Entaxy Docs

XQuery

Since Camel 1.0

Camel supports XQuery to allow an Expression or Predicate to be used in the DSL or Xml Configuration. For example you could use XQuery to create an Predicate in a Message Filter or as an Expression for a Recipient List.

XQuery Language options

The XQuery language supports 3 options, which are listed below.

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

Examples

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.

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:

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

<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:

    <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

You might also find the 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:

.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).

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-saxon</artifactId>
  <version>x.x.x</version>
</dependency>