在Spring MVC的帮助下开发Web应用程序意味着要创建几个逻辑架构层。 层之一是DAO（存储库）层。 它负责与数据库进行通信。 如果您至少开发了DAO层一次，则应该知道它涉及许多样板代码。 Spring Data本身就是与DAO相关的日常工作的一部分。

在帖子中，我将提供一个应用程序示例，它将结合Spring MVC，MySQL和Maven演示Spring Data（JPA） 。 Hibernate将用作JPA的实现。 您可能知道，我是基于Java的配置的忠实拥护者，因此我将使用这种方法来配置Spring Data。 在本教程的最后，您可以找到GitHub上示例项目的链接。

制备

在本文中，我将重点介绍Spring数据，因此我将忽略所有超出主题的内容。 但首先，我想提供大量链接，这些链接可以在本教程的上下文中为您提供帮助。

• 使用Maven在Eclipse中创建动态Web项目 。
• 具有基于Java配置的简单Spring MVC应用程序 。
• Spring MVC + Hibernate示例应用程序。

这些链接应为阅读文章期间可能发生的90％的问题提供答案。 让我们从在MySQL中创建表开始：

CREATE TABLE `shops` (`id` int(6) NOT NULL AUTO_INCREMENT,`name` varchar(60) NOT NULL,`employees_number` int(6) NOT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

现在我们可以继续执行Java代码：

@Entity
@Table(name = "shops")
public class Shop {@Id@GeneratedValueprivate Integer id;private String name;@Column(name = "employees_number")private Integer emplNumber;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;}public Integer getEmplNumber() {return emplNumber;}public void setEmplNumber(Integer emplNumber) {this.emplNumber = emplNumber;}
}

Spring数据的配置

我相信该项目的屏幕截图将帮助您了解正在发生的事情。

在属性文件中集中所有配置数据：

#DB properties:
db.driver=com.mysql.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/hibnatedb
db.username=hibuser
db.password=root#Hibernate Configuration:
hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
hibernate.show_sql=true
entitymanager.packages.to.scan=com.spr.model

WebAppConfig类包含所有基于Java的配置：

@Configuration
@EnableWebMvc
@EnableTransactionManagement
@ComponentScan("com.spr")
@PropertySource("classpath:application.properties")
@EnableJpaRepositories("com.spr.repository")
public class WebAppConfig {private static final String PROPERTY_NAME_DATABASE_DRIVER = "db.driver";private static final String PROPERTY_NAME_DATABASE_PASSWORD = "db.password";private static final String PROPERTY_NAME_DATABASE_URL = "db.url";private static final String PROPERTY_NAME_DATABASE_USERNAME = "db.username";private static final String PROPERTY_NAME_HIBERNATE_DIALECT = "hibernate.dialect";private static final String PROPERTY_NAME_HIBERNATE_SHOW_SQL = "hibernate.show_sql";private static final String PROPERTY_NAME_ENTITYMANAGER_PACKAGES_TO_SCAN = "entitymanager.packages.to.scan";@Resourceprivate Environment env;@Beanpublic DataSource dataSource() {DriverManagerDataSource dataSource = new DriverManagerDataSource();dataSource.setDriverClassName(env.getRequiredProperty(PROPERTY_NAME_DATABASE_DRIVER));dataSource.setUrl(env.getRequiredProperty(PROPERTY_NAME_DATABASE_URL));dataSource.setUsername(env.getRequiredProperty(PROPERTY_NAME_DATABASE_USERNAME));dataSource.setPassword(env.getRequiredProperty(PROPERTY_NAME_DATABASE_PASSWORD));return dataSource;}@Beanpublic LocalContainerEntityManagerFactoryBean entityManagerFactory() {LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();entityManagerFactoryBean.setDataSource(dataSource());entityManagerFactoryBean.setPersistenceProviderClass(HibernatePersistence.class);entityManagerFactoryBean.setPackagesToScan(env.
getRequiredProperty(PROPERTY_NAME_ENTITYMANAGER_PACKAGES_TO_SCAN));entityManagerFactoryBean.setJpaProperties(hibProperties());return entityManagerFactoryBean;}private Properties hibProperties() {Properties properties = new Properties();properties.put(PROPERTY_NAME_HIBERNATE_DIALECT,    env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_DIALECT));properties.put(PROPERTY_NAME_HIBERNATE_SHOW_SQL, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_SHOW_SQL));return properties;}@Beanpublic JpaTransactionManager transactionManager() {JpaTransactionManager transactionManager = new JpaTransactionManager();transactionManager.setEntityManagerFactory(entityManagerFactory().getObject());return transactionManager;}@Beanpublic UrlBasedViewResolver setupViewResolver() {UrlBasedViewResolver resolver = new UrlBasedViewResolver();resolver.setPrefix("/WEB-INF/pages/");resolver.setSuffix(".jsp");resolver.setViewClass(JstlView.class);return resolver;}}

