org.simpleframework.xml.core.MapFactory Maven / Gradle / Ivy
/*
* MapFactory.java July 2007
*
* Copyright (C) 2007, Niall Gallagher
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307 USA
*/
package org.simpleframework.xml.core;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
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 field this is the class for the owning object
*/
public MapFactory(Context context, Class field) {
super(context, field);
}
/**
* 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 type = field;
if(!isInstantiable(type)) {
type = getConversion(field);
}
if(!isMap(type)) {
throw new InstantiationException("Type is not a collection %s", field);
}
return type.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);
if(value != null) {
return getInstance(value);
}
if(!isInstantiable(field)) {
field = getConversion(field);
}
if(!isMap(field)) {
throw new InstantiationException("Type is not a map %s", field);
}
return context.getInstance(field);
}
/**
* 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 type = value.getType();
if(!isInstantiable(type)) {
type = getConversion(type);
}
if(!isMap(type)) {
throw new InstantiationException("Type is not a map %s", type);
}
return new ConversionInstance(context, value, type);
}
/**
* 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 type this is the type that is to be converted
*
* @return a collection that is assignable to the provided type
*/
public Class getConversion(Class type) throws Exception {
if(type.isAssignableFrom(HashMap.class)) {
return HashMap.class;
}
if(type.isAssignableFrom(TreeMap.class)) {
return TreeMap.class;
}
throw new InstantiationException("Cannot instantiate %s", 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);
}
}