code: private void writeForm(OutputStream out) throws IOException {
  		if (CollectionUtil.isNotEmpty(this.form)) {
  			StringBuilder builder = StrUtil.builder();
  			for (Entry<String, Object> entry : this.form.entrySet()) {
  				builder.append("--").append(BOUNDARY).append(StrUtil.CRLF);
  				builder.append(StrUtil.format(CONTENT_DISPOSITION_TEMPLATE, entry.getKey()));
  				builder.append(entry.getValue()).append(StrUtil.CRLF);
  			}
  			IoUtil.write(out, this.charset, false, builder);
  		}
  	}
docs: 发送普通表单内容
  
  @param out 输出流
  @throws IOException