org.apache.beehive.controls.runtime.bean.BeanPersistenceDelegate Maven / Gradle / Ivy
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* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* $Header:$
*/
package org.apache.beehive.controls.runtime.bean;
import java.beans.BeanInfo;
import java.beans.DefaultPersistenceDelegate;
import java.beans.Encoder;
import java.beans.EventSetDescriptor;
import java.beans.Expression;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PersistenceDelegate;
import java.beans.PropertyDescriptor;
import java.beans.Statement;
import java.beans.XMLEncoder;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Iterator;
import org.apache.beehive.controls.api.ControlException;
import org.apache.beehive.controls.api.properties.AnnotatedElementMap;
import org.apache.beehive.controls.api.properties.BeanPropertyMap;
import org.apache.beehive.controls.api.properties.PropertyKey;
import org.apache.beehive.controls.api.properties.PropertyMap;
/**
* The BeanPersistenceDelegate class supports the XML persistence of Control JavaBeans by
* implementing the java.beans.PersistenceDelegate API, and overriding the default
* persistence algorithm based upon the runtime structure for Controls. It selectively registers
* other PersistenceDelegate instances for other nested entities, as required, to ensure that
* runtime-defined state and object relationships are properly maintained.
*
* For the BeanInfo of all generated ControlJavaBeans, a BeanPersistenceDelegate instance will
* be registered as the "persistenceDelegate" attribute in the BeanDescriptor. The standard
* java.beans.Encoder persistence delegate lookup mechanism recognizes this attribute
* and will use the instance to persist an ControlBeans written to the encoding stream.
*
* The BeanPersistence class implements optimized property persistence based upon the
* fact that the ControlBean already has a map containing all non-default property state. Rather
* than using the standard (and slower) algorithm of comparing the encoding instance against a
* 'clean' instance, the delegate can simply retrieve the map and persist the values contained
* within it.
*
* @see java.beans.XMLEncoder
* @see java.beans.PersistenceDelegate
*/
public class BeanPersistenceDelegate extends DefaultPersistenceDelegate
{
/**
* The FieldPersistencersistence is an XMLEncoder PersistenceDelegate for the
* java.lang.reflect.Field claass. It is similar to the one that comes
* bundled with the JDK with one key exception: it works for non-public fields as
* well.
*/
class FieldPersistenceDelegate extends PersistenceDelegate
{
protected Expression instantiate(Object oldInstance, Encoder out)
{
Field f = (Field)oldInstance;
return new Expression(oldInstance, f.getDeclaringClass(), "getDeclaredField",
new Object[]{f.getName()});
}
}
/**
* PersistenceDelegate.instantiate()
*/
protected Expression instantiate(Object oldInstance, Encoder out)
{
XMLEncoder xmlOut = (XMLEncoder)out;
ControlBean control = (ControlBean)oldInstance;
//
// If processing a nested control, then use the parent bean's context as the
// constructor context
//
ControlBeanContext cbc = null;
if (xmlOut.getOwner() != null)
cbc = ((ControlBean)xmlOut.getOwner()).getControlBeanContext();
//
// See if the ControlBean has any associated PropertyMap in its delegation chain
// that was derived from an AnnotatedElement so this relationship (and any associated
// external config delegates) will be restored as part of the decoding process.
//
// BUGBUG: What about a user-created PropertyMap that was passed into the constructor?
//
AnnotatedElementMap aem = null;
PropertyMap pMap = control.getPropertyMap();
while (pMap != null)
{
if (pMap instanceof AnnotatedElementMap)
{
aem = (AnnotatedElementMap)pMap;
//
// Ignore a class-valued AnnotationElementMap.. this just refers to the
// Control type, and will be automatically reassociated at construction
// time
//
if (aem.getAnnotatedElement() instanceof Class)
aem = null;
xmlOut.setPersistenceDelegate(AnnotatedElementMap.class,
new AnnotatedElementMapPersistenceDelegate());
break;
}
pMap = pMap.getDelegateMap();
}
//
// Create a constructor that that uses the following form:
// new (ControlBeanContext cbc, String id, PropertyMap map)
// The context is set to null, so the current active container context will be
// used, the id will be the ID of the original control and the map will be
// any AnnotatedElementMap that was passed into the original constructor.
