一个EJB3.0小例子

    之前按照EJB3.0书籍写了一个新闻发布系统的简单例子，隔了很多天再重新发布发现问题重重，之前写的也忘之脑后。又费了九牛二虎之力才把其缕顺。特写下来以做参考。

 

 

    系统的结构图如下

  

       

 

 

 

1    主要涉及到与数据库打交道的实体类和 用于交互的 会话类。

   通过依赖注入来注入数据库JNDI 连接资源 并且持久化实体管理器EntityManager ：

@PersistenceContext(unitName="JEE_news_PU")protected EntityManager em;

 2 利用JDK6的注释功能 可以很轻松的配置实体类与数据库的映射

  

    

package com.news.entitybean;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@SuppressWarnings("serial")
@Entity
@Table(name="admin")
public class Admin implements Serializable{
	
	private int adminid;
    private String username;
	private String pwd;

	@Id()
	@GeneratedValue(strategy=GenerationType.AUTO)
	public int getAdminid() {
		return adminid;
	}

	public void setAdminid(int adminid) {
		this.adminid = adminid;
	}
    @Column(name="username",nullable=false) 
	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}
    @Column(nullable=false)
	public String getPwd() {
		return pwd;
	}

	public void setPwd(String pwd) {
		this.pwd = pwd;
	}

	
}

    

3 前台有对应的类 包装了用到的参数 并且通过JNDI来查找会话类：

 

package com.news.backbean;

import javax.naming.InitialContext;

import com.news.sessionbean.AdminLocal;

public class JSF_Loginbean {
	
	private String name;
	private String pwd;
	private String msg;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getPwd() {
		return pwd;
	}
	public void setPwd(String pwd) {
		this.pwd = pwd;
	}
	public String getMsg() {
		return msg;
	}
	public void setMsg(String msg) {
		this.msg = msg;
	}
	public String checkLogin(){
		try{
			InitialContext ctx = new InitialContext();
			AdminLocal adminLocal = (AdminLocal)ctx.lookup("AdminBean/local");
			if(this.name.trim()==""){
				this.msg = "the username is manadatory";
				return null;
			}if(this.pwd.trim()==""){
				this.msg="password is mandatory";
				return null;
			}
			if(adminLocal.checkLogin(name, pwd)){
				return "login_success";
			}else{
				this.msg="Login Failed";
				return null;
			}
			
		}catch(Exception e){
			this.msg="there is an innormal situation";
			e.printStackTrace();
			return null;
		}
	}

}

 

 会话类url注册 当web App容器跟EJB容器在同一个JVM环境下时候 用Local接口 不在的时候要用Remote Remote比Local更消耗系统性能

 

@Stateless
@Remote(AdminRemote.class)
@Local(AdminLocal.class)
public class AdminBean implements AdminRemote,AdminLocal {

。。。。。。。

  

  可以通过在faces-config.xml 配置managed-bean 可以控制前台包装类的显示名字 达到隐藏后台代码的目的

 

 

<managed-bean>
  <managed-bean-name>Loginbean</managed-bean-name>
  <managed-bean-class>com.news.backbean.JSF_Loginbean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
 </managed-bean>
 <managed-bean>
  <managed-bean-name>NewsListbean</managed-bean-name>
  <managed-bean-class>com.news.backbean.JSF_NewsListbean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
  <managed-property>
   <property-name>id</property-name>
   <value>#{param.id}</value>
  </managed-property>
  <managed-property>
   <property-name>currPage</property-name>
   <value>#{param.currPage}</value>
  </managed-property>
 </managed-bean>
 <managed-bean>
  <managed-bean-name>JSF_news</managed-bean-name>
  <managed-bean-class>com.news.backbean.JSF_AddNewsbean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
 </managed-bean>

 

在faces-config.xml 中配置页面导航规则

 

<navigation-rule>
  <from-view-id>/pages/JSF_Login.xhtml</from-view-id>
  <navigation-case>
   <from-outcome>login_success</from-outcome>
   <to-view-id>/pages/newsIndex.xhtml</to-view-id>
   <redirect/>
  </navigation-case>
 </navigation-rule>

 4 加过滤器 为了实现session失效时重新登录功能 在web.xml里配置了过滤器和session的失效时间

 

 <filter>
    <description>validate if has logined</description>
    <filter-name>Login Valid Filter</filter-name>
    <filter-class>com.news.backbean.Loginfilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>Login Valid Filter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  <session-config>
    <session-timeout>3</session-timeout>
  </session-config>