今天因閒來無事,研究了一下JPA,並做了一個簡單小示例來供大家分享,首先我們來簡要介紹下JPA,JPA是通過SUN JDK5.0的註解和XML用來描
述對象與關係表的映射,並將運行期間實體對象持久化到數據庫中去。
先來談下實體BEAN的規範,具有ORM元素數據的領域對象就叫做實體,它應具備如下四個條件:
一、必須使用 javax.persistence.Entity 註解或XML映射文件中有對應的<entity>元素
二、必須具有一個不帶參數的構造函數,類不能聲明爲final,方法和需要持久化的屬性也不能聲明爲final
三、如果流離狀態的實體對象需要以值的方式進行傳遞(如通過Session bean的遠程業務接口傳遞),則必須實現java.io.Serializable 接口
四、需要持久化的屬性,訪問修飾符不能是public,它必須通過實體類方法進行訪問
下面簡要介紹下spring2.0與 spring2.5 在 MVC模式上的改進
2.5 跟 2.0 的MVC實現模式以經完全不一樣,2.5 主要是引入了註解驅動,控制器不用再繼承任何類或實現任何接口(SimpleFormController
或 MultiActionController),也無需在spring配置文件中定義請求和控制器,2.5中的控制器,通過註解就可以讓一個POJO具有控制器的功能,
同時增強了框架的易用性、靈活性、擴展性、並提高一定的開發效率
下面是一個用 spring2.5 + jpa 實現的一個簡單小示例
首先在ECLIPSE中建立一個WEB Project,將所需要的類庫全部拷入到工程的LIB目錄,還有一點需要到
http://sourceforge.net/project/showfiles.php?group_id=40712&package_id=156160&release_id=405227
根據相應的平臺下載 hibernate-entitymanager.jar包放入到LIB目錄,否則會報java.lang.ClassNotFoundException:
org.hibernate.ejb.HibernatePersistence 異常
我把該過程分爲五步來寫:
一、在工程的src目建立一個META-INF 文件,在當中添加一個persistenct.xml 文件,代碼如下:
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<!-- 持久化單元名爲SPRING_JPA在spring配置文件中要對應起來,使用本地事務 -->
<persistence-unit name="SPRING_JPA" transaction-type="RESOURCE_LOCAL">
<!-- 聲明JPA規範由hibernate實現持久化 -->
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.SQLServerDialect"/>
<property name="hibernate.max_fetch_depth" value="3"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>
</persistence>
二、配置spring配置文件,分爲二個applicationContext.xml 和 springjpa-servlet.xml XML文件,applicationContext.xml 定義業務邏輯
相關的配置,springjpa-servlet.xml 定義 spring MVC 的相應配置,文件代碼如下:
springjpa-servlet.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<!-- 自動裝載注入 -->
<context:component-scan base-package="*"></context:component-scan>
<!-- 啓動springMVC的註解驅動 -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"></bean>
<!-- 模型視圖的解析 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" p:suffix=".jsp"></bean>
</beans>
applicationContext.xml 代碼如下:
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.microsoft.jdbc.sqlserver.SQLServerDriver"></property>
<property name="url" value="jdbc:microsoft:sqlserver://192.168.0.180:1433;databaseName=pubs"></property>
<property name="username" value="holpe"></property>
<property name="password" value="holpe20080801"></property>
</bean>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource"></property>
<property name="persistenceXmlLocation" value="classpath:META-INF/persistence.xml"></property>
<!-- <property name="persistenceUnitName" value="vissul"></property> -->
<property name="loadTimeWeaver">
<bean class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver"></bean>
</property>
</bean>
<bean id="txManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"></property>
</bean>
<tx:annotation-driven transaction-manager="txManager"/>
<!-- 自動裝載注入 -->
<context:component-scan base-package="*"/>
<bean id="loginDao" class="com.spring25jpa.dao.impl.LoginDaoImpl"/>
<bean id="loginService" class="com.spring25jpa.service.impl.LoginService"/>
</beans>
三、建立spring 控制器,業務層、數據層、和JPA註解域對象
首先控制器 LoginAction.java
package com.spring25jpa.action;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import com.spring25jpa.service.ILoginService;
/**
* <p>
* 創 建 人:ChenTao
* <p>
* 創建日期:2009-5-12 下午02:37:34
* <p>
*
*/
@Controller
public class LoginAction {
@Autowired
public ILoginService loginService;
@RequestMapping("/login.do")
public String login(String userName,String password,ModelMap model){
boolean succeed = loginService.login(userName,password);
if(succeed){
model.addAttribute("userName", userName);
return "success";
}
return "error";
}
}
業務處理類 LoginService.java
package com.spring25jpa.service.impl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;
import com.spring25jpa.dao.ILoginDao;
import com.spring25jpa.service.ILoginService;
/**
* <p>
* 創 建 人:ChenTao
* <p>
* 創建日期:2009-5-12 下午02:43:28
* <p>
*
*/
public class LoginService implements ILoginService {
@Autowired
private ILoginDao loginDao;
@Transactional
public boolean login(String userName,String password) {
return loginDao.login(userName,password);
}
}
數據處理類 LoginDaoImpl.java
package com.spring25jpa.dao.impl;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import com.spring25jpa.dao.ILoginDao;
/**
* <p>
* 創 建 人:ChenTao
* <p>
* 創建日期:2009-5-12 下午02:44:57
* <p>
*
*/
public class LoginDaoImpl implements ILoginDao{
@PersistenceContext
private EntityManager em;
public boolean login(String userName,String password) {
Query query = em.createQuery("from Users where userName=:userName and password=:password");
query.setParameter("userName", userName);
query.setParameter("password", password);
return query.getResultList().size() > 0 ? true : false;
}
}
持久化對象並進行了JPA註解
package com.spring25jpa.po;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
@SuppressWarnings("serial")
@Entity
@Table(name="users")
public class Users implements Serializable{
@Id
@GeneratedValue
private Integer uid;
@Column(name="username",nullable=true,length=20)
private String userName;
@Column(name="pwd",nullable=true,length=20)
private String password;
@Column(name="birthday")
private Date birthday;
public Users(){
}
get set ......
}
四、配置最重要的文件 web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<!-- spring 啓動監聽器 -->
<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
<!-- 處理請求的 servlet,它將加載 WEB-INF/springjpa-servlet.xml下的配置文件,以啓動springMVC模塊 -->
<servlet>
<servlet-name>springjpa</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>springjpa</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
接下來第五步就是編寫JSP頁面,JSP頁面就不貼出來了,相信大家都知道怎樣去寫,好了這樣一個簡單的示例就算寫完了,經過運行後完全正確,
這也是我寫的第一個 spring2.5+jpa的示例,有不當之處還請多多諒解
需要源碼可到此處下載: http://download.csdn.net/source/1301318