mxobjectcodec.java

经典的java图像处理程序源码

/**
 * $Id: mxObjectCodec.java,v 1.19 2008/10/22 13:33:45 gaudenz Exp $
 * Copyright (c) 2006, Gaudenz Alder
 */
package com.mxgraph.io;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;

import com.mxgraph.util.mxUtils;

/**
 * Generic codec for Java objects. See below for a detailed description of
 * the encoding/decoding scheme.
 * 
 * Note: Since booleans are numbers in JavaScript, all boolean values are
 * encoded into 1 for true and 0 for false.
 */
public class mxObjectCodec
{

	/**
	 * Immutable empty set.
	 */
	private static Set EMPTY_SET = new HashSet();

	/**
	 * Holds the template object associated with this codec.
	 */
	Object template;

	/**
	 * Array containing the variable names that should be ignored by the codec.
	 */
	Set exclude;

	/**
	 * Array containing the variable names that should be turned into or
	 * converted from references. See <mxCodec.getId> and <mxCodec.getObject>.
	 */
	Set idrefs;

	/**
	 * Maps from from fieldnames to XML attribute names.
	 */
	Map mapping;

	/**
	 * Maps from from XML attribute names to fieldnames.
	 */
	Map reverse;

	/**
	 * Constructs a new codec for the specified template object.
	 */
	public mxObjectCodec(Object template)
	{
		this(template, null, null, null);
	}

	/**
	 * Constructs a new codec for the specified template object. The variables
	 * in the optional exclude array are ignored by the codec. Variables in the
	 * optional idrefs array are turned into references in the XML. The
	 * optional mapping may be used to map from variable names to XML
	 * attributes. The argument is created as follows:
	 * 
	 * @param template Prototypical instance of the object to be encoded/decoded.
	 * @param exclude Optional array of fieldnames to be ignored.
	 * @param idrefs Optional array of fieldnames to be converted to/from references.
	 * @param mapping Optional mapping from field- to attributenames.
	 */
	public mxObjectCodec(Object template, String[] exclude, String[] idrefs,
			Map mapping)
	{
		this.template = template;

		if (exclude != null)
		{
			this.exclude = new HashSet();

			for (int i = 0; i < exclude.length; i++)
			{
				this.exclude.add(exclude[i]);
			}
		}
		else
		{
			this.exclude = EMPTY_SET;
		}

		if (idrefs != null)
		{
			this.idrefs = new HashSet();

			for (int i = 0; i < idrefs.length; i++)
			{
				this.idrefs.add(idrefs[i]);
			}
		}
		else
		{
			this.idrefs = EMPTY_SET;
		}

		if (mapping == null)
		{
			mapping = new Hashtable();
		}

		this.mapping = mapping;

		reverse = new Hashtable();
		Iterator it = mapping.entrySet().iterator();

		while (it.hasNext())
		{
			Map.Entry e = (Map.Entry) it.next();
			reverse.put(e.getValue().toString(), e.getKey().toString());
		}
	}

	/**
	 * Returns the template object associated with this codec.
	 * 
	 * @return Returns the template object.
	 */
	public Object getTemplate()
	{
		return template;
	}

	/**
	 * Returns a new instance of the template object for representing the given
	 * node.
	 * 
	 * @param node XML node that the object is going to represent.
	 * @return Returns a new template instance.
	 */
	protected Object cloneTemplate(Node node)
	{
		Object obj = null;

		try
		{
			obj = template.getClass().newInstance();

			// Special case: Check if the collection
			// should be a map. This is if the first
			// child has an "as"-attribute. This
			// assumes that all childs will have
			// as attributes in this case. This is
			// required because in JavaScript, the
			// map and array object are the same.
			if (obj instanceof Collection)
			{
				node = node.getFirstChild();

				if (node != null && node.hasAttributes()
						&& node.getAttributes().getNamedItem("as") != null)
				{
					obj = new Hashtable();
				}
			}
		}
		catch (InstantiationException e)
		{
			// ignore
			e.printStackTrace();
		}
		catch (IllegalAccessException e)
		{
			// ignore
			e.printStackTrace();
		}

		return obj;
	}

	/**
	 * Returns true if the given attribute is to be ignored by the codec. This
	 * implementation returns true if the given fieldname is in
	 * {@link #exclude}.
	 * 
	 * @param obj Object instance that contains the field.
	 * @param attr Fieldname of the field.
	 * @param value Value of the field.
	 * @param isWrite Boolean indicating if the field is being encoded or
	 * decoded. isWrite is true if the field is being encoded, else it is
	 * being decoded.
	 * @return Returns true if the given attribute should be ignored.
	 */
	public boolean isExcluded(Object obj, String attr, Object value,
			boolean isWrite)
	{
		return exclude.contains(attr);
	}

