JAXB

Since Camel 1.0

JAXB is a Data Format which uses the JAXB XML marshalling standard to unmarshal an XML payload into Java objects or to marshal Java objects into an XML payload.

Options

The JAXB dataformat supports the following options which are listed below.

Name Default Java Type Description

contextPath (common)

String

Required Package name where your JAXB classes are located.

contextPathIsClassName (common)

false

Boolean

This can be set to true to mark that the contextPath is referring to a classname and not a package name.

schema (common)

String

To validate against an existing schema. You can use the prefix classpath:, file: or http: to specify how the resource should be resolved. You can separate multiple schema files by using the comma character.

schemaSeverityLevel (common)

0

Enum

Sets the schema severity level to use when validating against a schema. The default value of 0 (warning) means that any error will trigger JAXB to stop. There are the following three levels: 0=warning, 1=error, 2=fatal error.

Enum values:

  • 0

  • 1

  • 2

prettyPrint (common)

true

Boolean

To enable pretty printing output nicely formatted. Is by default false.

objectFactory (advanced)

true

Boolean

Whether to allow using ObjectFactory classes to create the POJO classes during marshalling.

ignoreJAXBElement (advanced)

true

Boolean

Whether to ignore JAXBElement elements - only needed to be set to false in very special use-cases.

mustBeJAXBElement (advanced)

false

Boolean

Whether marshalling must be java objects with JAXB annotations. And if not then it fails. This option can be set to false to relax that, such as when the data is already in XML format.

filterNonXmlChars (advanced)

false

Boolean

To ignore non xml characters and replace them with an empty space.

encoding (common)

String

To overrule and use a specific encoding.

fragment (advanced)

false

Boolean

To turn on marshalling XML fragment trees. This is useful when generated code does not have XmlRootElement annotation and you need to unmarshall only part of the tree.

partClass (advanced)

String

Name of class used for fragment parsing.

partNamespace (advanced)

String

XML namespace to use for fragment parsing.

namespacePrefix (advanced)

Object

When marshalling using JAXB or SOAP then the JAXB implementation will automatically assign namespace prefixes, such as ns2, ns3, ns4 etc. To control this mapping, Camel allows you to refer to a map which contains the desired mapping.

xmlStreamWriterWrapper (advanced)

String

To use a custom xml stream writer.

schemaLocation (common)

String

To define the location of the schema.

noNamespaceSchemaLocation (advanced)

String

To define the location of the namespaceless schema.

jaxbProviderProperties (advanced)

String

Refers to a custom java.util.Map to lookup in the registry containing custom JAXB provider properties to be used with the JAXB marshaller.

contentTypeHeader (common)

true

Boolean

Whether the data format should set the Content-Type header with the type from the data format. For example application/xml for data formats marshalling to XML, or application/json for data formats marshalling to JSON.

accessExternalSchemaProtocols (security)

String

Only in use if schema validation has been enabled. Restrict access to the protocols specified for external reference set by the schemaLocation attribute, Import and Include element.

Usage

Using the Java DSL

The following example uses a named DataFormat of jaxb which is configured with a Java package name to initialize the JAXBContext .

Java-only: Java programmatic data format instantiation 
DataFormat jaxb = new JaxbDataFormat("com.acme.model");

from("activemq:My.Queue").
  unmarshal(jaxb).
  to("mqseries:Another.Queue");

You can, if you prefer, use a named reference to a data format which can then be defined in your Registry such as via your Spring XML file. e.g.

Java-only: Java DSL with named data format reference 
from("activemq:My.Queue").
  unmarshal("myJaxbDataType").
  to("mqseries:Another.Queue");

Using Spring XML

The following example shows how to configure the JaxbDataFormat and use it in multiple routes.

XML-only: Spring XML bean and route configuration 
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   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">

  <bean id="myJaxb" class="org.apache.camel.converter.jaxb.JaxbDataFormat">
    <property name="contextPath" value="org.apache.camel.example"/>
  </bean>

  <camelContext xmlns="http://camel.apache.org/schema/spring">
    <route>
      <from uri="direct:start"/>
      <marshal><custom ref="myJaxb"/></marshal>
      <to uri="direct:marshalled"/>
    </route>
    <route>
      <from uri="direct:marshalled"/>
      <unmarshal><custom ref="myJaxb"/></unmarshal>
      <to uri="mock:result"/>
    </route>
  </camelContext>

</beans>

Multiple context paths

It is possible to use this data format with more than one context path. You can specify multiple context paths using : as a separator, for example com.mycompany:com.mycompany2 .

Partial marshalling / unmarshalling

JAXB 2 supports marshalling and unmarshalling XML tree fragments. By default, JAXB looks for the @XmlRootElement annotation on a given class to operate on the whole XML tree. This is useful, but not always. Sometimes the generated code does not have the @XmlRootElement annotation, and sometimes you need to unmarshall only part of the tree.

In that case, you can use partial unmarshalling. To enable this behavior, you need set property partClass on the JaxbDataFormat . Camel will pass this class to the JAXB unmarshaller. If CamelJaxbPartClass is set as one of the exchange headers, its value is used to override the partClass property on the JaxbDataFormat .

For marshalling you have to add the partNamespace attribute with the QName of the destination namespace.

If CamelJaxbPartNamespace is set as one of the exchange headers, its value is used to override the partNamespace property on the JaxbDataFormat .

While setting partNamespace through the CamelJaxbPartNamespace header, please note that you need to specify its value in the format {namespaceUri}localPart , as per the example below. 

