Develop Reference

how to forward requests to another microservice using Spring?

We want to have an 'auth' service, using spring security, which:
authenticates incoming request,
if successful, adds userid to http header
forwards request (with header) to another service
What is the easiest way to achieve this kind of forwarding using Spring?

For this use case, we can create a new Spring Boot application (majorly know as API Gateway) that enables Zuul proxy (EnableZuulProxy). Create a custom Zuul PRE_TYPE filter that parses all the incoming requests. Its objective would be to check if an incoming request contains token, then call Authentication Service, retrieve the caller's information and add the user's identifier in the custom header.
Once the incoming request is passed through all the filters, then use zuul.routes.* properties to forward a request to appropriate services.
To call remote service (in this case, Authentication Service) we can use Spring's RemoteTokenServices class. And, BearerTokenExtractor class for extracting the token from incoming requests. Here's the sample code to get you started:
#Override
public Object run() {
final RequestContext requestContext = RequestContext.getCurrentContext();
final HttpServletRequest request = removeCustomHeaders(requestContext.getRequest());
requestContext.setRequest(request);
final Authentication authentication = tokenExtractor.extract(request);
if (Objects.nonNull(authentication)) {
try {
final OAuth2Authentication oAuth2Authentication = tokenServices.loadAuthentication(authentication.getPrincipal().toString());
final Map<String, String> userAuthDetails = (Map<String, String>) oAuth2Authentication.getUserAuthentication().getDetails();
requestContext.addZuulRequestHeader(USERNAME_HEADER, oAuth2Authentication.getPrincipal().toString());
// Add other required information in headers.
}
catch(final AuthenticationException | RestClientException |OAuth2Exception e){

Managing any HTTP request in a generic way

In my organisation, when I want to expose an API, I have to declare it with a swagger contract, same for any update, and it can take multiple weeks before the creation or change is taken into account.
That's why we've come with the idea to declare only one contract for all the APIs we need to expose, and manage the routing in an applicative reverse proxy (the request would include the necessary metadata to allow to route to the appropriate endpoint) :
{
"genericHttpRequest" : base64encodedByteArrayOfAnyHttpRequest
}
Now the question is :
how to manage this request without reimplementing HTTP ? Is it possible to put back the array of byte into a structured HttpServletRequest ?
/**
* Manage a generic request
*/
#RequestMapping(value = "/genericRequest", method = RequestMethod.POST)
public #ResponseBody void manageGenericRequest(#RequestBody GenericHttpRequestDto body) {
byte[] genericHttpRequest = body.getGenericHttpRequest();
//(...)
}

Spring will inject a HttpServletRequest if it is set as a method parameter. Furthermore, wildcard path mappings will enable the methods to be matched to every request:
#RestController
#RequestMapping("/generic-endpoint/**")
public class DemoController {
#RequestMapping
public ResponseEntity<Object> genericGetRequest(HttpServletRequest httpServletRequest) {
return ResponseEntity.ok().body(httpServletRequest.getMethod());
}
}
Optionally, you could return a ResponseEntity to gain more control over your HTTP response.

How to read request headers from incoming message in a graphQL endpoint in spring boot application

I have a spring boot application running with a graphql endpoint that validates and executes queries and mutations, however, I need to read one header in the incoming message in order to pass its value to another endpoint. Is there a way in graphql to read these values? some sort of getHeaders or something like that?

GraphQL itself does not define any things related to how to expose it over the network , so it does not define any things related to get HTTP header.It is up to developers to use their ways.So, it depends on the underlaying technologies you use to serve GraphQL over HTTP.
Consider you use graphql-spring-boot and graphql-java-tools , and assuming that you does not customize GraphQLContext , you can try to add DataFetchingEnvironment argument to your resolver function and then get the GraphQLContext from it. You can then get HttpServletRequest from the context and access the headers :
public Foo resolveFoo(Map<String,String> input , DataFetchingEnvironment env){
GraphQLContext context = env.getContext();
HttpServletRequest request = context.getHttpServletRequest().get();
request.getHeader("content-type");
}

The solution by #Ken Chan was not working for me. GraphQLContext had no method named getHttpServletRequest.
Solved it by using GraphQLServletContext instead. You can change the code to:
public Foo resolveFoo(Map<String,String> input , DataFetchingEnvironment env){
GraphQLServletContext context = env.getContext();
String header = context.getHttpServletRequest().getHeader("content-type");
}

Apparently the type of the context is not standardized. I use SPQR, and in my case I discovered (via debug):
DefaultGlobalContext<ServletWebRequest> context = handlerParameters.getDataFetchingEnvironment().getContext();
context.getNativeRequest().getHeader("something");

Not a direct answer to your problem statement, but one can use a Filter to handle it before the request hits the resolver endpoints (if that's a requirement):
public class HeaderFilter implements Filter {
#Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) {
final HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
String headerVal= httpServletRequest.getHeader("<header string>");
try {
filterChain.doFilter(httpServletRequest, servletResponse);
} catch (IOException | ServletException e) {
//handle as you wish
}
}

These answers are too old, for latest versions. There are two ways (1) you can try to autowire one HttpServletRequest in your controller, such as
#Slf4j
#Controller
public class YourQueryController {
#Autowired
private HttpServletRequest request;
....
Then implement following logic to get header:
request.getHeader("Authorization")
(2) To make use of out-of-box support of RequestContextHolder over HTTP requests
ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
val authorization = attributes.getRequest().getHeader("Authorization");

Google brought me this answer and unfortunately it was for Spring framework. Many use Spring framework but if you use Apache Tomcat with GraphQL integration like I do, you can do use this.
graphql.kickstart.servlet.context.DefaultGraphQLServletContext.DefaultGraphQLServletContext context = dataFetchingEnvironment.getContext();
jakarta.servlet.http.HttpServletRequest request = context.getHttpServletRequest();
String tokenBearer = request.getHeader("Authorization");
hth

