Error on SimpleTemplateEngine embedded in Java: Could not instantiate custom Metaclass for class: java.util.ArrayList

Question

I have a app where my users input a HTML template with SimpleTemplateEngine notation, and execute this template with code above, in a Java Class:

new SimpleTemplateEngine().createTemplate(templateStr).make(map).toString()

and I obtain this error:

groovy.lang.GroovyRuntimeException: Could not instantiate custom Metaclass for class: java.util.ArrayList. Reason: java.lang.NoSuchMethodException: groovy.runtime.metaclass.java.util.ArrayListMetaClass.<init>(groovy.lang.MetaClass)

I observe that error occurrs in a loop in a java.util.ArrayLIst in a JPA Entity loaded by Hibernate:

<%for(int k=0; k< Registro[i].listUsers.size();k++){%>

HTML CODE

<%}%>

Anyone can help me? I no have more ideas about this error... Thanks!

Answer 1

I'm guessing that the part Registro[i] is for getting the value of a static property which name is held under the variable i (or at least that is what will happen) unless the getAt(String) method has been overloaded on Registro.

Either way I also guess that returns an object that has a listUsers property that should be at least a Collection.

Maybe the problem is with the initialization of said listUsers property.

Some Registro code could be used for better understanding.