Spring Data JPA教程入门介绍 _SpringJPA

Spring Data JPA API提供了JpaTemplate类以将spring应用程序与JPA集成。
JPA(Java持久性API)是用于在企业应用程序中持久存储对象的sun规范。当前, 它用作复杂实体bean的替代品。
许多供应商提供了JPA规范的实现, 例如：

Hibernate
Toplink
iBatis
OpenJPA等

Spring JpaTemplate的优势你无需编写前后代码即可持久, 更新, 删除或搜索对象, 例如创建Persistence实例, 创建EntityManagerFactory实例, 创建EntityTransaction实例, 创建EntityManager实例, 提交EntityTransaction实例以及关闭EntityManager。
因此, 它节省了大量代码。
在此示例中, 我们将使用Hibernate模式来实现JPA。
Spring和JPA集成的示例
让我们看一下将Spring应用程序与JPA集成的简单步骤：

创建Account.java文件
创建Account.xml文件
创建AccountDao.java文件
创建persistence.xml文件
创建applicationContext.xml文件
创建AccountsClient.java文件

在这个示例中, 我们将把Hibernate应用程序与spring集成在一起。让我们看看带有Spring的jpa示例的目录结构。

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1) Account.java
这是一个简单的POJO类。

package com.srcmini; public class Account { private int accountNumber; private String owner; private double balance; //no-arg and parameterized constructor //getters and setters }

2)Account.xml
该映射文件包含持久类的所有信息。

< entity-mappings version="1.0" xmlns="http://java.sun.com/xml/ns/persistence/orm" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd "> < entity class="com.srcmini.Account"> < table name="account100"> < /table> < attributes> < id name="accountNumber"> < column name="accountnumber"/> < /id> < basic name="owner"> < column name="owner"/> < /basic> < basic name="balance"> < column name="balance"/> < /basic> < /attributes> < /entity> < /entity-mappings>

3) AccountDao.java

package com.srcmini; import java.util.List; import org.springframework.orm.jpa.JpaTemplate; import org.springframework.transaction.annotation.Transactional; @Transactional public class AccountsDao{ JpaTemplate template; public void setTemplate(JpaTemplate template) { this.template = template; } public void createAccount(int accountNumber, String owner, double balance){ Account account = new Account(accountNumber, owner, balance); template.persist(account); } public void updateBalance(int accountNumber, double newBalance){ Account account = template.find(Account.class, accountNumber); if(account != null){ account.setBalance(newBalance); } template.merge(account); } public void deleteAccount(int accountNumber){ Account account = template.find(Account.class, accountNumber); if(account != null) template.remove(account); } public List< Account> getAllAccounts(){ List< Account> accounts =template.find("select acc from Account acc"); return accounts; } }

4)persistence.xml

< ?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"> < persistence-unit name="ForAccountsDB"> < mapping-file> com/srcmini/Account.xml< /mapping-file> < class> com.srcmini.Account< /class> < /persistence-unit> < /persistence>

5)applicationContext.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:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd"> < tx:annotation-driven transaction-manager="jpaTxnManagerBean" proxy-target-class="true"/> < bean id="dataSourceBean" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> < property name="driverClassName" value="http://www.srcmini.com/oracle.jdbc.driver.OracleDriver"> < /property> < property name="url" value="http://www.srcmini.com/jdbc:oracle:thin:@localhost:1521:xe"> < /property> < property name="username" value="http://www.srcmini.com/system"> < /property> < property name="password" value="http://www.srcmini.com/oracle"> < /property> < /bean> < bean id="hbAdapterBean" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> < property name="showSql" value="http://www.srcmini.com/true"> < /property> < property name="generateDdl" value="http://www.srcmini.com/true"> < /property> < property name="databasePlatform" value="http://www.srcmini.com/org.hibernate.dialect.OracleDialect"> < /property> < /bean> < bean id="emfBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> < property name="dataSource" ref="dataSourceBean"> < /property> < property name="jpaVendorAdapter" ref="hbAdapterBean"> < /property> < /bean> < bean id="jpaTemplateBean" class="org.springframework.orm.jpa.JpaTemplate"> < property name="entityManagerFactory" ref="emfBean"> < /property> < /bean> < bean id="accountsDaoBean" class="com.srcmini.AccountsDao"> < property name="template" ref="jpaTemplateBean"> < /property> < /bean> < bean id="jpaTxnManagerBean" class="org.springframework.orm.jpa.JpaTransactionManager"> < property name="entityManagerFactory" ref="emfBean"> < /property> < /bean> < /beans>

generateDdl属性将自动创建表。
showSql属性将在控制台上显示sql查询。
6) Accountsclient.java

package com.srcmini; import java.util.List; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import org.springframework.context.support.FileSystemXmlApplicationContext; public class AccountsClient{ public static void main(String[] args){ ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); AccountsDao accountsDao = context.getBean("accountsDaoBean", AccountsDao.class); accountsDao.createAccount(15, "Jai Kumar", 41000); accountsDao.createAccount(20, "Rishi ", 35000); System.out.println("Accounts created"); //accountsDao.updateBalance(20, 50000); //System.out.println("Account balance updated"); /*List< Account> accounts = accountsDao.getAllAccounts(); for (int i = 0; i < accounts.size(); i++) { Account acc = accounts.get(i); System.out.println(acc.getAccountNumber() + " : " + acc.getOwner() + " (" + acc.getBalance() + ")"); }*///accountsDao.deleteAccount(111); //System.out.println("Account deleted"); } }

输出

Hibernate: insert into account100 (balance, owner, accountnumber) values (?, ?, ?) Hibernate: insert into account100 (balance, owner, accountnumber) values (?, ?, ?) Accounts created

【Spring Data JPA教程入门介绍】下载此示例(使用Myeclipse IDE开发)