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{{Mark|Updated with Version 9.6:}}
* Java objects are now wrapped into function items.
* New option {{Option|WRAPJAVA}}.
* Mapping rules were refined. The most important changes:
** {{Code|array(*)}} type added.
** {{Code|xs:integer}} values are converted to {{Code|long}} values.
** {{Code|xs:unsignedShort}} values are converted to {{Code|char}} values.
→Functions and Variables
Please bear in mind that the execution of Java code may cause side effects that conflict with the functional nature of XQuery, or may introduce new security risks to your project.
{{Mark|Updated with Version 9.6:}}
* With the middle dot notation, three adjacent dots can be used to specify array types.
* The path to the standard package {{Code|java.lang.}} can now be omitted.
* Java objects are now wrapped into function items.
* Results of constructor calls are always returned as function item.
* A new option {{Option|WRAPJAVA}} was added to control how Java values are converted to XQuery.
* The Mapping rules were refined and unified. The most important changes:
** {{Code|array(*)}} type added.
** {{Code|xs:integer}} values are converted to {{Code|long}} values.
** {{Code|xs:unsignedShort}} values are converted to {{Code|char}} values.
* All error messages were revised and improved.
=Identification=
# The last path segment of the URI is capitalized and rewritten to [https://en.wikipedia.org/wiki/CamelCase CamelCase].
The normalization steps are skipped if the URI is prefixed with {{Code|java:}}. The path to the standard package {{Code|java.lang.}} can be omitted:
* <code><nowiki>http://basex.org/modules/meta-data</nowiki></code> → <code>org.basex.modules.MetaData</code>
* <code>java:java.lang.String</code> → <code>java.lang.String</code>
* <code>StringBuilder</code> → <code>java.lang.StringBuilder</code>
==Functions and Variables==
Java constructors, functions and variables can be referenced and evaluated by the existing XQuery function syntax:
* The namespace of the function name identifies the Java class.
* The local part of the name, which is rewritten to camel case, identifies a variable or function of that class.
* The middle dot character <code>[https://www.fileformat.info/info/unicode/char/b7/index.htm ·]</code> (<code>&#xB7;</code>, a valid character in XQuery names, but not in Java) can be used to append exact Java parameter types to the function name. Class types must be referenced by their full path. Since {{Version|9.6}}, three Three adjacent dots can be used to address an array argument.
{| class="wikitable"
|- valign="top"
| Variable
| <code>Q{java.lang.Integer}MIN_VALUE()</code>
| <code>Integer.MIN_VALUE</code>
|- valign="top"
| Function
| <code>Q{java.lang.Object}hash-code($object)</code>
| <code>object.hashCode()</code>
|- valign="top"
| Function with argument
| <code>Q{java.lang.String}split·java.lang.String·intsplit·String·int($string, ';', xs:int(3))</code>
| <code>string.split(";", 3)</code>
|- valign="top"
| Function Constructor with array argument| <code>Q{java.lang.String}new·byte...(xs:hexBinary('414243'))</code>
| <code>new String(new byte[] { 41, 42, 43 })</code>
|}
=Namespace Declarations=
In the following example, Java’s the Java {{Code|Math}} class is referenced. When executed, the query returns the cosine of an angle by calling the static method {{Code|cos()}}, and the value of π by addressing the static variable via {{Code|PI()}}:
<syntaxhighlight lang="xquery">
</syntaxhighlight>
With the [[XQuery 3.0#Expanded QNames|Expanded QName]] notation of XQuery 3.0,the namespace can directly be embedded in the function call:
<syntaxhighlight lang="xquery">
<syntaxhighlight lang="xquery">
declare namespace fw = "'java:java.io.FileWriter"';
let $file := fw:new('output.txt')
return (
<syntaxhighlight lang="xquery">
declare namespace br = 'java:java.io.BufferedReader';declare namespace fr = 'java:java.io.FileReader';
declare option db:checkstrings 'false';
==Data Types==
===Conversion to Java===
===Conversion to XQuery===
By default, Java values with the most common types (as shown in the second and third column of the table) are converted to XQuery values. All other values are returned as ''Java items'', which are function items with an embedded a wrapped Java value. The results of constructor calls will are always be returned as Java items.
The conversion of the embedded wrapped Java value to XQuery is enforced by invoking the function item: Values in {{Code|Iterator}} and {{Code|Iterable}} instances (Lists, Sets and Collections) are converted to items, and maps are converted to XQuery maps:
<syntaxhighlight lang="xquery">
</syntaxhighlight>
If no conversion is defined, the value a string is returned, which is returned by resulting from the object’s {{Code|toString()}} methodof the object. This function method is also called if is the string repesentation representation of a Java item is requested:
<syntaxhighlight lang="xquery">
|- valign="top"
| {{Code|some}}
| The default: The Java values of the most common types are converted, others are wrapped into Java items.
|- valign="top"
| {{Code|none}}
| The All Java values are converted. If no conversion is enforceddefined, a string is returned, and no Java values will be wrappedresulting from the {{Code|toString()}} method.
|- valign="top"
| {{Code|all}}
| All Java values are wrapped into Java items (excluding those inheriting the internal type {{Code|org.basex.query.value.Value}}) are returned as Java items. This is helpful if Java function calls are chained, and if no intermediate conversion is required or desired.
|- valign="top"
| {{Code|instance}}
| The result If the method of a class instance was called, the Java call will be value is ignored, and a supplied class the instance (if there is any) wrapped into a Java item. Otherwise, the Java value is returned instead.
|- valign="top"
| {{Code|void}}
| The result of a Java call will be values are ignored, and an empty sequence is returned instead.
|}
(# db:wrapjava all #) {
Q{java.lang.Character}toChars(xs:int(33))
=> Q{java.nio.CharBuffer}wrap()
}
<syntaxhighlight lang="xquery">
(: Without Thanks to the pragma, set:add would return a boolean, indicating if a new entry was added the function calls can be chained :)
declare namespace set = 'java:java.util.HashSet';
