发布于 2015-06-05 21:08:00 | 269 次阅读 | 评论: 0 | 来源: 网友投递
EJB 3.0规范提供了注释字段或setter方法注入依赖可以应用。 EJB容器使用的全局JNDI注册表定位的依赖。以下注解在EJB 3.0中使用依赖注入。
@EJB - 用来注入其他EJB引用。
@Resource - 用于注入数据源或单例服务，如sessionContext，timerService等
@EJB 可以使用栏位或以下方式的方法。
public class LibraryMessageBean implements MessageListener {
//dependency injection on field.
@EJB
LibraryPersistentBeanRemote libraryBean;
...
}
public class LibraryMessageBean implements MessageListener {
LibraryPersistentBeanRemote libraryBean;
//dependency injection on method.
@EJB(beanName="com.tutorialspoint.stateless.LibraryPersistentBean")
public void setLibraryPersistentBean(
LibraryPersistentBeanRemote libraryBean)
{
this.libraryBean = libraryBean;
}
...
}
@Resource 通常用于注入EJB容器提供单例。
public class LibraryMessageBean implements MessageListener {
@Resource
private MessageDrivenContext mdctx;
...
}
让我们创建一个测试EJB应用程序来测试EJB服务的依赖注入。
| Step | Description |
|---|---|
| 1 | Create a project with a name EjbComponent under a package com.tutorialspoint.timer as explained in the EJB - Create Application chapter. |
| 3 | Use Beans created in the EJB - Message Driven Bean chapter. Keep rest of the files unchanged. |
| 5 | Clean and Build the application to make sure business logic is working as per the requirements. |
| 6 | Finally, deploy the application in the form of jar file on JBoss Application Server. JBoss Application server will get started automatically if it is not started yet. |
| 7 | Now create the ejb client, a console based application in the same way as explained in theEJB - Create Application chapter under topic Create Client to access EJB. |
package com.tuturialspoint.messagebean;
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import javax.annotation.Resource;
import javax.ejb.ActivationConfigProperty;
import javax.ejb.EJB;
import javax.ejb.MessageDriven;
import javax.ejb.MessageDrivenContext;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.ObjectMessage;
@MessageDriven(
name = "BookMessageHandler",
activationConfig = {
@ActivationConfigProperty( propertyName = "destinationType",
propertyValue = "javax.jms.Queue"),
@ActivationConfigProperty( propertyName = "destination",
propertyValue ="/queue/BookQueue")
}
)
public class LibraryMessageBean implements MessageListener {
@Resource
private MessageDrivenContext mdctx;
@EJB
LibraryPersistentBeanRemote libraryBean;
public LibraryMessageBean(){
}
public void onMessage(Message message) {
ObjectMessage objectMessage = null;
try {
objectMessage = (ObjectMessage) message;
Book book = (Book) objectMessage.getObject();
libraryBean.addBook(book);
} catch (JMSException ex) {
mdctx.setRollbackOnly();
}
}
}
package com.tutorialspoint.test;
import com.tutorialspoint.entity.Book;
import com.tutorialspoint.stateless.LibraryPersistentBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.jms.ObjectMessage;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class EJBTester {
BufferedReader brConsoleReader = null;
Properties props;
InitialContext ctx;
{
props = new Properties();
try {
props.load(new FileInputStream("jndi.properties"));
} catch (IOException ex) {
ex.printStackTrace();
}
try {
ctx = new InitialContext(props);
} catch (NamingException ex) {
ex.printStackTrace();
}
brConsoleReader =
new BufferedReader(new InputStreamReader(System.in));
}
public static void main(String[] args) {
EJBTester ejbTester = new EJBTester();
ejbTester.testMessageBeanEjb();
}
private void showGUI(){
System.out.println("**********************");
System.out.println("Welcome to Book Store");
System.out.println("**********************");
System.out.print("Options n1. Add Bookn2. Exit nEnter Choice: ");
}
private void testMessageBeanEjb(){
try {
int choice = 1;
Queue queue = (Queue) ctx.lookup("/queue/BookQueue");
QueueConnectionFactory factory =
(QueueConnectionFactory) ctx.lookup("ConnectionFactory");
QueueConnection connection = factory.createQueueConnection();
QueueSession session = connection.createQueueSession(
false, QueueSession.AUTO_ACKNOWLEDGE);
QueueSender sender = session.createSender(queue);
while (choice != 2) {
String bookName;
showGUI();
String strChoice = brConsoleReader.readLine();
choice = Integer.parseInt(strChoice);
if (choice == 1) {
System.out.print("Enter book name: ");
bookName = brConsoleReader.readLine();
Book book = new Book();
book.setName(bookName);
ObjectMessage objectMessage =
session.createObjectMessage(book);
sender.send(objectMessage);
} else if (choice == 2) {
break;
}
}
LibraryPersistentBeanRemote libraryBean =
(LibraryPersistentBeanRemote)
ctx.lookup("LibraryPersistentBean/remote");
List<Book> booksList = libraryBean.getBooks();
System.out.println("Book(s) entered so far: "
+ booksList.size());
int i = 0;
for (Book book:booksList) {
System.out.println((i+1)+". " + book.getName());
i++;
}
} catch (Exception e) {
System.out.println(e.getMessage());
e.printStackTrace();
}finally {
try {
if(brConsoleReader !=null){
brConsoleReader.close();
}
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
}
}
EJBTester做以下任务。
jndi.properties中加载和初始化的InitialContext对象。
JNDI查找testStatefulEjb（）方法，完成了名字 - “/queue/BookQueue”在JBoss获得参考。发件人使用队列会话创建。
然后用户显示一个库存储的用户界面和他/她被要求输入选择。
如果用户输入1，系统要求输入书籍名称和发件人发送本书的名字来排队。当JBoss容器接收到这个消息队列，它会调用我们的消息驱动bean的onMessage方法。消息驱动bean保存使用状态会话bean addBook（）方法的书。会话Bean持久化这本书中通过EntityManager调用数据库。
如果用户输入2，然后是另一个JNDI查找名字 - “LibraryStatefulSessionBean/remote”获取远程业务对象（状态EJB）再次上市的书籍完成。
在项目资源管理器中找到EJBTester.java。右键点击上EJBTester类，并选择run file.
在Netbeans控制台验证以下输出。
run:
**********************
Welcome to Book Store
**********************
Options
1. Add Book
2. Exit
Enter Choice: 1
Enter book name: Learn EJB
**********************
Welcome to Book Store
**********************
Options
1. Add Book
2. Exit
Enter Choice: 2
Book(s) entered so far: 2
1. learn java
1. learn EJB
BUILD SUCCESSFUL (total time: 15 seconds)
输出上面显示说我们的消息驱动bean接收消息和持久性存储和书籍从数据库中检索存储本书。
我们的消息驱动bean被使用LibraryPersistentBean使用@ EJB注释注入的情况下例外MessageDrivenContext对象用于回滚事务。