将Spring MVC RESTful Web服务迁移到Spring 4

1引言

Spring 4为MVC应用程序带来了一些改进。在这篇文章中，我将重点介绍宁静的Web服务，并通过采用Spring 3.2实现的项目并将其升级到Spring 4来尝试这些改进。以下几点总结了本文的内容：

从Spring 3.2迁移到Spring 4.0
变化中的@ResponseBody和包容的@RestController
同步和异步调用

以下项目的源代码可以在github上找到：

原始项目（Spring3.2）
迁移到Spring 4

2 Spring 3.2 RESTful示例

起始项目使用Spring 3.2（ pom.xml ）实现。它包含一个Spring MVC应用程序，该应用程序访问数据库以检索有关电视连续剧的数据。让我们看一下其REST API，以使其更加清晰：

Blog-rest-api

弹簧配置

<import resource="db-context.xml"/><!-- Detects annotations like @Component, @Service, @Controller, @Repository, @Configuration -->
<context:component-scan base-package="xpadro.spring.web.controller,xpadro.spring.web.service"/><!-- Detects MVC annotations like @RequestMapping -->
<mvc:annotation-driven/>

db-context.xml

<!-- Registers a mongo instance -->
<bean id="mongo" class="org.springframework.data.mongodb.core.MongoFactoryBean"><property name="host" value="localhost" />
</bean><bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate"><constructor-arg name="mongo" ref="mongo" /><constructor-arg name="databaseName" value="rest-db" />
</bean>

服务实施

此类负责从mongoDB数据库中检索数据：

@Service
public class SeriesServiceImpl implements SeriesService {@Autowiredprivate MongoOperations mongoOps;@Overridepublic Series[] getAllSeries() {List<Series> seriesList = mongoOps.findAll(Series.class);return seriesList.toArray(new Series[0]);}@Overridepublic Series getSeries(long id) {return mongoOps.findById(id, Series.class);}@Overridepublic void insertSeries(Series series) {mongoOps.insert(series);}@Overridepublic void deleteSeries(long id) {Query query = new Query();Criteria criteria = new Criteria("_id").is(id);query.addCriteria(criteria);mongoOps.remove(query, Series.class);}
}

控制器实施

该控制器将处理请求并与服务进行交互，以检索系列数据：

@Controller
@RequestMapping(value="/series")
public class SeriesController {private SeriesService seriesService;@Autowiredpublic SeriesController(SeriesService seriesService) {this.seriesService = seriesService;}@RequestMapping(method=RequestMethod.GET)@ResponseBodypublic Series[] getAllSeries() {return seriesService.getAllSeries();}@RequestMapping(value="/{seriesId}", method=RequestMethod.GET)public ResponseEntity<Series> getSeries(@PathVariable("seriesId") long id) {Series series = seriesService.getSeries(id);if (series == null) {return new ResponseEntity<Series>(HttpStatus.NOT_FOUND);}return new ResponseEntity<Series>(series, HttpStatus.OK);}@RequestMapping(method=RequestMethod.POST)@ResponseStatus(HttpStatus.CREATED)public void insertSeries(@RequestBody Series series, HttpServletRequest request, HttpServletResponse response) {seriesService.insertSeries(series);response.setHeader("Location", request.getRequestURL().append("/").append(series.getId()).toString());}@RequestMapping(value="/{seriesId}", method=RequestMethod.DELETE)@ResponseStatus(HttpStatus.NO_CONTENT)public void deleteSeries(@PathVariable("seriesId") long id) {seriesService.deleteSeries(id);}
}

整合测试

这些集成测试将在模拟Spring MVC环境中测试我们的控制器。这样，我们将能够测试处理程序方法的映射。为此， MockMvc类变得非常有用。如果您想学习如何编写Spring MVC控制器的测试，我强烈推荐Petri Kainulainen编写的Spring MVC Test Tutorial系列。

