I was using PATCH request with JMeter and I get following error - 
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java.net.ProtocolException: Invalid HTTP method: PATCH
 at java.net.HttpURLConnection.setRequestMethod(HttpURLConnection.java:428)
 at sun.net.www.protocol.https.HttpsURLConnectionImpl.setRequestMethod(HttpsURLConnectionImpl.java:374)
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The problem lies with HTTP Request implementation being used here. Java implementation of HTTP request does not support PATH request and you should be using HTTPClient 4 implementation to get rid of this error