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/*
* CompositeValue.java July 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.Type;
import org.simpleframework.xml.stream.InputNode;
import org.simpleframework.xml.stream.OutputNode;
import org.simpleframework.xml.stream.Style;
/**
* The CompositeValue object is used to convert an object
* to an from an XML element. This accepts only composite objects and
* will maintain all references within the object using the cycle
* strategy if required. This also ensures that should the value to
* be written to the XML element be null that nothing is written.
*
* @author Niall Gallagher
*
* @see org.simpleframework.xml.ElementMap
*/
class CompositeValue implements Converter {
/**
* This is the context used to support the serialization process.
*/
private final Context context;
/**
* This is the traverser used to read and write the value with.
*/
private final Traverser root;
/**
* This is the style used to style the names used for the XML.
*/
private final Style style;
/**
* This is the entry object used to provide configuration details.
*/
private final Entry entry;
/**
* This represents the type of object the value is written as.
*/
private final Type type;
/**
* Constructor for the CompositeValue object. This
* will create an object capable of reading an writing composite
* values from an XML element. This also allows a parent element
* to be created to wrap the key object if desired.
*
* @param context this is the root context for the serialization
* @param entry this is the entry object used for configuration
* @param type this is the type of object the value represents
*/
public CompositeValue(Context context, Entry entry, Type type) throws Exception {
this.root = new Traverser(context);
this.style = context.getStyle();
this.context = context;
this.entry = entry;
this.type = type;
}
/**
* This method is used to read the value object from the node. The
* value read from the node is resolved using the template filter.
* If the value data can not be found according to the annotation
* attributes then null is assumed and returned.
*
* @param node this is the node to read the value object from
*
* @return this returns the value deserialized from the node
*/
public Object read(InputNode node) throws Exception {
InputNode next = node.getNext();
Class expect = type.getType();
if(next == null) {
return null;
}
if(next.isEmpty()) {
return null;
}
return root.read(next, expect);
}
/**
* This method is used to read the value object from the node. The
* value read from the node is resolved using the template filter.
* If the value data can not be found according to the annotation
* attributes then null is assumed and returned.
*
* @param node this is the node to read the value object from
* @param value this is the value to deserialize in to
*
* @return this returns the value deserialized from the node
*
* @throws Exception if value is not null an exception is thrown
*/
public Object read(InputNode node, Object value) throws Exception {
Class expect = type.getType();
if(value != null) {
throw new PersistenceException("Can not read value of %s for %s", expect, entry);
}
return read(node);
}
/**
* This method is used to read the value object from the node. The
* value read from the node is resolved using the template filter.
* If the value data can not be found according to the annotation
* attributes then null is assumed and the node is valid.
*
* @param node this is the node to read the value object from
*
* @return this returns true if this represents a valid value
*/
public boolean validate(InputNode node) throws Exception {
Class expect = type.getType();
String name = entry.getValue();
if(name == null) {
name = context.getName(expect);
}
return validate(node, name);
}
/**
* This method is used to read the value object from the node. The
* value read from the node is resolved using the template filter.
* If the value data can not be found according to the annotation
* attributes then null is assumed and the node is valid.
*
* @param node this is the node to read the value object from
* @param key this is the name of the value element
*
* @return this returns true if this represents a valid value
*/
private boolean validate(InputNode node, String key) throws Exception {
String name = style.getElement(key);
InputNode next = node.getNext(name);
Class expect = type.getType();
if(next == null) {
return true;
}
if(next.isEmpty()) {
return true;
}
return root.validate(next, expect);
}
/**
* This method is used to write the value to the specified node.
* The value written to the node must be a composite object and if
* the object provided to this is null then nothing is written.
*
* @param node this is the node that the value is written to
* @param item this is the item that is to be written
*/
public void write(OutputNode node, Object item) throws Exception {
Class expect = type.getType();
String key = entry.getValue();
if(key == null) {
key = context.getName(expect);
}
String name = style.getElement(key);
root.write(node, item, expect, name);
}
}