如何：从Spring 4.0快速入门以构建简单的REST-Like API（演练）

关于使用Spring MVC创建Web API的另一篇教程。不太复杂。只是一个演练。生成的应用程序将提供简单的API，将Mongo作为其持久性，并将通过Spring Security进行保护。

入门– POM

当然，我仍然是Maven的忠实拥护者，因此该项目基于Maven。既然有可用的Spring 4.0 RC2，我决定使用其新的依赖项管理，从而产生以下pom.xml：转到Spring MVC应用程序非常简单。新的东西是dependencyManagement元素。对此的更多说明可以在这里找到： http : //spring.io/blog/2013/12/03/spring-framework-4-0-rc2-available

组态

使用JavaConfig配置该应用程序。我将其分为几个部分：

服务配置

@Configuration
public class ServicesConfig {@Autowiredprivate AccountRepository accountRepository;@Beanpublic UserService userService() {return new UserService(accountRepository);}@Beanpublic PasswordEncoder passwordEncoder() {return NoOpPasswordEncoder.getInstance();}
}

没有组件扫描。真的很简单。

持久性配置

具有所有可用存储库的MongoDB配置。在这个简单的应用程序中，我们只有一个存储库，因此配置非常简单。

@Configuration
class PersistenceConfig {@Beanpublic AccountRepository accountRepository() throws UnknownHostException {return new MongoAccountRepository(mongoTemplate());}@Beanpublic MongoDbFactory mongoDbFactory() throws UnknownHostException {return new SimpleMongoDbFactory(new Mongo(), "r");}@Beanpublic MongoTemplate mongoTemplate() throws UnknownHostException {MongoTemplate template = new MongoTemplate(mongoDbFactory(), mongoConverter());return template;}@Beanpublic MongoTypeMapper mongoTypeMapper() {return new DefaultMongoTypeMapper(null);}@Beanpublic MongoMappingContext mongoMappingContext() {return new MongoMappingContext();}@Beanpublic MappingMongoConverter mongoConverter() throws UnknownHostException {MappingMongoConverter converter = new MappingMongoConverter(mongoDbFactory(), mongoMappingContext());converter.setTypeMapper(mongoTypeMapper());return converter;}
}

安全配置

从理论上讲，Spring Security 3.2可以使用JavaConfig进行完全配置。对我来说，这仍然是一种理论，因此我在这里使用XML：

@Configuration
@ImportResource("classpath:spring-security-context.xml")
public class SecurityConfig {}

XML：如您所见，API将使用基本身份验证。

WebAppInitializer

我们不需要web.xml，因此我们使用以下代码来配置Web应用程序：

@Order(2)
public class WebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {@Overrideprotected String[] getServletMappings() {return new String[]{"/"};}@Overrideprotected Class[] getRootConfigClasses() {return new Class[] {ServicesConfig.class, PersistenceConfig.class, SecurityConfig.class};}@Overrideprotected Class[] getServletConfigClasses() {return new Class[] {WebMvcConfig.class};}@Overrideprotected Filter[] getServletFilters() {CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();characterEncodingFilter.setEncoding("UTF-8");characterEncodingFilter.setForceEncoding(true);return new Filter[] {characterEncodingFilter};}@Overrideprotected void customizeRegistration(ServletRegistration.Dynamic registration) {        registration.setInitParameter("spring.profiles.active", "default");}
}

WebAppSecurityInitializer

Spring Security的新功能3。

@Order(1)
public class WebAppSecurityInitializer extends AbstractSecurityWebApplicationInitializer {}

WebMvcConfig

调度程序Servlet配置。真的很基础。只有关键组件才能构建简单的API。

@Configuration
@ComponentScan(basePackages = { "pl.codeleak.r" }, includeFilters = {@Filter(value = Controller.class)})
public class WebMvcConfig extends WebMvcConfigurationSupport {private static final String MESSAGE_SOURCE = "/WEB-INF/i18n/messages";@Overridepublic RequestMappingHandlerMapping requestMappingHandlerMapping() {RequestMappingHandlerMapping requestMappingHandlerMapping = super.requestMappingHandlerMapping();requestMappingHandlerMapping.setUseSuffixPatternMatch(false);requestMappingHandlerMapping.setUseTrailingSlashMatch(false);return requestMappingHandlerMapping;}@Bean(name = "messageSource")public MessageSource messageSource() {ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();messageSource.setBasename(MESSAGE_SOURCE);messageSource.setCacheSeconds(5);return messageSource;}@Overridepublic Validator getValidator() {LocalValidatorFactoryBean validator = new LocalValidatorFactoryBean();validator.setValidationMessageSource(messageSource());return validator;}@Overridepublic void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {configurer.enable();}
}

