使用入站适配器公开HTTP Restful API。第1部分（XML）

1.简介

这篇文章的目的是使用Spring Integration HTTP入站适配器实现HTTP Restful API。本教程分为两个部分：

XML配置示例（同一篇文章）。
Java DSL示例。这将在本教程的下一部分中进行说明，展示如何使用Spring Integration Java DSL配置应用程序，并提供Java 7和Java 8的示例。

在查看代码之前，让我们看一下下图，该图显示了应用程序公开的不同服务：

GET操作由HTTP入站网关处理，而其余操作（PUT，POST和DELETE）由HTTP入站通道适配器处理，因为没有响应主体发送回客户端。以下各节将说明每个操作：

介绍
应用配置
进行操作
放置和发布操作
删除操作
结论

源代码可从Github获得。

2.应用程序配置

web.xml文件包含分派器Servlet的定义：

<servlet><servlet-name>springServlet</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:xpadro/spring/integration/configuration/http-inbound-config.xml</param-value></init-param>
</servlet>
<servlet-mapping><servlet-name>springServlet</servlet-name><url-pattern>/spring/*</url-pattern>
</servlet-mapping>

以下各节将说明http-inbound-config.xml文件。

下面是pom.xml文件的详细信息。重要的是要注意杰克逊库。由于我们将使用JSON表示资源，因此这些库必须存在于类路径中。否则，框架将不会注册所需的转换器。

<properties><spring-version>4.1.3.RELEASE</spring-version><spring-integration-version>4.1.0.RELEASE</spring-integration-version><slf4j-version>1.7.5</slf4j-version><junit-version>4.9</junit-version><jackson-version>2.3.0</jackson-version>
</properties><dependencies><!-- Spring Framework - Core --><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>${spring-version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring-version}</version></dependency><!-- Spring Framework - Integration --><dependency><groupId>org.springframework.integration</groupId><artifactId>spring-integration-core</artifactId><version>${spring-integration-version}</version></dependency><dependency><groupId>org.springframework.integration</groupId><artifactId>spring-integration-http</artifactId><version>${spring-integration-version}</version></dependency><!-- JSON --><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>${jackson-version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>${jackson-version}</version></dependency><!-- Testing --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit-version}</version><scope>test</scope></dependency><!-- Logging --><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>${slf4j-version}</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId><version>${slf4j-version}</version></dependency>
</dependencies>

3.进行操作

该流程的配置如下所示：

http-inbound-config.xml

网关接收到以下路径的请求：/ persons / {personId}。请求到达后，将创建一条消息并将其发送到httpGetChannel通道。然后，网关将等待服务激活器（personEndpoint）返回响应：

现在，需要解释一些要点：

支持的方法 ：此属性指示网关支持哪些方法（仅GET请求）。
payload-expression ：我们在这里所做的是从URI模板中的personId变量获取值并将其放入消息的有效负载中。例如，请求路径“ / persons / 3”将成为一条值为“ 3”的消息作为有效负载。
request-mapping ：我们可以包含此元素以指定多个属性，并过滤哪些请求将被映射到网关。在示例中，此网关仅处理包含Content-Type头（consumes属性）和Accept头（produces属性）的值“ application / json”的请求。

将请求映射到此网关后，便会生成一条消息并将其发送到服务激活器。在示例中，我们定义了一个简单的Bean，它将从服务中获取所需的信息：

@Component
public class PersonEndpoint {private static final String STATUSCODE_HEADER = "http_statusCode";@Autowiredprivate PersonService service;public Message<?> get(Message<String> msg) {long id = Long.valueOf(msg.getPayload());ServerPerson person = service.getPerson(id);if (person == null) {return MessageBuilder.fromMessage(msg).copyHeadersIfAbsent(msg.getHeaders()).setHeader(STATUSCODE_HEADER, HttpStatus.NOT_FOUND).build(); }return MessageBuilder.withPayload(person).copyHeadersIfAbsent(msg.getHeaders()).setHeader(STATUSCODE_HEADER, HttpStatus.OK).build();}//Other operations
}

根据从服务收到的响应，我们将返回被请求的人员或指示未找到人员的状态代码。

现在，我们将测试一切是否按预期进行。首先，我们定义将响应转换为的ClientPerson类：

@JsonIgnoreProperties(ignoreUnknown = true)
public class ClientPerson implements Serializable {private static final long serialVersionUID = 1L;@JsonProperty("id")private int myId;private String name;public ClientPerson() {}public ClientPerson(int id, String name) {this.myId = id;this.name = name;}//Getters and setters
}

