Freemarker converting a hash to String

Question

To iterate over hashmaps one can use the hash built-in to access values and keys of a Map. Now I want to operate on the key, ie to upperCase the key (which is a string):

<#assign keys = formats?keys>
<#list keys as key>
  ${key.toUpperCase()} = ${formats[key].getFileName()}
</#list>

But I get the error

For "." left-hand operand: Expected a hash, but this has evaluated to a string (wrapper: f.t.SimpleScalar):
==> key  [in template "src/main/resources/test.ftl" at line 41, column 69]

----
FTL stack trace ("~" means nesting-related):
- Failed at: ${key.toString().toUpperCase()}  [in template "src/main/resources/test.ftl" at line 41, column 67]
----

Any hint how to get the key (which is lowercase) to upper case in the template? or how to convert the hash to a String?

Answer 1

In FreeMarker the Java API of many basic classes (such as String , Number , List , etc.) is hidden. Instead of their API-s, you are supposed to use so called "built-ins", like in this case: key?upper_case . (See also: http://freemarker.org/docs/ref_builtins.html )