Re: RFE: StringTemplate interpolation with custom function

[Jim Laskey]

I think I’m missing something. Why wouldn’t you just;

import java.lang.StringTemplate.Processor;

Processor<URL, RuntimeException> urlEncode = template -> 
URLEncoder.encode(template.interpolate(), UTF_8));

Processor<String, RuntimeException> CSV = template -> 
StringEscapeUtils.escapeCsv<https://commons.apache.org/proper/commons-lang/apidocs/src-html/org/apache/commons/lang3/StringEscapeUtils.html#line.768>(template.interpolate());


On Oct 26, 2023, at 4:47 PM, Rob Spoor <open...@icemanx.nl> wrote:

I've been reading up on string templates, and I think it's a very cool feature. 
However, writing a custom processor can be a lot of copy-paste work if you want 
STR but with some extra translation applied. For instance, if I'd want to have 
a URL encoding processor I would have to write everything from scratch.

I think it would be useful to overload interpolate (both static and non-static) 
with a custom Function<Object, String> as additional arguments. This would work 
like STR if that provided String::valueOf as function.

With this method, creating a URL encoding processor would be as simple as this:

   var urlEncode = template -> template.interpolate(o ->
           URLEncoder.encode(String.valueOf(o), UTF_8));

   var url = urlEncode."https://host/path/\{id}?param=\{value\}";;


Likewise, a processor backed by Apache Commons Text's StringEscapeUtils would 
now be just as simple:

   var CSV = template -> template.interpolate(o ->
           StringEscapeUtils.ESCAPE_CSV.translate(String.valueOf(o));

   var csv = CSV."""
           Header1, Header2, Header3
           "\{value1}", "\{value2}", "\{value3}"
           """;


If the JVM allows it, the existing interpolate method can even delegate to the 
new overload providing String::valueOf.