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Spring application/x-www-form-urlencoded prevent encoding of string

We have a #PostMapping which is a webhook provided to a third party, which is called whenever an event occurs on the third party.
#PostMapping(path = "/some-api", consumes = {MediaType.APPLICATION_FORM_URLENCODED_VALUE})
public void proessWebhook(#RequestBody String request) {
The request strings keys are encoded in the String request. For our internal requirements, we need the key to not be pre-encoded when spring sets it to the String request variable. We tried URL decoding the variable, however, the problem is that there are values that we don't want to decode, so decoding the entire string decodes the key and the values.
An example if in the CURL request the input is some key=some%20value, the request variable would be set to some%20key=some%20value. Whereas we only need the key decoded.
On top of this, the order of the parameters also change from the input, it is important for the order to be the same.
How do we go about doing this?

if your method parameter is of a type MultiValueMap, you can use either the #RequestParam or #RequestBody annotation to bind it appropriately with the body of the HTTP request.
#PostMapping(
path = "/some-api",
consumes = {MediaType.APPLICATION_FORM_URLENCODED_VALUE})
public ResponseEntity<String> funName(
#RequestParam MultiValueMap<String,String> paramMap) throws Exception {
}

Distinguish Spring Boot PostMapping based on key in RequestBody

I have a REST endpoint with a PostMapping that should be able to accept different objects in the body and map them based on existence of keys.
When I use the same PostMapping for both functions, it gives me an "Ambiguous mapping" error.
When I use params similar to https://www.baeldung.com/spring-requestmapping, the default mapping is called even if the specialKey exists in the request body.
Is there any workaround to achieve this?
#PostMapping(value = "/classes", params = {"specialKey"})
public ResponseEntity<Class> createClass(#Valid #RequestBody SpecialClass class) throws URISyntaxException {
// do something special
}
#PostMapping("/classes")
public ResponseEntity<Class> createClass(#Valid #RequestBody Class class) throws URISyntaxException {
// do something
}

Based on Mapping the same url to different methods based on request body in spring it's not possible (or at least wasn't at the time). The params needs a separate request parameter, it can't be used to look for things inside the request body like that.
You could include the parameter in the URI, the special endpoint would be /classes?specialKey, and the normal endpoint just /classes. But I would just use different paths.

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 { }

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

Spring MVC using same path on endpoints to return different content?

I'm going to use a very basic hello world endpoint as an example
#RequestMapping("/hello")
public String hello(#RequestParam(value="name", required=false, defaultValue="World") String name, Model model) {
model.addAttribute("name", name);
return "helloworld";
}
If I have this endpoint and I want to be able to go to /hello and retrieve the helloworld view.
Is it possible for me to use the SAME /hello path to retrieve model as json if I pass in a specific request param like content-type?

You could try passing in a parameter using the RequestMapping params option. This does require modifying the URL, but the mapping is still the same and a mapped method without a params tag could be added as a default.
#RequestMapping(value="/hello" params= param1)
public returnType method(#RequestParam("param1") p) { ... }
#RequestMapping(value="/hello" params= param2)
public differentreturnType method2(#RequestParam("param2") p) { ... }
So to handle the first, request URL : http://etc.com/hello?param1=x and the second http://etc.com/hello?param2=y.
Params section of #RequestMapping docs: http://docs.spring.io/spring/docs/4.0.5.RELEASE/javadoc-api/org/springframework/web/bind/annotation/RequestMapping.html#params--

I'm not sure I understand what you mean.
If you mean that you want to be able to send a request to /hello and get two different responses, with different content types, yes, you can do that.
#RequestMapping identifies a method as being a request handler, but it also provides options for restricting when the handler should be used.
In this case, you should use the Accept header in your HTTP request and set it to application/json for a response containing JSON and text/html for a response containing HTML.
You can then have two #RequestMapping methods like
#RequestMapping(value = "/hello", produces = "application/json")
public SomeType handleJson() {...}
#RequestMapping(value = "/hello", produces = "text/html")
public String handleHtml() {...}
Spring will determine which method to use based on the request's Accept header and the method's produces value.