Checking if the object is new in JSTL

[shivang sarawagi]

I am working on a Spring project where there are two controllers

AddOwnerForm.java & EditOwnerForm.java. Both the forwarding the flow to form.jsp

AddOwnerForm passes a new Owner object to jsp whereas EditOwnerForm fetches the Owner object from the db then passes it to the jsp.

Below is the JSP code.

Form.jsp

<%@ include file="/WEB-INF/view/include.jsp" %>
<%@ include file="/WEB-INF/view/header.jsp" %>
<c:choose>
    <c:when test="${owner['new']}"><c:set var="method" value="post"/></c:when>
    <c:otherwise><c:set var="method" value="put"/></c:otherwise>
</c:choose>

<h2><c:if test="${owner['new']}">New </c:if>Owner:</h2>
<form:form modelAttribute="owner" method="${method}">
  <table>
     <tr>
       <th>
         First Name:
         <br/>
         <form:input path="firstName" size="30" maxlength="80"/>
       </th>
     </tr>
     <tr>
       <th>
         Last Name:
         <br/>
         <form:input path="lastName" size="30" maxlength="80"/>
       </th>
     </tr>
     <tr>
       <th>
         Address:
         <br/>
         <form:input path="address" size="30" maxlength="80"/>
       </th>
     </tr>
     <tr>
       <th>
         City:
         <br/>
         <form:input path="city" size="30" maxlength="80"/>
       </th>
     </tr>
     <tr>
       <th>
         Telephone:
         <br/>
         <form:input path="telephone" size="20" maxlength="20"/>
       </th>
     </tr>
     <tr>
       <td>
         <c:choose>
           <c:when test="${owner['new']}">
             <p class="submit"><input type="submit" value="Add Owner"/></p>
           </c:when>
           <c:otherwise>
             <p class="submit"><input type="submit" value="Update Owner"/></p>
           </c:otherwise>
         </c:choose>
       </td>
     </tr>
   </table>
</form:form>

<%@ include file="/WEB-INF/view/footer.jsp" %>

I don't understand this code snippet

<c:choose>
        <c:when test="${owner['new']}"><c:set var="method" value="post"/></c:when>
        <c:otherwise><c:set var="method" value="put"/></c:otherwise>
</c:choose>

A. How is the Jstl tag checking if the Owner object is new. Is "new" a keyword for JSTL?

B. Why are they using a PUT method for editing the owner why not POST?

[Albareto McKenzie]

A: ${object['property']} is one way to access a property on an object in Expression Language, same as ${object.property}

B: Please, have a look at the question and the answer here: http://stackoverflow.com/questions/630453/put-vs-post-in-rest

[Bear Bibeault]

The person who wrote this expression: test="${owner['new']}" needs to be chastised.

While it's technically correct, the long form to reference properties should not be used with a literal string in this way simply because it is unconventional, unexpected, and confusing. The OP's question reflects that. The expression should have been written as: test="${owner.new}"

Not following conventions is a sure way to make your code look like it was written by a novice.

Then it becomes much clearer that "new" is not some magic JSTL property, it's simply a property of the owner bean.