title: How to send a MultiValueMap<String, String> in a POST request
body: <p>I am using Spring and in my controller I have a `@ModelAttribute("params")'.</p>
  
  <p>like this </p>
  
  <pre><code>@ModelAttribute("params")
  public MultiValueMap&lt;String, String&gt; populateParams()
  {
  
  
      final MultiValueMap&lt;String, String&gt; params = new LinkedMultiValueMap&lt;&gt;();
  
      params.add("signature", token.generate());
      params.add("params", token.generate());
      params.add("mockpayment", "true");
      params.add("req_reference_number", cartService.getSessionCart().getCode());
      params.add("reason_code", "100");
      return params;
  }
  </code></pre>
  
  <p>this is used here in my ControllerA which is in charge to send it back to ControllerB using a POST, so in ControllerA I have a code like this :</p>
  
  <pre><code>@RequestMapping(value="/somePath", method =
  { RequestMethod.POST, RequestMethod.GET }))
  public String test(final Model model, final RedirectAttributes redirectAttrs)
  {       
      MultiValueMap&lt;String, String&gt; params = new LinkedMultiValueMap&lt;&gt;();
  
  
  params = (MultiValueMap&lt;String, String&gt;) model.asMap().get("params");
  ...
  }
  </code></pre>
  
  <p>What I want to do next is to send this Data structure Via a POST to ControllerB, how can I do that?</p>