Struts 2 s:select tag dynamic id

问题

I have multiple fields of various types in a JSP page and one button. These fields are generated based on the info got from a metadata table that I have created.

Since I don't know how many and what type of fields are present, I am giving dynamic id's to them. I am using Struts 2 tags in my JSP.

The issue is with the <s:select> tag: when I give scriplet within the id attribute, it displays the following error :

org.apache.jasper.JasperException: /success.jsp(83,12) quote symbol expected

<s:if test="%{#masterColDO.controlType=='dropdown'}">
    <s:select styleClass="login-textbox" 
                   style="width:130px"  
                    list="#masterColDO.validation"     
                    name="chngdColumnValues" 
                      id=<%="columnId" + count%> />
</s:if> 
<s:else>
    <input type=<s:property value="#masterColDO.controlType" /> 
          class="login-textbox " 
           name="chngdColumnValues" 
             id=<%="columnId" + count%> />
</s:else>

Javascript is as follows:

var addUpdateBtnId = document.getElementById('addUpdateBtnId');
addUpdateBtnId.value='Update';
addUpdateBtnId.onclick = function() {
    onClickUpdateBtn(rowIndex);
};
var selectedUpdateRow = xmlhttp.responseText.split(",");
for(var i = 0; i < selectedUpdateRow.length; i++){
    var columnElementId = "columnId"+i;
    document.getElementById(columnElementId).value = selectedUpdateRow[i];
}
document.getElementById("columnId"+(primaryKeyPos-1)).readOnly = true;

回答1:

Scriptlets are the old way of doing things, you should avoid writing Java code in JSP's at all;
Struts2 helps you achieving the same goals using its tags and OGNL only.

The <input /> part is working because you are injecting a scriptlet inside an HTML tag, that is allowed.

The <s:select /> part is not working because you are injecting a scriptlet inside an Struts2 tag, that is not allowed.

To make it work, you should use #attr syntax in OGNL to access the Java variables declared in Scriptlets and pushed by you in the Page Context, like this (completely untested):

<%
    for (int counter=0;counter<myList.size();counter++) {
       // pushing it into the pageContext
       pageContext.setAttribute("counter",counter);
%>
        <s:select cssClass="login-textbox" 
                  cssStyle="width:130px" 
                      list="#masterColDO.validation" 
                      name="chngdColumnValues"      
                        id="%{'columnId' + #attr['counter']}" />
<%    
    }
%>

However, even if it's technically possible, it is discouraged. You should use the pure Struts2 way for that, that would be the following:

<s:iterator value="myList" status="ctr">
    <s:select cssClass="login-textbox" 
              cssStyle="width:130px" 
                  list="#masterColDO.validation" 
                  name="chngdColumnValues" 
                    id="%{'columnId' + #ctr.index}" />
</s:iterator>

P.S: Struts tags doesn't have any styleClass attribute; you can use cssClass and/or cssStyle;
And, if controlType is a String, you should use .equals instead of ==: <s:if test="%{#masterColDO.controlType.equals('dropdown')}">.