Spring教程-Spring Data JPA 教程

Spring Data JPA API 提供了 JpaTemplate 类，用于将 Spring 应用程序与 JPA 进行整合。

JPA（Java 持久化 API）是用于在企业应用程序中持久化对象的 Sun 规范。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，如：

Hibernate
Toplink
iBatis
OpenJPA 等。

Spring JpaTemplate 的优势

您无需编写持久化、更新、删除或搜索对象的前后代码，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。

因此，它节省了大量的代码。

在这个例子中，我们将使用 Hibernate 来实现 JPA。

Spring 和 JPA 整合示例

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

在这个例子中，我们将集成 Hibernate 应用程序与 Spring。让我们看一下 JPA 示例与 Spring 的目录结构

1) Account.java

这是一个简单的 POJO 类。

package cn.javatiku;  
  
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="cn.javatiku.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 cn.javatiku;  
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>cn/javatiku/Account.xml</mapping-file>  
        <class>cn.javatiku.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="cn.javatiku.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>

属性 generateDdl 会自动创建表。

属性 showSql 会在控制台上显示 SQL 查询。

6) AccountsClient.java

package cn.javatiku;  
  
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教程-Spring Data JPA 教程

Spring JpaTemplate 的优势

Spring 和 JPA 整合示例

输出

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