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Chapter 149. StAX
StAX Component
Available as of Camel 2.9
The StAX component allows messages to be process through a SAX ContentHandler. Another feature of this component is to allow to iterate over JAXB records using StAX, for example using the Splitter EIP.
Maven users will need to add the following dependency to their
pom.xml for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-stax</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>URI format
stax:content-handler-class
example:
stax:org.superbiz.FooContentHandler
From Camel 2.11.1 onwards you can lookup a
org.xml.sax.ContentHandler bean from the Registry using the # syntax as shown:
stax:#myHandler
Usage of a content handler as StAX parser
The message body after the handling is the handler itself.
Here an example:
from("file:target/in")
.to("stax:org.superbiz.handler.CountingHandler")
// CountingHandler implements org.xml.sax.ContentHandler or extends org.xml.sax.helpers.DefaultHandler
.process(new Processor() {
@Override
public void process(Exchange exchange) throws Exception {
CountingHandler handler = exchange.getIn().getBody(CountingHandler.class);
// do some great work with the handler
}
});Iterate over a collection using JAXB and StAX
First we suppose you have JAXB objects.
For instance a list of records in a wrapper object:
import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "records")
public class Records {
@XmlElement(required = true)
protected List<Record> record;
public List<Record> getRecord() {
if (record == null) {
record = new ArrayList<Record>();
}
return record;
}
}
and
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlType;
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "record", propOrder = { "key", "value" })
public class Record {
@XmlAttribute(required = true)
protected String key;
@XmlAttribute(required = true)
protected String value;
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
Then you get a XML file to process:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <records> <record value="v0" key="0"/> <record value="v1" key="1"/> <record value="v2" key="2"/> <record value="v3" key="3"/> <record value="v4" key="4"/> <record value="v5" key="5"/> </record>
The StAX component provides an
StAXBuilder which can be used when iterating XML elements with the Camel Splitter.
from("file:target/in")
.split(stax(Record.class)).streaming()
.to("mock:records");
Where
stax is a static method on org.apache.camel.component.stax.StAXBuilder which you can static import in the Java code. The stax builder is by default namespace aware on the XMLReader it uses. From Camel 2.11.1 onwards you can turn this off by setting the boolean parameter to false, as shown below:
from("file:target/in")
.split(stax(Record.class, false)).streaming()
.to("mock:records");
The previous example with XML DSL
The example above could be implemented as follows in XML DSL
<!-- use STaXBuilder to create the expression we want to use in the route below for splitting the XML file -->
<!-- notice we use the factory-method to define the stax method, and to pass in the parameter as a constructor-arg -->
<bean id="staxRecord" class="org.apache.camel.component.stax.StAXBuilder" factory-method="stax">
<!-- FQN class name of the POJO with the JAXB annotations -->
<constructor-arg index="0" value="org.apache.camel.component.stax.model.Record"/>
</bean>
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<!-- pickup XML files -->
<from uri="file:target/in"/>
<split streaming="true">
<!-- split the file using StAX (ref to bean above) -->
<!-- and use streaming mode in the splitter -->
<ref>staxRecord</ref>
<!-- and send each splitted to a mock endpoint, which will be a Record POJO instance -->
<to uri="mock:records"/>
</split>
</route>
</camelContext>