"Steve O'Hara" <[EMAIL PROTECTED]> writes:
>A while back I chastised someone for not using proper String comparison
>operators in their templates. I looked in the Velocity code and sure
>enough "==" operators are translated into equals. So I was looking a bit
>stupid.
>Somebody challenged me to come up with a situation where the equality
>"==" operator doesn't work with Strings.
>Well, finally, I've just found an example in my code;
> #if ($SummarySortField==$Field.getUdmFieldName())
> #if ($SummarySortField==${Field.getUdmFieldName()})
> #if ($SummarySortField.equalsIgnoreCase($Field.getUdmFieldName()))
>I thought perhaps I was going mad before when I raised this and plenty
>of people on this list questioned me, but can anyone explain this?
equalsIngoreCase != equals.
In Java, equals != ==
Look at this:
public class Test {
public static void main(String [] argv) throws Exception {
String s1 = "foo";
String s2 = "foobar".substring(0,3);
System.out.println(s1);
System.out.println(s2);
System.out.println(s1 == s2);
System.out.println(s1.equals(s2));
}
}
outputs
foo
foo
false
true
However, in Velocity:
--- cut ---
import java.io.OutputStreamWriter;
import org.apache.commons.lang.ObjectUtils;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
public class Demo {
public static void main(String[] args) {
try {
Velocity.init();
VelocityContext vc = new VelocityContext();
String s1 = "foo";
String s2 = "foobar".substring(0,3);
vc.put("s1", s1);
vc.put("s2", s2);
vc.put("s1info", ObjectUtils.appendIdentityToString(null,
s1).toString());
vc.put("s2info", ObjectUtils.appendIdentityToString(null,
s2).toString());
Template template = Velocity.getTemplate("DemoTemplate.vm");
OutputStreamWriter osw = new OutputStreamWriter(System.out);
template.merge(vc, osw);
osw.flush();
osw.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
--- cut ---
String1: ${s1}, Type is $s1.Class.Name
String2: ${s2}, Type is $s2.Class.Name
String1 Info: ${s1info}
String2 Info: ${s2info}
Equals:
#if ($s1.equals($s2))
True
#else
False
#end
Compare:
#if ($s1 == $s2)
True
#else
False
#end
--- cut ---
produces:
String1: foo, Type is java.lang.String
String2: foo, Type is java.lang.String
String1 Info: [EMAIL PROTECTED]
String2 Info: [EMAIL PROTECTED]
Equals:
True
Compare:
True
So Velocity == is not the same as Java == for Strings. It is the same
as equals().
Best regards
Henning
--
Dipl.-Inf. (Univ.) Henning P. Schmiedehausen INTERMETA GmbH
[EMAIL PROTECTED] +49 9131 50 654 0 http://www.intermeta.de/
RedHat Certified Engineer -- Jakarta Turbine Development -- hero for hire
Linux, Java, perl, Solaris -- Consulting, Training, Development
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