.setHeader("CamelJaxbPartNamespace", constant("{http://www.camel.apache.org/jaxb/example/address/1}address"));

Fragment

JaxbDataFormat has a property named fragment which can set the Marshaller.JAXB_FRAGMENT property on the JAXB Marshaller. If you don’t want the JAXB Marshaller to generate the XML declaration, you can set this option to be true . The default value of this property is false .

Ignoring Non-XML Characters

JaxbDataFormat supports ignoring Non-XML Characters , you need to set the filterNonXmlChars property to true . The JaxbDataFormat will replace any non-XML character with a space character ( " " ) during message marshalling or unmarshalling. You can also set the Exchange property Exchange.FILTER_NON_XML_CHARS .

JDK 1.5 JDK 1.6+

Filtering in use

StAX API and implementation

No

Filtering not in use

StAX API only

No

This feature has been tested with Woodstox 3.2.9 and Sun JDK 1.6 StAX implementation.

JaxbDataFormat now allows you to customize the XMLStreamWriter used to marshal the stream to XML. Using this configuration, you can add your own stream writer to completely remove, escape, or replace non-XML characters.

Java-only: Java programmatic data format configuration 
JaxbDataFormat customWriterFormat = new JaxbDataFormat("org.apache.camel.foo.bar");
customWriterFormat.setXmlStreamWriterWrapper(new TestXmlStreamWriter());

The following example shows using the Spring DSL and also enabling Camel’s non-XML filtering: 

<bean id="testXmlStreamWriterWrapper" class="org.apache.camel.jaxb.TestXmlStreamWriter"/>
<jaxb filterNonXmlChars="true" contextPath="org.apache.camel.foo.bar" xmlStreamWriterWrapper="#testXmlStreamWriterWrapper" />

Working with the ObjectFactory

If you use XJC to create the java class from the schema, you will get an ObjectFactory for your JAXB context. Since the ObjectFactory uses JAXBElement to hold the reference of the schema and element instance value, JaxbDataformat will ignore the JAXBElement by default, and you will get the element instance value instead of the JAXBElement object from the unmarshaled message body.

If you want to get the JAXBElement object form the unmarshaled message body, you need to set the JaxbDataFormat ignoreJAXBElement property to be false .

Setting the encoding

You can set the encoding option on the JaxbDataFormat to configure the Marshaller.JAXB_ENCODING encoding property on the JAXB Marshaller.

You can set up which encoding to use when you declare the JaxbDataFormat . You can also provide the encoding in the Exchange property Exchange.CHARSET_NAME . This property will override the encoding set on the JaxbDataFormat .

Controlling namespace prefix mapping

When marshalling using JAXB or SOAP then the JAXB implementation will automatically assign namespace prefixes, such as ns2 , ns3 , ns4 etc. To control this mapping, Camel allows you to refer to a map which contains the desired mapping.

For example, in Spring XML we can define a Map with the mapping. In the mapping file below, we map SOAP to use soap as a prefix. While our custom namespace http://www.mycompany.com/foo/2 is not using any prefix. 

 <util:map id="myMap">
    <entry key="http://www.w3.org/2003/05/soap-envelope" value="soap"/>
    <!-- we don't want any prefix for our namespace -->
    <entry key="http://www.mycompany.com/foo/2" value=""/>
 </util:map>

To use this in JAXB or SOAP data formats, you refer to this map, using the namespacePrefixRef attribute as shown below. Then Camel will look up in the Registry a java.util.Map with the id myMap , which was what we defined above. 

 <marshal>
    <soap version="1.2" contextPath="com.mycompany.foo" namespacePrefixRef="myMap"/>
 </marshal>

Schema validation

The JaxbDataFormat supports validation by marshalling and unmarshalling from / to XML. You can use the prefix classpath: , file: or http: to specify how the resource should be resolved. You can separate multiple schema files by using the , character.

if the XSD schema files import/access other files, then you need to enable file protocol (or others to allow access)

Using the Java DSL, you can configure it in the following way:

Java-only: Java programmatic data format configuration 
JaxbDataFormat jaxbDataFormat = new JaxbDataFormat();
jaxbDataFormat.setContextPath(Person.class.getPackage().getName());
jaxbDataFormat.setSchema("classpath:person.xsd,classpath:address.xsd");
jaxbDataFormat.setAccessExternalSchemaProtocols("file");

You can do the same using the XML DSL: 

<marshal>
    <jaxb id="jaxb" schema="classpath:person.xsd,classpath:address.xsd"
          accessExternalSchemaProtocols="file"/>
</marshal>

Schema Location

The JaxbDataFormat supports to specify the SchemaLocation when marshalling the XML.

Using the Java DSL, you can configure it in the following way:

Java-only: Java programmatic data format configuration 
JaxbDataFormat jaxbDataFormat = new JaxbDataFormat();
jaxbDataFormat.setContextPath(Person.class.getPackage().getName());
jaxbDataFormat.setSchemaLocation("schema/person.xsd");

You can do the same using the XML DSL: 

<marshal>
    <jaxb id="jaxb" schemaLocation="schema/person.xsd"/>
</marshal>

Marshal data that is already XML

The JAXB marshaller requires that the message body is JAXB compatible, e.g., it is a JAXBElement , a java instance that has JAXB annotations, or extends JAXBElement . There can be situations where the message body is already in XML, e.g., from a String type.

JaxbDataFormat has an option named mustBeJAXBElement which you can set to false to relax this check and have the JAXB marshaller only attempt marshalling on JAXBElement ( javax.xml.bind.JAXBIntrospector#isElement returns true ). In those situations, the marshaller will fall back to marshal the message body as-is.

Dependencies

To use JAXB in your Camel routes, you need to add a dependency on camel-jaxb , which implements this data format.

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

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