org.simpleframework.xml.core.LabelFactory Maven / Gradle / Ivy
/*
* LabelFactory.java July 2006
*
* Copyright (C) 2006, 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 java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import org.simpleframework.xml.Attribute;
import org.simpleframework.xml.Element;
import org.simpleframework.xml.ElementArray;
import org.simpleframework.xml.ElementList;
import org.simpleframework.xml.ElementMap;
import org.simpleframework.xml.Text;
import org.simpleframework.xml.Version;
/**
* The LabelFactory object is used to create instances of
* the Label object that can be used to convert an XML
* node into a Java object. Each label created requires the contact it
* represents and the XML annotation it is marked with.
*
* The Label objects created by this factory a selected
* using the XML annotation type. If the annotation type is not known
* the factory will throw an exception, otherwise a label instance
* is created that will expose the properties of the annotation.
*
* @author Niall Gallagher
*/
final class LabelFactory {
/**
* Creates a Label using the provided contact and XML
* annotation. The label produced contains all information related
* to an object member. It knows the name of the XML entity, as
* well as whether it is required. Once created the converter can
* transform an XML node into Java object and vice versa.
*
* @param contact this is contact that the label is produced for
* @param label represents the XML annotation for the contact
*
* @return returns the label instantiated for the field
*/
public static Label getInstance(Contact contact, Annotation label) throws Exception {
Label value = getLabel(contact, label);
if(value == null) {
return value;
}
return new CacheLabel(value);
}
/**
* Creates a Label using the provided contact and XML
* annotation. The label produced contains all information related
* to an object member. It knows the name of the XML entity, as
* well as whether it is required. Once created the converter can
* transform an XML node into Java object and vice versa.
*
* @param contact this is contact that the label is produced for
* @param label represents the XML annotation for the contact
*
* @return returns the label instantiated for the field
*/
private static Label getLabel(Contact contact, Annotation label) throws Exception {
Constructor factory = getConstructor(label);
if(!factory.isAccessible()) {
factory.setAccessible(true);
}
return (Label)factory.newInstance(contact, label);
}
/**
* Creates a constructor that can be used to instantiate the label
* used to represent the specified annotation. The constructor
* created by this method takes two arguments, a contact object
* and an Annotation of the type specified.
*
* @param label the XML annotation representing the label
*
* @return returns a constructor for instantiating the label
*
* @throws Exception thrown if the annotation is not supported
*/
private static Constructor getConstructor(Annotation label) throws Exception {
return getEntry(label).getConstructor();
}
/**
* Creates an entry that is used to select the constructor for the
* label. Each label must implement a constructor that takes a
* contact and the specific XML annotation for that field. If the
* annotation is not know this method throws an exception.
*
* @param label the XML annotation used to create the label
*
* @return this returns the entry used to create a suitable
* constructor for the label
*
* @throws Exception thrown if the annotation is not supported
*/
private static Entry getEntry(Annotation label) throws Exception{
if(label instanceof Element) {
return new Entry(ElementLabel.class, Element.class);
}
if(label instanceof ElementList) {
return new Entry(ElementListLabel.class, ElementList.class);
}
if(label instanceof ElementArray) {
return new Entry(ElementArrayLabel.class, ElementArray.class);
}
if(label instanceof ElementMap) {
return new Entry(ElementMapLabel.class, ElementMap.class);
}
if(label instanceof Attribute) {
return new Entry(AttributeLabel.class, Attribute.class);
}
if(label instanceof Version) {
return new Entry(VersionLabel.class, Version.class);
}
if(label instanceof Text) {
return new Entry(TextLabel.class, Text.class);
}
throw new PersistenceException("Annotation %s not supported", label);
}
/**
* The Entry object is used to create a constructor
* that can be used to instantiate the correct label for the XML
* annotation specified. The constructor requires two arguments
* a Contact and the specified XML annotation.
*
* @see java.lang.reflect.Constructor
*/
private static class Entry {
/**
* This is the XML annotation type within the constructor.
*/
public Class argument;
/**
* This is the label type that is to be instantiated.
*/
public Class label;
/**
* Constructor for the Entry object. This pairs
* the label type with the XML annotation argument used within
* the constructor. This allows constructor to be selected.
*
* @param label this is the label type to be instantiated
* @param argument type that is used within the constructor
*/
public Entry(Class label, Class argument) {
this.argument = argument;
this.label = label;
}
/**
* Creates the constructor used to instantiate the label for
* the XML annotation. The constructor returned will take two
* arguments, a contact and the XML annotation type.
*
* @return returns the constructor for the label object
*/
public Constructor getConstructor() throws Exception {
return getConstructor(Contact.class);
}
/**
* Creates the constructor used to instantiate the label for
* the XML annotation. The constructor returned will take two
* arguments, a contact and the XML annotation type.
*
* @param type this is the XML annotation argument type used
*
* @return returns the constructor for the label object
*/
private Constructor getConstructor(Class type) throws Exception {
return label.getConstructor(type, argument);
}
}
}