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
@ContextConfiguration(locations={"classpath:xpadro/spring/web/test/configuration/test-root-context.xml","classpath:xpadro/spring/web/configuration/app-context.xml"})
public class SeriesIntegrationTest {private static final String BASE_URI = "/series";private MockMvc mockMvc;@Autowiredprivate WebApplicationContext webApplicationContext;@Autowiredprivate SeriesService seriesService;@Beforepublic void setUp() {reset(seriesService);mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();when(seriesService.getAllSeries()).thenReturn(new Series[]{new Series(1, "The walking dead", "USA", "Thriller"), new Series(2, "Homeland", "USA", "Drama")});when(seriesService.getSeries(1L)).thenReturn(new Series(1, "Fringe", "USA", "Thriller"));}@Testpublic void getAllSeries() throws Exception {mockMvc.perform(get(BASE_URI).accept(MediaType.APPLICATION_JSON)).andExpect(status().isOk()).andExpect(content().contentType("application/json;charset=UTF-8")).andExpect(jsonPath("$", hasSize(2))).andExpect(jsonPath("$[0].id", is(1))).andExpect(jsonPath("$[0].name", is("The walking dead"))).andExpect(jsonPath("$[0].country", is("USA"))).andExpect(jsonPath("$[0].genre", is("Thriller"))).andExpect(jsonPath("$[1].id", is(2))).andExpect(jsonPath("$[1].name", is("Homeland"))).andExpect(jsonPath("$[1].country", is("USA"))).andExpect(jsonPath("$[1].genre", is("Drama")));verify(seriesService, times(1)).getAllSeries();verifyZeroInteractions(seriesService);}@Testpublic void getJsonSeries() throws Exception {mockMvc.perform(get(BASE_URI + "/{seriesId}", 1L).accept(MediaType.APPLICATION_JSON)).andExpect(status().isOk()).andExpect(content().contentType("application/json;charset=UTF-8")).andExpect(jsonPath("$.id", is(1))).andExpect(jsonPath("$.name", is("Fringe"))).andExpect(jsonPath("$.country", is("USA"))).andExpect(jsonPath("$.genre", is("Thriller")));verify(seriesService, times(1)).getSeries(1L);verifyZeroInteractions(seriesService);}@Testpublic void getXmlSeries() throws Exception {mockMvc.perform(get(BASE_URI + "/{seriesId}", 1L).accept(MediaType.APPLICATION_XML)).andExpect(status().isOk()).andExpect(content().contentType(MediaType.APPLICATION_XML)).andExpect(xpath("/series/id").string("1")).andExpect(xpath("/series/name").string("Fringe")).andExpect(xpath("/series/country").string("USA")).andExpect(xpath("/series/genre").string("Thriller"));verify(seriesService, times(1)).getSeries(1L);verifyZeroInteractions(seriesService);}
}

我正在展示一些已实施的测试。检查SeriesIntegrationTesting以获得完整的实现。

功能测试

该应用程序使用RestTemplate类包含一些功能测试。您需要部署Web应用程序才能对此进行测试。

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:xpadro/spring/web/configuration/root-context.xml","classpath:xpadro/spring/web/configuration/app-context.xml"})
public class SeriesFunctionalTesting {private static final String BASE_URI = "http://localhost:8080/spring-rest-api-v32/spring/series";private RestTemplate restTemplate = new RestTemplate();@Autowiredprivate MongoOperations mongoOps;@Beforepublic void setup() {List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();converters.add(new StringHttpMessageConverter());converters.add(new Jaxb2RootElementHttpMessageConverter());converters.add(new MappingJacksonHttpMessageConverter());restTemplate.setMessageConverters(converters);initializeDatabase();}private void initializeDatabase() {try {mongoOps.dropCollection("series");mongoOps.insert(new Series(1, "The walking dead", "USA", "Thriller"));mongoOps.insert(new Series(2, "Homeland", "USA", "Drama"));} catch (DataAccessResourceFailureException e) {fail("MongoDB instance is not running");}}@Testpublic void getAllSeries() {Series[] series = restTemplate.getForObject(BASE_URI, Series[].class);assertNotNull(series);assertEquals(2, series.length);assertEquals(1L, series[0].getId());assertEquals("The walking dead", series[0].getName());assertEquals("USA", series[0].getCountry());assertEquals("Thriller", series[0].getGenre());assertEquals(2L, series[1].getId());assertEquals("Homeland", series[1].getName());assertEquals("USA", series[1].getCountry());assertEquals("Drama", series[1].getGenre());}@Testpublic void getJsonSeries() {List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();converters.add(new MappingJacksonHttpMessageConverter());restTemplate.setMessageConverters(converters);String uri = BASE_URI + "/{seriesId}";ResponseEntity<Series> seriesEntity = restTemplate.getForEntity(uri, Series.class, 1l);assertNotNull(seriesEntity.getBody());assertEquals(1l, seriesEntity.getBody().getId());assertEquals("The walking dead", seriesEntity.getBody().getName());assertEquals("USA", seriesEntity.getBody().getCountry());assertEquals("Thriller", seriesEntity.getBody().getGenre());assertEquals(MediaType.parseMediaType("application/json;charset=UTF-8"), seriesEntity.getHeaders().getContentType());}@Testpublic void getXmlSeries() {String uri = BASE_URI + "/{seriesId}";ResponseEntity<Series> seriesEntity = restTemplate.getForEntity(uri, Series.class, 1L);assertNotNull(seriesEntity.getBody());assertEquals(1l, seriesEntity.getBody().getId());assertEquals("The walking dead", seriesEntity.getBody().getName());assertEquals("USA", seriesEntity.getBody().getCountry());assertEquals("Thriller", seriesEntity.getBody().getGenre());assertEquals(MediaType.APPLICATION_XML, seriesEntity.getHeaders().getContentType());}
}

就是这样，Web应用程序已经过测试并正在运行。现在是时候迁移到Spring 4了。

3迁移到Spring 4

检查此页面以阅读有关从早期版本的Spring框架进行迁移的信息

3.1更改Maven依赖项

本节说明应修改哪些依赖项。您可以在此处查看完整的pom.xml。

第一步是将Spring依赖版本从3.2.3.RELEASE更改为4.0.0.RELEASE：

<dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>4.0.0.RELEASE</version>
</dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>4.0.0.RELEASE</version>
</dependency>

