if statement - Tapestry use Java expression into <t:if> component -

i'm beginner in tapestry , wondering if possible use java expression test component

i've been trying way it's not working

<t:loop source="pathologies" value="valuefromcda">   <t:if test="valuefromcda instanceof string"> 

the error following 1 :

could not convert 'valuefromcda instanceof strucdoclist' component parameter binding: error parsing property expression 'valuefromcda instanceof strucdoclist': line 1:0 no viable alternative @ input 'valuefromcda' 

valuefromcda , pathologies properties in controller:

@property private object valuefromcda;  @property private list<object> pathologies; 

thank answers ! have afternoon ;)

the "test" parameter expects property-binding default. tapestry property "valuefromcda instanceof string" or pojo-like getter ("isxxx" boolean return types ok) "getvaluefromcda instanceof string", can’t find because there’s no such property or method in page/component.

instead should write 1 this:

tml

<t:if test="valueinstanceofstring"> 

component

public boolean isvalueinstanceofstring() {     return valuefromcda instanceof string; }