Since version 1.2.0 (released 2015-11-12), you can do it as follows:
Map<String, Object> params = new HashMap<String, Object>(); params.put("string", "a string can contain &"); params.put("number", 4711); params.put("null", null); params.put("empty", ""); Response<String> response = webb .post("/my-url") .params(params) .asString();
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