Improve this question. Sitansu 3, 7 7 gold badges 30 30 silver badges 58 58 bronze badges. Sebi Sebi 3, 13 13 gold badges 55 55 silver badges 97 97 bronze badges. Add a comment. Active Oldest Votes. Improve this answer. You can try two things: Compile and run your code from the command line. Add any jar files found in the EE installation directory to the build path.
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The home interface specifies one or more create methods. For each create method, a corresponding ejbCreate method must be defined in the bean implementation. All of the create methods return the bean type; all of the ejbCreate methods return void. The client invokes the create method declared within the home interface. The container turns around and calls the ejbCreate method, with the appropriate parameter signature, within your bean implementation.
The parameter arguments can be used to initialize the state of a new EJB object. EJBHome extends java. The methods in the EJBHome interface are implemented by the container. A client can remove an EJB object using the remove methods defined in either of its home or remote interfaces. All create methods must throw the following exceptions: javax. CreateException either java. RemoteException or javax. See the Oracle9i Java Tools Reference for a full description of deployejb.
Example The following code sample shows a home interface called EmployeeHome. The create method contains no arguments. Some methods in the Employee class can throw the EmpException exception. For an exception to be transported from the object to the client, you need to define a class for the exception. The following code defines an exception class and is found in EmpException.
The bean contains the business logic for your bean. It implements the following methods:. The bean in the example application consists of one class, EmployeeBean , that retrieves an employee's information. The ejbCreate methods that corresponds to the create methods declared in the home interface. The container invokes the ejbCreate method when the client invokes the corresponding create method. This example implements the SessionBean interface. Basically, a session bean is used for process oriented beans--those beans that perform tasks to achieve an end.
Entity beans are complex remote objects that are organized around persistent data. See "Definition of an Entity Bean" for more information on the differences between the two types of beans. The session bean implements the javax. SessionBean interface, which has the following definition:. At a minimum, an EJB must implement the following methods, as specified in the javax. SessionBean interface:. This method performs any required clean-up, for example closing external resources such as file handles.
The container calls this method after the bean creation. The enterprise bean can store the reference to the context object in an instance variable, for use in transaction management. Beans that manage their own transactions can use the session context to get the transaction context.
Using setSessionContext This method is used by a session bean instance to retain a reference to its context. Session beans have session contexts that the container maintains and makes available to the beans. The bean may use the methods in the session context to make callback requests to the container. The container invokes setSessionContext method, after it first instantiates the bean, to enable the bean to retrieve the session context.
The container will never call this method from within a transaction context. If the bean does not save the session context at this point, the bean will never gain access to the session context. When the container calls this method, it passes the reference of the SessionContext object to the bean. The bean can then store the reference for later use. The following example shows the bean saving the session context in the sessctx variable. A bean needs the session context when it wants to perform the operations listed in Table This is only valid for beans that have been designated transactional.
Bean Implementation Example The following code implements methods of a session bean called EmployeeBean. The SessionBean interface methods are implemented along with the public methods declared in the remote interface. Then the setInt method is used to associate the empNumber input parameter for the getEmployee method with the'? This is identical to the JDBC code that you would write in a client application.
All EJB clients perform the following to instantiate a bean, invoke its methods, and destroy the bean:. Create instances of the bean in the server through the home interface. Invoking the create method on the home interface causes a new bean to be instantiated. This returns a bean reference to the bean's remote interface. Invoke the methods defined in the remote interface.
The container forwards the requests to the instantiated bean. After the bean is no longer needed, invoke the remove method to destroy the bean.
These steps are completely illustrated by example in Figure As a quick example, suppose that EmployeeHome is a reference that you have obtained to the home interface of a bean called Employee.
The Employee home interface must have at least one create method that lets you instantiate the bean. You create a new instance of the bean on the remote server by coding:.
When you use the getEJBHome method to retrieve the home interface given an object reference, you cannot cast the returned object to the home interface's type. Instead, the returned object is of type org. Once received, the object is cast to the correct home interface type through the Helper. The following shows the Hello example retrieve Hello's home interface using JNDI, creating the remote interface, and then later retrieving the home interface again using the getEJBHome interface.
Notice that the HelloHomeHelper. A parameter that you pass to a bean method--or a return value from a bean method--can be any Java type that is serializable.
Java primitive types, such as int , double , are serializable. Any non-remote object that implements the java. Serializable interface can be passed.
A non-remote object passed as a parameter to a bean or returned from a bean is passed by value , not by reference. So, for example, if you call a bean method as follows:. If the bean changes the value of theNumber object on the server, this change is not reflected back to the client, because of pass-by-value semantics.
If the non-remote object is complex--such as a class containing several fields--only the non-static and non-transient fields are copied. When passing a remote object as a parameter, the stub for the remote object is passed. A remote object passed as a parameter must extend remote interfaces.
The next section demonstrates parameter passing to a bean and remote objects as return values. The EmployeeBean getEmployee method returns an EmpRecord object, so this object must be defined somewhere in the application. The class is declared as public , and must implement the java.
Serializable interface so that it can be passed back to the client by value, as a serialized remote object. The declaration is as follows:. Note: The java. Serializable interface specifies no methods, it just indicates that the class is serializable.
Therefore, there is no need to implement extra methods in the EmpRecord class. The Client Code This section shows the client code that you can use to send messages to the example bean described above, and get and print results from it. This client code demonstrates how a client:.
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