How to check the incoming request URL in rest api

Question

I have a Rest API which takes json input from the user and makes connection (TCP connection) with the load balancer. One of the server behind the load balancer will process the request and sends back the response to the Rest API.

The Rest API accepts request from two different endpoints or URL's. Currently I have one load balancer which process the request from both the endpoints. I want to add one more load balancer.

Inside one of the method where I am making connection with the load balancer,I want to check the URL and redirect the request to particular load balancer depending upon the endpoint/URL.

Ex: URL1 request ---> redirect to load balancer 1.

URL2 request ----> redirect to load balancer 2.

Answer 1

You can redirect manually the request from client to specific LB based on requested path or you can use a api gateway like ZUUL .

Manually redirect exmaple:

@RequestMapping(value = { "/", " * " })
public ResponseEntity<?> redirectRequest(HttpServletRequest httpServletRequest) {
        String bodyRequest = "";
    String baseURL = "";
    if ("POST".equalsIgnoreCase(httpServletRequest.getMethod())
            || "PUT".equalsIgnoreCase(httpServletRequest.getMethod())) {
        try {
            bodyRequest = httpServletRequest.getReader().lines()
                    .collect(Collectors.joining(System.lineSeparator()));
        } catch (IOException e) {

        }
    }

    HttpEntity<?> request = new HttpEntity<>(bodyRequest);
    Enumeration<String> headerNames = httpServletRequest.getHeaderNames();

    if (headerNames != null) {
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            request.getHeaders().add(headerName, httpServletRequest.getHeader(headerName));
        }
    }

    if (httpServletRequest.getContextPath().contains("api/lb1"))
        baseURL = "lb ur1";
    else
        baseURL = "lb url 2";
    return restTemplate.exchange(baseURL + httpServletRequest.getContextPath(),
            HttpMethod.resolve(httpServletRequest.getMethod()), request, ResponseEntity.class,
            httpServletRequest.getRequestURI());

}