在JSTL el表达式中转义引号时，为什么会出现JSP错误“属性未正确终止”？

Question

I have been developing on Mac for over 8 years and I wanted to give Windows 10 another chance. So I checked in all my projects into GitHub on the Mac and then synchronised the projects on my Windows 10 machine.

Once I ran the project in NetBeans and navigated to certain JSP pages, I received the following error...

18-May-2018 09:46:24.335 SEVERE [http-nio-8084-exec-27] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [jsp] in context with path [/Project] threw exception [/WEB-INF/tags/config.tag (line: 46, column: 34) attribute for " is not properly terminated] with root cause org.apache.jasper.JasperException: /WEB-INF/tags/config.tag (line: 46, column: 34) attribute for " is not properly terminated

On the line specified I have the following...

<c:when test="${storageType == \"boolean\"}">

And whilst I could change it to the following...

<c:when test="${storageType == 'boolean'}">

I have many places in my tags and JSP where I've escaped the quotation ("), I don't see why I have to change this. My project is working in production as-is, so I don't want to unnecessarily touch JSP / tag files.

On my Mac, which is using JDK 1.8.0_102 it works fine

On my Windows 10, which is using JDK 1.8.0_172 it is not working

I'm using NetBeans, with the forementioned JDKs.

Tomcat on Windows = 8.0.27.0

Tomcat on Mac = 8.0.23.0

UPDATE

This works..

<c:if test="${key == 'testing'}">
    <div>TESTING-A</div>
</c:if>

This does NOT work...

<c:if test="${key == \"testing\"}">
    <div>TESTING-A</div>
</c:if>

The latter causes the error at runtime

[/WEB-INF/tags/config.tag (line: 27, column: 12) attribute for " is not properly terminated] with root cause org.apache.jasper.JasperException: /WEB-INF/tags/config.tag (line: 27, column: 12) attribute for " is not properly terminated.

I note column 12 is the first quotation …

To be clear, escaping in the JSTL expression seems to be the root cause - but why is it not working on a newer Tomcat?

Answer 1

If your storageType variable really is a boolean, you can check it like so:

<c:if test="${storageType eq false}">

If however it's just a string with value 'false' you should do a string comparison:

<c:if test="${storageType eq 'false'}">

Considering your particular example, you could do something like this:

<c:when test="${storageType eq true || storageType eq false}">

or for string comparrison

<c:when test="${storageType eq 'true' || storageType eq 'false'}">

But you really should first perform the first checks to see if your variable really is a boolean type and not just a string.