Spring MVC：带有CNVR卷的REST应用程序。 1个

不久前，我阅读了Paul Chapman撰写的有关内容协商视图解析器（CNVR）的文章。 Spring Framework Blog上的那篇文章启发了我研究这个框架的领域。因此，我开发了一个基于Spring MVC和CNVR的 REST示例应用程序。该应用程序演示了REST服务的基本流程-实体的创建，删除，读取和版本。

Spring Framework很长时间以来都支持REST服务，您可以更早地使用Message Converters开发一些服务。在Spring 3.2中，所有这些东西在配置和开发中变得更加容易。因此，让我们停止交谈，因为我将展示带有CNVR的Spring REST服务的基本设置和开发。

CNVR的基本思想是，根据CNVR从客户端请求中获取的信息，定义资源的哪种表示形式回馈给客户端。您可以问我：请求中可影响CNVR决策的信息是什么？答案很简单：

网址后缀（例如.xml，.json，.html等
URL参数（默认格式）
HTTP Accept标头属性

这是高级CNVR工作流程的图示：

Spring-MVC-CNVR模式

有关更多信息，我建议阅读Paul Chapman的完整文章。

使用CNVR设置Spring MVC REST项目

我将与一个Maven项目一起工作，一如既往，我将提供一个指向项目的GitHub存储库的链接。这是整个项目的屏幕截图：

CNVR项目

我已经多次解释了如何在Eclipse中设置Dynamic Web Project，因此现在我仅提供带有一些简短说明的源文件。您可以在下面找到所需的Maven依赖项：

<properties><mysql.connector>5.1.25</mysql.connector><hibernate.version>4.2.3.Final</hibernate.version><spring.version>3.2.3.RELEASE</spring.version><spring.data.version>1.3.2.RELEASE</spring.data.version><jackson.version>1.9.12</jackson.version></properties><dependencies><!-- DataBase libs --><dependency><groupid>mysql</groupid><artifactid>mysql-connector-java</artifactid><version>${mysql.connector}</version></dependency><dependency><groupid>commons-dbcp</groupid><artifactid>commons-dbcp</artifactid><version>1.4</version></dependency><!-- Hibernate --><dependency><groupid>org.hibernate</groupid><artifactid>hibernate-core</artifactid><version>${hibernate.version}</version></dependency><dependency><groupid>org.hibernate</groupid><artifactid>hibernate-entitymanager</artifactid><version>${hibernate.version}</version></dependency><!-- Spring --><dependency><groupid>org.springframework</groupid><artifactid>spring-webmvc</artifactid><version>${spring.version}</version></dependency><dependency><groupid>org.springframework.data</groupid><artifactid>spring-data-jpa</artifactid><version>${spring.data.version}</version><exclusions><exclusion><artifactid>spring-aop</artifactid><groupid>org.springframework</groupid></exclusion></exclusions></dependency><dependency><groupid>org.springframework</groupid><artifactid>spring-orm</artifactid><version>${spring.version}</version></dependency><dependency><groupid>org.springframework</groupid><artifactid>spring-tx</artifactid><version>${spring.version}</version></dependency><!-- CGLIB is required to process @Configuration classes --><dependency><groupid>cglib</groupid><artifactid>cglib</artifactid><version>3.0</version></dependency><!-- Other --><dependency><groupid>javax.servlet</groupid><artifactid>javax.servlet-api</artifactid><version>3.0.1</version><scope>provided</scope></dependency><dependency><groupid>jstl</groupid><artifactid>jstl</artifactid><version>1.2</version></dependency><!-- CNVR resources --><dependency><groupid>org.codehaus.jackson</groupid><artifactid>jackson-mapper-asl</artifactid><version>${jackson.version}</version></dependency></dependencies>

您可以在GitHub上找到pom.xml文件的完整版本。因此，让我们继续进行准备。我将使用MySQL作为数据库。我需要在其中创建一个下表：

CREATE TABLE `smartphones` (`id` int(6) NOT NULL AUTO_INCREMENT,`producer` varchar(20) NOT NULL,`model` varchar(20) NOT NULL,`price` double NOT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8;

现在我们需要适当的java对象，它将代表智能手机表：

@Entity
@Table(name="smartphones")
public class Smartphone {@Id@GeneratedValueprivate Integer id;private String producer;private String model;private double price;/*** Method updates already existed {@link Smartphone} object with values from the inputed argument.* @param sPhone - Object which contains new Smartphone values.* @return {@link Smartphone} object to which this method applied.*/public Smartphone update(Smartphone sPhone) {this.producer = sPhone.producer;this.model = sPhone.model;this.price = sPhone.price;return this;}@Overridepublic String toString() {return producer+": "+model+" with price "+price;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getProducer() {return producer;}public void setProducer(String producer) {this.producer = producer;}public String getModel() {return model;}public void setModel(String model) {this.model = model;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}}

