[jira] Updated: (STR-2330) [taglib] Struts tags must check attribute values using isEmpty(), not against nulls

["Paul Benedict (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/struts/browse/STR-2330?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paul Benedict updated STR-2330:
-------------------------------

    Fix Version/s: Future
         Assignee:     (was: Struts Developers)

> [taglib] Struts tags must check attribute values using isEmpty(), not against nulls
> -----------------------------------------------------------------------------------
>
>                 Key: STR-2330
>                 URL: https://issues.apache.org/struts/browse/STR-2330
>             Project: Struts 1
>          Issue Type: Improvement
>          Components: Taglibs
>    Affects Versions: 1.2.6 Beta
>         Environment: Operating System: All
> Platform: PC
>            Reporter: Firepica
>            Priority: Minor
>             Fix For: Future
>
>         Attachments: normalize-in-setter.patch.txt
>
>
> There is an architectural problem with Struts tags used in tag files.
> As you know, in every Struts tag decision on whether attribute has a value set
> is based on comparison to null. Example: 
>         if (accesskey != null) {
>             results.append(" accesskey=\"");
>             results.append(accesskey);
>             results.append("\"");
>         }
> Where "accesskey" is an attribute of html:select tag.
> The following example shows why usage of Struts tags is substantially restricted
> in tag files because of that feature.
> The following "icon" tag renders a hyperlink based on "type" attribute (say,
> "remove" or "add"), displaying corresponding icon. It has 2 mutually exclusive
> attributes: "action" and "href" and one optional attribute "onclick".
> === icon.tagx begins ===
> <?xml version="1.0" encoding="UTF-8"?>
> <jsp:root xmlns:jsp="http://java.sun.com/JSP/Page"
> xmlns:html="http://struts.apache.org/tags-html" version="2.0" >
>   <jsp:directive.tag body-content="empty"/>
>   <jsp:directive.attribute name="type" required="true" rtexprvalue="true" />
>   <jsp:directive.attribute name="action" required="false" rtexprvalue="true" />
>   <jsp:directive.attribute name="href" required="false" rtexprvalue="true" />
>   <jsp:directive.attribute name="onclick" required="false" rtexprvalue="true" />
>   <html:link action="${action}">
>       <html:img page="images/${type}.gif" border="0"/>
>   </html:link>
> </jsp:root>
> === icon.tagx ends ===
> Question here is how should we invoke html:link tag based on value of the
> attributes? Ok, we could use <c:choose> like:
> <c:choose>
>   <c:if test="${not empty action}">
>     <!-- use value of action atribute -->
>     <html:link action="${action}">
>        <html:img page="images/${type}.gif" border="0"/>
>     </html:link>
>   </c:if>
>   <c:otherwise>
>     <!-- use value of href atribute -->
>     <html:link href="${href}">
>        <html:img page="images/${type}.gif" border="0"/>
>     </html:link>
>   </c:otherwise>
> </c:choose>
> this would be correct if we had only "action" and "href", but we also have
> "onclick". That means, that in every if/otherwise section we need to add same
> check for presence of "onclick" attribute. If we had not 3 but 10 attributes,
> then total number of <if> statements would be 2^9 which is far beyond reasonable
> limits.
> The most obvious and conscious solution would be to use the following
> construction instead:
>   <html:link action="${action}" href="${href}" onclick="${onclick}">
>       <html:img page="images/${type}.gif" border="0"/>
>   </html:link>
> So if icon tag is invoked via <my:icon action="/Action" type="add"/> then "href"
> and "onclick" attributes would be nulls and, say, href="${href}" will not change
> the default value (null) of the html:link "href" property (call setHref(null);
> on tag handler). But this is not true because EL evaluates nulls into empty
> strings, so what happens is that html:link tag receives empty (not null) "href"
> and "onclick" properties which produces an error message (setHref(""); on tag
> handler).
> The solution would be to make Struts to check attributes for emptiness (like
> StringUtils.isEmpty(), i.e. == null or ""), not just for nulls. Then it would work.
> Example:
>         if (StringUtils.isNotEmpty(accesskey)) {
>             results.append(" accesskey=\"");
>             results.append(accesskey);
>             results.append("\"");
>         }
> Where StringUtils is from jakarta commons lang package.

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