Sending multipart HTTP requests using Spring's RestTemplate

Most of the time, we have implemented file upload functionality in our application. Files are sent over HTTP as a multipart request.

In this section, let us see how we can configure the inbound channel adapter using RestTemplate to send a file over HTTP request.

Let us configure the server with the inbound channel adapter and then write a client for it:

<int-http:inbound-channel-adapter id="httpInboundAdapter"
  channel="receiveChannel"
  name="/inboundAdapter.htm"
  supported-methods="GET, POST"/>
<int:channel id="receiveChannel"/>
<int:service-activator input-channel="receiveChannel">
  <bean class="org.springframework.integration.samples.multipart.MultipartReceiver"/>
</int:service-activator>
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>

The httpInboundAdapter will receive the request and convert it to a message with a payload LinkedMultiValueMap...