NetBean 8 建立EJB

時間 2019-11-11

標籤 netbean 建立 ejb 简体版

原文原文鏈接

一. 介紹html

百度了一下關於在NetBean開發環境裏建立EJB的教程，沒有找到好的例子，2天的調試過程，寫下來幫助後人。java

EJB (Enterprise Java Bean) 是一套高擴展性的開發企業級應用的開發結構，一般部署在JBoss, Glassfish, WildFly等服務器上，更多介紹可參看連接。數據庫

1. Entity Bean: 域模型對象，用於實現O/R映射，負責將數據庫中的表記錄映射爲內存中的Entity對象，事實上，建立一個Entity Bean對象至關於新建一條記錄，刪除一個Entity Bean會同時從數據庫中刪除對應記錄，修改一個Entity Bean時，容器會自動將Entity Bean的狀態和數據庫同步。瀏覽器

2. Session Bean: 用於實現業務邏輯，它能夠是有狀態的，也能夠是無狀態的。每當客戶端請求時，容器就會選擇一個Session Bean來爲客戶端服務。Session Bean能夠直接訪問數據庫，但更多時候，它會經過Entity Bean實現數據訪問。服務器

3. Message Driven Bean: MDB是EJB2.0中引入的新的企業Bean，它基於JMS消息，只能接收客戶端發送的JMS消息而後處理。MDB其實是一個異步的無狀態Session Bean，客戶端調用MDB後無需等待，馬上返回，MDB將異步處理客戶請求。這適合於須要異步處理請求的場合，好比訂單處理，這樣就能避免客戶端長時間的等待一個方法調用直到返回結果。 session

二. 建立EJB模塊less

點擊File --> New Project, 在Java EE目錄下選擇EJB Module:異步

給項目取一個名字Sample-EJB,選擇合適的項目目錄，而後點擊下一步編輯器

選擇Server, 我選的是GlassFish Server 4.1， Java EE Version是Jave EE 7.ide

三. 建立Application Class Library項目

點擊File --> New Project, 在Java目錄下選擇Java Class Library:

給項目取一個名字Sample-Client,選擇合適的項目目錄，而後點擊Next:

四. 建立Entity Bean

接下來建立一個Peoplede的entity class. Antity Class 通常對應了數據庫的一個表，當你建立Entity Class 後NetBeans IDE會給該類添加@Entity標記來表示它是一個Entity類.

每個Entity Class都必須有primary key. IDE會添加@ID標籤在primary key上面, @GeneratedValue來表示primary key 是怎麼產生的.

右擊Projects窗口的Sample-Client --> New --> Other選擇Persistence目錄裏的Entity Class：

下面的Create Persistence Unit能夠不選擇！

當點擊Finish後，IDE會打開People.java文件編輯器，對People.java作以下修改：

 1 /*
 2  * To change this license header, choose License Headers in Project Properties.
 3  * To change this template file, choose Tools | Templates
 4  * and open the template in the editor.
 5  */
 6 package com.bruceyo.example.entity;
 7 
 8 import java.io.Serializable;
 9 import javax.persistence.Entity;
10 import javax.persistence.GeneratedValue;
11 import javax.persistence.GenerationType;
12 import javax.persistence.Id;
13 
14 /**
15  *
16  * @author bruce_000
17  */
18 @Entity
19 public class People implements Serializable {
20     private static final long serialVersionUID = 1L;
21     @Id
22     @GeneratedValue(strategy = GenerationType.AUTO)
23     private Long id;
24     private String firstName;
25 
26     public String getFirstName() {
27         return firstName;
28     }
29 
30     public void setFirstName(String firstName) {
31         this.firstName = firstName;
32     }
33 
34     public String getLastName() {
35         return lastName;
36     }
37 
38     public void setLastName(String lastName) {
39         this.lastName = lastName;
40     }
41     private String lastName;
42     
43     public Long getId() {
44         return id;
45     }
46 
47     public void setId(Long id) {
48         this.id = id;
49     }
50 
51     @Override
52     public int hashCode() {
53         int hash = 0;
54         hash += (id != null ? id.hashCode() : 0);
55         return hash;
56     }
57 
58     @Override
59     public boolean equals(Object object) {
60         // TODO: Warning - this method won't work in the case the id fields are not set
61         if (!(object instanceof People)) {
62             return false;
63         }
64         People other = (People) object;
65         if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
66             return false;
67         }
68         return true;
69     }
70 
71     @Override
72     public String toString() {
73         return "com.bruceyo.example.entity.Customer[ id=" + id + " ]";
74     }
75     
76 }

People.java代碼

五. 建立Session Bean

EJB3.1可以輕鬆建立stateless的session bean， stateless session bean不保存相關用戶的狀態. 但它能夠保存它的實例的狀態.

一般用EJB Container來建立bean對象池，而後用對象池裏的對象來處理用戶請求.

