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Zuul proxy - how to forward requests to services depending on request path

Problem
How to forward requests in Spring Cloud application? I need to forward requests to other services depending on the part of uri.
For example
HTTP GET http://user-application/api/users, returns users JSON.
HTTP GET http://user-application/api/proxy/jobs-application/api/jobs, returns jobs JSON, but this request should be forwarded to another application:
HTTP GET http://jobs-application/api/jobs.
Any HTTP method is allowed, not only GET.
Context
I have a SpringBoot Application, User application which has REST end-points which return data.
For example GET http://user-application/api/users would return users in the JSON format.
User application also has an HTTP end-point which should forward the request to other applications - let's call one of them Jobs application.
This end-point is HTTP {ANY_METHOD} /api/proxy/{dynamic-service}/{dynamic-path} as an example,
GET http://user-application/api/proxy/jobs-application/api/jobs
Please, note, initial request comes to the User application, while then it is forwarded to the Jobs application.
Approaches
I put some my approaches which I think about. Maybe you have done similar things in the past, so you could share your experience doing so. Or even improve one of my approaches.
ProxyController approach
I would create a ProxyController in User application with mapping /proxy
#Controller
#RequestMaping("/proxy/**")
ProxyController
public void proxy(final HttpServletRequest request, HttpResponse response) {
final String requestUri = request.getRequestUri();
if (!requestUri.startsWith("/api/proxy/")) {
return null; // Do not proxy
}
final int proxyIndex = "/api/proxy/".lenght(); // Can be made a constant
final String proxiedUrl = requestUri.subString(proxyIndex, requestUri.lenght());
final Optional<String> payload = retrievePayload(request);
final Headers headers = retrieveHeaders(request);
final HttpRequest proxyRequest = buildProxyRequest(request, headers);
payload.ifPresent(proxyRequest::setPayload);
final HttpResponse proxyResponse = httpClient.execute(proxyRequest)
pdateResponse(response, proxyResponse);
}
The problem with this approach, I have to write a lot of code t build a proxy request, to check if it has payload and if it has, copy it into proxy request, then copy headers, cookies etc to the proxy request, copy HTTP verb into proxy request. Then when I get proxy response, I have to populate its details into the response.
Zuul approach
I was inspired by ZuulFilters:
https://www.baeldung.com/spring-rest-with-zuul-proxy
https://stackoverflow.com/a/47856576/4587961
#Component
public class ProxyFilter extends ZuulFilter {
private static final String PROXY_PART = "/api/proxy";
private static final int PART_LENGTH = PROXY_PART.length();
#Autowired
public ProxyFilter() {
}
#Override
public boolean shouldFilter() {
final RequestContext context = RequestContext.getCurrentContext();
final String requestURI = retrieveRequestUri(context);
return requestURI.startsWith(PROXY_PART);
}
#Override
public Object run() {
final RequestContext context = RequestContext.getCurrentContext();
final String requestURI = retrieveRequestUri(context);
final String forwardUri = requestURI.substring(PART_LENGTH);
context.setRouteHost(buildUrl(forwardUri));
return null;
}
#Override
public String filterType() {
return "proxy";
}
#Override
public int filterOrder() {
return 0;
}
private String retrieveRequestUri(final RequestContext context) {
final HttpServletRequest request = context.getRequest();
return request.getRequestURI();
}
private URL buildUrl(final String uri) {
try {
return new URL(uri);
} catch (MalformedURLException e) {
throw new RuntimeException(String.format("Failed to forward request uri %s}.", uri), e);
}
}
}
This code allows me to forward requests with less effort. However, we also use client side load balancer Ribbon and circuit breaker Hystrix in Spring Cloud Zuul out of box. How to enable these features? Will they be enabled out of box in context.setRouteHost(forwardUrl);

I would like to add another approach, maybe it can also work.
Static application.yml file to configure Zuul proxy approach
This approach does not requre dynamic Zuul Filters.
application.yml
zuul:
routes:
user-application:
path: /api/users/**
serviceId: user-service
stripPrefix: false
sensitiveHeaders:
# I have to define all other services similarly.
jobs-application:
path: /api/proxy/jobs/**
serviceId: jobs-application
stripPrefix: true
sensitiveHeaders:
It will work only if I know all the services my clients need to call before I deploy the User application. What if a new application is added dynamically? Then I will have to update the configuration.

spring mvc Proxy server - maintaining url context (contextpath)

