Jump to: navigation, search

Difference between revisions of "EclipseLink/Release/2.4.0/JAXB RI Extensions/XML Accessor Factory"

Line 65: Line 65:
 
     }
 
     }
  
     public Object get(Object arg0) throws AccessorException {
+
     public Object get(Object obj) throws AccessorException {
 
         if (MyLazyInitUtil.isInitialized(obj, field)) {
 
         if (MyLazyInitUtil.isInitialized(obj, field)) {
 
             try {
 
             try {

Revision as of 14:22, 4 June 2012

Design Documentation: XML Accessor Factory

ER 372403

In the current JAXB RI, developed by Sun, there is a series of "proprietary" JAXB extensions which provide advanced functionality outside of the JAXB specification (these extension classes and properties reside in the com.sun.xml.bind package).

By providing implementations of Accessor and AccessorFactory classes, the user can provide their own logic for getting and setting property values, at both the Class and Package level.

This document will outline EclipseLink MOXY's support for this feature.


Behaviour

Classes (or packages) annotated with XmlAccessorFactory will use the supplied AccessorFactory subclass to create Accessors responsible for setting and getting the values of JAXB properties. By implementing custom Accessor classes, the user will have complete control over the setting and getting of property values. This could be used, for example, to implement a custom lazy-loading strategy.


Configuration

First, define an implementation of the com.sun.xml.bind.AccessorFactory interface, which specifies two methods: createFieldAccessor() and createPropertyAccessor(). This allows you to provide different functionality for Field access and Property access by defining separate Accessor classes.

import java.lang.reflect.Field;
import java.lang.reflect.Method;
 
import javax.xml.bind.JAXBException;
 
import com.sun.xml.bind.AccessorFactory;
import com.sun.xml.bind.v2.runtime.reflect.Accessor;
 
public class MyAccessorFactory implements AccessorFactory {
 
    public Accessor createFieldAccessor(Class type, Field field, boolean isReadOnly) throws JAXBException {
        return new MyFieldAccessor(type, field, isReadOnly);
    }
 
    public Accessor createPropertyAccessor(Class type, Method getMethod, Method setMethod) throws JAXBException {
        return new MyPropertyAccessor(type, getMethod, setMethod);
    }
 
}

Next, define one or more subclasses of com.sun.xml.bind.v2.runtime.reflect.Accessor, to be returned from the AccessorFactory:

import java.lang.reflect.Field;
 
import com.sun.xml.bind.api.AccessorException;
import com.sun.xml.bind.v2.runtime.reflect.Accessor;
 
public class MyFieldAccessor extends Accessor {
 
    private Field field;
    private boolean readOnly;    
 
    protected MyFieldAccessor(Class type, Field field, boolean isReadOnly) {
        super(type);
        this.field = field;
        this.readOnly = isReadOnly;
    }
 
    public Object get(Object obj) throws AccessorException {
        if (MyLazyInitUtil.isInitialized(obj, field)) {
            try {
                return field.get(obj);
            } catch (Exception e) {
                throw new AccessorException(e);
            }
        } else {
            return null;
        }
    }
 
 
    public void set(Object obj, Object value) throws AccessorException {
        if (!readOnly) {
            try {
                field.set(obj, value);
            } catch (Exception e) {
                throw new AccessorException(e);
            }
        }
    }
 
}

Finally, add com.sun.xml.bind.XmlAccessorFactory annotations to your JAXB classes or package-info to enable the AccessorFactory:

Employee.java

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;
 
import com.sun.xml.bind.XmlAccessorFactory;
 
@XmlRootElement
@XmlAccessorType(XmlAccessType.NONE)
@XmlAccessorFactory(MyAccessorFactory.class)
public class Employee {
 
   ...
 
}

package-info.java

@XmlAccessorFactory(MyAccessorFactory.class)
package org.mypackage;
 
import com.sun.xml.bind.AccessorFactory;