org.simpleframework.xml.core.ConversionInstance Maven / Gradle / Ivy
/*
* CoversionInstance.java April 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 ConversionInstance object is used to promote the
* type to some more specialized type. For example if a field or
* method that represents a List is annotated then this
* might create a specialized type such as a Vector. It
* typically used to promote a type either because it is abstract
* or because another type is required.
*
* This is used by the CollectionFactory to convert the
* type of a collection field from an abstract type to a instantiable
* type. This is used to simplify strategy implementations.
*
* @author Niall Gallagher
*
* @see org.simpleframework.xml.core.CollectionFactory
*/
class ConversionInstance implements Instance {
/**
* This is the context that is used to create the instance.
*/
private final Context context;
/**
* This is the new class that is used for the type conversion.
*/
private final Class convert;
/**
* This is the value object that will be wrapped by this.
*/
private final Value value;
/**
* This is used to specify the creation of a conversion type that
* can be used for creating an instance with a class other than
* the default class specified by the Value object.
*
* @param context this is the context used for instantiation
* @param value this is the type used to create the instance
* @param convert this is the class the type is converted to
*/
public ConversionInstance(Context context, Value value, Class convert) throws Exception {
this.context = context;
this.convert = convert;
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 created = getInstance(convert);
if(created != null) {
setInstance(created);
}
return created;
}
/**
* 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 of the instance to create
*
* @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) throws Exception {
if(value != null) {
value.setValue(object);
}
return object;
}
/**
* 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 convert;
}
/**
* This will return true if the Value object provided
* is a reference type. Typically a reference type refers to a
* type that is substituted during the deserialization process
* and so constitutes an object that does not need initialization.
*
* @return this returns true if the type is a reference type
*/
public boolean isReference() {
return value.isReference();
}
}