这就是配置。简单。

索引控制器

为了验证配置是否正确，我创建了一个IndexController，它提供简单的“ Hello，World”之类的文本：

@Controller
@RequestMapping("/")
public class IndexController {@RequestMapping@ResponseBodypublic String index() {return "This is an API endpoint.";}
}

运行应用程序时，您应该在浏览器中看到此文本。

构建API

用户服务

要完成Spring Security配置，实际上实际上仍然需要一部分：UserService哪个实例是先前创建的：

public class UserService implements UserDetailsService {private AccountRepository accountRepository;public UserService(AccountRepository accountRepository) {this.accountRepository = accountRepository;}@Overridepublic UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {Account account = accountRepository.findByEmail(username);if(account == null) {throw new UsernameNotFoundException("user not found");}return createUser(account);}public void signin(Account account) {SecurityContextHolder.getContext().setAuthentication(authenticate(account));}private Authentication authenticate(Account account) {return new UsernamePasswordAuthenticationToken(createUser(account), null, Collections.singleton(createAuthority(account)));  }private User createUser(Account account) {return new User(account.getEmail(), account.getPassword(), Collections.singleton(createAuthority(account)));}private GrantedAuthority createAuthority(Account account) {return new SimpleGrantedAuthority(account.getRole());}}

要求是建立一个处理3种方法的API端点：获取当前登录的用户，获取所有用户（不是很安全），创建新帐户。因此，让我们开始吧。

帐户

该帐户将是我们的第一个Mongo文档。这真的很容易：

@SuppressWarnings("serial")
@Document
public class Account implements java.io.Serializable {@Idprivate String objectId;@Email@Indexed(unique = true)private String email;@JsonIgnore@NotBlankprivate String password;private String role = "ROLE_USER";private Account() {}public Account(String email, String password, String role) {this.email = email;this.password = password;this.role = role;}// getters and setters
}

资料库

我从界面开始：

public interface AccountRepository {Account save(Account account);List findAll();Account findByEmail(String email);
}

以及后来的Mongo实现：

public class MongoAccountRepository implements AccountRepository {private MongoTemplate mongoTemplate;public MongoAccountRepository(MongoTemplate mongoTemplate) {this.mongoTemplate = mongoTemplate;}@Overridepublic Account save(Account account) {mongoTemplate.save(account);return account;}@Overridepublic List findAll() {return mongoTemplate.findAll(Account.class);}@Overridepublic Account findByEmail(String email) {return mongoTemplate.findOne(Query.query(Criteria.where("email").is(email)), Account.class);}
}

API控制器

所以我们快到了。我们需要将内容提供给用户。因此，让我们创建端点：

@Controller
@RequestMapping("api/account")
class AccountController {private AccountRepository accountRepository;@Autowiredpublic AccountController(AccountRepository accountRepository) {this.accountRepository = accountRepository;}@RequestMapping(value = "current", method = RequestMethod.GET)@ResponseStatus(value = HttpStatus.OK)@ResponseBody@PreAuthorize(value = "isAuthenticated()")public Account current(Principal principal) {Assert.notNull(principal);return accountRepository.findByEmail(principal.getName());}@RequestMapping(method = RequestMethod.GET)@ResponseStatus(value = HttpStatus.OK)@ResponseBody@PreAuthorize(value = "isAuthenticated()")public Accounts list() {List accounts = accountRepository.findAll();return new Accounts(accounts);}@RequestMapping(method = RequestMethod.POST)@ResponseStatus(value = HttpStatus.CREATED)@ResponseBody@PreAuthorize(value = "permitAll()")public Account create(@Valid Account account) {accountRepository.save(account);return account;}private class Accounts extends ArrayList {public Accounts(List accounts) {super(accounts);}}
}

希望您注意到我们直接与存储库进行通讯，因此不会对密码进行编码。如果需要，可以稍后修复一些小细节。现在可以了。

整理起来

我最后需要的是一些错误处理程序，以便使用者可以用JSON而不是HTML看到错误消息。使用Spring MVC和@Controller建议，这很简单。

@ControllerAdvice
public class ErrorHandler {@ExceptionHandler(value = Exception.class)@ResponseStatus(HttpStatus.BAD_REQUEST)@ResponseBodypublic ErrorResponse errorResponse(Exception exception) {return new ErrorResponse(exception.getMessage());}}public class ErrorResponse {private String message;public ErrorResponse(String message) {this.message = message;}public String getMessage() {return message;}
}

如果您想在Spring 4中看到@ControllerAdvice的更多高级用法，请阅读
这个帖子。