下一步是更新到Servlet 3.0规范。这一步很重要，因为某些Spring功能基于Servlet 3.0，因此将不可用。事实上，试图执行SeriesIntegrationTesting将导致一个ClassNotFoundException由于这个原因，这也解释了这里。

<dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version>
</dependency>

3.2更新Spring名称空间

不要忘记更改spring配置文件的名称空间：

http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd

请查看第2节中链接的信息页面，因为有关mvc名称空间的某些更改。

3.3弃用杰克逊库

如果再次检查SeriesFunctionalTesting（设置方法），您会发现杰克逊转换器已被弃用。如果您尝试运行测试，由于Jackson库中的方法更改，它将抛出NoSuchMethodError：

java.lang.NoSuchMethodError: org.codehaus.jackson.map.ObjectMapper.getTypeFactory()Lorg/codehaus/jackson/map/type/TypeFactory

在Spring4中，已不再支持Jackson 1.x，而支持Jackson v2。让我们更改旧的依赖项：

<dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-mapper-asl</artifactId><version>1.4.2</version>
</dependency>

对于这些：

<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.3.0</version>
</dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.3.0</version>
</dependency>

最后，如果要显式注册消息转换器，则需要为新版本更改不推荐使用的类：

//converters.add(new MappingJacksonHttpMessageConverter());
converters.add(new MappingJackson2HttpMessageConverter());

3.4迁移完成

迁移完成。现在，您可以运行该应用程序并执行其测试。下一节将回顾我在本文开头提到的一些改进。

4 Spring 4 Web改进

4.1 @ResponseBody和@RestController

如果您的REST API以JSON或XML格式提供内容，则某些API方法（用@RequestMapping注释）的返回类型将用@ResponseBody注释。使用此注释，返回类型将包含在响应主体中。在Spring4中，我们可以通过两种方式简化此过程：

用@ResponseBody注释控制器

现在可以在类型级别添加此注释。这样，注释就被继承了，我们不必强迫将注释放在每个方法中。

@Controller
@ResponseBody
public class SeriesController {

用@RestController注释控制器

@RestController
public class SeriesController {

此注释甚至进一步简化了控制器。如果我们检查此注释，我们将看到它本身已使用@Controller和@ResponseBody进行了注释：

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController {

包括此注释将不会影响使用@ResponseEntity注释的方法。处理程序适配器查找返回值处理程序的列表，以确定谁有能力处理响应。的
在ResponseBody类型之前会先询问负责处理ResponseEntity返回类型的处理程序，因此，如果方法中存在ResponseEntity批注，则将使用该处理程序。

4.2异步调用

使用实用程序类RestTemplate调用RESTful服务将阻塞线程，直到它收到响应为止。 Spring 4包含AsyncRestTemplate以便执行异步调用。现在，您可以拨打电话，继续进行其他计算，并在以后检索响应。

@Test
public void getAllSeriesAsync() throws InterruptedException, ExecutionException {logger.info("Calling async /series");Future<ResponseEntity<Series[]>> futureEntity = asyncRestTemplate.getForEntity(BASE_URI, Series[].class);logger.info("Doing other async stuff...");logger.info("Blocking to receive response...");ResponseEntity<Series[]> entity = futureEntity.get();logger.info("Response received");Series[] series = entity.getBody();assertNotNull(series);assertEquals(2, series.length);assertEquals(1L, series[0].getId());assertEquals("The walking dead", series[0].getName());assertEquals("USA", series[0].getCountry());assertEquals("Thriller", series[0].getGenre());assertEquals(2L, series[1].getId());assertEquals("Homeland", series[1].getName());assertEquals("USA", series[1].getCountry());assertEquals("Drama", series[1].getGenre());
}

带回调的异步调用

尽管前面的示例进行了异步调用，但如果尚未发送响应，则尝试使用futureEntity.get（）检索响应时，线程将阻塞。

AsyncRestTemplate返回ListenableFuture ，它扩展了Future并允许我们注册一个回调。以下示例进行异步调用，并继续执行其自己的任务。当服务返回响应时，它将由回调处理：

@Test
public void getAllSeriesAsyncCallable() throws InterruptedException, ExecutionException {logger.info("Calling async callable /series");ListenableFuture<ResponseEntity<Series[]>> futureEntity = asyncRestTemplate.getForEntity(BASE_URI, Series[].class);futureEntity.addCallback(new ListenableFutureCallback<ResponseEntity<Series[]>>() {@Overridepublic void onSuccess(ResponseEntity<Series[]> entity) {logger.info("Response received (async callable)");Series[] series = entity.getBody();validateList(series);}@Overridepublic void onFailure(Throwable t) {fail();}});logger.info("Doing other async callable stuff ...");Thread.sleep(6000); //waits for the service to send the response
}