title: Invalid property in <set>: "null" in new ArrayList at JSP
body: <p>I have got a Set of objects. I need to iterate it and add too my new ArrayList that I created at JSP page. But I have got an error</p>
  
  <blockquote>
    <p>javax.servlet.jsp.JspTagException: Invalid property in &lt;set&gt;:  "null"</p>
  </blockquote>
  
  <p>Here is my code</p>
  
  <pre><code>&lt;jsp:useBean id="idList" class="java.util.ArrayList"/&gt;
                          &lt;c:forEach items="${car.tape.idSet}" var="item"&gt;
                              &lt;c:set target="${idList}" value="${item.id}"/&gt;
                          &lt;/c:forEach&gt;
                          &lt;aui:input class="form-check" checked="${idList.contains(1)?'true':''}" inlineLabel="right"
                                     name="name1"
                                     type="checkbox" value="1"
                                     label="Name1"/&gt;
                          &lt;aui:input class="form-check" checked="${idList.contains(2)?'true':''}" inlineLabel="right"
                                     name="name2" type="checkbox" value="2"
                                     label="name2"/&gt;
  </code></pre>