Spring ORM示例 – JPA，Hibernate，事务

2 年 ago
清, 宇
7 minutes

欢迎来到Spring ORM示例教程。今天我们将学习使用Hibernate JPA事务管理的Spring ORM示例。我将为您展示一个具备以下特性的非常简单的Spring独立应用示例。

  • Dependency Injection (@Autowired annotation)
  • JPA EntityManager (provided by Hibernate)
  • Annotated transactional methods (@Transactional annotation)

春季ORM示例

我在Spring ORM示例中使用了内存数据库，因此不需要任何数据库设置（但是您可以在spring.xml数据源部分将其更改为其他任何数据库）。这是一个独立的Spring ORM应用程序，以尽量减少所有依赖关系（但是如果您熟悉Spring，可以通过配置轻松将其更改为Web项目）。注意：对于基于Spring AOP的事务处理（无需使用@Transactional注释的方法解析方法），请查看此教程：Spring ORM AOP事务管理。下图显示了我们最终的Spring ORM示例项目。让我们逐个了解每个Spring ORM示例项目组件。

Spring ORM依赖的Maven依赖项

下面是我们最终的pom.xml文件，包含了Spring ORM的依赖。在我们的Spring ORM示例中，我们使用了Spring 4和Hibernate 4。

<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>hu.daniel.hari.learn.spring</groupId>
	<artifactId>Tutorial-SpringORMwithTX</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<properties>
		<!-- Generic properties -->
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<java.version>1.7</java.version>

		<!-- SPRING & HIBERNATE / JPA -->
		<spring.version>4.0.0.RELEASE</spring.version>
		<hibernate.version>4.1.9.Final</hibernate.version>

	</properties>

	<dependencies>
		<!-- LOG -->
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>

		<!-- Spring -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-orm</artifactId>
			<version>${spring.version}</version>
		</dependency>

		<!-- JPA Vendor -->
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-entitymanager</artifactId>
			<version>${hibernate.version}</version>
		</dependency>

		<!-- IN MEMORY Database and JDBC Driver -->
		<dependency>
			<groupId>hsqldb</groupId>
			<artifactId>hsqldb</artifactId>
			<version>1.8.0.7</version>
		</dependency>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<source>${java.version}</source>
					<target>${java.version}</target>
				</configuration>
			</plugin>
		</plugins>
	</build>

</project>
  • We need spring-context and spring-orm as Spring dependencies.
  • We use hibernate-entitymanager for Hibernate as JPA implementation. hibernate-entitymanager is dependent on hibernate-core this why we don’t have to put hibernate-core in pom.xml explicitly. It’s being pulled into our project through maven transitive dependencies.
  • We also need JDBC driver as dependency for database access. We are using HSQLDB that contains the JDBC driver and a working in memory database.

Spring框架的ORM模型类

我们可以在我们的模型Bean中使用标准的JPA注解来映射，因为Hibernate提供了JPA的实现。

package hu.daniel.hari.learn.spring.orm.model;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Product {

	@Id
	private Integer id;
	private String name;

	public Product() {
	}

	public Product(Integer id, String name) {
		this.id = id;
		this.name = name;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "Product [id=" + id + ", name=" + name + "]";
	}

}

我们使用 @Entity 和 @Id JPA 注解来将我们的POJO标识为实体，并定义它的主键。

Spring ORM DAO 类

春季ORM DAO 类

我们创建了一个非常简单的DAO类，它提供了persist和findAll方法。

package hu.daniel.hari.learn.spring.orm.dao;

import hu.daniel.hari.learn.spring.orm.model.Product;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Component;

@Component
public class ProductDao {

	@PersistenceContext
	private EntityManager em;

	public void persist(Product product) {
		em.persist(product);
	}

	public List<Product> findAll() {
		return em.createQuery("SELECT p FROM Product p").getResultList();
	}

}
  • @Component is Spring annotation that tell the Spring container that we can use this class through Spring IoC (Dependency Injection).
  • We use JPA @PersistenceContext annotation that indicate dependency injection to an EntityManager. Spring injects a proper instance of EntityManager according to the spring.xml configuration.

Spring ORM服务类

我们简单的服务类有2个写方法和1个读方法-添加（add），全部添加（addAll）和列出全部（listAll）。

package hu.daniel.hari.learn.spring.orm.service;

import hu.daniel.hari.learn.spring.orm.dao.ProductDao;
import hu.daniel.hari.learn.spring.orm.model.Product;

import java.util.Collection;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.transaction.annotation.Transactional;

@Component
public class ProductService {

	@Autowired
	private ProductDao productDao;

	@Transactional
	public void add(Product product) {
		productDao.persist(product);
	}
	
	@Transactional
	public void addAll(Collection<Product> products) {
		for (Product product : products) {
			productDao.persist(product);
		}
	}

	@Transactional(readOnly = true)
	public List<Product> listAll() {
		return productDao.findAll();

	}

}
  • We use Spring @Autowired annotation to inject ProductDao in our service class.
  • We want to use transaction management, so methods are annotated with @Transactional Spring annotation. The listAll method only reads the database so we set the @Transactional annotation to read-only for optimisation.

