org.simpleframework.xml.core.ValueInstance Maven / Gradle / Ivy
/*
* ValueInstance.java January 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 org.simpleframework.xml.strategy.Value;
/**
* The ValueInstance object is used to create an object
* by using a Value instance to determine the type. If
* the provided value instance represents a reference then this will
* simply provide the value of the reference, otherwise it will
* instantiate a new object and return that.
*
* @author Niall Gallagher
*/
class ValueInstance implements Instance {
/**
* This is the instantiator used to create the objects.
*/
private final Instantiator creator;
/**
* This is the internal value that contains the criteria.
*/
private final Value value;
/**
* This is the type that is to be instantiated by this.
*/
private final Class type;
/**
* Constructor for the ValueInstance object. This
* is used to represent an instance that delegates to the given
* value object in order to acquire the object.
*
* @param creator this is the instantiator used to create objects
* @param value this is the value object that contains the data
*/
public ValueInstance(Instantiator creator, Value value) {
this.type = value.getType();
this.creator = creator;
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 = creator.getObject(type);
if(value != null) {
value.setValue(object);
}
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. Values that are
* references could be substitutes objects or 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;
}
}