org.simpleframework.xml.strategy.WriteGraph Maven / Gradle / Ivy
/*
* WriteGraph.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.strategy;
import org.simpleframework.xml.stream.NodeMap;
import java.util.IdentityHashMap;
import java.lang.reflect.Array;
/**
* The WriteGraph object is used to build the graph that
* is used to represent the serialized object and its references. The
* graph is stored in an IdentityHashMap which will
* store the objects in such a way that this graph object can tell if
* it has allready been written to the XML document. If an object has
* already been written to the XML document an reference attribute
* is added to the element representing the object and serialization
* of that object is complete, that is, no more elements are written.
*
* The attribute values written by this are unique strings, which
* allows the deserialization process to identify object references
* easily. By default these references are incrementing integers
* however for deserialization they can be any unique string value.
*
* @author Niall Gallagher
*/
class WriteGraph extends IdentityHashMap {
/**
* This is used to specify the length of array instances.
*/
private String length;
/**
* This is the label used to mark the type of an object.
*/
private String label;
/**
* This is the attribute used to mark the identity of an object.
*/
private String mark;
/**
* This is the attribute used to refer to an existing instance.
*/
private String refer;
/**
* Constructor for the WriteGraph object. This is
* used to build the graph used for writing objects to the XML
* document. The specified strategy is used to acquire the names
* of the special attributes used during the serialization.
*
* @param contract this is the name scheme used by the strategy
*/
public WriteGraph(Contract contract) {
this.refer = contract.getReference();
this.mark = contract.getIdentity();
this.length = contract.getLength();
this.label = contract.getLabel();
}
/**
* This is used to write the XML element attributes representing
* the serialized object instance. If the object has already been
* serialized to the XML document then a reference attribute is
* inserted and this returns true, if not, then this will write
* a unique identity marker attribute and return false.
*
* @param field this is the type of the object to be serialized
* @param value this is the instance that is to be serialized
* @param node this is the node that contains the attributes
*
* @return returns true if the element has been fully written
*/
public boolean setElement(Class field, Object value, NodeMap node){
Class type = value.getClass();
Class real = type;
if(type.isArray()) {
real = setArray(type, value, node);
}
if(type != field) {
node.put(label, real.getName());
}
return setReference(value, node);
}
/**
* This is used to write the XML element attributes representing
* the serialized object instance. If the object has already been
* serialized to the XML document then a reference attribute is
* inserted and this returns true, if not, then this will write
* a unique identity marker attribute and return false.
*
* @param value this is the instance that is to be serialized
* @param node this is the node that contains the attributes
*
* @return returns true if the element has been fully written
*/
private boolean setReference(Object value, NodeMap node) {
String name = get(value);
if(name != null) {
node.put(refer, name);
return true;
}
String unique = getKey();
node.put(mark, unique);
put(value, unique);
return false;
}
/**
* This is used to add a length attribute to the element due to
* the fact that the serialized value is an array. The length
* of the array is acquired and inserted in to the attributes.
*
* @param field this is the field type for the array to set
* @param value this is the actual value for the array to set
* @param node this is the map of attributes for the element
*
* @return returns the array component type that is set
*/
private Class setArray(Class field, Object value, NodeMap node){
int size = Array.getLength(value);
if(!containsKey(value)) {
node.put(length, String.valueOf(size));
}
return field.getComponentType();
}
/**
* This is used to generate a unique key, which is used to mark
* the serialized object. This currently returns an incrementing
* integer value as a string, but it can be any unique value.
*
* @return a unique key used to identify an object instance
*/
private String getKey() {
return String.valueOf(size());
}
}