I want to upload a file (an image specifically) to a REST Server using HTTP POST. I have already imported/add to build path httpmime-4.3.1.jar and
You seem to be missing a dependency.
I have httpclient-4.2.5, httpcleint-cache-4.2.5, httpcore-4.2.4 and httpmime-4.2.5 with commons-lang3-3.1 and commons-logging-1.1.2 jars in my class path.
I also use entity.addPart(formFieldName, new FileBody(file, "image/jpeg")); instead of using the header property.
Take a look at Internet media type for more details