右擊Projects窗口的Sample-EJB --> New --> Other選擇Enterprise JavaBean目錄裏的Session Bean：

給EJB取名字叫AccountService, 並寫上包名; 選擇Stateless, 同時下面的Remote in Project要選上！

按finish後，IDE會打開AccountService.java文件編輯器，修改文件以下：

 1 /*
 2  * To change this license header, choose License Headers in Project Properties.
 3  * To change this template file, choose Tools | Templates
 4  * and open the template in the editor.
 5  */
 6 package com.bruceyo.sample.service;
 7 
 8 import com.bruceyo.example.entity.People;
 9 import javax.ejb.Stateless;
10 import javax.persistence.EntityManager;
11 import javax.persistence.PersistenceContext;
12 
13 /**
14  *
15  * @author bruce_000
16  */
17 @Stateless
18 public class AccountService implements AccountServiceRemote {
19 
20     @PersistenceContext
21     private EntityManager em;
22     
23     @Override
24     public People createAccount(String firstName, String lastName) {
25         People customer = new People();
26         customer.setFirstName(firstName);
27         customer.setLastName(lastName);
28         
29         em.persist(customer);
30         return customer;
31     }
32 
33     // Add business logic below. (Right-click in editor and choose
34     // "Insert Code > Add Business Method")
35 }

AccountService.Java代碼

六. 建立持久單元Persistence Unit

建立一個Persistence Unit做爲數據源的容器來管理Entities,

右擊Projects窗口的Sample-EJB --> New --> Other選擇Persistence目錄裏的Persistence Unit：

選擇Data Source爲jdbc/sample; 勾選Drop and Create, 若是數據庫裏有的話就丟棄原來的，記得查看下jdbc/sample裏有哪些表！EJB的

打開剛剛建立的persistence.xml, 去掉Include All Entity Classes的勾，而後添加Entity Class.

結果以下：

七. 部署(Deploy) EJB模塊

右鍵EJB模塊，選擇Build --> Deploy， NetBeans會自動部署EJB服務，能夠到Services窗口查看GlassFish本地服務器有沒有自動開啓.

八. 建立一個Servlet Class來測試EJB

1, 建立一個Web Module:

點擊File --> New Project, 在Java Web目錄下選擇Web Application:

添加項目名字Sample-Web, 選擇合適的項目位置：

點擊下一步，添加Context Path: /Sample-Web, 部署Web Application的時候要用到這個路徑訪問網站.

2, 建立 Servlet

右擊Projects窗口的Sample-EJB --> New --> Other選擇Enterprise JavaBean目錄裏的Session Bean：

點擊Next--> Finish後，IDE打開AccountController.java的編輯器，修改以下：

 1 /*
 2  * To change this license header, choose License Headers in Project Properties.
 3  * To change this template file, choose Tools | Templates
 4  * and open the template in the editor.
 5  */
 6 package com.bruceyo.example.tester;
 7 
 8 import com.bruceyo.example.entity.People;
 9 import com.bruceyo.sample.service.AccountServiceRemote;
10 import java.io.IOException;
11 import java.io.PrintWriter;
12 import javax.ejb.EJB;
13 import javax.servlet.ServletException;
14 import javax.servlet.annotation.WebServlet;
15 import javax.servlet.http.HttpServlet;
16 import javax.servlet.http.HttpServletRequest;
17 import javax.servlet.http.HttpServletResponse;
18 
19 /**
20  *
21  * @author jGauravGupta
22  */
23 @WebServlet(name = "AccountController", urlPatterns = {"/AccountController"})
24 public class AccountController extends HttpServlet {
25     @EJB
26     private AccountServiceRemote accountService;
27 
28     
29     /**
30      * Handles the HTTP <code>POST</code> method.
31      *
32      * @param request servlet request
33      * @param response servlet response
34      * @throws ServletException if a servlet-specific error occurs
35      * @throws IOException if an I/O error occurs
36      */
37     @Override
38     protected void doPost(HttpServletRequest request, HttpServletResponse response)
39             throws ServletException, IOException {
40        response.setContentType("text/html;charset=UTF-8");
41         try (PrintWriter out = response.getWriter()) {
42             String firstName = request.getParameter("firstName");
43             String lastName = request.getParameter("lastName");
44             
45             People customer = accountService.createAccount(firstName, lastName);
46             out.println("Customer["+customer.getFirstName()+"] : " + customer.getId());
47         }
48     }
49 
50 }

AccountController.java代碼

九. 添加HTML頁面

編輯Sample-Web裏的Index.html網頁文件以下：

 1 <!DOCTYPE html>
 2 <!--
 3 To change this license header, choose License Headers in Project Properties.
 4 To change this template file, choose Tools | Templates
 5 and open the template in the editor.
 6 -->
 7 <html>
 8     <head>
 9         <title>TODO supply a title</title>
10         <meta charset="UTF-8">
11         <meta name="viewport" content="width=device-width, initial-scale=1.0">
12     </head>
13     <body>
14         <form action="AccountController" method="post" >
15         <input type="text" name="firstName" placeholder="First Name" />
16         <input type="text" name="lastName" placeholder="Last Name"/>
17         <input type="submit" value="Create"/>
18         </form>
19     </body>
20 </html>