Encode issue with feign.template.Template#resolveExpression

I customized an AnnotatedParameterProcessor implementation class.
But I encountered a problem: when I use the following code to put the parameter into the request body.

feign.RequestTemplate#resolve(java.util.Map<java.lang.String,?>) {
if (this.bodyTemplate != null) {
      resolved.body(this.bodyTemplate.expand(variables));
    }
}

Such as the bodyTemplate‘s value is: %7B"ab":{ab}%7D, and the variable(ab) is a Array or a List.

feign.template.Template#resolveExpression
feign.template.Expressions.SimpleExpression#expand

String expand(Object variable, boolean encode) {
  StringBuilder expanded = new StringBuilder();
  if (Iterable.class.isAssignableFrom(variable.getClass())) {
    expanded.append(this.expandIterable((Iterable<?>) variable));
  } else {
    expanded.append((encode) ? encode(variable) : variable);
  }

  /* return the string value of the variable */
  String result = expanded.toString();
  if (!this.matches(result)) {
    throw new IllegalArgumentException("Value " + expanded
        + " does not match the expression pattern: " + this.getPattern());
  }
  return result;
}

When the variable is of type Iterable, it will be handle and encode. But I don't want to handle my variable.
How should i control it.

I customized an AnnotatedParameterProcessor to encapsulate the parameters on the feignclient method（POST） into a format like {"a":{a},"b":{b},"c":{c}}, and then put it into the bodyTemplate. Then, in feign.RequestTemplate#resolve(java.util.Map<java.lang.String,?>) replace {a} in the body with the real value, and put this string into the request body (JSON format). However, if {c} is a List, it will be encoded.
{"a":1,"b":test,"c":[],"d":{}}，but variable c will be processed into other formats and encoded (like in URLs).

Start with feign.template.Template#resolveExpression and feign.template.Expressions.SimpleExpression#expand, then reproduce the bodyTemplate case where a List variable is expanded. Compare the intended JSON request body with the current encoded output; done means collection values are handled according to the requested body semantics without breaking existing template expansion behavior.