Hi Andreas,

Unfortunately, it’s a pretty sophisticated challenge to define a comprehensive and unambiguous mapping for Java and XQuery types.

As there is no ideal counterpart in XQuery for char (xs:unsignedShort may be closest, but it’s normally used to represent numbers, not characters), both char and String is currently mapped to xs:string, and xs:string is converted back to a String instance. In your example, it looks as if xs:string could also be converted to a char value, but as a constructor or Java function might also expect a generic Object as argument, there is no chance to define a static mapping for such types.

In some cases, such as for char, we might be successful to detect better mappings at runtime – but as a general guideline, I tend to recommend users to write some additional Java/XQuery wrapper code and use it as entry point for XQuery function calls. If required, the result can also be packaged and (un)installed in the BaseX repository, as shown in [1].

Hope this helps, Christian

[1] https://docs.basex.org/wiki/Repository#Combined

On Thu, Apr 15, 2021 at 4:19 AM Andreas Mixich mixich.andreas@gmail.com wrote:

Hi

I can successfully create an object instance of https://www.stringtemplate.org/api/index.html when using the parameter-less default init:

declare namespace ST = 'java:org.stringtemplate.v4.ST';
let $template := "Hello <who>"
let $stInstance := ST:new($template)
let $call := ST:add($stInstance, "who", "World!")
return ST:render($stInstance)

Template delimiters can be changed by supplying left and right delimiters (type char) upon init (by default ST4 uses < and > as template delimiters). The signature for this would be:

ST(java.lang.String template, char delimiterStartChar, char

delimiterStopChar)

Documentation is at https://www.stringtemplate.org/api/org/stringtemplate/v4/ST.html#ST-java.lan...

So I defined the types at invocation, but executing following code I get an error.

declare namespace ST = 'java:org.stringtemplate.v4.ST';
let $template := "Hello $who$"
let $stInstance := ST:new·java.lang.String·char·char($template,"$","$")
let $call := ST:add($stInstance, "who", "World!")
return ST:render($stInstance)

The error is:

[XPTY0004] java.lang.IllegalArgumentException: argument type mismatch.
Caused by: org.stringtemplate.v4.ST(String, String, String).

The query plan of this unsuccessfull invocation is:

<QueryPlan compiled="true" updating="false">
  <GFLWOR type="item()*">
    <Let type="item()*" name="$stInstance" id="1">
      <DynJavaConstr name="org.stringtemplate.v4.ST" type="item()*">
        <Str type="xs:string" size="1">Hello $who$</Str>
        <Str type="xs:string" size="1">$</Str>
        <Str type="xs:string" size="1">$</Str>
      </DynJavaConstr>
    </Let>
    <List type="item()*">
      <ProfVoid name="prof:void" type="empty-sequence()" size="0">
        <DynJavaFunc name="org.stringtemplate.v4.ST:add" type="item()*">
          <VarRef type="item()*" name="$stInstance" id="1"/>
          <Str type="xs:string" size="1">who</Str>
          <Str type="xs:string" size="1">World!</Str>
        </DynJavaFunc>
      </ProfVoid>
      <DynJavaFunc name="org.stringtemplate.v4.ST:render"

type="item()*"> <VarRef type="item()*" name="$stInstance" id="1"/> </DynJavaFunc> </List> </GFLWOR> </QueryPlan>

I can see no deviation from https://docs.basex.org/wiki/Java_Bindings#Functions_and_Variables in my code. What am I doing wrong? Thanks.

-- Goody Bye, Minden jót, Mit freundlichen Grüßen, Andreas Mixich