Question

I have this peace of code:

<%
ArrayList<Utente> lista=null;
try{
    lista= (ArrayList<Utente>)request.getAttribute("lista");
}catch(Exception e){
    e.printStackTrace();
}
    if(lista!=null){                    
for(int i=0;i<lista.size();i++){                                                                                        out.print("<tr>");
                        out.print("<td>"+lista.get(i).getNome()+"</td>");
                        out.print("<td>"+lista.get(i).getCognome()+"</td>");
                        out.print("<td>"+lista.get(i).getPosizione()+"</td>");
                        out.print("<td>"+lista.get(i).getTelefono()+"</td>");
                        out.print("<td><img src='imm/view.png'>&nbsp"+
                                "<a href='' id='"+lista.get(i).getIdUtente()+"' class='view'>Vedi</a>&nbsp &nbsp" 
                                +"<img src='imm/mod.png'>&nbsp"+
                                "<a href='InfoUtente&id="+lista.get(i).getIdUtente()+"' id='"+lista.get(i).getIdUtente()+"' class='mod'>Modifica   </a>&nbsp &nbsp"+
                                 "<img src='imm/del.png'>&nbsp"+
                                "<a href='' id='"+lista.get(i).getIdUtente()+"' class='del' name='"+lista.get(i).getNome()+" "+lista.get(i).getCognome()+"'>Elimina   </a></td>");
                         }

                }
                        %>

What I want to do now is to call the servlet InfoUtente when I click on the link Modifica on a certain index. And so I want to pass the index parameter to the servlet.
How can I do?

Answer 1

Just as you did, except the query string must start with a ? and not with a &:

<a href='InfoUtente?id="+lista.get(i).getIdUtente()
                   ^-- here

& is used to separate the parameters inside the query string. And it must be HTML-escaped. So if you had a second parameter to pass, you would need to generate the following URL:

<a href='InfoUtente?id=" + theId + "&amp;foo=bar"

Note that generating HTML from Java code is not a good practice. It leads to hard-to read, unmaintainable code. Scriptlets should be avoided. You should do that using JSTL tags and the JSP EL:

<c:forEach var="utente" items="${lista}">
    <tr>
        <td><c:out value="${utente.nome}"/></td>
        <td><c:out value="${utente.cognome}"/></td>
        <td><c:out value="${utente.posizione}"/></td>
        <td><c:out value="${utente.telefono}"/></td>
        <td>
           <img src="imm/view.png"/>&nbsp;
           <a href="" id="${utente.idUtente}" class="view">Vedi</a>
           &nbsp;&nbsp;
           <img src="imm/mod.png"/>&nbsp;
           <a href="<c:url value="InfoUtente">
                        <c:param name="id" value="${utente.idUtente}"/>
                    </c:url>" class="mod">Modifica</a>
           &nbsp;&nbsp;
           <img src="imm/del.png"/>&nbsp;
           <a href="" class="del" name="<c:out value="${utente.nome} ${utente.cognome}"/>">Elimina</a>
        </td>
    </tr>
</c:forEach>

Note how the structure is much more readable. Also note that

• it’s   and not &nbsp
• you can’t have several elements with the same ID. This is invalid.
• <c:out> allows escaping special characters. So if any of the attributes contains a < or a > or a & for example, it won’t lead to invalid HTML (or worse: to an XSS attack)
• using <c:url> allows using absolute paths instead of relative paths without hard-coding the context path, and it URL-encodes the parameters.