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/*
* ObjectInstance.java April 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 org.simpleframework.xml.strategy.Value;
/**
* The ObjectInstance
is used to instantiate an object
* from the criteria provided in the given Value
. If
* the value contains a reference then the reference is provided
* from this type. For performance the Context
object
* is used to instantiate the object as it contains a reflection
* cache of constructors.
*
* @author Niall Gallagher
*/
class ObjectInstance implements Instance {
/**
* This is the context that is used to create the instance.
*/
private final Context context;
/**
* This is the value object that will be wrapped by this.
*/
private final Value value;
/**
* This is the new class that is used for the instantiation.
*/
private final Class type;
/**
* Constructor for the ObjectInstance
object. This
* is used to create an instance of the type described by the
* value object. If the value object contains a reference then
* this will simply provide that reference.
*
* @param context this is used to instantiate the object
* @param value this is the value describing the instance
*/
public ObjectInstance(Context context, Value value) {
this.type = value.getType();
this.context = context;
this.value = value;
}
/**
* This method is used to acquire an instance of the type that
* is defined by this object. If for some reason the type can
* not be instantiated an exception is thrown from this.
*
* @return an instance of the type this object represents
*/
public Object getInstance() throws Exception {
if(value.isReference()) {
return value.getValue();
}
Object object = getInstance(type);
if(value != null) {
value.setValue(object);
}
return object;
}
/**
* This method is used to acquire an instance of the type that
* is defined by this object. If for some reason the type can
* not be instantiated an exception is thrown from this.
*
* @param type this is the type that is to be instantiated
*
* @return an instance of the type this object represents
*/
public Object getInstance(Class type) throws Exception {
Instance value = context.getInstance(type);
Object object = value.getInstance();
return object;
}
/**
* This method is used acquire the value from the type and if
* possible replace the value for the type. If the value can
* not be replaced then an exception should be thrown. This
* is used to allow primitives to be inserted into a graph.
*
* @param object this is the object to insert as the value
*
* @return an instance of the type this object represents
*/
public Object setInstance(Object object) {
if(value != null) {
value.setValue(object);
}
return object;
}
/**
* This is used to determine if the type is a reference type.
* A reference type is a type that does not require any XML
* deserialization based on its annotations. Types that are
* references could be substitutes objects are existing ones.
*
* @return this returns true if the object is a reference
*/
public boolean isReference() {
return value.isReference();
}
/**
* This is the type of the object instance that will be created
* by the getInstance
method. This allows the
* deserialization process to perform checks against the field.
*
* @return the type of the object that will be instantiated
*/
public Class getType() {
return type;
}
}