Spring MVC handle same request parameter in common place for different URIs - spring-mvc

Question

I've spent a few days researching this, but haven't found a suitable answer for my situation. I have a Spring 3.1 MVC application. Currently, some vendors log into the application via a web client in which case the user information is stored in the session. I want to expose some services to other vendors via RESTFul web services, but have the vendor pass their vendor id as a part of the URI or via PARAMS. Is there a way to handle the vendor id in a single place that then forwards to the respective controller for request processing? Should the vendor id be a part of the URI or should the vendor id be passed in the request body? I've looked into Interceptors, but how would I do this with multiple URIs or for every controller for the RESTFul webservice? Any suggestion would be greatly appreciated

Answer 1

Having a custom header is the most clean option but parameters also work equally well.
In the interceptors preHandle method you could lookup the vendor by either a header or a parameter and attach it to the request by adding the object to it's attributes.
request.addAttribute("vendor", myVendorInstance);
From that point on the vendor can be retrieved from the request like:
Vendor vendor = (Vendor) request.getAttribute("vendor");
Interceptors can be mapped to any URL you like using a mapping e.g.
<mvc:interceptor>
<mvc:mapping path="/vendors/**" />
<bean class="my.package.VendorLookupInterceptor" />
</mvc:interceptor>
Another way of making the vendor object available to controllers is to inject it. For instance, say that controllers interested in the object should implement this interface.
public interface VendorAware {
public void setVendor(Vendor vendor);
}
Controllers implementing this interface could be handled by the interceptor and get the vendor injected.
if (handler instanceof HandlerMethod) {
Object bean = ((HandlerMethod) handler).getBean();
if (bean instanceof VendorAware) {
Vendor vendor = getVendor();
((VendorAware) bean).setVendor(vendor);
}
}

Answer 2

Obviously the problem with adding the vendor id to the URI is that it affects all your URL's, so cannot easily make the controller generic.
Another way is to have the vendor id passed as a header to the controllers. You could use the X-User header.
Then you can write some kind of handler to check for this header, possibilities:
spring interceptor
servlet filter
spring security
aspectj