Re: [OT] tomcat 7, null tag attributes

[Christopher Schultz <ch...@christopherschultz.net>]

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Naga,

Please don't hijack threads. If you wish to ask a question, please
post a new message (don't REPLY to an old one) to the list.

Thanks,
- -chris

On 6/13/17 1:00 PM, Naga Ramesh wrote:
> All,
> 
> As of now we are using the below parameters for tomcat8 version on 
> production environment, please recheck and confirm, these are fine 
> or anything need to add or change.
> 
> Please confirm me.
> 
> export CATALINA_OPTS="$CATALINA_OPTS -Xms1024m" export 
> CATALINA_OPTS="$CATALINA_OPTS -Xmx8192m" export 
> CATALINA_OPTS="$CATALINA_OPTS -server" export
> JAVA_OPTS="$JAVA_OPTS -Xverify:none" export
> CATALINA_OPTS="$CATALINA_OPTS -XX:+TieredCompilation
> -XX:+AggressiveOpts -XX:+UseG1GC -XX:SurvivorRatio=1 -XX:NewRatio=2
> -XX:MaxTenuringThreshold=15 -XX:+UseTLAB -XX:G1HeapRegionSize=32m
> -XX:-UseAdaptiveSizePolicy -XX:MaxMetaspaceSize=512m
> -XX:-UseSplitVerifier "
> 
> 
> 
> -----Original Message----- From: Chris Cheshire 
> [mailto:yahoonomas@gmail.com] Sent: Tuesday, June 13, 2017 7:58 PM
>  To: Tomcat Users List Subject: Re: tomcat 7, null tag attributes
> 
> On Tue, Jun 6, 2017 at 2:29 PM, Mark Thomas <ma...@apache.org> 
> wrote:
> 
>> On 31/05/17 23:31, Chris Cheshire wrote:
>>> I am using tomcat 7 on CentOS 7 and I need to pass a null
>>> value to tag attributes of type Long/Integer/Float, however it
>>> is *always* coerced to zero.
>>> 
>>> <%@attribute name="parentId" required="true" rtexprvalue="true"
>>> type="java.lang.Long" %>
>>> 
>>> Changing required to false does nothing. I tried setting the 
>>> system property org.apache.el.parser.COERCE_TO_ZERO to false
>>> in tomcat.conf (-Dorg.apache.el.parser.COERCE_TO_ZERO=false
>>> with my other JAVA_OPTS)
>> but
>>> this does nothing.
>> 
>> As expected. That system property only affects evaluation of EL 
>> expressions.
>> 
>> 
> But isn't <tag:thing val="${val}" /> evaluation of an EL 
> expression? Why is it treated differently than the evaluation of 
> ${val} when it is used in the same scope as it is 
> declared/assigned?
> 
> For instance, this tests in a JSP :
> 
> <core:set var="l" value="${null}" /> <core:if test="${l eq 
> null}"><p>l is null</p></core:if>
> 
> will succeed.
> 
> The moment I pass l into a tag and try the exact same evaluation 
> inside, it fails because it has been coerced to 0.
> 
> 
>> 
>>> How do I pass a null Long/Float/Integer as a tag attribute and 
>>> have it
>> kept
>>> as null and not turned into an incorrect value?
>> 
>> Use parentId="<%=null%>" rather than parentId=""
>> 
>> Ugly, but it does the job. Scriplets aren't coerced.
>> 
>> Mark
>> 
> 
> 
> I can't use that because I'm not trying to pass the value null, 
> rather a variable that possibly equates to null.
> 
> Also, if I have a custom bean
> 
> public class Foo { private Long val;
> 
> public Foo() { } public Long getVal() { return val; } public void 
> setVal(Long val) { this.val = val; } }
> 
> and I pass an instance of Foo into a tag, then val stays as null.
> 
> It seems the only solutions are to use a sentinel value that 
> "shouldn't" get used (cringeworthy in its own right), or to wrap 
> everything in a custom bean (also extremely ugly).
> 
> I'm bewildered at why tomcat operates this way when it comes to 
> Numbers and Strings. Why is it insistent on coercion when null and 
> zero are absolutely not the same value.  If this is because of 
> autoboxing, then isn't that a bug? A long is not a Long, and when 
> tag attributes must be objects and not atomic types, shouldn't
> they be treated accordingly?
> 
> 
> Chris
> 
> 
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