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/*
* MapFactory.java July 2007
*
* Copyright (C) 2007, Niall Gallagher
*
* Licensed 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 org.simpleframework.xml.core;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
import org.simpleframework.xml.strategy.Type;
import org.simpleframework.xml.strategy.Value;
import org.simpleframework.xml.stream.InputNode;
/**
* The MapFactory
is used to create map instances that
* are compatible with the field type. This performs resolution of
* the map class by consulting the specified Strategy
* implementation. If the strategy cannot resolve the map class
* then this will select a type from the Java Collections framework,
* if a compatible one exists.
*
* @author Niall Gallagher
*/
class MapFactory extends Factory {
/**
* Constructor for the MapFactory
object. This is
* given the field type as taken from the owning object. The
* given type is used to determine the map instance created.
*
* @param context this is the context object for this factory
* @param type this is the class for the owning object
*/
public MapFactory(Context context, Type type) {
super(context, type);
}
/**
* Creates a map object that is determined from the field type.
* This is used for the ElementMap
to get a map
* that does not have any overrides. This must be done as the
* inline list does not contain an outer element.
*
* @return a type which is used to instantiate the map
*/
public Object getInstance() throws Exception {
Class expect = getType();
Class real = expect;
if(!isInstantiable(real)) {
real = getConversion(expect);
}
if(!isMap(real)) {
throw new InstantiationException("Invalid map %s for %s", expect, type);
}
return real.newInstance();
}
/**
* Creates the map object to use. The Strategy
object
* is consulted for the map object class, if one is not resolved
* by the strategy implementation or if the collection resolved is
* abstract then the Java Collections framework is consulted.
*
* @param node this is the input node representing the list
*
* @return this is the map object instantiated for the field
*/
public Instance getInstance(InputNode node) throws Exception {
Value value = getOverride(node);
Class expect = getType();
if(value != null) {
return getInstance(value);
}
if(!isInstantiable(expect)) {
expect = getConversion(expect);
}
if(!isMap(expect)) {
throw new InstantiationException("Invalid map %s for %s", expect, type);
}
return context.getInstance(expect);
}
/**
* This creates a Map
object instance from the type
* provided. If the type provided is abstract or an interface then
* this can promote the type to a map object type that can be
* instantiated. This is done by asking the type to convert itself.
*
* @param value the type used to instantiate the map object
*
* @return this returns a compatible map object instance
*/
public Instance getInstance(Value value) throws Exception {
Class expect = value.getType();
if(!isInstantiable(expect)) {
expect = getConversion(expect);
}
if(!isMap(expect)) {
throw new InstantiationException("Invalid map %s for %s", expect, type);
}
return new ConversionInstance(context, value, expect);
}
/**
* This is used to convert the provided type to a map object type
* from the Java Collections framework. This will check to see if
* the type is a Map
or SortedMap
and
* return a HashMap
or TreeSet
type. If
* no suitable match can be found this throws an exception.
*
* @param require this is the type that is to be converted
*
* @return a collection that is assignable to the provided type
*/
public Class getConversion(Class require) throws Exception {
if(require.isAssignableFrom(HashMap.class)) {
return HashMap.class;
}
if(require.isAssignableFrom(TreeMap.class)) {
return TreeMap.class;
}
throw new InstantiationException("Cannot instantiate %s for %s", require, type);
}
/**
* This determines whether the type provided is a object map type.
* If the type is assignable to a Map
object then
* this returns true, otherwise this returns false.
*
* @param type given to determine whether it is a map type
*
* @return true if the provided type is a map object type
*/
private boolean isMap(Class type) {
return Map.class.isAssignableFrom(type);
}
}