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Difference between revisions of "EclipseLink/UserGuide/MOXy/Overview/DynamicEntities"
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{{tip||When using static classes with JAXB, you can take advantage of JAXB's defaulting behaviour and only annotate things which differ from the default. For example, all fields on a Java class will default to being mapped to an XML element, so no annotation is needed on the 'name' field. We want the 'id' field, however, to map to an XML attribute, so have annotated it as such.}} | {{tip||When using static classes with JAXB, you can take advantage of JAXB's defaulting behaviour and only annotate things which differ from the default. For example, all fields on a Java class will default to being mapped to an XML element, so no annotation is needed on the 'name' field. We want the 'id' field, however, to map to an XML attribute, so have annotated it as such.}} | ||
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The code below demonstrates how to unmarshal, modify, and marshal object using static JAXB: | The code below demonstrates how to unmarshal, modify, and marshal object using static JAXB: | ||
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*You want EclipseLink to generate classes from an XML schema (XSD). | *You want EclipseLink to generate classes from an XML schema (XSD). | ||
*You do not want to deal with concrete Java domain classes. | *You do not want to deal with concrete Java domain classes. | ||
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===Dynamic Entities=== | ===Dynamic Entities=== |
Revision as of 14:10, 15 March 2011
EclipseLink MOXy
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Contents
Static and Dynamic Entities
Using Static MOXy
The most common way to use EclipseLink JAXB is with existing Java classes, mapped to XML using Java annotations and/or EclipseLink OXM metadata. These classes might be ones that you have written yourself, or they could be generated from an XML Schema using the XJC compiler tool.
Using this approach, you will be dealing with your actual domain objects when converting to and from XML. The following example shows a simple Java class that can be used with JAXB:
import javax.xml.bind.annotation.XmlAttribute; import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class Customer { @XmlAttribute private long id; private String name; // ... // get() and set() methods // ... }
The code below demonstrates how to unmarshal, modify, and marshal object using static JAXB:
JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class, Address.class); Customer customer = (Customer) jaxbContext.createUnmarshaller().unmarshal(instanceDoc); Address address = new Address(); address.setStreet("1001 Fleet St."); customer.setAddress(address); jaxbContext.createMarshaller().marshal(customer, System.out);
Using Dynamic MOXy
With EclipseLink Dynamic MOXy, you can bootstrap a JAXBContext from a variety of metadata sources and use existing JAXB APIs to marshal and unmarshal data… without having compiled Java class files on the classpath. This allows you to alter the metadata as needed, without having to update and recompile the previously-generated Java source code.
You should consider using Dynamic MOXy when:
- You want EclipseLink to generate classes from an XML schema (XSD).
- You do not want to deal with concrete Java domain classes.
Dynamic Entities
Instead of using actual Java classes (such as Customer.class or Address.class), Dynamic MOXy uses a simple get(propertyName)/set(propertyName, propertyValue) API to manipulate data. EclipseLink generates (in memory) a DynamicType associated with each DynamicEntity.
The code below demonstrates how to unmarshal, modify, and marshal object using dynamic JAXB:
DynamicJAXBContext dynamicJAXBContext = DynamicJAXBContextFactory.createContextFromXSD(xsdInputStream, null, myClassLoader, null); DynamicEntity customer = (DynamicEntity) dynamicJAXBContext.createUnmarshaller().unmarshal(instanceDoc); String lastName = customer.get("lastName"); List orders = customer.get("orders"); ... DynamicEntity address = dynamicJAXBContext.newDynamicEntity("mynamespace.Address"); address.set("street", "1001 Fleet St."); customer.set("lastName", lastName + "Jr."); customer.set("address", address); dynamicJAXBContext.createMarshaller().marshal(customer, System.out);
For more information, see Appendix D: Binding XML Names to Java Identifiers in the JPA Specification.
Creating Dynamic Entities
To create and use Dynamic MOXy entities, create a JAXBContext by using the DynamicJAXBContextFactory class. You can create a DynamicJAXBContext from an XML Schema file (XSD), EclipseLink OXM metadata file, or from an EclipseLink Project specified in the EclipseLink sessions.xml file.
- Bootstrapping from XML schema (XSD)
- Bootstrapping from EclipseLink OXM metadata
- Bootstrapping from EclipseLink project (sessions.xml)
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