[[xquery-language]]
== XQuery Language

*Available as of Camel version 1.0*

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

### XQuery Language options

// language options: START
The XQuery language supports 3 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
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|===
// language options: END
// spring-boot-auto-configure options: START
=== Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-saxon-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>
----


The component supports 9 options, which are listed below.



[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *camel.component.xquery.basic-property-binding* | Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | Boolean
| *camel.component.xquery.configuration* | To use a custom Saxon configuration. The option is a net.sf.saxon.Configuration type. |  | String
| *camel.component.xquery.configuration-properties* | To set custom Saxon configuration properties. The option is a java.util.Map<java.lang.String,java.lang.Object> type. |  | String
| *camel.component.xquery.enabled* | Enable xquery component | true | Boolean
| *camel.component.xquery.module-u-r-i-resolver* | To use the custom ModuleURIResolver. The option is a net.sf.saxon.lib.ModuleURIResolver type. |  | String
| *camel.component.xquery.resolve-property-placeholders* | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | Boolean
| *camel.language.xquery.enabled* | Enable xquery language | true | Boolean
| *camel.language.xquery.trim* | Whether to trim the value to remove leading and trailing whitespaces and line breaks | true | Boolean
| *camel.language.xquery.type* | Sets the class name of the result type (type from output) The default result type is NodeSet |  | String
|===
// spring-boot-auto-configure 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>
-------------------------------------------------------------------------------

### 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);
-------------------------------------------------------------

 

### Using XQuery as an endpoint

Sometimes an XQuery expression can be quite large; it can essentally be
used for Templating. So you may want to use an
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>
-------------------------------------------------------------------------

### 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
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
Message Filter

### 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

*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)
------------------------------------------------------------------------------

### 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>
--------------------------------------
