Changes

{{Mark|Updated Please bear in mind that the execution of Java code may cause side effects that conflict with Version 8.4}}: A Java class is identified by a namespace URIthe functional nature of XQuery, or may introduce new security risks to your project. The original URI is rewritten as follows:

==Classes== A Java class is identified by a namespace URI. The original URI is rewritten as follows: # The [[#URI Rewriting|URI Rewriting]] steps are applied to the URI.# Slashes in the resulting URI are replaced with dots.# The last path segment of the URI is capitalized and rewritten to [https://en.wikipedia.org/wiki/CamelCase CamelCase]. The normalization steps can be are skipped by prefixing if the URI is prefixed with {{Code|java:}}. See the following examples:

Function names are ==Functions and Variables== Java 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 Java’s camel case notation, identifies a variable or function of that class.* The middle dot character <code>·</code> ([http://www.fileformat.info/info/unicode/char/b7/index.htm &amp;#xB7;], 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. {| class="wikitable"|- valign="top"! Type! XQuery! Java|- valign="top"| Variable| <code>Q{java.lang.Integer}MIN_VALUE()</code>| <code>[https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#MAX_VALUE Integer.MIN_VALUE]</code>|- valign="top"| Function| <code>Q{java.lang.Object}hash-code()</code>| <code>[https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#hashCode() object.hashCode()]</code>|- valign="top"| Function with types| <code>Q{java.lang.String}split·java.lang.String·int(';', 3)</code>| <code>[https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#split-java.lang.String-int- string.split(";", 3)]</code>|} As XQuery and Java have different type systems, XQuery arguments are converted to equivalent Java values, and the result of a Java function is converted back to an XQuery value (see [[#Data Types|Data Types]]).

* <code>get-contents($x as If a Java function is not found, XQuery values may need to be cast the target type. For example, if a Java function expects a primitive {{Code|int}} value, you will need to convert your XQuery integers to {{Code|xs:string)</code> → <code>getContents(String x)</code><br/> int}}.

Java classes can be declared via namespaces. The namespace can then be used to call static functions contained in that class. Variables are represented as function with 0 parameters. The In the following example uses , Java’s {{Code|Math}} class to return 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()}}:

The new With the [[XQuery 3.0#Expanded QNames|Expanded QName]] notation of XQuery 3.0,allows you to the namespace can directly specify a namespace URI instead of be embedded in the prefixfunction call:

The constructor of a class can be invoked by calling the virtualfunction {{Code|new()}}. Instance methods can then called bypassing on the resulting Java object as first argument. In the following example, 256 bytes are written to the file {{Code|output.txt}}.First, a new {{Code|FileWriter}} instance is created, and its {{Code|write()}}function is called in the next step:

Note that Java code cannot be pre-compiled, and will often as such be evaluated slower than optimizedXQuery code.

An alternative solution is to access Java code can also be integrated by ''importing'' classes as modules.A new instance of the addressed class is will be created, which can then be accessed referenced in the query body.

An The following (side-effecting) example (returns the number of distinct values added to a hash set. The boolean values returned by {{Code|set:add()}} are ignored)will be swallowed:

import module namespace set = "java:java.util.HashSet";let $loop prof:= void( set:addfor $s in ("checkone", "two"), set:add("whatone"), return set:add("happens"$s)),return set:size()

The advantages of this approach is that the execution of imported code classes is executed faster more efficient than the execution of instances that are created at runtime via {{Code|new()}}. A drawback is that no arguments can be passed on to the class constructor. As a consequence, the import only works fails if the addressed class provides a has no default constructor, but at least one constructor with no arguments.

=Context-AwarenessIntegration=

Java classes can be coupled even more closely to the BaseX core library.If a class inherits the abstract [https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/QueryModule.java QueryModule] class, the two variables [https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/QueryContext.java queryContext] and [https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/StaticContext.java staticContext] get available, which provide access to the global and static context of a query. Additionally The [https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/QueryResource.java QueryResource] interface can be implemented to enforce finalizing operations, such as the default closing of opened connections or resources in a module. Its {{Code|close()}} method will be called after a query has been fully evaluated. ==Annotations== The internal properties of functions can be changed assigned via annotations:

==Locking==

* UpdatesUpdated: Rewriting rules ;Version 8.2 * Added: [[#URI Rewriting|URI Rewriting]]: support for URNs

 * Added: [[Category:XQuery#Packaging|Packaging]], [[Category:API#URI Rewriting|URI Rewriting]]