准备工作大部分完成。服务和DAO层是我需要做的最后一件事。我将使用Spring Data作为DAO层，在我以前的一篇文章中，我对它的设置进行了详细的回顾。

public interface SmartphoneRepository extends JpaRepository< Smartphone, Integer >{ }

这里是对应的服务接口及其实现：

public interface SmartphoneService {public Smartphone create(Smartphone sp);public Smartphone get(Integer id);public List< Smartphone > getAll();public Smartphone update(Smartphone sp) throws SmartphoneNotFoundException;public Smartphone delete(Integer id) throws SmartphoneNotFoundException;}

服务实施：

@Service
@Transactional(rollbackFor=SmartphoneNotFoundException.class)
public class SmartphoneServiceImpl implements SmartphoneService {@Autowiredprivate SmartphoneRepository smartphoneRepository;@Overridepublic Smartphone create(Smartphone sp) {return smartphoneRepository.save(sp);}@Overridepublic Smartphone get(Integer id) {return smartphoneRepository.findOne(id);}@Overridepublic List< Smartphone > getAll() {return smartphoneRepository.findAll();}@Overridepublic Smartphone update(Smartphone sp) throws SmartphoneNotFoundException {Smartphone sPhoneToUpdate = get(sp.getId());if (sPhoneToUpdate == null)throw new SmartphoneNotFoundException(sp.getId().toString());sPhoneToUpdate.update(sp);return sPhoneToUpdate;}@Overridepublic Smartphone delete(Integer id) throws SmartphoneNotFoundException {Smartphone sPhone = get(id);if (sPhone == null)throw new SmartphoneNotFoundException(id.toString());smartphoneRepository.delete(id);return sPhone;}
}

在项目设置的最后，让我们考虑配置的“核心”： Initializer和WebAppConfig文件。

@Configuration
@EnableWebMvc
@EnableTransactionManagement
@ComponentScan("com.mobapp")
@PropertySource("classpath:application.properties")
@EnableJpaRepositories("com.mobapp.repository")
public class WebAppConfig extends WebMvcConfigurerAdapter {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;}@Overridepublic void configureContentNegotiation(ContentNegotiationConfigurer configurer) {configurer.favorPathExtension(true).useJaf(false).ignoreAcceptHeader(true).mediaType("html", MediaType.TEXT_HTML).mediaType("json", MediaType.APPLICATION_JSON).defaultContentType(MediaType.TEXT_HTML);}@Beanpublic ViewResolver contentNegotiatingViewResolver(ContentNegotiationManager manager) {List< ViewResolver > resolvers = new ArrayList< ViewResolver >();InternalResourceViewResolver r1 = new InternalResourceViewResolver();r1.setPrefix("/WEB-INF/pages/");r1.setSuffix(".jsp");r1.setViewClass(JstlView.class);resolvers.add(r1);JsonViewResolver r2 = new JsonViewResolver();resolvers.add(r2);ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();resolver.setViewResolvers(resolvers);resolver.setContentNegotiationManager(manager);return resolver;}/*** View resolver for returning JSON in a view-based system. Always returns a* {@link MappingJacksonJsonView}.*/public class JsonViewResolver implements ViewResolver {public View resolveViewName(String viewName, Locale locale)throws Exception {MappingJacksonJsonView view = new MappingJacksonJsonView();view.setPrettyPrint(true);return view;}}}

尽管文件足够大，但我只想将您的注意力集中在几件事上。第一个是JsonViewResolver内部类。处理JSON请求是必需的。当然，可以将其与WebAppConfig类分开声明，也可以将其导入其中。但是我决定将其直接放在WebAppConfig中，以避免分散注意力。第二个是configureContentNegotiation方法。在这里，我为内容协商视图解析器设置了选项。最后，在contentNegotiatingViewResolver bean中，我确定了哪些视图解析器将在我的应用程序中可用。

public class Initializer implements WebApplicationInitializer {private static final String DISPATCHER_SERVLET_NAME = "dispatcher";@Overridepublic void onStartup(ServletContext servletContext) throws ServletException {AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();ctx.register(WebAppConfig.class);ctx.setServletContext(servletContext);		registerHiddenHttpMethodFilter(servletContext);	Dynamic servlet = servletContext.addServlet(DISPATCHER_SERVLET_NAME, new DispatcherServlet(ctx));servlet.addMapping("/");servlet.setLoadOnStartup(1);}private void registerHiddenHttpMethodFilter(ServletContext servletContext) {FilterRegistration.Dynamic fr = servletContext.addFilter("hiddenHttpMethodFilter", HiddenHttpMethodFilter.class);fr.addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD), false, DISPATCHER_SERVLET_NAME);}}

在Initializer类中，本教程仅涉及一件事。它是registerHiddenHttpMethodFilter方法。此方法将有助于处理诸如PUT和DELETE之类的HTTP方法。

希望您不要感到疲倦，因为最有趣的内容将在本教程的以下部分等您。

参考： Spring MVC：具有CNVR卷的REST应用程序。 Fruzenshtein的笔记博客中来自JCG合作伙伴 Alexey Zvolinskiy的1 。