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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more 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.
*/
package groovy.lang;
import org.codehaus.groovy.runtime.GeneratedClosure;
import org.codehaus.groovy.runtime.metaclass.ClosureMetaClass;
import java.lang.reflect.Constructor;
import java.util.Iterator;
/**
* A MetaClassRegistry is an object that is responsible for managing the a cache of MetaClass instances. Each
* java.lang.Class instance has an associated MetaClass and client code can query this interface for the MetaClass for
* a given associated java.lang.Class
*
* @see groovy.lang.MetaClass
*
* @author John Wilson
* @author Graeme Rocher
* @author Jochen Theodorou
*
*/
public interface MetaClassRegistry {
/**
* The main function of the registry
* If a meta class exists then return it
* otherwise create one, put it in the registry and return it
*/
MetaClass getMetaClass(Class theClass);
/**
* Adds a metaclass to the registry for the given class
*
* @param theClass The class
* @param theMetaClass The MetaClass for theClass
*/
void setMetaClass(Class theClass, MetaClass theMetaClass);
/**
* Removes a cached MetaClass from the registry
*
* @param theClass The Java class of the MetaClass to remove
*/
void removeMetaClass(Class theClass);
/**
* Retrieves the MetaClassCreationHandle that is responsible for constructing MetaClass instances
*
* @return The MetaClassCreationHandle instance
*/
MetaClassCreationHandle getMetaClassCreationHandler();
/**
* Sets the MetaClassCreationHandle instance that is responsible for constructing instances
*
* @param handle The handle instance
*/
void setMetaClassCreationHandle(MetaClassCreationHandle handle);
/**
* Adds a meta class change listener for constant meta classes
*
* @param listener - the update listener
*/
void addMetaClassRegistryChangeEventListener(MetaClassRegistryChangeEventListener listener);
/**
* Adds a meta class change listener for constant meta classes.
* This listener cannot be removed!
*
* @param listener - the update listener
*/
void addNonRemovableMetaClassRegistryChangeEventListener(MetaClassRegistryChangeEventListener listener);
/**
* Removes a meta class change listener for constant meta classes
*
* @param listener - the update listener
*/
void removeMetaClassRegistryChangeEventListener(MetaClassRegistryChangeEventListener listener);
/**
* Returns all registered class change listener for constant meta classes.
*
* @return an array containing all change listener
*/
MetaClassRegistryChangeEventListener[] getMetaClassRegistryChangeEventListeners();
/**
* Gets a snapshot of the current constant meta classes and returns it as Iterator.
* Modifications done using this Iterator will not cause a ConcurrentModificationException.
* If a MetaClass is removed using this Iterator, then the MetaClass will only
* be removed if the MetaClass was not replaced by another MetaClass in the meantime.
* If a MetaClass is added while using this Iterator, then it will be part of the Iteration.
* If a MetaClass replaces another constant meta class, then the Iteration might show two
* meta classes for the same class.
*
* Note: This Iterator may not used with multiple threads.
*
* @return Iterator for the constant meta classes
*/
Iterator iterator();
/**
* Class used as base for the creation of MetaClass implementations.
* The Class defaults to MetaClassImpl, if the class loading fails to
* find a special meta class. The name for such a meta class would be
* the class name it is created for with the prefix
* "groovy.runtime.metaclass." By replacing the handle in the registry
* you can have any control over the creation of what MetaClass is used
* for a class that you want to have.
* WARNING: experimental code, likely to change soon
* @author Jochen Theodorou
*/
class MetaClassCreationHandle {
private boolean disableCustomMetaClassLookup;
/**
* Creates a metaclass implementation for theClass.
* @param theClass The class to create a metaclass for
* @param registry The metaclass registry the metaclass we be registered in.
*/
public final MetaClass create(Class theClass, MetaClassRegistry registry) {
if (disableCustomMetaClassLookup)
return createNormalMetaClass(theClass, registry);
return createWithCustomLookup(theClass, registry);
}
private MetaClass createWithCustomLookup(Class theClass, MetaClassRegistry registry) {
try {
final Class customMetaClass = Class.forName("groovy.runtime.metaclass." + theClass.getName() + "MetaClass");
if (DelegatingMetaClass.class.isAssignableFrom(customMetaClass)) {
final Constructor customMetaClassConstructor = customMetaClass.getConstructor(MetaClass.class);
MetaClass normalMetaClass = createNormalMetaClass(theClass, registry);
return (MetaClass)customMetaClassConstructor.newInstance(normalMetaClass);
}
else {
final Constructor customMetaClassConstructor = customMetaClass.getConstructor(MetaClassRegistry.class, Class.class);
return (MetaClass)customMetaClassConstructor.newInstance(registry, theClass);
}
}
catch (final ClassNotFoundException e) {
return createNormalMetaClass(theClass, registry);
} catch (final Exception e) {
throw new GroovyRuntimeException("Could not instantiate custom Metaclass for class: " + theClass.getName() + ". Reason: " + e, e);
}
}
protected MetaClass createNormalMetaClass(Class theClass,MetaClassRegistry registry) {
if (GeneratedClosure.class.isAssignableFrom(theClass)) {
return new ClosureMetaClass(registry,theClass);
} else {
return new MetaClassImpl(registry, theClass);
}
}
/**
* Returns whether custom meta classes are disabled.
*/
public boolean isDisableCustomMetaClassLookup() {
return disableCustomMetaClassLookup;
}
/**
* Set flag saying to disable lookup of custom meta classes
* It's enough to call this method only once in your application for handle which was set in to registry
* as every new handle will inherit this property
* @param disableCustomMetaClassLookup flag saying to disable lookup of custom meta classes
*/
public void setDisableCustomMetaClassLookup(boolean disableCustomMetaClassLookup) {
this.disableCustomMetaClassLookup = disableCustomMetaClassLookup;
}
}
}