Java Bindings

This article is part of the Query Portal. It shows how to call Java code from XQuery.

The Java Binding query feature is an extensibility mechanism which enables developers to directly access Java variables and execute code from XQuery. Java classes are identified by namespaces; the namespace URI must be of the form java:fully.qualified.ClassName.

The following example uses Java’s Math class and returns the cosine of an angle:

declare namespace math = "java:java.lang.Math";
math:cos(xs:double(0))

Please Note: To directly call a method it has to be set as static in your java code.

The next example writes 256 bytes to the file output.txt. To call the write method of the FileWriter class, you have to pass a class instance as first argument:

declare namespace fw = "java:java.io.FileWriter";
 
let $file := fw:new('output.txt')
return (
  for $i in 0 to 255
  return fw:write($file, xs:int($i)),
  fw:close($file)
)

Note that we recommend to use XQuery expressions and functions whenever possible, as Java code cannot be pre-compiled by BaseX, and will most probably be evaluated slower than pure XQuery code. Next, admin permissions are required to execute Java code.