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The following In the (side-effecting) example returns below, the number size of distinct values added to a Java hash setis returned. The boolean values that are returned by {{Code|set:add()}} will be are swallowed:
The In the following XQuery code invokes two Java methods. The first Java function retrieves , information from the static query contextis returned by the first function, and the second one throws a query exceptionis raised by the second function:
The following table lists the mappings of XQuery and Java typesare mapped as follows:
no edit summary
# 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:}}. See the following examples:
* <code><nowiki>http://basex.org/modules/meta-data</nowiki></code> → <code>org.basex.modules.MetaData</code>
* 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>·</code> ([http://www.fileformat.info/info/unicode/char/b7/index.htm ·]</code> (&#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"
| Function
| <code>Q{java.lang.Object}hash-code($object)</code>
| <code>[https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#hashCode() object.hashCode()]</code>
|- valign="top"
| Function with types
| <code>Q{java.lang.String}split·java.lang.String·int($string, ';', xs: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>
|}
</pre>
If the result of a Java call contains invalid XML characters, it will be rejected. The validity check can be disabled by setting the [[Options#CHECKSTRINGS{{Option|CHECKSTRINGS]] option }} to false. The following query writes In the example below, a file with a single {{Code|00-}} byteis written, which and this file will then be successfully read accessed by via Java functions:
<pre class="brush:xquery">
An alternative solution is to access Java code by ''importing'' classes as modules. A new instance of the addressed class will be created, which can then be referenced in the query body.
<pre class="brush:xquery">
</pre>
The advantages of this approach is the execution of imported classes is 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 fails if the addressed class has no default constructor, but at least one constructor with arguments.
=Integration=
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.
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 closing of opened connections or resources in a module. Its {{Code|close()}} method will be called after a query the XQuery expression has been fully evaluated.
==Annotations==
* Java code is treated as ''focus-independent''. If a function accesses the current context item, position or size, it should be annotated as {{Code|@FocusDependent}}
<pre class="brush:xquery">
context:user()
},
try { element to-int { try { context:to-int('abc') }} catch basex:error { catch * element error { 'Error in line', $err:line-number description }
}
</pre>
/**
* Returns the name of the logged in user.
* @return userstring
*/
@Requires(Permission.NONE)
/**
* Converts the specified string to an integer.
* @param value string representationto be converted * @return resulting integer
* @throws QueryException query exception
*/
return Integer.parseInt(value);
} catch(NumberFormatException ex) {
throw new QueryException(ex.getMessage()"Integer conversion failed: " + value);
}
}
@Override
public void close() {
// see description abovedefined in QueryResource interface, will be called after query evaluation
}
}
<pre class="brush:xml">
<user>admin</admin>
<to-interror>Error in line 6Integer conversion failed: abc</to-interror>
</pre>
==Data Types==
{| class="wikitable"
# If the resulting string ends with a slash, the {{Code|index}} string is appended.
If the resulting path has no file suffix, it may point to either an XQuery module or a Java archive.The following examples show some rewritings:
* {{Code|<nowiki>http://basex.org/modules/hello/World</nowiki>}} → {{Code|org/basex/modules/hello/World}}
