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Javax REST Response entity = null

I am using javax to create a REST service to send an Java Object from one system to another.
I send the data like follows:
WebTarget wt = client.target(baseUrl.toString()).path(restUrlSuffix);
response = wt.request(MediaType.APPLICATION_JSON).post(Entity.json(transferJSON));
I defined a method which should receive the entity as a JSON:
#POST
#Path("/post")
#Consumes("application/json")
#Produces("application/json")
public Response saveWorkflowDefinition(#Valid String json) {
.....
.....
String message = "Message to return";
Response res = Response.ok(message).build();
return res;
}
With this method everything is fine. Data arrives as JSON, colud be transformed back to my java class and I can work with the object again.
Also it seems, that the Response is correct.
If I debug my code, the response is properly filled.
But on the side where I want to receive this response and check it, the entity part is empty.
I have no idea why?
Screen 1 is my response before sending it:
Screen 2 is the response after receiving it:

I found a solution.
I had to add a "valid" readEntity to my WebTarget request.
I my case I have written a response object, maybe a String.class might work too. I need my response class later in my code to transfer some more detailed information.
response = wt.request(MediaType.APPLICATION_JSON).post(Entity.json(transferJSON)).readEntity(WFResponse.class);

GET call with request body - request body not accessible at controller

I am trying to do a get call with request body(JSON) as the request parameter list exceeds the limit. I am able to send the request via postman/insomnia and request is reaching till controller without any error. But the "requstBody" is empty at controller. What i am missing here?
#GET
#Path("\path")
#Consumes(APPLICATION_JSON)
#Produces(APPLICATION_JSON)
public Response getResponse(String requestBody) throws IOException { }
When I replaced #GET with #POST, requestBody has value. For GET call do we need to add anything more?

I am trying to do a get call with request body(JSON) as the request parameter list exceeds the limit. I am able to send the request via postman/insomnia and request is reaching till controller without any error. But the "requstBody" is empty at controller. What i am missing here?
One thing you are missing is the fact that the semantics of a request body with GET are not well defined.
RFC 7231, Section 4.3.1:
A payload within a GET request message has no defined semantics; sending a payload body on a GET request might cause some existing implementations to reject the request.

There are two ways for sending parameters in an Http Get method. PathVariable and RequestParam. In this way, sent parameters are visible in the request URL. for example:
www.sampleAddress.com/countries/{parameter1}/get-time?city=someValues
In the above request, parameter1 is a path variable and parameter2 is a request parameter. So an example of a valid URL would be:
www.sampleAddress.com/countries/Germany/get-time?city=berlin
To access these parameters in a java controller, you need to define a specific name for the parameters. For example the following controller will receive this type of requests:
#GetMapping(value = "/countries/{parameter1}/get-time", produces = "application/json; charset=utf-8")
public String getTimeOfCities(
#PathVariable(value = "parameter1") String country,
#RequestParam(value = "city") String city
){
return "the method is not implemented yet";
}
You are able to send RequestBody through a Get request but it is not recommended according to this link.
yes, you can send a body with GET, and no, it is never useful
to do so.
This elaboration in elasticsearch website is nice too:
The HTTP libraries of certain languages (notably JavaScript) don’t allow GET requests to have a request body. In fact, some users are suprised that GET requests are ever allowed to have a body.
The truth is that RFC 7231—the RFC that deals with HTTP semantics and
content—does not define what should happen to a GET request with a
body! As a result, some HTTP servers allow it, and some—especially
caching proxies—don’t.
If you want to use Post method, you are able to have RequestBody too. In the case you want to send data by a post request, an appropriate controller would be like this:
#PostMapping(value = "/countries/{parameter1}/get-time", produces = "application/json; charset=utf-8")
public String getTimeOfCitiesByPost(
#PathVariable(value = "parameter1") String country,
#RequestParam(value = "city") String city,
#RequestBody Object myCustomObject
){
return "the method is not implemented yet";
}
myCustomObject could have any type of data you defined in your code. Note that in this way, you should send request body as a Json string.

put #RequestBody on String requestBody parameter

#RequestMapping("/path/{requestBody}")
public Response getResponse(#PathVariable String requestBody) throws IOException { }

POST doesn't work Spring java

I have an web application and I'm trying to creat a simple POSt method that will have a value inside the body request:
#RequestMapping(value = "/cachettl", method = RequestMethod.POST)
#CrossOrigin(origins = "http://localhost:3000")
public #ResponseBody String updateTtl(#RequestBody long ttl) {
/////Code
}
My request which I call from some rest client is:
POST
http://localhost:8080/cachettl
Body:
{
"ttl": 5
}
In the response I get 403 error "THE TYPE OF THE RESPONSE BODY IS UNKNOWN
The server did not provide the mandatory "Content-type" header."
Why is that happening? I mention that other GET requests are working perfectly.
Thanks!
Edit:
When I tried it with postman the error message I got is "Invalid CORS request".

