StAX

Since Camel 2.9

Only producer is supported

The StAX component allows messages to be process through a SAX ContentHandler.
Another feature of this component is to allow iterating over JAXB records using StAX, for example using the Split 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

You can lookup a org.xml.sax.ContentHandler bean from the Registry using the # syntax as shown:

stax:#myHandler

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. 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.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

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

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

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

Component Options

The StAX component supports 2 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

Endpoint Options

The StAX endpoint is configured using URI syntax:

stax:contentHandlerClass

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

contentHandlerClass (producer)

Required The FQN class name for the ContentHandler implementation to use.

String

Query Parameters (1 parameters)

Name Description Default Type

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

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 have static import in the Java code. The stax builder is by default namespace aware on the XMLReader it uses. 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 Spring XML

  <!-- 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>

Spring Boot Auto-Configuration

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

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-stax-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 3 options, which are listed below.

Name Description Default Type

camel.component.stax.autowired-enabled

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

camel.component.stax.enabled

Whether to enable auto configuration of the stax component. This is enabled by default.

Boolean

camel.component.stax.lazy-start-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
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