StringTemplate list of attributes defined for a given template

Question

I am getting started with StringTemplate 4 and I am trying to create a template from a simple string stored in a database. I use something like this:

STGroup group = new STGroupString(null, someTemplateString, '$', '$');
ST st = group.getInstanceOf(someTemplateName);
st.add(someAttribute, someValue);

Now everything works fine if I define all or less than the attribute defined for the template someTemplateName. Now if I try to add an attribute that doesn't exist, I get the following exception:

no such attribute: fake
java.lang.IllegalArgumentException: no such attribute: fake
  ...

which makes sense. However, it seems like there's no way for me to know beforehand which attributes are defined for the template someTemplateName. I was expecting to find something like:

bool isDef = st.isDefined(someAttribute);

but there's no such method. Am I correct? Is there any way around this?

Nial

Answer 1

You can use st.impl.formalArguments to access the Map<String, FormalArgument> where the arguments are defined. Note that for some templates this field will be null.

Stillman

st.impl.formalArguments only gives you the arguments which you define on the template. It does not give you the names of the attributes used. – Barthol

Answer 2

The documentation for CompiledST states tokens is only for debug. Not sure what that means.

ST template = new ST("Hello <username>, how are you? Using <if(condition)>expression<endif> in condition works, and repeating <username> is not a problem.");
Set<String> expressions = new HashSet<String>();
TokenStream tokens = template.impl.tokens;
for (int i = 0; i < tokens.range(); i++) {
    Token token = tokens.get(i);
    if (token.getType() == STLexer.ID) {
        expressions.add(token.getText());
    }
}

Gives you the Strings username and condition.

Barthol