We Keep Coding

How to have different JSON responses registered for a GET call

GET http://localhost/foo/api/v1/bars/:id
How to have different JSON responses registered for a GET call. We would like the GET call to return a separate response based on whether a CLI is invoking or the user interface is calling the API by passing a query parameter. But how do we register different serializers dynamically on the response.

You can use a User-Agent request header to identify the application doing the request. There are good tutorials to check how to access the headers in Spring, like this Baeldung one.

Dynamic Cookies For Retrofit 2 Requests

I've been using retrofit for quite a long time and haven't faced any serious usability issue before now. So my use case is very simple, I've to fetch an entity from another API that we're using to process a few data. Now the only issue is the service is using Cookies to accept entity id.
So this means that each request needs to have dynamic set of cookie associated with it. But currently I cannot see anything such that in Retrofit. I can see a old PR, but it was rejected for unknown reason.
Can anyone from Retrofit team can help in this matter. I think it will be very helpful. If you need code examples I can provide that in an edit.
TIA

Implement a custom CookieJar and set on the OkHttpClient
https://square.github.io/okhttp/4.x/okhttp/okhttp3/-cookie-jar/
abstract fun loadForRequest(url: HttpUrl): List<Cookie>
Load cookies from the jar for an HTTP request to url. This method returns a possibly empty list of cookies for the network request.

Changing HTTP method in RequestDispatcher

How do I change HTTP method in javax,servlet.RequestDispatcher?
I have some old service APIs that support GET and POST, The new version supports DELETE method for removing a record which used to happen through POST earlier.
We are decommissioning old version APIs by setting RequestDispatcher.forward() for old end points (stop gap arrangement until clients change). everything was cool except this POST to DELETE mapping.
Any solution there for this problem without adding POST end point for delete operation in new API?>

Although I agree using the next layer after your servlets would be a better choice, this is interesting. It use to be common to wrap an incoming request to add request based functionality (IE: auth state, etc). The HttpServletRequestWrapper was used to accomplish this. You could do the following if you just need to change the method:
class PostDeleteAdapter extends HttpServletRequestWrapper {
public String getMethod(){ return "POST"; }
}
You may also change other aspects of the incoming request if you need to further adapt the request. This may play well with your servlet containers RequestDispatcher, however it's dependent upon the container entirely.

I think you can't do it using servlet API. You can do what you want creating a new request, processing it's response and sending it back through the original response (in the servlet).
Some http clientes might help you. See Apache HTTP client:
http://hc.apache.org/httpclient-3.x/methods/delete.html)

Grizzly HttpServer: Set permanent header for every response

I am using a Grizzly HttpServer and i want to add a specific header in every response. Specifically, i want to avoid CORS problems by adding an 'Access-Control-Allow-Origin' header.
So, ideally, i want something like this:
HttpServer server = GrizzlyServerFactory.createHttpServer(uri, crc);
server.setHeader("Access-Control-Allow-Origin" , "*");
Generally, i am looking for a solution that does not require that i have to manually insert this header in every request-response action.
Is there any way to do this?

As #alexey said, there is no way (from the current Grizzly Server version) to do this. If anyone finds something else that works, i will gladly confirm it as an accepted answer.
The best alternative that works quite well is to extend the 'ContainerResponseFilter' class and override the 'filter' method.
Here is an example for 1.x API
Here is an example for 2.x API (minor changes)

Apache Camel - http Producer don't use GET-Method with enrich Pattern

I have a RESTful Webservice which I want to use with a content enricher in a Camel-Route.
See this similar Code:
from("direct:in") // Here comes XML
.to("validator:something.xsd") // validate it
.unmarshal("something-jaxb") // put it into a POJO
.setHeader(Exchange.HTTP_URI, simple("http://localhost:12345/restws/${header.foo}")) // Create the dynamic URI with simple
.setHeader(Exchange.HTTP_METHOD, constant("GET")) // set the HTTP-Method to use
.enrich("http://dummy", new MyAggregator()) // fetch some Information from a Restful Webservice
.to("direct:out"); // send the Message to another route
If I run this, I get the following error:
No type converter available to convert from type: de.my.Class to the required type: java.io.InputStream with value de.my.Class#620ee765.
It seems to me, he tries to send the body of the Exchange to the http-Endpoint, although I set the HTTP-Method to GET. I've read the documentation (https://camel.apache.org/http.html) and below Calling using GET or POST it describes that the Algorithm which selects the Method first look at the Header (1. Use method provided in header).
I found some workarounds, which describes how to move the body to a Exchange-property and move it back again after the Webservice-Call, but this can't be it...
EDIT:
Like Claus Ibsen mentioned enrich doesn't support dynamic uris. Fixed this in the example!

Neither enrich nor pollEnrich supports dynamic uris for their endpoints. Instead of using enrich, you can use the recipient list which support dynamic uris, and the aggregation strategy as well.

If it's "full of lists" of resources, sounds like you would want to split the lists and do a get on each resource

What's in the pojo? Your GET parameter should be a resource identifier and query parameters. That requires a custom converter.
http://fusesource.com/docs/esb/4.2/rest/RESTIntro.html
maybe consider using restlet instead... it's easier I think.
http://camel.apache.org/restlet.html