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 HTTP Inbound Channel Adapter or Gateway. To support the HTTP Inbound Adapters, they need to be deployed within a servlet container such as Apache Tomcat or Jetty. The easiest way to do this is to use Spring's HttpRequestHandlerServlet, by providing the following servlet definition in the web.xml file: inboundGateway o.s.web.context.support.HttpRequestHandlerServlet ]]> Notice that the servlet name matches the bean name. For more information on using the HttpRequestHandlerServlet, see chapter "Remoting and web services using Spring", which is part of the Spring Framework Reference documentation. If you are running within a Spring MVC application, then the aforementioned explicit servlet definition is not necessary. In that case, the bean name for your gateway can be matched against the URL path just like a Spring MVC Controller bean. For more information, please see the chapter "Web MVC framework", which is part of the Spring Framework Reference documentation. For a sample application and the corresponding configuration, please see the Spring Integration Samples repository. It contains the Http Sample application demonstrating Spring Integration's HTTP support. Below is an example bean definition for a simple HTTP inbound endpoint. ]]> The HttpRequestHandlingMessagingGateway accepts a list of HttpMessageConverter instances or else relies on a default list. The converters allow customization of the mapping from HttpServletRequest to Message. The default converters encapsulate simple strategies, 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, when using the default converters, that request will be converted to a Message payload that is a MultiValueMap containing values that may be byte arrays, Strings, or instances of Spring's MultipartFile depending on the content type of the individual parts. The HTTP inbound Endpoint 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 a 'viewName' to be resolved by the Spring MVC ViewResolver. In the case that the gateway should expect a reply to the Message then setting the expectReply flag (constructor argument) will cause the gateway to wait for a reply Message before creating an HTTP response. Below is an example of a gateway configured to serve as a Spring MVC Controller with a view name. Because of the constructor arg value of TRUE, it wait for a reply. This also shows how to customize the HTTP methods accepted by the gateway, which are POST and GET by default. GET DELETE ]]> The reply message will be available in the Model map. The key that is used for that map entry by default is 'reply', but this can be overridden by setting the 'replyKey' 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. In the case of the Outbound Gateway, the reply message produced by the gateway will contain all Message Headers present in the request message. Cookies Basic cookie support is provided by the transfer-cookies attribute on the outbound gateway. When set to true (default is false), a Set-Cookie header received from the server in a response will be converted to Cookie in the reply message. This header will then be used on subsequent sends. This enables simple stateful interactions, such as... ...->logonGateway->...->doWorkGateway->...->logoffGateway->... If transfer-cookies is false, any Set-Cookie header received will remain as Set-Cookie in the reply message, and will be dropped on subsequent sends.

Spring Integration provides an http namespace and the corresponding schema definition. To include it in your configuration, simply provide the following namespace declaration in your application context configuration file: ... ]]> Inbound The XML Namespace provides two components for handling HTTP Inbound requests. In order to process requests without returning a dedicated response, use the inbound-channel-adapter: ]]> To process requests that do expect a response, use an inbound-gateway: ]]> Beginning with Spring Integration 2.1 the HTTP Inbound Gateway and the HTTP Inbound Channel Adapter should use the path attribute instead of the name attribute for specifying the request path. The name attribute for those 2 components has been deprecated. If you simply want to identify component itself within your application context, please use the id attribute. Defining the UriPathHandlerMapping In order to use the HTTP Inbound Gateway or the HTTP Inbound Channel Adapter you must define a UriPathHandlerMapping. This particular implementation of the HandlerMapping matches against the value of the path attribute. ]]> For more information regarding Handler Mappings, please see: URI Template Variables and Expressions By Using the path attribute in conjunction with the payload-expression attribute as well as the header sub-element, you have a high degree of flexiblity for mapping inbound request data. In the following example configuration, an Inbound Channel Adapter is configured to accept requests using the following URI: /first-name/{firstName}/last-name/{lastName} Using the payload-expression attribute, the URI template variable {firstName} is mapped to be the Message payload, while the {lastName} URI template variable will map to the lname Message header. ]]> For more information about URI template variables, please see the Spring Reference Manual: Outbound 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 contain the ResponseEntity as long as it's http status is a success (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. Beginning with Spring Integration 2.1 the request-timeout attribute of the HTTP Outbound Gateway was renamed to reply-timeout to better reflect the intent. ]]> Since Spring Integration 2.2, Java serialization over HTTP is no longer enabled by default. Previously, when setting the expected-response-type attribute to a Serializable object, the Accept header was not properly set up. Since Spring Integration 2.2, the SerializingHttpMessageConverter has now been updated to set the Accept header to application/x-java-serialized-object. However, because this could cause incompatibility with existing applications, it was decided to no longer automatically add this converter to the HTTP endpoints. If you wish to use Java serialization, you will need to add the SerializingHttpMessageConverter to the appropriate endpoints, using the message-converters attribute, when using XML configuration, or using the setMessageConverters() method. Alternatively, you may wish to consider using JSON instead which is enabled by simply having Jackson on the classpath. Beginning with Spring Integration 2.2 you can also determine the HTTP Method dynamically using SpEL and the http-method-expression attribute. Note that this attribute is obviously murually exclusive with http-method You can also use expected-response-type-expression attribute instead of expected-response-type and provide any valid SpEL expression that determines the type of the response. ]]> 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: ]]> To specify the URL; you can use either the 'url' attribute or the 'url-expression' attribute. The 'url' is a simple string (with placedholders for URI variables, as described below); the 'url-expression' is a SpEL expression, with the Message as the root object, enabling dynamic urls. The url resulting from the expression evaluation can still have placeholders for URI variables. In previous releases, some users used the place holders to replace the entire URL with a URI variable. Changes in Spring 3.1 can cause some issues with escaped characters, such as '?'. For this reason, it is recommended that if you wish to generate the URL entirely at runtime, you use the 'url-expression' attribute. Mapping URI variables If your URL contains URI variables, you can map them using the uri-variable sub-element. This sub-element is available for the Http Outbound Gateway and the Http Outbound Channel Adapter. ]]> The uri-variable sub-element defines two attributes: name and expression. The name attribute identifies the name of the URI variable, while the expression attribute is used to set the actual value. Using the expression attribute, you can leverage the full power of the Spring Expression Language (SpEL) which gives you full dynamic access to the message payload and the message headers. For example, in the above configuration the getZip() method will be invoked on the payload object of the Message and the result of that method will be used as the value for the URI variable named 'zipCode'.

