在Spring框架中集成JPA實例

火星人 @ 2014-03-10 , reply:0


Hibernate 3.2支持JPA註解,Spring集成JPA是可選的.

下面是Spring集成JPA的一個例子.

實體類MyUser,使用JPA註解實現到資料庫表myUser的映射,如下所示:

   package org.shirdrn.entity;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Transient;
@Entity
public class MyUser {
private Long id;
private String userName;
private String password;
private String gender;
private Integer age;
private Integer birthYear;
private String addr;
private String email;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(name="userName")
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
@Column(name="password")
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Column(name="gender")
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Column(name="age")
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Column(name="addr")
public String getAddr() {
return addr;
}
public void setAddr(String addr) {
this.addr = addr;
}
@Column(name="email")
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Transient
public Integer getBirthYear() {
return new Integer(2008-age);
}
public void setBirthYear(Integer age) {
this.birthYear = new Integer(2008-age);
}
}


其中,birthYear不是資料庫中的欄位,使用JPA的@Transient註解,在映射的時候,會忽略掉該成員.

持久層DAO介面如下:

   package org.shirdrn.dao;
import java.util.List;
import org.shirdrn.entity.MyUser;
import org.springframework.transaction.annotation.Transactional;
@Transactional
public interface MyUserDAO {
public void createMyUser(MyUser myUser);
public void deleteMyUser(MyUser myUser);
public void updateMyUser(MyUser myUser);
public List queryMyUser(String queryString);
public List queryAll();
}


這裡,使用了JPA註解,聲明事務.

DAO實現類,如下所示:

    package org.shirdrn.dao.impl;
import java.util.List;
import org.shirdrn.dao.MyUserDAO;
import org.shirdrn.entity.MyUser;
import org.springframework.orm.jpa.support.JpaDaoSupport;
public class MyUserDAOImpl extends JpaDaoSupport implements MyUserDAO {
public void createMyUser(MyUser myUser) {
getJpaTemplate().persist(myUser);
}
public void deleteMyUser(MyUser myUser) {
MyUser dbMyUser = getJpaTemplate().find(MyUser.class, myUser.getId());
getJpaTemplate().remove(dbMyUser);
}
public void updateMyUser(MyUser myUser) {
MyUser dbMyUser = getJpaTemplate().find(MyUser.class, myUser.getId());
if(myUser.getUserName() != null){
dbMyUser.setUserName(myUser.getUserName());
}
if(myUser.getAddr() != null){
dbMyUser.setAddr(myUser.getAddr());
}
getJpaTemplate().merge(dbMyUser);
}
@SuppressWarnings("unchecked")
public List queryMyUser(String queryString) {
return (List)getJpaTemplate().find(queryString);
}
@SuppressWarnings("unchecked")
public List queryAll() {
return (List)getJpaTemplate().find("from MyUser");
}
}


因為繼承了JpaDaoSupport,索引需要獲取一個JpaTemplate來實現訪問資料庫,在Spring的配置文件中要注入一個org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.

Spring的配置文件applicationContext.xml的內容如下所示:

   <?xmlversion="1.0"encoding="UTF-8"?>
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">


















<?xml:namespace prefix = tx />
abstract="false"lazy-init="default"autowire="default"
dependency-check="default">



 

在META-INF目錄下,還要加一個persistence.xml配置文件,如下所示:
    <?xmlversion="1.0"encoding="UTF-8"?>
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">

org.hibernate.ejb.HibernatePersistence
org.shirdrn.entity.MyUser


接著,對增刪改查操作進行測試,如下所示:

插入記錄:

   packageorg.shirdrn.test;
importorg.shirdrn.dao.MyUserDAO;
importorg.shirdrn.entity.MyUser;
importorg.springframework.context.ApplicationContext;
importorg.springframework.context.support.ClassPathXmlApplicationContext;
publicclassTestCreateMyUser{
publicstaticvoidmain(String[]args){
MyUserDAOmyUserDAO=(MyUserDAO)ctx.getBean("myUserDAOImpl");
MyUsermyUser=newMyUser();
myUser.setUserName("JohnXa");
myUser.setPassword("123456");
myUser.setGender("男");
myUser.setAge(newInteger(25));
myUser.setAddr("NewYork");
myUser.setEmail("john@hotmail.com");
myUserDAO.createMyUser(myUser);
}
}

刪除記錄:
    packageorg.shirdrn.test;

importorg.shirdrn.dao.MyUserDAO;
importorg.shirdrn.entity.MyUser;
importorg.springframework.context.ApplicationContext;
importorg.springframework.ClassPathXmlApplicationContext;
publicclassTestDeleteMyUser{
publicstaticvoidmain(String[]args){
ApplicationContextctx=newClassPathXml("applicationContext.xml");
MyUserDAOmyUserDAO=(MyUserDAO)ctx.getBean("myUserDAOImpl");
MyUsermyUser=newMyUser();
myUser.setId(newLong(29));
myUserDAO.deleteMyUser(myUser);

修改記錄:
    packageorg.shirdrn.test;
importorg.shirdrn.dao.MyUserDAO;
importorg.shirdrn.entity.MyUser;
importorg.springframework.context.ApplicationContext;
importorg.springframework.context.ClassPathXmlApplicationContext;

publicclassTestUpdateMyUser{
publicstaticvoidmain(String[]args){
ApplicationContextctx=newClassPathXmlApplicationContext("applicationContext.xml");
MyUserDAOmyUserDAO=(MyUserDAO)ctx.getBean("myUserDAOImpl");
MyUsermyUser=newMyUser();
myUser.setId(newLong(28));
myUser.setAddr("北京市");
myUserDAO.updateMyUser(myUser);
}
}


查詢記錄:
   packageorg.shirdrn.test;
importjava.util.List;
importorg.shirdrn.dao.MyUserDAO;
importorg.shirdrn.entity.MyUser;
importorg.springframework.context.ApplicationContext;
importorg.springframework.context.ClassPathXmlApplicationContext;
publicclassTestQueryAllMyUser{
publicstaticvoidmain(String[]args){
ApplicationContextctx=newClassPathXmContext("applicationContext.xml");
MyUserDAOmyUserDAO=(MyUserDAO)ctx.getBean("myUserDAOImpl");
Listlist=myUserDAO.queryMyUser("fromMyUser");
for(MyUseruser:list){
System.out.println("ID:" user.getId()
"|姓名:" user.getUserName()
"|密碼:" user.getPassword()
"|性別:" user.getGender()
"|年齡:" user.getAge()
"|住址:" user.getAddr()
"|郵箱:" user.getEmail());
}
}
}

心得總結

感覺自己對JPA的理解還是不怎麼深刻.

JpaTemplate提供的一些操作的方法,感覺不是很快就能理解的.

似乎使用JpaTemplate沒有使用HibernateTemplate方便,尤其是在執行插入、修改、刪除記錄的時候.修改和刪除記錄需要先把資料庫中對應的記錄載入出來,才能執行修改和刪除操作.

查詢資料庫倒是很容易,因為根本不需要事務,如果沒有事務,插入、修改和刪除操作就不能實現.

在Spring中使用JPA,感覺代價比較大,使用起來不容易,出錯不容易調試.

比較好的地方就是.如果資料庫中的表很多,無需編寫大量的XML文件去映射,只需要從POJO中就可以非常直觀地看到各個表之間的關係.





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