然后我们执行测试。在buildHeaders方法中，我们指定了Accept和Content-Type标头。请记住，我们在这些标头中使用'application / json'值限制了请求。

@RunWith(BlockJUnit4ClassRunner.class)
public class GetOperationsTest {private static final String URL = "http://localhost:8081/int-http-xml/spring/persons/{personId}";private final RestTemplate restTemplate = new RestTemplate();private HttpHeaders buildHeaders() {HttpHeaders headers = new HttpHeaders();headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));headers.setContentType(MediaType.APPLICATION_JSON); return headers;}@Testpublic void getResource_responseIsConvertedToPerson() {HttpEntity<Integer> entity = new HttpEntity<>(buildHeaders());ResponseEntity<ClientPerson> response = restTemplate.exchange(URL, HttpMethod.GET, entity, ClientPerson.class, 1);assertEquals("John" , response.getBody().getName());assertEquals(HttpStatus.OK, response.getStatusCode());}@Testpublic void getResource_responseIsReceivedAsJson() {HttpEntity<Integer> entity = new HttpEntity<>(buildHeaders());ResponseEntity<String> response = restTemplate.exchange(URL, HttpMethod.GET, entity, String.class, 1);assertEquals("{\"id\":1,\"name\":\"John\",\"age\":25}", response.getBody());assertEquals(HttpStatus.OK, response.getStatusCode());}@Test(expected=HttpClientErrorException.class)public void getResource_sendXml_415errorReturned() {HttpHeaders headers = new HttpHeaders();headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));headers.setContentType(MediaType.APPLICATION_XML);HttpEntity<Integer> entity = new HttpEntity<>(headers);restTemplate.exchange(URL, HttpMethod.GET, entity, ClientPerson.class, 1);}@Test(expected=HttpClientErrorException.class)public void getResource_expectXml_receiveJson_406errorReturned() {HttpHeaders headers = new HttpHeaders();headers.setAccept(Arrays.asList(MediaType.APPLICATION_XML));headers.setContentType(MediaType.APPLICATION_JSON);HttpEntity<Integer> entity = new HttpEntity<>(headers);restTemplate.exchange(URL, HttpMethod.GET, entity, ClientPerson.class, 1);}@Test(expected=HttpClientErrorException.class)public void getResource_resourceNotFound_404errorReturned() {HttpEntity<Integer> entity = new HttpEntity<>(buildHeaders());restTemplate.exchange(URL, HttpMethod.GET, entity, ClientPerson.class, 8);}
}

在Content-Type标头中未指定正确的值将导致415不支持的媒体类型错误，因为网关不支持此媒体类型。

另一方面，在Accept标头中指定不正确的值将导致406 Not Acceptable错误，因为网关返回的内容类型不同于预期。

4.放置和发布操作

对于PUT和POST操作，我们使用相同的HTTP入站通道适配器，从而可以为它定义多个路径和方法。一旦请求到达，路由器将负责将消息传递到正确的端点。

http-inbound-config.xml

<int-http:inbound-channel-adapter channel="routeRequest" status-code-expression="T(org.springframework.http.HttpStatus).NO_CONTENT"supported-methods="POST, PUT" path="/persons, /persons/{personId}"request-payload-type="xpadro.spring.integration.server.model.ServerPerson"><int-http:request-mapping consumes="application/json"/>
</int-http:inbound-channel-adapter><int:router input-channel="routeRequest" expression="headers.http_requestMethod"><int:mapping value="PUT" channel="httpPutChannel"/><int:mapping value="POST" channel="httpPostChannel"/>
</int:router><int:service-activator ref="personEndpoint" method="put" input-channel="httpPutChannel"/>
<int:service-activator ref="personEndpoint" method="post" input-channel="httpPostChannel"/>

此通道适配器包括两个新属性：

status-code-expression ：默认情况下，通道适配器确认已收到请求，并返回200状态码。如果要覆盖此行为，可以在此属性中指定其他状态代码。在这里，我们指定这些操作将返回204 No Content状态代码。
request-payload-type ：此属性指定将请求主体转换为哪个类。如果我们没有定义它，它将无法转换为服务激活器期望的类（ServerPerson）。

收到请求后，适配器会将其发送到路由器期望它的routeRequest通道。该路由器将检查消息头，并根据“ http_requestMethod”头的值将其传递到适当的端点。

