The HTTP support allows for the execution of HTTP requests and the processing of inbound HTTP requests. Because interaction over HTTP is always synchronous, even if all that is returned is a 200 status code, the HTTP support consists of two gateway implementations: HttpInboundEndpoint and HttpRequestExecutingMessageHandler.

To receive messages over HTTP you need to use an HttpInboundEndpoint. In common with the HttpInvoker support the Http Inbound Gateway needs to be deployed within a servlet container. The easiest way to do this is to provide a servlet definition in web.xml, see for further details. Below is an example bean definition for a simple HttpInboundEndpoint ]]> The HttpInboundEndpoint accepts an instance of InboundRequestMapper which allows customisation of the mapping from HttpServletRequest to Message. If none is provided an instance of DefaultInboundRequestMapper will be used. This encapsulates a simple strategy, which for example will create a String message for a POST request where the content type starts with "text", see the Javadoc for full details. Starting with this release MultiPart File support was implemented. If the request has been wrapped as a MultipartHttpServletRequest, then the 'content type' can be checked. If it is known, and begins with "text", then the MultipartFile will be copied to a String in the parameter map. If the content type does not begin with "text", then the MultipartFile will be copied to a byte array within the parameter map instead. The HttpInboundEndpoint will locate a MultipartResolver in the context if one exists with the bean name "multipartResolver" (the same name expected by Spring's DispatcherServlet). If it does in fact locate that bean, then the support for MultipartFiles will be enabled on the inbound request mapper. Otherwise, it will fail when trying to map a multipart-file request to a Spring Integration Message. For more on Spring's support for MultipartResolvers, refer to the Spring Reference Manual. In sending a response to the client there are a number of ways to customize the behavior of the gateway. By default the gateway will simply acknowledge that the request was received by sending a 200 status code back. It is possible to customize this response by providing an implementation of the Spring MVC View which will be invoked with the created Message. In the case that the gateway should expect a reply to the Message then setting the expectReply flag will cause the gateway to wait for a response Message before creating an Http response. Below is an example of a gateway configured to use a custom view and to wait for a response. It also shows how to customize the Http methods accepted by the gateway, which are POST and GET by default. GET DELETE ]]> The message created from the request will be available in the Model map. The key that is used for that map entry by default is 'requestMessage', but this can be overridden by setting the 'requestKey' property on the endpoint's configuration.

To configure the HttpRequestExecutingMessageHandler write a bean definition like this: ]]> This bean definition will execute HTTP requests by delegating to a RestTemplate. That template in turn delegates to a list of HttpMessageConverters to generate the HTTP request body from the Message payload. You can configure those converters as well as the ClientHttpRequestFactory instance to use: ]]> By default the HTTP request will be generated using an instance of SimpleClientHttpRequestFactory which uses the JDK HttpURLConnection. Use of the Apache Commons HTTP Client is also supported through the provided CommonsClientHttpRequestFactory which can be injected as shown above.

Spring Integration provides an "http" namespace and schema definition. To include it in your configuration, simply provide the following URI within a namespace declaration: 'http://www.springframework.org/schema/integration/http'. The schema location should then map to 'http://www.springframework.org/schema/integration/http/spring-integration-http.xsd'. To configure an inbound http channel adapter which is an instance of HttpInboundEndpoint configured not to expect a response. ]]> To configure an inbound http gateway which expects a response. ]]> To configure the outbound gateway you can use the namespace support as well. The following code snippet shows the different configuration options for an outbound Http gateway. Most importantly, notice that the 'http-method' and 'expected-response-type' are provided. Those are two of the most commonly configured values. The default http-method is POST, and the default response type is null. With a null response type, the payload of the reply Message would only contain the status code (e.g. 200) as long as it's a successful status (non-successful status codes will throw Exceptions). If you are expecting a different type, such as a String, then provide that fully-qualified class name as shown below. ]]> If your outbound adapter is to be used in a unidirectional way, then you can use an outbound-channel-adapter instead. This means that a successful response will simply execute without sending any Messages to a reply channel. In the case of any non-successful response status code, it will throw an exception. The configuration looks very similar to the gateway: ]]>