The stateless session bean is a component that can imitate the business process, which can be performed in a separate method call. The Stateless Session bean is not able to maintain a status of a call customer. In a method call, the Stateless Session bean maintains the status of the calling customer. When the method is executed, the status is not maintained. After the call is completed, the Stateless Session bean is immediately released into the buffer pool, so the Stateless Session bean has good scalability and can support a large number of users.
Features of stateless session beans
No dialog
The stateless session bean can have internal status, and their status cannot be customized for special clients. This means that all stateless beans have no differences for the client, and the client cannot separate them. The client must pass all necessary client data to the parameter of the business logic method to the stateless bean, and the stateless bean can obtain the required data from an external resource (such as a database).
Initialization stateless bean has only one way
We know that the initialization of the session bean calls the ejbcreate () method, because the stateless session bean is not able to reserve the status between the method call, so it cannot be reserved after the client is transferred to ejbcreate (). Call EJBCREATE () or CREATE () without parameters.
Container can gather and reuse stateless session beans
Build "Hello, World!" Remote Interface
Package com.wiley.compbooks.roman.session.helloworld; import javax.ejb. *; import java.rmi.remoteException; import java.rmi.Remote;
/ ** * This is the HelloBean remote interface * * This interface is what clients operate on when * they interact with EJB objects The container * vendor will implement this interface;.. The * implemented object is the EJB object, which * delegates invocations To the actual bean. * /
Public interface hello extends ejbobject {
/ ** * The one method - hello - returns a greeting to the client. * /
Public string hello () throws java.rmi.remoteException;} Source 4.1 Hello.java.
The Hello interface inherits the EJBOBJECT interface, EJBObject inherits the Remote interface, so Hello can throw RMI exceptions.
Establish a bean to achieve business methods: Hello ().
He implements a javax.ejb.sessionBean interface
Package com.wiley.compbooks.roman.session.helloworld; import javax.ejb. *;
/ ** * Demonstration stateless session bean. * /
Public class hellobean implements sessionbean {
// // ejb-required methods // public void ejbcreate () {system.out.println ("ejbcreate ()");} public void ejbremove () {system.out.println ("ejbremove ()");} public void ejbActivate () {System.out.println ( "ejbActivate ()");} public void ejbPassivate () {System.out.println ( "ejbPassivate ()");} public void setSessionContext (SessionContext ctx) {System. Out.println ("SetSessionContext ()");}
/// Business methods //
Public String Hello () {system.out.println ("Hello ()"); return "Hello, World!"
}
Source 4.2 hellobean.java
Note: You don't need to implement your own remote interface, the initialization method does not have parameters. When destroying beans, use a relatively simple EJBREMOVE () method. Ejbactivate () and EJBPassivate () methods do not need to be applied in stateless session beans, so these two methods are empty.
Establish "Hello, World!" HOME interface
The HOME interface inherits Javax.ejb.ejbhome. The HOME interface extends a method that does not have a parameter for the EJB object ?? Create () method.
Package com.wiley.compbooks.roman.session.helloworld; import javax.ejb. *; import java.rmi.remoteException;
/ ** * This is the home interface for HelloBean This interface * is implemented by the EJB Server's glue-code tools -.. The * implemented object is called the Home Object and serves * as a factory for EJB Objects * * One Create () Method is in this home interface, which * corresponds to the ejbcreate () method in hellobean. * /
Public interface hellohome extends ejbhome {
/ * * This method creates the ejb object. * * @Return the newly created ejb object. * /
Hello Create () Throws RemoteException, CreateException;} Creat method throws a java.rmi.RemoteException and aavax.ejb.createException. Exception. Write configuration descriptor
In EJB1.0, the configuration descriptor is a Java object stored on the disk as a file. In EJB1.1, the configuration descriptor is an XML document. The EJB container or IDE environment should provide a tool for generating a configuration descriptor.
Configuration descriptor settings
Bean home
Enterprise bean class name
HOME interface class name
Remote interface class name
RE-Entrant
State or stateless
Session time
Hellobean configuration descriptor
Environmental properties
BEAN is adapted to different special environments by using this information.
EJB-JAR file
We need to pack our needs into the EJB-JAR file.
Enterprise-class bean
Remote interface
HOME interface
Configuration descriptor, including properties
These these must be included in the EJB-JAR file. In EJB1.0, the JAR file has a list of text files. It represents the details of JAR. It is used to identify which business bean is in the EJB-JAR file. In EJB1.1, the XML file contains all necessary information.
Generate EJB-JAR files
JAR CMF ../manifest helloworld.jar * Configure Bean
Finally, we also need to configure Bean in the EJB container. Often perform steps:
EJB-JAR file inspection
Container tools to generate EJB objects and home objects
Container tools to generate stubs and skeletons required for RMI
Customer code written in stateless bean
Package com.wiley.compbooks.roman.session.helloworld; import javax.ejb. *; import javax.naming. *; import java.rmi. *; import java.util.properties;
/ ** * this class is an esample of client code That Invokes * Methods on a Simple Stateless Session bean. * /
Public class helloclient {public static void main (string [] args) {try {
/ * * Get System Properties for JNDI INITIALIZATION * /
Properties PROPS = system.getproperties ();
/ * Form an initial context * /
Context CTX = New InitialContext (PrOPS); / * * Get a reason to the home object * (The factory for ejb objects) * / hellohome home = (HelloHome) CTX.lookup ("HelloHome"); / * * Use the factory To create the ejb object * / hello hello = home.create (); / * * call the hello () method, and print it * / system.out.Println (Hello Hello ()); / * * Done with EJB Object, so remove it * / hello.remove ();} catch (exception e) {E.PrintStackTrace ();}}} client code performs a task: Positioning Home Interface
Estim EJB object using the Home interface
Call Hello () on the EJB object
Remove EJB object
run
First run the application server. For BEA WebLogic, execution
T3Server
Client execution:
java -Djava.naming.factory.initial = weblogic.jndi.TengahInitialContextFactory -Djava.naming.provider.url = t3: // localhost: 7001 com.wiley.compBooks.roman.session.helloworld.HelloClient server output:
SetSessionContext () Ejbcreate () Hello () EJBREMOVE ()
Client output:
Hello, World!