I have the below piece spring REST controller class.
#RestController
#RequestMapping("/global")
public class ProxyController extends BaseController{
#RequestMapping(value = "/**")
public ResponseEntity<String> proxy(HttpServletRequest request, HttpServletResponse response ) throws Exception {
try {
String restOfTheUrl = (String) request.getAttribute(
HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
URL uri = new URL("https://myrealserver" +
restOfTheUrl);
HttpHeaders headers = new HttpHeaders();
HttpEntity<String> httpEntity = new HttpEntity<>(headers);
RestTemplate restTemplate = new RestTemplate();
return resp;
} catch (Exception e) {
logger.error("Error ", e);
return new ResponseEntity<String>(HttpStatus.INTERNAL_SERVER_ERROR);
}
}
}
What I am trying to achieve here is to hide a server behind a proxy, which blindly forwards requests to the server.
This piece of code is invoked with url
https://myproxyserver/myapp1/end/point1
which in turn returns an html page with few clickable links. Now when the user clicks I am expecting the link to be invoked as
https://myproxyserver/myapp1/end/point2
Where as actually the endpoint invoked is
https://myproxyserver/end/point2
In the html page returned by the actual server, the path is end/point2 and has no mention of myapp1. So on click on those links my context changes to https://myproxyserver/end/point2 instead of https://myproxyserver/myapp1/end/point2
How do I ensure that the root context is always https://myproxyserver/myapp1 and not https://myproxyserver ?

You want to get your server context path. this is sample code.
like this :
public static String getServerNameAndContextPath(HttpServletRequest req) {
return "https://" + req.getServerName() + req.getContextPath();
}

Finally I resolved the problem by taking what D D suggested. I scanned through the whole response body, fortunately I had a pattern that I could use to scan and appended the context of the url to where ever required. That resolved the problem for me this problem.

Embedded Jetty web server not working, handler not invoked

I'm trying to embed Jetty 8 (8.1.18.v20150929) into a Java (jdk1.7.0_67) application. I have the following code:
public static final String HTTP_PATH = "/session";
public static final int HTTP_PORT = 9995;
// Open the HTTP server for listening to requests.
logger.info("Starting HTTP server, Port: " + HTTP_PORT + ", Path: "
+ "/session");
httpServer = new Server();
SelectChannelConnector connector = new SelectChannelConnector();
connector.setPort(HTTP_PORT);
connector.setHost("localhost");
httpServer.addConnector(connector);
TestHttpHandler handler = new TestHttpHandler(this);
ContextHandler ch = new ContextHandler();
ch.setContextPath(HTTP_PATH);
ch.setHandler(handler);
httpServer.setHandler(ch);
try {
httpServer.start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
My handler is pretty basic as a test:
public void handle(String target, Request baseRequest,
HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
logger.debug("Handling");
}
If I run the app and then use CURL to send a GET request to http://localhost:9995/session, then it returns a 200 status but there's no debug output.
If I access http://localhost:9995/session2, I get a 404 error.
I've read many examples online but for some reason I can't seem to get the handler to work properly. Am I doing something wrong? Thanks

I had exactly the same problem, and this is just a misunderstanding about how the Jetty API works. I was expecting to use ContextHandlers as a minimal implementation of REST services, however ContextHandlers are meant to handle requests to an entire context base (for example http://server:80/context-base, i.e. the equivalent of an app in Tomcat). The correct way to solve this question is to use Servlets:
Server server = new Server(9995);
ServletContextHandler root = new ServletContextHandler(ServletContextHandler.NO_SECURITY | ServletContextHandler.NO_SESSIONS);
root.setContextPath("/");
ServletHolder holder = new ServletHolder(new HttpServlet() {
public void doGet(HttpServletRequest req, HttpServletResponse resp) {
logger.debug("Handling");
}
});
server.start();
server.join();

Cannot find a handler for POST with boundary

I'm in the midst of testing my application which is using an HTTP-server. Instead of mocking I decided to go with a HTTP server fixture. Meaning that I do not have to mock any productional code. To accomplish this goal I currently chose for a free to use 3rd party library fixd.
I was able to successfully create several unit tests - which are working by means of a GET request. Most are quite simple, i.e.:
#Test
public void verifyConnectionTest()
{
try
{
final String body = FileUtils.readFileToString(RESOURCE);
final String path = "/";
this.server.handle(Method.GET, path).with(
new HttpRequestHandler() {
#Override
public void handle(final HttpRequest request,
final HttpResponse response)
{
response.setStatusCode(200);
response.setContentType("text/xml");
response.setBody(body);
}
});
// Setting up my HTTP client
// Execute some tasks
// asserting of everything was valid
}
catch (final IOException e)
{
fail(e.getMessage());
}
}
But I now have to send a POST request with multipart/form-data. Which does not make much of a difference other than changing the method and content-type:
#Test
public void executeStepTest()
{
try
{
final String body = FileUtils.readFileToString(SERVICE_RESPONSE);
final String path = "/";
this.server.handle(Method.POST, path, "multipart/form-data").with(
new HttpRequestHandler() {
#Override
public void handle(final HttpRequest request,
final HttpResponse response)
{
response.setStatusCode(200);
response.setContentType("text/xml");
response.setBody(body);
}
});
// Setting up my HTTP client
// Execute some tasks
// asserting of everything was valid
}
catch (final IOException e)
{
fail(e.getMessage());
}
}
However I get the following error: [ERROR] could not find a handler for POST - / - multipart/form-data; boundary=bqCBI7t-VW1xaJW7BADmTiGMg9w_YM2sHH8ukJYx and my guess is that fixd doesn't recognize the boundary-party. Since the documentation does not show an example I'm quite stuck on this part.
I tried using some wildcards such as '*', no succes. Thus; I need a way to either tell fixd to accept that boundary or use some wildcards I didn't yet discover. Any help would be great, thanks!

