[[xquery-language]]
= XQuery Language
:docTitle: XQuery
:artifactId: camel-saxon
:description: Evaluate an XQuery expressions against an XML payload.
:since: 1.0
:supportLevel: Stable
include::{cq-version}@camel-quarkus:ROOT:partial$reference/languages/xquery.adoc[opts=optional]

*Since Camel {since}*

Camel supports http://www.w3.org/TR/xquery/[XQuery] to allow an
Expression or Predicate to be
used in the DSL or xref:manual::xml-configuration.adoc[Xml
Configuration]. For example you could use XQuery to create an
Predicate in a xref:{eip-vc}:eips:filter-eip.adoc[Message
Filter] or as an Expression for a
Recipient List.

== XQuery Language options

// language options: START
The XQuery language supports 4 options, which are listed below.



[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
| configurationRef |  | String | Reference to a saxon configuration instance in the registry to use for xquery (requires camel-saxon). This may be needed to add custom functions to a saxon configuration, so these custom functions can be used in xquery expressions.
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|===
// language options: END

== 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);
-----------------------------------------------------------------------------

== 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*.
|=======================================================================

== Using XML configuration

If you prefer to configure your routes in your 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>
-------------------------------------------------------------------------------

== 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

== Loading script from external resource

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)
------------------------------------------------------------------------------

== 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
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>
--------------------------------------

include::{page-component-version}@camel-spring-boot::page$saxon-starter.adoc[]