Spring ORM的示例Bean配置XML

我们的Spring ORM示例项目的Java类已经准备好了，现在让我们来看看我们的Spring bean配置文件。spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="https://www.springframework.org/schema/beans" 
	xmlns:p="https://www.springframework.org/schema/p"
	xmlns:context="https://www.springframework.org/schema/context" 
	xmlns:tx="https://www.springframework.org/schema/tx" 
	xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
		https://www.springframework.org/schema/beans
		https://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		https://www.springframework.org/schema/context
		https://www.springframework.org/schema/context/spring-context-3.0.xsd
		https://www.springframework.org/schema/tx
		https://www.springframework.org/schema/tx/spring-tx.xsd
		">
	
	<!-- Scans the classpath for annotated components that will be auto-registered as Spring beans -->
	<context:component-scan base-package="hu.daniel.hari.learn.spring" />
	<!-- Activates various annotations to be detected in bean classes e.g: @Autowired -->
	<context:annotation-config />

	<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		<property name="driverClassName" value="org.hsqldb.jdbcDriver" />
		<property name="url" value="jdbc:hsqldb:mem://productDb" />
		<property name="username" value="sa" />
		<property name="password" value="" />
	</bean>
	
	<bean id="entityManagerFactory" 
			class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
			p:packagesToScan="hu.daniel.hari.learn.spring.orm.model"
            p:dataSource-ref="dataSource"
			>
		<property name="jpaVendorAdapter">
			<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
				<property name="generateDdl" value="true" />
				<property name="showSql" value="true" />
			</bean>
		</property>
	</bean>

	<!-- Transactions -->
	<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>
	<!-- enable the configuration of transactional behavior based on annotations -->
	<tx:annotation-driven transaction-manager="transactionManager" />

</beans>
    1. 首先，我们告诉Spring我们想要使用类路径扫描Spring组件（Services，DAOs），而不是在Spring XML中逐个定义它们。我们还启用了Spring注解检测。

 

    1. 添加数据源，目前是HSQLDB内存数据库。

 

    1. 我们建立了一个JPA EntityManagerFactory，应用程序将使用它来获取一个EntityManager。Spring支持3种不同的方式来实现这一点，我们使用了LocalContainerEntityManagerFactoryBean以获得完整的JPA功能。我们设置了LocalContainerEntityManagerFactoryBean的属性，包括：

packagesToScan属性指向我们的模型类包。
在Spring配置文件中先前定义的数据源。
将jpaVendorAdapter设置为Hibernate，并设置一些Hibernate属性。

我们创建了一个Spring PlatformTransactionManager实例，作为一个JpaTransactionManager。这个事务管理器适用于使用单个JPA EntityManagerFactory进行事务数据访问的应用程序。
我们启用基于注解的事务行为配置，并设置了我们创建的transactionManager。

春季ORM Hibernate JPA示例测试程序

我们的Spring ORM JPA Hibernate示例项目已经准备就绪，现在让我们为我们的应用程序编写一个测试程序。

public class SpringOrmMain {
	
	public static void main(String[] args) {
		
		//Create Spring application context
		ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:/spring.xml");
		
		//Get service from context. (service's dependency (ProductDAO) is autowired in ProductService)
		ProductService productService = ctx.getBean(ProductService.class);
		
		//Do some data operation
		
		productService.add(new Product(1, "Bulb"));
		productService.add(new Product(2, "Dijone mustard"));
		
		System.out.println("listAll: " + productService.listAll());
		
		//Test transaction rollback (duplicated key)
		
		try {
			productService.addAll(Arrays.asList(new Product(3, "Book"), new Product(4, "Soap"), new Product(1, "Computer")));
		} catch (DataAccessException dataAccessException) {
		}
		
		//Test element list after rollback
		System.out.println("listAll: " + productService.listAll());
		
		ctx.close();
		
	}
}

你可以看到我们如何从主方法中轻松启动Spring容器。在Spring上下文初始化后，我们将获取我们的第一个依赖注入的入口点，即服务类实例。在初始化完成后，将ProductDao类引用注入到ProductService类中。在获得ProductService实例后，我们可以测试它的方法，所有方法调用都将由于Spring的代理机制而具有事务性。我们还在这个示例中测试了回滚。如果你运行上述Spring ORM示例测试程序，你将会得到下面的日志记录。

Hibernate: insert into Product (name, id) values (?, ?)
Hibernate: insert into Product (name, id) values (?, ?)
Hibernate: select product0_.id as id0_, product0_.name as name0_ from Product product0_
listAll: [Product [id=1, name=Bulb], Product [id=2, name=Dijone mustard]]
Hibernate: insert into Product (name, id) values (?, ?)
Hibernate: insert into Product (name, id) values (?, ?)
Hibernate: insert into Product (name, id) values (?, ?)
Hibernate: select product0_.id as id0_, product0_.name as name0_ from Product product0_
listAll: [Product [id=1, name=Bulb], Product [id=2, name=Dijone mustard]]

请注意第二次交易被回滚了，这就是为什么产品列表没有变化。如果您使用附带的源代码中的log4j.properties文件，您可以看到底层发生了什么。参考资料：https://docs.spring.io/spring/docs/current/spring-framework-reference/html/orm.html 您可以从下面的链接下载最终的Spring ORM JPA Hibernate示例项目，并通过它进行实践，以便更多地学习。

下载带有事务的Spring ORM项目

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