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GET request with illegal character in Java

I'm trying to create a GET call in Java on an API with a path variable containing an illegal character.
GET http://api.example.com/key/foo<bar
The path contains the character <. The HTTP client encodes it as %3C but I need to keep it as <, because API server don't decode it.
I have to do this call, and the API provider doesn't want to change anything to be more compliant.
Calling the GET request with illegal character works with Postman.
I'm trying to do it in Java now.
I've tried with Feign, HttpClient, WebClient and OkHttp, I don't find a way to do it.
Do you know a Java Http client that will allow me to do it ? Or the proper encoding option for the clients above ?
I've tried to create a RequestInterceptor with Feign to update uri, but it works only for some characters, as defined in RFC 6570, but not for <, which is re-replaced with %3C after my replacement.
Thanks

Sending UTF-8 values in HTTP headers results in Mojibake

i want to send arabic data from servlet using HTTPServletResponse to client
i am trying this
response.setCharacterEncoding("UTF-8");
response.setHeader("Info", arabicWord);
and i receive the word like this
String arabicWord = response.getHeader("Info");
in client(receiving) also tried this
byte[]d = response.getHeader("Info").getBytes("UTF-8");
arabicWord = new String(d);
but seems like there is no unicode because i receive strange english words,so please how can i send and receive arabic utf8 words?

HTTP headers doesn't support UTF-8. They officially support ISO-8859-1 only. See also RFC 2616 section 2:
Words of *TEXT MAY contain characters from character sets other than ISO- 8859-1 [22] only when encoded according to the rules of RFC 2047 [14].
Your best bet is to URL-encode and decode them.
response.setHeader("Info", URLEncoder.encode(arabicWord, "UTF-8"));
and
String arabicWord = URLDecoder.decode(response.getHeader("Info"), "UTF-8");
URL-encoding will transform them into %nn format which is perfectly valid ISO-8859-1. Note that the data sent in the headers may have size limitations. Rather send it in the response body instead, in plain text, JSON, CSV or XML format. Using custom HTTP headers this way is namely a design smell.

I don't know where word variable is comming from, but try this:
arabicWord = new String(d, "UTF-8");
UPDATE: Looks like the problem is with UTF-8 encoded data in HTTP headers, see: HTTP headers encoding/decoding in Java for detailed discussion.

jetty ,websockets and UTF8 encoding

I'm having a little problem. I'm building a small server in java, based on jetty websockets implementations.
The clients are the browsers and I send information using the websockets javascript api.
Everything works great until I send those special characters such as : ă Ț î ș ê ñ ü
So here is the problem. Client 1 sends a message to the server with one of this characters. Server prints the message and then send the message to client 2.
Client 2 receives the message and prints the message on a browser html page and works great The characters are showed correctly.
The problem is when I wanna print the String on the server site. Instead of ă is shows me the ? char. This is causing me problems because I want to insert the text in a database(mysql- with ut8 encoding enabled)
So.. what seems to be problem. The text that is send from the browser is not UT8 encoded? or the jetty websocket implementation is not receiving String in utf8 encoding??
Thanks

Here's a function I use to HTML-encode all special characters in a string (but not html itself (like < or >)). If you apply it before sending a string to the server, everybody should see the same and you can store it in a database table:
function toHtmlEncoded(string){
return string.replace(/[\u0080-\uC350]/g,
function(a) {return '&#'+a.charCodeAt(0)+';';}
);
}

First read this http://kunststube.net/encoding/
Then check everywhere you've converted bytes into Strings (or the reverse). Common places to make a mistake include calling getBytes() on a String without specifying an encoding. Other pitfalls include not setting the encoding in the database connection string.

How to encode a URL that I want to pass as a query string

I'm trying to send a URL as paramter of a query string like this example:
http://localhost.com/myapp.jsp?pathToFileURL=http://192.168.0.1/my_file.pdf
What I did is I used encode URL to encode the path before sending it to the server, problem is im getting a "400 Invalid URI: noSlash" because of this.
From what I read the problem is the tomcat security and that I should add a parameter to the tomcat startup
-Dorg.apache.tomcat.util.buf.UDecoder.ALLOW_ENCODED_SLASH=true
But I can't modify the parameters of the tomcat, so is it possible to do it other way?
Thanks

You can do URLSafebase64 encoding at the client side and URLSafebase64 decoding at the server side.
Check URLEncoder class for more details:
http://docs.oracle.com/javase/1.5.0/docs/api/java/net/URLEncoder.html
You can test manually before coding using any of the online URL Encoder/Decoder. Just google for "URL Encoder/Decoder"

Complete stab in the dark but you could try escaping the slashes with backslashes or you could try replacing them with %2F which is the URL encoded version of forward slash.
Hope this helps.

Base64 the URL then on the receiving end base64 decode to get the original URL without any alteration

Safe Data serialization for Plain HTTP GET & POST communication

I'm using the client's browser to submit HTTP request.
For report generation the securityToken is submitted as POST, for report download the same token needs to be submitted by the user browser, this time using GET.
What encoding would you recommend for the securityToken which actually represents encrypted data.
I've tried BASE64 but this fails because the standard can include the "+" character which gets translated in HTTP GET to ' ' (blank space).
Then I tried URL Encoding, but this fails because for HTTP POST stuff such as %3d are transmitted without translation but when browser does HTTP GET with the data %3d is converted to '='.
What encoding would you recommend, to allow safe transmission over HTTP POST & GET without data being misinterpreted.
The environment is Java, Tomcat.
Thank you,
Maxim.

Hex string.
Apache commons-codec has a Hex class that provides this functionality.
It will look like this:
http://youraddress.com/context/servlet?param=ac7432be432b21

Well, you can keep the Base64 and use this solution:
Code for decoding/encoding a modified base64 URL