How to make Zuul dynamic routing based on HTTP method and resolve target host by 'serviceId'? - spring

Question

How to make Zuul dynamic routing based on HTTP method (GET/POST/PUT...)?
For example, when you need to route the POST request to the different host instead of the default one described in 'zuul.routes.*'...
zuul:
routes:
first-service:
path: /first/**
serviceId: first-service
stripPrefix: false
second-service:
path: /second/**
serviceId: second-service
stripPrefix: false
I.e. when we request 'GET /first' then Zuul route the request to the 'first-service', but if we request 'POST /first' then Zuul route the request to the 'second-service'.

Answer 1

To implement dynamic routing based on HTTP method we can create a custom 'route' type ZuulFilter and resolve 'serviceId' through DiscoveryClient. Fore example:
#Component
public class PostFilter extends ZuulFilter {
private static final String REQUEST_PATH = "/first";
private static final String TARGET_SERVICE = "second-service";
private static final String HTTP_METHOD = "POST";
private final DiscoveryClient discoveryClient;
public PostOrdersFilter(DiscoveryClient discoveryClient) {
this.discoveryClient = discoveryClient;
}
#Override
public String filterType() {
return "route";
}
#Override
public int filterOrder() {
return 0;
}
#Override
public boolean shouldFilter() {
RequestContext context = RequestContext.getCurrentContext();
HttpServletRequest request = context.getRequest();
String method = request.getMethod();
String requestURI = request.getRequestURI();
return HTTP_METHOD.equalsIgnoreCase(method) && requestURI.startsWith(REQUEST_PATH);
}
#Override
public Object run() {
RequestContext context = RequestContext.getCurrentContext();
List<ServiceInstance> instances = discoveryClient.getInstances(TARGET_SERVICE);
try {
if (instances != null && instances.size() > 0) {
context.setRouteHost(instances.get(0).getUri().toURL());
} else {
throw new IllegalStateException("Target service instance not found!");
}
} catch (Exception e) {
throw new IllegalArgumentException("Couldn't get service URL!", e);
}
return null;
}
}

Answer 2

#Cepr0's solution is right. Here I am proposing just a simpler way (without service discovery). Assuming you have that route:
zuul:
routes:
first:
path: /first/**
# No need for service id or url
Then you can route requests for '/first' route in 'route' type filter just by setting location to request context.
#Component
public class RoutingFilter extends ZuulFilter {
#Override
public String filterType() {
return ROUTE_TYPE;
}
#Override
public int filterOrder() {
return 0;
}
#Override
public boolean shouldFilter() {
return true;
}
#Override
public Object run() throws ZuulException {
/* Routing logic goes here */
URL location = getRightLocationForRequest();
ctx.setRouteHost(location);
return null;
}
}