[[XQuery-XQuery]]
XQuery
~~~~~~

Camel supports http://www.w3.org/TR/xquery/[XQuery] to allow an
link:expression.html[Expression] or link:predicate.html[Predicate] to be
used in the link:dsl.html[DSL] or link:xml-configuration.html[Xml
Configuration]. For example you could use XQuery to create an
link:predicate.html[Predicate] in a link:message-filter.html[Message
Filter] or as an link:expression.html[Expression] for a
link:recipient-list.html[Recipient List].

[[XQuery-Options]]
XQuery Language options
^^^^^^^^^^^^^^^^^^^^^^^

// language options: START
The XQuery language supports 3 options which are listed below.



{% raw %}
[width="100%",cols="2,1m,1m,6",options="header"]
|=======================================================================
| Name | Default | Java Type | Description
| type |  | String | Sets the class name of the result type (type from output) The default result type is NodeSet
| headerName |  | String | Name of header to use as input instead of the message body
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|=======================================================================
{% endraw %}
// language options: END

[[XQuery-Examples]]
Examples
^^^^^^^^

[source,java]
---------------------------
from("queue:foo").filter().
  xquery("//foo").
  to("queue:bar")
---------------------------

You can also use functions inside your query, in which case you need an
explicit type conversion (or you will get a org.w3c.dom.DOMException:
HIERARCHY_REQUEST_ERR) by passing the Class as a second argument to the
*xquery()* method.

[source,java]
-----------------------------------------------------------------------------
from("direct:start").
  recipientList().xquery("concat('mock:foo.', /person/@city)", String.class);
-----------------------------------------------------------------------------

[[XQuery-Variables]]
Variables
^^^^^^^^^

The IN message body will be set as the `contextItem`. Besides this these
Variables is also added as parameters:

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Variable |Type |Description

|exchange |Exchange |The current Exchange

|in.body |Object |The In message's body

|out.body |Object |The OUT message's body (if any)

|in.headers.* |Object |You can access the value of exchange.in.headers with key *foo* by using
the variable which name is in.headers.foo

|out.headers.* |Object |You can access the value of exchange.out.headers with key *foo* by using
the variable which name is out.headers.foo variable

|*key name* |Object |Any exchange.properties and exchange.in.headers and any additional
parameters set using `setParameters(Map)`. These parameters is added
with they own key name, for instance if there is an IN header with the
key name *foo* then its added as *foo*.
|=======================================================================

[[XQuery-UsingXMLconfiguration]]
Using XML configuration
^^^^^^^^^^^^^^^^^^^^^^^

If you prefer to configure your routes in your link:spring.html[Spring]
XML file then you can use XPath expressions as follows

[source,xml]
---------------------------------------------------------------------------------------------------------------
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:foo="http://example.com/person"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">

  <camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
    <route>
      <from uri="activemq:MyQueue"/>
      <filter>
        <xquery>/foo:person[@name='James']</xquery>
        <to uri="mqseries:SomeOtherQueue"/>
      </filter>
    </route>
  </camelContext>
</beans>
---------------------------------------------------------------------------------------------------------------

Notice how we can reuse the namespace prefixes, *foo* in this case, in
the XPath expression for easier namespace based XQuery expressions!

When you use functions in your XQuery expression you need an explicit
type conversion which is done in the xml configuration via the *@type*
attribute:

[source,xml]
-------------------------------------------------------------------------------
    <xquery type="java.lang.String">concat('mock:foo.', /person/@city)</xquery>
-------------------------------------------------------------------------------

[[XQuery-UsingXQueryastransformation]]
Using XQuery as transformation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

We can do a message translation using transform or setBody in the route,
as shown below:

[source,java]
----------------------------------------
from("direct:start").
   transform().xquery("/people/person");
----------------------------------------

Notice that xquery will use DOMResult by default, so if we want to grab
the value of the person node, using text() we need to tell xquery to use
String as result type, as shown:

[source,java]
-------------------------------------------------------------
from("direct:start").
   transform().xquery("/people/person/text()", String.class);
-------------------------------------------------------------

 

[[XQuery-UsingXQueryasanendpoint]]
Using XQuery as an endpoint
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Sometimes an XQuery expression can be quite large; it can essentally be
used for link:templating.html[Templating]. So you may want to use an
link:xquery-endpoint.html[XQuery Endpoint] so you can route using XQuery
templates.

The following example shows how to take a message of an ActiveMQ queue
(MyQueue) and transform it using XQuery and send it to MQSeries.

[source,java]
-------------------------------------------------------------------------
  <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
      <from uri="activemq:MyQueue"/>
      <to uri="xquery:com/acme/someTransform.xquery"/>
      <to uri="mqseries:SomeOtherQueue"/>
    </route>
  </camelContext>
-------------------------------------------------------------------------

[[XQuery-Examples.1]]
Examples
^^^^^^^^

Here is a simple
http://svn.apache.org/repos/asf/camel/trunk/components/camel-saxon/src/test/java/org/apache/camel/builder/saxon/XQueryFilterTest.java[example]
using an XQuery expression as a predicate in a
link:message-filter.html[Message Filter]

This
http://svn.apache.org/repos/asf/camel/trunk/components/camel-saxon/src/test/java/org/apache/camel/builder/saxon/XQueryWithNamespacesFilterTest.java[example]
uses XQuery with namespaces as a predicate in a
link:message-filter.html[Message Filter]

[[XQuery-LearningXQuery]]
Learning XQuery
^^^^^^^^^^^^^^^

XQuery is a very powerful language for querying, searching, sorting and
returning XML. For help learning XQuery try these tutorials

* Mike Kay's http://www.stylusstudio.com/xquery_primer.html[XQuery
Primer]
* the W3Schools http://www.w3schools.com/xquery/default.asp[XQuery
Tutorial]

You might also find the http://www.w3.org/TR/xpath-functions/[XQuery
function reference] useful

[[XQuery-Loadingscriptfromexternalresource]]
Loading script from external resource
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

*Available as of Camel 2.11*

You can externalize the script and have Camel load it from a resource
such as `"classpath:"`, `"file:"`, or `"http:"`. +
 This is done using the following syntax: `"resource:scheme:location"`,
eg to refer to a file on the classpath you can do:

[source,java]
------------------------------------------------------------------------------
.setHeader("myHeader").xquery("resource:classpath:myxquery.txt", String.class)
------------------------------------------------------------------------------

[[XQuery-Dependencies]]
Dependencies
^^^^^^^^^^^^

To use XQuery in your camel routes you need to add the a dependency on
*camel-saxon* which implements the XQuery language.

If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see
link:download.html[the download page for the latest versions]).

[source,java]
--------------------------------------
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-saxon</artifactId>
  <version>x.x.x</version>
</dependency>
--------------------------------------
