EJB攔截器

EJB 3.0規(guī)范提供攔截業(yè)務(wù)方法調(diào)用使用由@AroundInvoke注釋的方法。攔截器方法被調(diào)用之前ejbContainer業(yè)務(wù)方法調(diào)用攔截。下面是示例攔截器方法的簽名

@AroundInvoke
public Object methodInterceptor(InvocationContext ctx) throws Exception
{
   System.out.println("*** Intercepting call to LibraryBean method: " 
   + ctx.getMethod().getName());
   return ctx.proceed();
}

攔截器方法可以應(yīng)用或綁定三個層面

• Default-在部署中每個 bean 調(diào)用默認(rèn)攔截器。默認(rèn)攔截器，可用于僅通過 xml (ejb-jar.xml)。
  

• Class-類級別的每個方法調(diào)用攔截器bean。類級別攔截器可以應(yīng)用通過注釋的xml(ejb-jar.xml)。
  

• Method-方法級調(diào)用攔截器bean的特定方法。方法級攔截器可以應(yīng)用通過注釋的xml(ejb-jar.xml)。
  

我們在這里討論的類級別的攔截器。

攔截器類

package com.tutorialspoint.interceptor;

import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;

public class BusinessInterceptor {
   @AroundInvoke
   public Object methodInterceptor(InvocationContext ctx) throws Exception
   {
      System.out.println("*** Intercepting call to LibraryBean method: " 
      + ctx.getMethod().getName());
      return ctx.proceed();
   }
}

遠(yuǎn)程接口

import javax.ejb.Remote;

@Remote
public interface LibraryBeanRemote {
   //add business method declarations
}

截獲無狀態(tài)EJB

@Interceptors ({BusinessInterceptor.class})
@Stateless
public class LibraryBean implements LibraryBeanRemote {
   //implement business method 
}

示例應(yīng)用程序

讓我們創(chuàng)建一個測試 EJB 應(yīng)用程序來測試被截取的無狀態(tài) EJB

EJBComponent（EJB模塊）

LibraryBeanRemote.java

package com.tutorialspoint.interceptor;

import java.util.List;
import javax.ejb.Remote;

@Remote
public interface LibraryBeanRemote {
   void addBook(String bookName);
   List getBooks();
}

LibraryBean.java

package com.tutorialspoint.interceptor;

import java.util.ArrayList;
import java.util.List;
import javax.ejb.Stateless;
import javax.interceptor.Interceptors;

@Interceptors ({BusinessInterceptor.class})
@Stateless
public class LibraryBean implements LibraryBeanRemote {
    
   List<String> bookShelf;    

   public LibraryBean(){
      bookShelf = new ArrayList<String>();
   }

   public void addBook(String bookName) {
      bookShelf.add(bookName);
   }    

   public List<String> getBooks() {
      return bookShelf;
   }   
}

• 一旦你部署JBoss上EjbComponent項目，注意jboss的日志。

• JBoss已經(jīng)具備自動創(chuàng)建我們的會話bean JNDI入口- LibraryBean中/remote。

• 我們將使用此查找字符串來獲得類型的遠(yuǎn)程業(yè)務(wù)對象- com.tutorialspoint.interceptor.LibraryBeanRemote

JBoss應(yīng)用服務(wù)器日志輸出

...
16:30:01,401 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:
   LibraryBean/remote - EJB3.x Default Remote Business Interface
   LibraryBean/remote-com.tutorialspoint.interceptor.LibraryBeanRemote - EJB3.x Remote Business Interface
16:30:02,723 INFO  [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryBean,service=EJB3
16:30:02,723 INFO  [EJBContainer] STARTED EJB: com.tutorialspoint.interceptor.LibraryBeanRemote ejbName: LibraryBean
16:30:02,731 INFO  [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

   LibraryBean/remote - EJB3.x Default Remote Business Interface
   LibraryBean/remote-com.tutorialspoint.interceptor.LibraryBeanRemote - EJB3.x Remote Business Interface
...   

EJBTester（EJB客戶端）

jndi.properties

java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=localhost

• 這些屬性是用來初始化java命名服務(wù)的InitialContext對象
  

• InitialContext對象將被用于查找無狀態(tài)會話bean

EJBTester.java

package com.tutorialspoint.test;
   
import com.tutorialspoint.stateful.LibraryBeanRemote;
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.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.testInterceptedEjb();
   }
   
   private void showGUI(){
      System.out.println("**********************");
      System.out.println("Welcome to Book Store");
      System.out.println("**********************");
      System.out.print("Options 
1. Add Book
2. Exit 
Enter Choice: ");
   }
   
   private void testInterceptedEjb(){

      try {
         int choice = 1; 

         LibraryBeanRemote libraryBean =
         LibraryBeanRemote)ctx.lookup("LibraryBean/remote");

         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);
               libraryBean.addBook(book);          
            } else if (choice == 2) {
               break;
            }
         }

         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執(zhí)行以下任務(wù)。

• 從jndi.properties負(fù)荷特性和初始化InitialContext對象。

• 在testInterceptedEjb（）方法，JNDI查找與名行 - “LibraryBean中/遠(yuǎn)程”，以獲得遠(yuǎn)程業(yè)務(wù)對象（無狀態(tài)EJB）。

• 然后用戶顯示庫存儲用戶界面和他（她）被要求輸入選擇/。

• 如果用戶輸入1，系統(tǒng)要求書名并保存使用無狀態(tài)會話bean addBook（）方法的書。會話bean存儲本書的實例變量。

• 如果用戶輸入2，系統(tǒng)檢索使用無狀態(tài)會話bean getBooks（）方法，并退出書籍。

運行客戶端訪問EJB

在項目資源管理器中找到EJBTester.java。右鍵單擊EJBTester類并選擇運行文件（run file） 。

驗證以下在Netbeans控制臺的輸出

run:
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 1
Enter book name: Learn Java
**********************
Welcome to Book Store
**********************
Options 
1. Add Book
2. Exit 
Enter Choice: 2
Book(s) entered so far: 1
1. Learn Java
BUILD SUCCESSFUL (total time: 13 seconds)

JBoss應(yīng)用服務(wù)器日志輸出

驗證下面的輸出在 JBoss 應(yīng)用服務(wù)器日志輸出。

....
09:55:40,741 INFO  [STDOUT] *** Intercepting call to LibraryBean method: addBook
09:55:43,661 INFO  [STDOUT] *** Intercepting call to LibraryBean method: getBooks