//
return new Expression(control, control.getClass(), "new",
new Object [] {cbc, control.getLocalID(), aem});
}
/**
* PersistenceDelegate.initialize()
*/
protected void initialize(Class type, Object oldInstance, Object newInstance, Encoder out)
{
//
// Get the bean and associated beanInfo for the source instance
//
ControlBean control = (ControlBean)oldInstance;
BeanInfo beanInfo;
try
{
beanInfo = Introspector.getBeanInfo(control.getClass());
}
catch (IntrospectionException ie)
{
throw new ControlException("Unable to locate BeanInfo", ie);
}
//
// Cast the encoding stream to an XMLEncoder (only encoding supported) and then set
// the stream owner to the bean being persisted
//
XMLEncoder xmlOut = (XMLEncoder)out;
Object owner = xmlOut.getOwner();
xmlOut.setOwner(control);
try
{
//
// The default implementation of property persistence will use BeanInfo to
// incrementally compare oldInstance property values to newInstance property values.
// Because the bean instance PropertyMap holds only the values that have been
// modified, this process can be optimized by directly writing out only the properties
// found in the map.
//
BeanPropertyMap beanMap = control.getPropertyMap();
PropertyDescriptor [] propDescriptors = beanInfo.getPropertyDescriptors();
for (PropertyKey pk : beanMap.getPropertyKeys())
{
//
// Locate the PropertyDescriptor for the modified property, and use it to write
// the property value to the encoder stream
//
String propName = pk.getPropertyName();
boolean found = false;
for (int i = 0; i < propDescriptors.length; i++)
{
if (propName.equals(propDescriptors[i].getName()))
{
found = true;
// Only write the property if it is not flagged as transient
Object transientVal = propDescriptors[i].getValue("transient");
if (transientVal == null || transientVal.equals(Boolean.FALSE))
{
xmlOut.writeStatement(
new Statement(oldInstance,
propDescriptors[i].getWriteMethod().getName(),
new Object [] {beanMap.getProperty(pk)}));
}
}
}
if (found == false)
{
throw new ControlException("Unknown property in bean PropertyMap: " + pk);
}
}
//
// Get the bean context associated with the bean, and persist any nested controls
//
ControlBeanContext cbc = control.getControlBeanContext();
if (cbc.size() != 0)
{
xmlOut.setPersistenceDelegate(ControlBeanContext.class,
new ContextPersistenceDelegate());
Iterator nestedIter = cbc.iterator();
while (nestedIter.hasNext())
{
Object bean = nestedIter.next();
if (bean instanceof ControlBean)
{
xmlOut.writeStatement(
new Statement(cbc, "add", new Object [] { bean } ));
}
}
}
//
// Restore any listeners associated with the control
//
EventSetDescriptor [] eventSetDescriptors = beanInfo.getEventSetDescriptors();
for (int i = 0; i < eventSetDescriptors.length; i++)
{
EventSetDescriptor esd = eventSetDescriptors[i];
Method listenersMethod = esd.getGetListenerMethod();
String addListenerName = esd.getAddListenerMethod().getName();
if (listenersMethod != null)
{
//
// Get the list of listeners, and then add statements to incrementally
// add them in the same order
//
try
{
Object [] lstnrs = (Object [])listenersMethod.invoke(control,
new Object []{});
for (int j = 0; j < lstnrs.length; j++)
{
//
// If this is a generated EventAdaptor class, then set the delegate
// explicitly
//
if (lstnrs[j] instanceof EventAdaptor)
xmlOut.setPersistenceDelegate(lstnrs[j].getClass(),
new AdaptorPersistenceDelegate());
xmlOut.writeStatement(
new Statement(control, addListenerName, new Object [] {lstnrs[j]}));
}
}
catch (Exception iae)
{
throw new ControlException("Unable to initialize listeners", iae);
}
}
}
//
// See if the control holds an implementation instance, if so, we need to include
// it (and any nested controls or state) in the encoding stream
//
Object impl = control.getImplementation();
if (impl != null)
{
//
// Set the persistence delegate for the impl class to the Impl delegate,
// set the current stream owner to the bean, and then write the implementation
//
Class implClass = impl.getClass();
if (xmlOut.getPersistenceDelegate(implClass) instanceof DefaultPersistenceDelegate)
xmlOut.setPersistenceDelegate(implClass, new ImplPersistenceDelegate());
//
// HACK: This bit of hackery pushes the impl into the persistence stream
// w/out actually requiring it be used as an argument elsewhere, since there
// is no public API on the bean that takes an impl instance as an argument.
//
xmlOut.writeStatement(
new Statement(impl, "toString", null));
}
}
finally
{
// Restore the previous encoding stream owner
xmlOut.setOwner(owner);
}
}
/**
* PersistenceDelegate.writeObject()
*/
public void writeObject(Object oldInstance, Encoder out)
{
// Override the default FieldPersistence algorithm for the encoder, so private fields
// can also be encoded
out.setPersistenceDelegate(Field.class, new FieldPersistenceDelegate());
super.writeObject(oldInstance, out);
}
}