Spring Data JPA 教程

2025年3月17日 | 阅读 3 分钟

Spring Data JPA API 提供了 JpaTemplate 类来将 spring 应用程序与 JPA 集成。

JPA（Java 持久化 API）是 sun 规范，用于在企业应用程序中持久化对象。它目前被用作复杂实体 bean 的替代品。

JPA 规范的实现由许多供应商提供，例如

Hibernate
Toplink
iBatis
OpenJPA 等。

Spring JpaTemplate 的优势

您不需要编写用于持久化、更新、删除或搜索对象的代码，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 实例和关闭 EntityManager。

所以，它节省了大量的代码。

在本例中，我们将使用 hibernate 来实现 JPA。

Spring 和 JPA 集成的示例

让我们看看将 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

在本例中，我们将把 hibernate 应用程序与 spring 集成。让我们看看 spring 中 jpa 示例的目录结构。

spring jpa example with directory structure

1) Account.java

它是一个简单的 POJO 类。

package com.javatpoint;

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

2) Account.xml

此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.javatpoint.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.javatpoint;
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/javatpoint/Account.xml</mapping-file>
		<class>com.javatpoint.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="oracle.jdbc.driver.OracleDriver"></property>
		<property name="url" value="jdbc:oracle:thin:@localhost:1521:xe"></property>
		<property name="username" value="system"></property>
		<property name="password" value="oracle"></property>
	</bean>
	 	 
 	  <bean id="hbAdapterBean" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
	 	<property name="showSql" value="true"></property>
	 	<property name="generateDdl" value="true"></property>
	 	<property name="databasePlatform" value="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.javatpoint.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.javatpoint;

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

下载此示例（使用 Myeclipse IDE 开发）

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