Send selected option value by parameter

Question

I’m developing an application Java in which I take the database data and present it in a <select><option> but I don’t know how to catch the value selected and sent by parameter.

JSP

<c:choose>
<c:when test="${!empty param.descricao}">
<c:forEach items="${requestScope.produtos}" var="registro"> 
 <div class="col-sm-6 col-md-6"> 
  <h3>${registro.descricao}</h3>
  <p>${registro.codigo}</p>
  <div class="linha_compra"></div><br/><br/> 
  <div class="col-sm-6 col-md-6">
  <p>${registro.valor}</p> 

  <select id="parcelas">
   <option value="1"> ${registro.prod_parc1}</option>
   <option value="2">${registro.prod_parc2}</option>
   <option value="3">${registro.prod_parc3}</option>
   <option value="4">${registro.prod_parc4}</option>
   <option value="5">${registro.prod_parc5}</option>
   <option value="6">${registro.prod_parc6}</option>
   <option value="7">${registro.prod_parc7}</option>
   <option value="8">${registro.prod_parc8}</option>
   <option value="9">${registro.prod_parc9}</option>
   <option value="10">${registro.prod_parc10}</option>
  </select><br/><br/>  
  <div class="col-sm-6 col-md-6">
   <button type="button" onclick="" class="botao_comprar"><a href="http://localhost:8080/EccomerceJSP2/Carrinho?descricao=${registro.descricao}&valor=${registro.valor}&parcela=">COMPRAR</a></button> 
  </div>
 </div>
</c:foreach>

Answer 1

Good morning buddy, before I help you, let’s consider some changes.

Are you wearing a link to make a request, in case:

<a href="http://localhost:8080/EccomerceJSP2/Carrinho?descricao=${registro.descricao}&valor=${registro.valor}&parcela=">COMPRAR</a>

When using an anchor with href you automatically send the request with method GET.

According to the standards HTTP, the method GET should be used to recover the data and not to send or edit anything, just recover. What your code is doing is sending data on URL for some business logic on backend.

That’s not only not following standards, it’s not safe. Fine, your request has no sensitive data, but imagine that you want to add the credit card field, for example. You will send the user’s credit card number on URL? Obviously not.

Generally, the secure partner of GET, the method POST.

This method does not cache or keep the user’s data in the browser history, as well as send it safely to the backend. Does not appear in the URL, and is much harder to intercept than the simple method GET.

To use, you open a tag form and starts the attribute method to "POST".

It would look something like:

<form method="POST"></form>

To tag form has another important attribute, which is the action.

This attribute specifies the URL to which you will send the POST request.

It would look something like:

<form method="POST" action="http://localhost:8080/EccomerceJSP2/Carrinho"></form>

Note that it was taken from link the attributes in URL, you will now send them via POST.

Just create the form as follows:

<form method="POST" action="http://localhost:8080/EccomerceJSP2/Carrinho">
 <input name="descricao" value="${registro.descricao}" readonly="readonly"/>
 <input name="codigo" value="${registro.codigo}" readonly="readonly"/>
 <input name="valor" value="${registro.valor}" readonly="readonly"/>
 <select id="parcelas" name="parcelas">
  <option value="1"> ${registro.prod_parc1}</option>
  <option value="2">${registro.prod_parc2}</option>
  <option value="3">${registro.prod_parc3}</option>
  <option value="4">${registro.prod_parc4}</option>
  <option value="5">${registro.prod_parc5}</option>
  <option value="6">${registro.prod_parc6}</option>
  <option value="7">${registro.prod_parc7}</option>
  <option value="8">${registro.prod_parc8}</option>
  <option value="9">${registro.prod_parc9}</option>
  <option value="10">${registro.prod_parc10}</option>
 </select>
 <button type="submit" class="botao_comprar">COMPRAR</button>
</form>

Note that each input has an attribute name which is precisely the parameters you were passing on URL formerly.

In his Servlet, now, instead of implementing the method doGet, you will implement the method doPost and will recover the data in the same way:

request.getParameter("descricao"); //descrição vindo do formulário

I hope I’ve helped you. Any questions just comment.

Hugs.