请注意@EnableJpaRepositories批注。 它允许使用JPA存储库。 com.spr.repository软件包将被扫描以检测存储库。 在entityManagerFactory bean中，我确定了将Hibernate用作JPA实现。

初始化器类将被省略。

DAO和服务层

Shop实体的存储库：

package com.spr.repository;import org.springframework.data.jpa.repository.JpaRepository;import com.spr.model.Shop;public interface ShopRepository extends JpaRepository<shop, integer=""> {}

无疑，它是本教程中最简单的代码段。 但这需要最高的关注。 JpaRepository接口包含可以用任何实体执行的基本操作（CRUD操作）。 您可以在官方文档页面上找到更多信息。

这是ShopService接口的代码：

public interface ShopService {public Shop create(Shop shop);public Shop delete(int id) throws ShopNotFound;public List findAll();public Shop update(Shop shop) throws ShopNotFound;public Shop findById(int id);}

并实现服务接口：

import java.util.List;import javax.annotation.Resource;import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;import com.spr.exception.ShopNotFound;
import com.spr.model.Shop;
import com.spr.repository.ShopRepository;@Service
public class ShopServiceImpl implements ShopService {@Resourceprivate ShopRepository shopRepository;@Override@Transactionalpublic Shop create(Shop shop) {Shop createdShop = shop;return shopRepository.save(createdShop);}@Override@Transactionalpublic Shop findById(int id) {return shopRepository.findOne(id);}@Override@Transactional(rollbackFor=ShopNotFound.class)public Shop delete(int id) throws ShopNotFound {Shop deletedShop = shopRepository.findOne(id);if (deletedShop == null)throw new ShopNotFound();shopRepository.delete(deletedShop);return deletedShop;}@Override@Transactionalpublic List findAll() {return shopRepository.findAll();}@Override@Transactional(rollbackFor=ShopNotFound.class)public Shop update(Shop shop) throws ShopNotFound {Shop updatedShop = shopRepository.findOne(shop.getId());if (updatedShop == null)throw new ShopNotFound();updatedShop.setName(shop.getName());updatedShop.setEmplNumber(shop.getEmplNumber());return updatedShop;}}

这样，就可以使用ShopRepository。

控制者

最后，我可以在控制器中使用ShopSrviceImpl类。 所有JSP页面将被省略，因此您可以在GitHub上找到它们的源代码。

@Controller
@RequestMapping(value="/shop")
public class ShopController {@Autowiredprivate ShopService shopService;@RequestMapping(value="/create", method=RequestMethod.GET)public ModelAndView newShopPage() {ModelAndView mav = new ModelAndView("shop-new", "shop", new Shop());return mav;}@RequestMapping(value="/create", method=RequestMethod.POST)public ModelAndView createNewShop(@ModelAttribute Shop shop, final RedirectAttributes redirectAttributes) {ModelAndView mav = new ModelAndView();String message = "New shop "+shop.getName()+" was successfully created.";shopService.create(shop);mav.setViewName("redirect:/index.html");redirectAttributes.addFlashAttribute("message", message);    return mav;     }@RequestMapping(value="/list", method=RequestMethod.GET)public ModelAndView shopListPage() {ModelAndView mav = new ModelAndView("shop-list");List shopList = shopService.findAll();mav.addObject("shopList", shopList);return mav;}@RequestMapping(value="/edit/{id}", method=RequestMethod.GET)public ModelAndView editShopPage(@PathVariable Integer id) {ModelAndView mav = new ModelAndView("shop-edit");Shop shop = shopService.findById(id);mav.addObject("shop", shop);return mav;}@RequestMapping(value="/edit/{id}", method=RequestMethod.POST)public ModelAndView editShop(@ModelAttribute Shop shop,@PathVariable Integer id,final RedirectAttributes redirectAttributes) throws ShopNotFound {ModelAndView mav = new ModelAndView("redirect:/index.html");String message = "Shop was successfully updated.";shopService.update(shop);redirectAttributes.addFlashAttribute("message", message);   return mav;}@RequestMapping(value="/delete/{id}", method=RequestMethod.GET)public ModelAndView deleteShop(@PathVariable Integer id,final RedirectAttributes redirectAttributes) throws ShopNotFound {ModelAndView mav = new ModelAndView("redirect:/index.html");      Shop shop = shopService.delete(id);String message = "The shop "+shop.getName()+" was successfully deleted.";redirectAttributes.addFlashAttribute("message", message);return mav;}}

摘要

Spring Data是非常强大的武器，它可以帮助您更快地开发应用程序并避免数百个样板代码字符串。 使用Spring Data是在应用程序中创建DAO层的最便捷方法，因此请不要在项目中忽略它。

翻译自: https://www.javacodegeeks.com/2013/05/spring-jpa-data-hibernate-mysql-maven.html