Spring integration outbound-gateway want to use UR

Question

spring Integration,in outbound-gateway want to use URL as dynamic like

    <bean id="requestValues"    class="com.src.model.RequestValues"/>
    <int-http:outbound-gateway
                request-channel="reqChannel" url="${UrlValue}"
                http-method="${reqmethod}" expected-response-type="java.lang.String"  header-mapper="headerMapper"
                charset="UTF-8" reply-timeout="5000" reply-channel="responseChannel"  >
            <int-http:uri-variable name="UrlValue" expression="#{requestValues.getUrl()}" />
           <int-http:uri-variable name="reqmethod" expression="#{requestValues.getReqMethod()}" />
        </int-http:outbound-gateway>

Here Requestvalues is simple POJO it like

@Data
public class Requestvalues {

    public String Url;
    public String reqMethod;

}

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.integration.http.outbound.HttpRequestExecutingMessageHandler#0': Cannot create inner bean '(inner bean)#6ea2bc93' of type [org.springframework.integration.config.ExpressionFactoryBean] while setting bean property 'uriVariableExpressions' with key [url]; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)#6ea2bc93': Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.integration.config.ExpressionFactoryBean]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: expressionString must not be empty or null

Answer 1

The http-method is not part of the URI; it does not support or use uri-variables.

Use http-method-expression="payload.reqMethod" instead.

Similarly, Accept is not part of the uri - set the Accept header in the outbound message, it will be mapped.

EDIT

You are confusing runtime expressions with bean declaration expressions and, as I said, you need to use method expression if you want a runtime method selection.

However, since you are using a bean for your Requestvalues you don't need runtime expressions at all.

<int-http:outbound-gateway
            request-channel="reqChannel" url="#{requestValues.getUrl()}"
            http-method=""#{requestValues.getReqMethod()}" expected-response-type="java.lang.String"  header-mapper="headerMapper"
            charset="UTF-8" reply-timeout="5000" reply-channel="responseChannel"  >
</int-http:outbound-gateway>

If you want to select the method and url at runtime, based on the message, you would use something like...

<int-http:outbound-gateway
            request-channel="reqChannel" url="${UrlValue}"
            http-method-expression="headers['method']" expected-response-type="java.lang.String"  header-mapper="headerMapper"
            charset="UTF-8" reply-timeout="5000" reply-channel="responseChannel"  >
        <int-http:uri-variable name="UrlValue" expression="headers['url']" />
</int-http:outbound-gateway>

Where the headers are set dynamically somewhere upstream, or

<int-http:outbound-gateway
            request-channel="reqChannel" url="${UrlValue}"
            http-method-expression="@requestValues.getReqMethod()" expected-response-type="java.lang.String"  header-mapper="headerMapper"
            charset="UTF-8" reply-timeout="5000" reply-channel="responseChannel"  >
        <int-http:uri-variable name="UrlValue" expression="@requestValues.getUrl()" />
</int-http:outbound-gateway>

Notice the use of @ to refer to beans in runtime expressions.

Answer 2

You can set meta data like URL or http method as headers. You can even use Spring EL when setting the header, f.e.

<int:header-enricher>
    <int:header name="url" value="${url.base}/reports/"/>
</int:header-enricher>

and then use an expression for the outbound gateway

 <int-http:outbound-gateway id='httpGateway'
 url-expression="headers['url']"
...
  />