Revision as of 11:31, 17 June 2011

bugzilla id: rick.barkhouse (at) oracle.com

committer id: rbarkhous

Location: Ottawa, Canada - Eastern Standard Time

• Committer on Eclipse Persistence Services project - EclipseLink

Profession: Software Engineer

Currently working for Oracle Corporation on their TopLink product.

Also working with Eclipse Foundation on their EclipseLink product.

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Key API

• JAXBHelper
• JAXBContext (EclipseLink)

Refreshing Metadata

EclipseLink MOXy 2.3 introduces the ability to refresh your JAXBContext's metadata at runtime. This allows you to make changes to existing mappings in a live application environment and see those changes immediately without having to create a new JAXBContext.

In order to use the Metadata Refresh feature, your metadata information must be provided in one of the following formats:

• javax.xml.transform.Source
• org.w3c.dom.Node
• org.eclipse.persistence.jaxb.metadata.MetadataSource

Example

Our example will be bootstrapped from the following EclipseLink OXM file:

<?xml version="1.0"?>
<xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="example">
    <java-types>
        <java-type name="Root">
            <java-attributes>
                <xml-element java-attribute="name" name="orig-name"/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

Our JAXBContext is created in the standard way:

...
ClassLoader classLoader = ClassLoader.getSystemClassLoader();
 
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
DocumentBuilder db = dbf.newDocumentBuilder();
InputStream metadataStream = classLoader.getResourceAsStream("example/eclipselink-oxm.xml";
Document metadataDocument = db.parse(metadataStream);
metadataStream.close();
 
Map<String, Object> props = new HashMap<String, Object>(1);
props.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, metadataDocument);
JAXBContext context = JAXBContextFactory.createContext(new Class[] { Root.class }, props);
...

At this point, if we were to marshal a Root object to XML, it would look like this:

<root>
    <orig-name>RootName</orig-name>
</root>

For this example, we will modify the metadata Document directly to change the XML name for the name field. We can then refresh the metadata using the refeshMetadata() API:

...
Element xmlElementElement = (Element) metadataDocument.getElementsByTagNameNS("http://www.eclipse.org/eclipselink/xsds/persistence/oxm", "xml-element").item(0);
xmlElementElement.setAttribute("name", "new-name");
JAXBHelper.getJAXBContext(jc).refeshMetadata();
...

After refreshing metadata, the same Root object will be marshalled as follows:

<root>
    <new-name>RootName</new-name>
</root>