SessionId lost when I make a request between backend of microservices

I am trying to make request between microservices in order to retrieve a list of users with the same roles. For this, first I make a request between FrontEnd and Backend inside the microservice 1. Following, I call an endpoint in the microservice 2 from Microservice 1 backend, but the session Id is lost in it, and I can retrieve the context.
I am using spring security and Redis for the session Control.
Manually, I retrieve the session Id from the microservice 1 and I add it as an attribute of the header of the second call, to the microservice 2. But it does not work.
String sessionID= RequestContextHolder.currentRequestAttributes().getSessionId();
RestTemplate rest = new RestTemplate();
HttpHeaders headers= new HttpHeaders();
headers.set("Session",sessionID);
HttpEntity<ResponseData> entity = new HttpEntity<ResponseData>(headers);
ResponseEntity<ResponseData> responseEntity =rest.exchange(targetApi, HttpMethod.GET, entity,ResponseData.class);

Finally, I resolved the problem adding an interceptor as a component:
#Component
public class SpringSessionClientHttpRequestInterceptor implements ClientHttpRequestInterceptor {
#Override
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution)
throws IOException {
request.getHeaders().add("Cookie", "SESSION=" + sessionId);
return execution.execute(request, body);
}
}
And I created a #Bean to configure the rest template:
#Bean
public RestTemplate restTemplate(){
RestTemplate rest = new RestTemplate();
ClientHttpRequestInterceptor interceptor= new SpringSessionClientHttpRequestInterceptor();
List<ClientHttpRequestInterceptor> interceptors = new ArrayList<ClientHttpRequestInterceptor>();
interceptors.add(interceptor);
rest.setInterceptors(interceptors);
return rest;
}

I don't know the exact answer to your question but in terms of your design I'd question if you really want to make your microservice1 depending on microsevice2. A microservice should be autonomous in the way it works and being able to be deployed on it's own (in theory anyway!). May be you could have an orchestrating microservice that receives your session information and then calls the 2 other microservices to pass that information on via 'standard' attributes.

headers.set("Session",sessionID);
I assume that the problem is that you are using the wrong identifier. As far as I know, it is JSESSIONID by default.
Another problem that I can see here is that JSESSIONID expected to be in cookies. Try to put it in cookies when sending a request to your 'microservice2'.

Spring Cloud Zuul: RedirectView redirecting to service and not gateway

I'm a bit new to microservices and Spring. I have Spring Cloud microservices (ports: 8xxx-8xxx) with a Zuul gateway running on port 9000. There's a method inside a controller on a UI service which should do a login and then return to a index.html page:
#RequestMapping(value="/do-login", method = RequestMethod.POST)
public RedirectView doLogin (#ModelAttribute("authEntity") final AuthEntity authEntity, final Model model) {
model.addAttribute(VERSION, applicationVersion);
model.addAttribute("authEntity", new AuthEntity());
authenticatedStatus = true;
model.addAttribute(AUTHENTICATED, authenticatedStatus);
return new RedirectView("index");
}
The problem is that when above method completes it returns an url of the microservice itself localhost:8888/index but not localhost:9000/services/ui/.
If I use a simpler method:
#RequestMapping(value="/do-login", method = RequestMethod.POST)
public String doLogin (#ModelAttribute("authEntity") final AuthEntity authEntity, final Model model) {
model.addAttribute(VERSION, applicationVersion);
model.addAttribute("authEntity", new AuthEntity());
authenticatedStatus = true;
model.addAttribute(AUTHENTICATED, authenticatedStatus);
return "index";
}
This returns correctly an url of gateway localhost:9000/services/ui/do-login but with a /do-login which I do not need.
Maybe I can get rid of /do-login/ part of url? Or maybe there is a solution for the incorrect redirect?
Thanks in advance!

If you use relative path like in return "index"; the result of the POST request sent to http://localhost:9000/services/ui/do-login will include URLs to http://localhost:9000/... unless coded otherwise in the jsp / freemarker / thymeleaf file.
If you want to get rid of the do-login, you would need to implement what's called a Redirect After Post (or redirect after form submit) approach so that a page refresh doesn't resubmit the form. If you take this approach, which seem what you were doing when using: return new RedirectView("index");, I can think of a couple ways of fixing the URL and set it to the proxy host.
1) http://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/servlet/view/RedirectView.html, there are a couple of constructors that takes a host parameter, you would need to inject the proxy host in the controller class and most-likely in every controller class that implements Redirect After Post.
2) http://tuckey.org/urlrewrite/, include UrlRewriteFilter and configure rules to rewrite from webapp host to proxy host when webapp http status code response is 302. With this approach it would only be once rule and no need to inject proxy host to controller classes or change the return new RedirectView("index");`
3) Maybe this rewriting is implemented in Zuul and you don't need include and configure UrlRewriteFilter as suggested in 2).
As a side note, I have configured Nginx's proxy_pass to a Java webapps (where I implemented Redirect After Post) in the past and I don't recall having this issue. Will have to take a look at both UrlRewriteFilter and Nginx config files to expand on this.

I found that this (thanks to answer in here: Spring redirect url issue when behind Zuul proxy) seems to work as required (but is considered a 'workaround'):
#RequestMapping(value="/do-login", method = RequestMethod.POST)
public void doLogin (#ModelAttribute("authEntity") final AuthEntity authEntity,
final Model model,
HttpServletResponse servletResponse) throws IOException {
...
String rUrl = ServletUriComponentsBuilder.fromCurrentContextPath().path("/").build().toUriString();
servletResponse.sendRedirect(rUrl);
}