Spring application just doesn't know how to parse your message's body.
You should provide "header" for your POST request to tell Spring how to parse it.
"Content-type: application/json" in your case.
You can read more about http methods here: https://developer.mozilla.org/en-US/docs/Learn/HTML/Forms/Sending_and_retrieving_form_data
Updated:
Just in case of debug, remove useless annotations to test only POST mechanism. Also, change types of arg and return type. And try to use case-sensitive header.
#RequestMapping(value = "/cachettl", method = RequestMethod.POST)
public void updateTtl(#RequestBody String ttl) {
System.out.println("i'm working");
}

Since the error is about the response type, you should consider adding a produces attribute, i.e :
#RequestMapping(value = "/cachettl", method = RequestMethod.POST, produces=MediaType.APPLICATION_JSON_VALUE)
Since you are also consuming JSON, adding a consumes attribute won't hurt either :
#RequestMapping(value = "/cachettl", method = RequestMethod.POST, consumes=MediaType.APPLICATION_JSON_VALUE, produces=MediaType.APPLICATION_JSON_VALUE)

The error message is slightly misleading. Your server code is not being hit due an authentication error.
Since you say spring-security is not in play then I suspect you're being bounced by a CORS violation maybe due to a request method restriction. The response body generated by this failure (if any at all) is automatic and will not be of the application/json type hence the client failure. I suspect if you hit the endpoint with something that doesn't care for CORS such as curl then it will work.
Does your browser REST client allow you to introspect the CORS preflight requests to see what it's asking for?

Spring MVC Override Received Content Type

I'm working on a Spring MVC application and have a client that I have no control over. This client is POSTing JSON data but transmitting a application/x-www-form-urlencoded header. Spring naturally trusts this header and tries to receive the data but can't because its JSON. Has anyone had experience overriding the header that Spring receives or just specifying exactly what type of data is coming, regardless of the headers?

You can do two things;
Change the client to send the Content-Type:
application/json header
Write a Servlet Filter or Spring Interceptor which is on top of the Spring Controller and checks for the header Content-Type. If it is not application/json then it changes it to application/json.

Why don't you write a separate controller to handle application/x-www-form-urlencoded requests. If the request is a valid JSON, then you can parse it and forward it to to appropriate service.
This way you can also handle a case in future where you get request of same type which is not a valid JSON.
#RequestMapping(value = "/handleURLEncoded", method = RequestMethod.POST, consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public #ResponseBody Object handleURLEncoded(HttpEntity<String> httpEntity) {
String json = httpEntity.getBody();
//now you have your request as a String
//you can manipulate it in any way
if(isJSONValid(json)) {
JSONObject jsonObj = new JSONObject(json);
//forward request or call service directly from here
//...
}
//other cases where it's not a valid JSON
}
Note: isJSONValid() method copied from this answer

How to create endpoint in Jersey for POST requests with or without body

I have an API created with Jersey
There's currently an endpoint to which users can make POST requests. There is no body required, as all the information is in the url.
#POST
#Path("entries")
#Produces(MEDIATYPE_JSON_AND_XML)
public Response createEntry(){
...
}
A new, empty, entry is created and the id is returned.
Content-Type of the request doesn't matter, as there is no request body data.
Now it should also be possible to set specific fields of the new entry during the request, using FormData. For this request a body is necessary, and the Content-Type must be multipart/form-data.
So I've created a second function:
#POST
#Path("entries")
#Consumes("multipart/form-data");
#Produces(MEDIATYPE_JSON_AND_XML)
public Response createEntryWithParam(#FormDataParam('param') String param){
...
}
This second function works te send the parameter in the request. But by adding it, the first stops working.
Sending a request without Content-Type will throw a NullPointerException. Probably because the #Consumes triggers some kind of Content-Type-check, which fails.
Is there a way to have one endpoint accepting POST requests with or without request-body?
edit So, I would like to receive all multipart/form-data requests in the seconds function, and use the first as a kind of catch-all for other POST requests to that endpoint

Currently I have a work-around in place.
If a POST request comes in without MediaType (Content-Type) or request-body, I automatically add an empty JSON object and set the Content-Type accordingly.
#Provider
public class ContentTypeRequestFilter implements ContainerRequestFilter {
#Override
public void filter(ContainerRequestContext crc) throws IOException {
if (crc.getMethod().equals("POST") && crc.getMediaType() == null && crc.getLength() == -1){
crc.getHeaders().add("content-type", MediaType.APPLICATION_JSON);
InputStream in = IOUtils.toInputStream("{}");
crc.setEntityStream(in);
}
}
}
This works, but is kinda hacky in my opinion. I'm interested to know if there are better ways to achieve my desired result.