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Difference between revisions of "EclipseLink/UserGuide/MOXy/Overview/DynamicEntities"
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− | 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'''. | + | 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'''. |
{{tip||'''DynamicTypes''' are similar to Java classes; whereas '''DynamicEntities''' can be thought of as instances of a '''DynamicType'''.}} | {{tip||'''DynamicTypes''' are similar to Java classes; whereas '''DynamicEntities''' can be thought of as instances of a '''DynamicType'''.}} |
Revision as of 15:01, 15 March 2011
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Contents
Static and Dynamic Entities
There are two high-level ways to use EclipseLink JAXB; Using pre-existing Java classes (Static MOXy), or using EclipseLink-generated in-memory Java classes (Dynamic MOXy).
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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