In the context of HTTP components, there are two timing areas that have to be considered. Timeouts when interacting with Spring Integration Channels Timeouts when interacting with a remote HTTP server First, the components interact with Message Channels, for which timeouts can be specified. For example, an HTTP Inbound Gateway will forward messages received from connected HTTP Clients to a Message Channel (Request Timeout) and consequently the HTTP Inbound Gateway will receive a reply Message from the Reply Channel (Reply Timeout) that will be used to generate the HTTP Response. Please see the figure below for an illustration. How timeout settings apply to an HTTP Inbound Gateway For outbound endpoints, the second thing to consider is timing while interacting with the remote server. How timeout settings apply to an HTTP Outbound Gateway You may want to configure the HTTP related timeout behavior, when making active HTTP requests using the HTTP Oubound Gateway or the HTTP Outbound Channel Adapter. In those instances, these two components use Spring's RestTemplate support to execute HTTP requests. In order to configure timeouts for the HTTP Oubound Gateway and the HTTP Outbound Channel Adapter, you can either reference a RestTemplate bean directly, using the rest-template attribute, or you can provide a reference to a ClientHttpRequestFactory bean using the request-factory attribute. Spring provides the following implementations of the ClientHttpRequestFactory interface: SimpleClientHttpRequestFactory - Uses standard J2SE facilities for making HTTP Requests HttpComponentsClientHttpRequestFactory - Uses Apache HttpComponents HttpClient (Since Spring 3.1) ClientHttpRequestFactory - Uses Jakarta Commons HttpClient (Deprecated as of Spring 3.1) If you don't explicitly configure the request-factory or rest-template attribute respectively, then a default RestTemplate which uses a SimpleClientHttpRequestFactory will be instantiated. With some JVM implementations, the handling of timeouts using the URLConnection class may not be consistent. E.g. from the Java™ Platform, Standard Edition 6 API Specification on setConnectTimeout: Some non-standard implmentation of this method may ignore the specified timeout. To see the connect timeout set, please call getConnectTimeout(). Please test your timeouts if you have specific needs. Consider using the HttpComponentsClientHttpRequestFactory which, in turn, uses Apache HttpComponents HttpClient instead. Here is an example of how to configure an HTTP Outbound Gateway using a SimpleClientHttpRequestFactory, configured with connect and read timeouts of 5 seconds respectively: ]]> HTTP Outbound Gateway For the HTTP Outbound Gateway, the XML Schema defines only the reply-timeout. The reply-timeout maps to the sendTimeout property of the org.springframework.integration.http.outbound.HttpRequestExecutingMessageHandler class. More precisely, the property is set on the extended AbstractReplyProducingMessageHandler class, which ultimatelly sets the property on the MessagingTemplate. The value of the sendTimeout property defaults to "-1" and will be applied to the connected MessageChannel. This means, that depending on the implementation, the Message Channel's send method may block indefinitely. Furthermore, the sendTimeout property is only used, when the actual MessageChannel implementation has a blocking send (such as 'full' bounded QueueChannel). HTTP Inbound Gateway For the HTTP Inbound Gateway, the XML Schema defines the request-timeout attribute, which will be used to set the requestTimeout property on the HttpRequestHandlingMessagingGateway class (on the extended MessagingGatewaySupport class). Secondly, the reply-timeout attribute exists and it maps to the replyTimeout property on the same class. The default for both timeout properties is "1000ms". Ultimately, the request-timeout property will be used to set the sendTimeout on the used MessagingTemplate instance. The replyTimeout property on the other hand, will be used to set the receiveTimeout property on the used MessagingTemplate instance. In order to simulate connection timeouts, connect to a non-routable IP address, for example 10.255.255.10.