I've been making some debug and it seems to be that the problem is in the fixd core.
Basically, fixd indexes every RequestHandlerImpl by a HandlerKey (which includes ContentType as part of the key) in the map handlerMap. See method org.bigtesting.fixd.core.FixtureContainer#resolve.
...
HandlerKey key = new HandlerKey(method, route, contentType);
RequestHandlerImpl handler = handlerMap.get(key);
if (handler == null) {
// Error
}
...
Problem: When the request is multipart/form-data, boundary data (which it's generated dinamically every request) is part of the content type. So, any handler is found in handlerMap because the key changes with every running.
I've made a little test only to check that this is the cause of the problem, passing the contentType to fixd server.handle after the creation of the multipart request, and it works fine.
See the test below:
#Test
public void verifyConnectionTest_multipart() {
try {
// 1. Create multipart request (example with http-commons 3.1)
PostMethod filePost = new PostMethod(url);
Part[] parts = { new StringPart("param", "value") };
MultipartRequestEntity request = new MultipartRequestEntity(parts, filePost.getParams());
filePost.setRequestEntity(request);
// 2. fixd server handle (passing the request content type)
this.server.handle(Method.POST, "/", request.getContentType()).with(
new HttpRequestHandler() {
#Override
public void handle(final HttpRequest request,
final HttpResponse response) {
response.setStatusCode(200);
response.setContentType("text/xml");
}
});
// 3. Execute multipart request
HttpClient client = new HttpClient();
int status = client.executeMethod(filePost);
// 4. Assertions
Assert.assertEquals(200, status);
} catch (Exception e) {
Assert.fail(e.getMessage());
}
}
Hope it helps you to clarify the problem. Cheers

This was a bug in fixd, and has been fixed in version 1.0.3. Your original code should work using this new version of fixd.

Java Servlet 3.0 server push: Sending data multiple times using same AsyncContext

Lead by several examples and questions answered here ( mainly
http://www.javaworld.com/javaworld/jw-02-2009/jw-02-servlet3.html?page=3 ), I want to have server sending the response multiple times to a client without completing the request. When request times out, I create another one and so on.
I want to avoid long polling, since I have to recreate request every time I get the response. (and that quite isn't what async capabilities of servlet 3.0 are aiming at).
I have this on server side:
#WebServlet(urlPatterns = {"/home"}, name = "async", asyncSupported = true)
public class CometServlet extends HttpServlet {
public void doGet(final HttpServletRequest request, final HttpServletResponse response) throws IOException, ServletException {
AsyncContext ac = request.startAsync(request, response);
HashMap<String, AsyncContext> store = AppContext.getInstance().getStore();
store.put(request.getParameter("id"), ac);
}
}
And a thread to write to async context.
class MyThread extends Thread {
String id, message;
public MyThread(String id, String message) {
this.id = id;
this.message = message;
}
public void run() {
HashMap<String, AsyncContext> store = AppContext.getInstance().getStore();
AsyncContext ac = store.get(id);
try {
ac.getResponse().getWriter().print(message);
} catch (IOException e) {
e.printStackTrace();
}
}
}
But when I make the request, data is sent only if I call ac.complete(). Without it request will always timeout. So basically I want to have data "streamed" before request is completed.
Just to make a note, I have tried this with Jetty 8 Continuation API, I also tried with printing to OutputStream instead of PrintWriter. I also tried flushBuffer() on response. Same thing.
What am I doing wrong?
Client side is done like this:
var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://localhost:8080/home', true);
xhr.onreadystatechange = function () {
if (xhr.readyState == 3 || xhr.readyState == 4) {
document.getElementById("dynamicContent").innerHTML = xhr.responseText;
}
}
xhr.send(null);
Can someone at least confirm that server side is okay? :)

Your server-side and client-side code is indeed ok.
The problem is actually with your browser buffering text/plain responses from your web-server.
This is the reason you dont see this issue when you use curl.
I took your client-side code and I was able to see incremental responses, with only just one little change:
response.setContentType("text/html");
The incremental responses showed up immediately regardless of their size.
Without that setting, when my output was a small message, it was considered as text/plain and wasnt showing up at the client immediately. When I kept adding more and more to the client responses, it got accumulated until the buffer size reached about 1024 bytes and then the whole thing showed up on the client side. After that point, however, the small increments showed up immediately (no more accumulation).

I know this is a bit old, but you can just flushBuffer on the response as well.