one right after the other, when the client invokes the create method on the remote home interface. The findByPrimaryKey method is not defined in container-managed bean classes.
Instead, find methods are generated at deployment and implemented by the container. With bean-managed entity beans, find methods must be defined in the bean class. In Chapter 10 , when you develop bean-managed entity beans, you will define the find methods in the bean classes you develop. The CabinBean class implements javax.
The container uses these callback methods to notify the CabinBean of certain events in its life cycle. Although the callback methods are implemented, the implementations are empty. Summary Testing Java Microservices teaches you to implement unit and integration tests for microservice systems running ….
The EJB 3 framework provides a standard way to capture business logic in manageable server-side modules, …. Distributed systems have become more fine-grained as organizations shift from code-heavy monolithic applications to smaller, self-contained …. Go is rapidly becoming the preferred language for building web services. There are plenty of tutorials …. Skip to main content. Start your free trial. Enterprise JavaBeans, Third Edition by. Buy on Amazon.
Show and hide more. Now the best only gets better! In the new 3rd edition, Enterprise JavaBeans has been completely revised and updated with a thorough introduction to the new 2. Significantly different from the earlier version, the 2. Most significant is the introduction of the relationship fields, which allow entity beans to declare relationships with each other as natural references. In order to make this huge leap in component relationships possible, EJB 2.
Our new 3rd edition examines this critical CMP model in detail. Local interfaces are thoroughly discussed as well.
Local interfaces allow beans that are co-located to interact without the overhead of remote method calls. This improves the performance of beans considerably and complements the CMP relationship fields. Message driven beans are a new kind of enterprise bean based on asynchronous messaging and the Java Message service JMS. An entire chapter is devoted to message-driven beans and how to use them effectively.
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