If you are behind a proxy and need to configure proxy settings for HTTP outbound adapters and/or gateways, you can apply one of two approaches. In most cases, you can rely on the standard Java System Properties that control the proxy settings. Otherwise, you can explicitly configure a Spring bean for the HTTP client request factory instance. Standard Java Proxy configuration There are 3 System Properties you can set to configure the proxy settings that will be used by the HTTP protocol handler: http.proxyHost - the host name of the proxy server. http.proxyPort - the port number, the default value being 80. http.nonProxyHosts - a list of hosts that should be reached directly, bypassing the proxy. This is a list of patterns separated by '|'. The patterns may start or end with a '*' for wildcards. Any host matching one of these patterns will be reached through a direct connection instead of through a proxy. And for HTTPS: https.proxyHost - the host name of the proxy server. https.proxyPort - the port number, the default value being 80. For more information please refer to this document: http://download.oracle.com/javase/6/docs/technotes/guides/net/proxies.html Spring's SimpleClientHttpRequestFactory If for any reason, you need more explicit control over the proxy configuration, you can use Spring's SimpleClientHttpRequestFactory and configure its 'proxy' property as such: ]]>

Spring Integration provides support for Http Header mapping for both HTTP Request and HTTP Responses. By default all standard Http Headers as defined here http://en.wikipedia.org/wiki/List_of_HTTP_header_fields will be mapped from the message to HTTP request/response headers without further configuration. However if you do need further customization you may provide additional configuration via convenient namespace support. You can provide a comma-separated list of header names, and you can also include simple patterns with the '*' character acting as a wildcard. If you do provide such values, it will override the default behavior. Basically, it assumes you are in complete control at that point. However, if you do want to include all of the standard HTTP headers, you can use the shortcut patterns: HTTP_REQUEST_HEADERS and HTTP_RESPONSE_HEADERS. Here are some examples: ]]> The adapters and gateways will use the DefaultHttpHeaderMapper which now provides two static factory methods for "inbound" and "outbound" adapters so that the proper direction can be applied (mapping HTTP requests/responses IN/OUT as appropriate). If further customization is required you can also configure a DefaultHttpHeaderMapper independently and inject it into the adapter via the header-mapper attribute. ]]> Of course, you can even implement the HeaderMapper strategy interface directly and provide a reference to that if you need to do something other than what the DefaultHttpHeaderMapper supports.

This example demonstrates how simple it is to send a Multipart HTTP request via Spring's RestTemplate and receive it with a Spring Integration HTTP Inbound Adapter. All we are doing is creating a MultiValueMap and populating it with multi-part data. The RestTemplate will take care of the rest (no pun intended) by converting it to a MultipartHttpServletRequest . This particular client will send a multipart HTTP Request which contains the name of the company as well as an image file with the company logo. httpResponse = template.exchange(uri, HttpMethod.POST, request, null);]]> That is all for the client. On the server side we have the following configuration: ]]> The 'httpInboundAdapter' will receive the request, convert it to a Message with a payload that is a LinkedMultiValueMap. We then are parsing that in the 'multipartReceiver' service-activator; multipartRequest){ System.out.println("### Successfully received multipart request ###"); for (String elementName : multipartRequest.keySet()) { if (elementName.equals("company")){ System.out.println("\t" + elementName + " - " + ((String[]) multipartRequest.getFirst("company"))[0]); } else if (elementName.equals("company-logo")){ System.out.println("\t" + elementName + " - as UploadedMultipartFile: " + ((UploadedMultipartFile) multipartRequest.getFirst("company-logo")). getOriginalFilename()); } } } ]]> You should see the following output: