Camel Components

XQuery

Since Camel 1.0

Only producer is supported

Camel supports XQuery component for message transformation

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The XQuery component supports the following options which are listed below.

Name Description Default Type

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

configuration (advanced)

To use a custom Saxon configuration.

Configuration

configurationProperties (advanced)

To set custom Saxon configuration properties.

Map

moduleURIResolver (advanced)

To use the custom ModuleURIResolver.

ModuleURIResolver

Endpoint Options

The XQuery endpoint is configured using URI syntax:

xquery:resourceUri

With the following path and query parameters:

Path Parameters

Name Description Default Type

resourceUri (producer)

Required The name of the template to load from classpath or file system.

String

Query Parameters

Name Description Default Type

allowStAX (producer)

Whether to allow using StAX mode.

false

boolean

namespacePrefixes (producer)

Allows to control which namespace prefixes to use for a set of namespace mappings.

Map

resultsFormat (producer)

What output result to use.

Enum values:

  • Bytes

  • BytesSource

  • DOM

  • DOMSource

  • List

  • String

  • StringSource

DOM

ResultFormat

resultType (producer)

What output result to use defined as a class.

Class

source (producer)

Source to use, instead of message body. You can prefix with variable:, header:, or property: to specify kind of source. Otherwise, the source is assumed to be a variable. Use empty or null to use default source, which is the message body.

String

stripsAllWhiteSpace (producer)

Whether to strip all whitespaces.

true

boolean

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

configuration (advanced)

To use a custom Saxon configuration.

Configuration

configurationProperties (advanced)

To set custom Saxon configuration properties.

Map

moduleURIResolver (advanced)

To use the custom ModuleURIResolver.

ModuleURIResolver

parameters (advanced)

Additional parameters.

Map

properties (advanced)

Properties to configure the serialization parameters.

Properties

staticQueryContext (advanced)

To use a custom Saxon StaticQueryContext.

StaticQueryContext

Message Body

The message body at each side of the XQuery component: Consumer is the body of the messages the consumer creates, Consumer reply the bodies a consumer that answers its caller can reply with, Producer input the bodies the producer can send or write, and Producer output the body after the producer.

Side Body Description

Producer input

text, bytes, stream, file or pojo, as xml

The XML to query: text, bytes, a stream, a file, a DOM or another javax.xml.transform.Source. A Map or no body fails.

Not known when source is set.

Producer output

pojo (org.w3c.dom.Document)

The result of the query as a DOM Document. A query that gives text, a number or more than one element fails with the default DOM: set resultsFormat to String or List.

  • With resultsFormat=Bytes: bytes (byte[])

  • With resultsFormat=BytesSource: pojo (org.apache.camel.util.xml.BytesSource)

  • With resultsFormat=DOMSource: text (java.lang.String)

  • With resultsFormat=List: list

  • With resultsFormat=String: text (java.lang.String)

  • With resultsFormat=StringSource: pojo (org.apache.camel.util.xml.StringSource)

Not known when resultType is set.

The bodies are the ones with the default options. A side that is not listed is not known, and tooling does not guess it. The carriers, the sides and the tools that use them are described in Message Body Types.

Examples

  • Java

  • XML

  • YAML

from("queue:foo")
  .filter().xquery("//foo")
    .to("queue:bar");
<route>
  <from uri="queue:foo"/>
  <filter>
    <xquery>//foo</xquery>
    <to uri="queue:bar"/>
  </filter>
</route>
- route:
    from:
      uri: queue:foo
      steps:
        - filter:
            xquery:
              expression: //foo
            steps:
              - to:
                  uri: queue:bar

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

Java-only: xquery() with class literal parameter
from("direct:start")
  .recipientList().xquery("concat('mock:foo.', /person/@city)", String.class);

Usage

Variables

The IN message body will be set as the contextItem. Besides this, these Variables are 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 are added with their own key name, for instance, if there is an IN header with the key name foo then it is 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

  • Java

  • XML

  • YAML

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

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 resultType attribute:

<xquery resultType="java.lang.String">concat('mock:foo.', /person/@city)</xquery>

Using XQuery as an endpoint

Sometimes an XQuery expression can be quite large; it can essentially 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.

  • Java

  • XML

  • YAML

from("activemq:MyQueue")
    .to("xquery:com/acme/someTransform.xquery")
    .to("mqseries:SomeOtherQueue");
<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>
- route:
    from:
      uri: activemq:MyQueue
      steps:
        - to:
            uri: xquery:com/acme/someTransform.xquery
        - to:
            uri: mqseries:SomeOtherQueue

Loading script from external resource

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

Java-only: setHeader with xquery() and class literal
.setHeader("myHeader").xquery("resource:classpath:myxquery.txt", String.class)

Learning XQuery

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

Dependencies

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

If you use Maven, you could add the following to your pom.xml, substituting the version number for the latest release.

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