在Spring Integration中将HTTP请求标头设置为LinkedList

Question

We are trying to set the request parameters from an HTTP inbound request to the header. We have managed to successfully set the request value to the header, however it is not set in the way we want.

The request header mapping value is set to the message header as a java.util.LinkedList instead of String which is the expected request parameter type.

The following is the configuration

<int-http:inbound-gateway id="inboundApplicationDataRequestGateway"
        supported-methods="GET"
        request-channel="applicationDataRequest"
        reply-channel="applicationDataResponse"
        mapped-response-headers="HTTP_REQUEST_HEADERS"
        path="/services/application/that/data"
        reply-timeout="50000">

            <int-http:header name="dataVersion" expression="#requestParams['data_version']"/>
        </int-http:inbound-gateway>

<int:service-activator id="applicationDataServiceActivator"
                    input-channel="applicationDataRequest"
                    output-channel="applicationDataResponse"
                    ref="dataService"
                    method="getData"
                    requires-reply="false"
                    send-timeout="60000"/>  

The following is the sample service method

public void getData(Message<?> inMessage){
        MessageHeaders headers = inMessage.getHeaders();
        logger.info("DATA VERSION : " + (String)headers.get("dataVersion"));
    }

The following is the stacktrace

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.messaging.MessageHandlingException: java.lang.ClassCastException: java.util.LinkedList cannot be cast to java.lang.String
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:973)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:690)

How can we have dataVersion set as a string instead of a linked list?

Also we would need to do the following for POST requests in other http inbound gateway methods as well

Any help is appreciated.

Regards, MilindaD

Answer 1

That's because servletRequest.getParameterMap() returns Map<String, String[]> and Spring Integration converts it to the MultiValueMap<String, String> . And when you ask it to get some value it really returns LinkedList<String> .

So, to get only single value from that List (and here you are really sure that there is only one item) you should use this:

<int-http:header name="dataVersion" expression="#requestParams.getFirst('data_version')"/>