PUT和POST操作都由同一个bean处理：

@Component
public class PersonEndpoint {@Autowiredprivate PersonService service;//Get operationpublic void put(Message<ServerPerson> msg) {service.updatePerson(msg.getPayload());}public void post(Message<ServerPerson> msg) {service.insertPerson(msg.getPayload());}
}

返回类型为空，因为没有期望的响应；入站适配器将处理状态码的返回。

PutOperationsTest验证是否返回了正确的状态码以及资源是否已更新：

@RunWith(BlockJUnit4ClassRunner.class)
public class PutOperationsTest {private static final String URL = "http://localhost:8081/int-http-xml/spring/persons/{personId}";private final RestTemplate restTemplate = new RestTemplate();//build headers method@Testpublic void updateResource_noContentStatusCodeReturned() {HttpEntity<Integer> getEntity = new HttpEntity<>(buildHeaders());ResponseEntity<ClientPerson> response = restTemplate.exchange(URL, HttpMethod.GET, getEntity, ClientPerson.class, 4);ClientPerson person = response.getBody();person.setName("Sandra");HttpEntity<ClientPerson> putEntity = new HttpEntity<ClientPerson>(person, buildHeaders());response = restTemplate.exchange(URL, HttpMethod.PUT, putEntity, ClientPerson.class, 4);assertEquals(HttpStatus.NO_CONTENT, response.getStatusCode());response = restTemplate.exchange(URL, HttpMethod.GET, getEntity, ClientPerson.class, 4);person = response.getBody();assertEquals("Sandra", person.getName());}
}

PostOperationsTest验证是否已添加新资源：

@RunWith(BlockJUnit4ClassRunner.class)
public class PostOperationsTest {private static final String POST_URL = "http://localhost:8081/int-http-xml/spring/persons";private static final String GET_URL = "http://localhost:8081/int-http-xml/spring/persons/{personId}";private final RestTemplate restTemplate = new RestTemplate();//build headers method@Testpublic void addResource_noContentStatusCodeReturned() {ClientPerson person = new ClientPerson(9, "Jana");HttpEntity<ClientPerson> entity = new HttpEntity<ClientPerson>(person, buildHeaders());ResponseEntity<ClientPerson> response = restTemplate.exchange(POST_URL, HttpMethod.POST, entity, ClientPerson.class);assertEquals(HttpStatus.NO_CONTENT, response.getStatusCode());HttpEntity<Integer> getEntity = new HttpEntity<>(buildHeaders());response = restTemplate.exchange(GET_URL, HttpMethod.GET, getEntity, ClientPerson.class, 9);person = response.getBody();assertEquals("Jana", person.getName());}
}

5.删除操作

我们的RESTful API的最后一个操作是删除操作。这次我们为此使用一个单通道适配器：

<int-http:inbound-channel-adapter channel="httpDeleteChannel" status-code-expression="T(org.springframework.http.HttpStatus).NO_CONTENT"supported-methods="DELETE" path="/persons/{personId}" payload-expression="#pathVariables.personId"><int-http:request-mapping consumes="application/json"/>
</int-http:inbound-channel-adapter><int:service-activator ref="personEndpoint" method="delete" input-channel="httpDeleteChannel"/>

通道适配器使我们可以定义返回的状态代码，并且正在使用有效负载表达式属性将请求的personId映射到消息正文。该配置与先前操作中的配置略有不同，但是这里没有任何未解释的内容。

服务激活者，我们的人员端点，将请求人员服务删除此资源。

public void delete(Message<String> msg) {long id = Long.valueOf(msg.getPayload());service.deletePerson(id);
}

最后，所需的测试：

@RunWith(BlockJUnit4ClassRunner.class)
public class DeleteOperationsTest {private static final String URL = "http://localhost:8081/int-http-xml/spring/persons/{personId}";private final RestTemplate restTemplate = new RestTemplate();//build headers method@Testpublic void deleteResource_noContentStatusCodeReturned() {HttpEntity<Integer> entity = new HttpEntity<>(buildHeaders());ResponseEntity<ClientPerson> response = restTemplate.exchange(URL, HttpMethod.DELETE, entity, ClientPerson.class, 3);assertEquals(HttpStatus.NO_CONTENT, response.getStatusCode());try {response = restTemplate.exchange(URL, HttpMethod.GET, entity, ClientPerson.class, 3);Assert.fail("404 error expected");} catch (HttpClientErrorException e) {assertEquals(HttpStatus.NOT_FOUND, e.getStatusCode());}}
}