	/**
	 * Returns true if the given fieldname is to be treated as a textual
	 * reference (ID). This implementation returns true if the given fieldname
	 * is in {@link #idrefs}.
	 * 
	 * @param obj Object instance that contains the field.
	 * @param attr Fieldname of the field.
	 * @param value Value of the field.
	 * @param isWrite Boolean indicating if the field is being encoded or
	 * decoded. isWrite is true if the field is being encoded, else it is being
	 * decoded.
	 * @return Returns true if the given attribute should be handled as a
	 * reference.
	 */
	public boolean isReference(Object obj, String attr, Object value,
			boolean isWrite)
	{
		return idrefs.contains(attr);
	}

	/**
	 * Encodes the specified object and returns a node representing then given
	 * object. Calls beforeEncode after creating the node and afterEncode
	 * with the resulting node after processing.
	 * 
	 * Enc is a reference to the calling encoder. It is used to encode complex
	 * objects and create references.
	 * 
	 * This implementation encodes all variables of an object according to the
	 * following rules:
	 * 
	 * <ul>
	 * <li>If the variable name is in {@link #exclude} then it is ignored.</li>
	 * <li>If the variable name is in {@link #idrefs} then
	 * {@link mxCodec#getId(Object)} is used to replace the object with its ID.
	 * </li>
	 * <li>The variable name is mapped using {@link #mapping}.</li>
	 * <li>If obj is an array and the variable name is numeric (ie. an index) then it
	 * is not encoded.</li>
	 * <li>If the value is an object, then the codec is used to create a child
	 * node with the variable name encoded into the "as" attribute.</li>
	 * <li>Else, if {@link com.mxgraph.io.mxCodec#isEncodeDefaults()} is true or
	 * the value differs from the template value, then ...
	 * <ul>
	 * <li>... if obj is not an array, then the value is mapped to an
	 * attribute.</li>
	 * <li>... else if obj is an array, the value is mapped to an add child
	 * with a value attribute or a text child node, if the value is a function.
	 * </li>
	 * </ul>
	 * </li>
	 * </ul>
	 * 
	 * If no ID exists for a variable in {@link #idrefs} or if an object cannot be
	 * encoded, a warning is printed to System.err.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object to be encoded.
	 * @return Returns the resulting XML node that represents the given object. 
	 */
	public Node encode(mxCodec enc, Object obj)
	{
		String name = mxCodecRegistry.getName(obj.getClass());
		Node node = enc.document.createElement(name);

		obj = beforeEncode(enc, obj, node);
		encodeObject(enc, obj, node);

		return afterEncode(enc, obj, node);
	}

	/**
	 * Encodes the value of each member in then given obj
	 * into the given node using {@link #encodeFields(mxCodec, Object, Node)}
	 * and {@link #encodeElements(mxCodec, Object, Node)}.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object to be encoded.
	 * @param node XML node that contains the encoded object.
	 */
	protected void encodeObject(mxCodec enc, Object obj, Node node)
	{
		mxCodec.setAttribute(node, "id", enc.getId(obj));
		encodeFields(enc, obj, node);
		encodeElements(enc, obj, node);
	}

	/**
	 * Encodes the declared fields of the given object into the given node.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object whose fields should be encoded.
	 * @param node XML node that contains the encoded object.
	 */
	protected void encodeFields(mxCodec enc, Object obj, Node node)
	{
		Class type = obj.getClass();

		while (type != null)
		{
			Field[] fields = type.getDeclaredFields();

			for (int i = 0; i < fields.length; i++)
			{
				Field f = fields[i];

				if ((f.getModifiers() & Modifier.TRANSIENT) != Modifier.TRANSIENT)
				{
					String fieldname = f.getName();
					Object value = getFieldValue(obj, fieldname);
					encodeValue(enc, obj, fieldname, value, node);
				}
			}

			type = type.getSuperclass();
		}
	}

	/**
	 * Encodes the child objects of arrays, maps and collections.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object whose child objects should be encoded.
	 * @param node XML node that contains the encoded object.
	 */
	protected void encodeElements(mxCodec enc, Object obj, Node node)
	{
		if (obj.getClass().isArray())
		{
			Object[] tmp = (Object[]) obj;

			for (int i = 0; i < tmp.length; i++)
			{
				encodeValue(enc, obj, null, tmp[i], node);
			}
		}
		else if (obj instanceof Map)
		{
			Iterator it = ((Map) obj).entrySet().iterator();

			while (it.hasNext())
			{
				Map.Entry e = (Map.Entry) it.next();
				encodeValue(enc, obj, String.valueOf(e.getKey()), e.getValue(),
						node);
			}
		}
		else if (obj instanceof Collection)
		{
			Iterator it = ((Collection) obj).iterator();

			while (it.hasNext())
			{
				Object value = it.next();
				encodeValue(enc, obj, null, value, node);
			}
		}
	}

	/**
	 * Converts the given value according to the mappings
	 * and id-refs in this codec and uses
	 * {@link #writeAttribute(mxCodec, Object, String, Object, Node)}
	 * to write the attribute into the given node.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object whose field is going to be encoded.
	 * @param fieldname Name if the field to be encoded.
	 * @param value Value of the property to be encoded.
	 * @param node XML node that contains the encoded object.
	 */
	protected void encodeValue(mxCodec enc, Object obj, String fieldname,
			Object value, Node node)
	{
		if (value != null && !isExcluded(obj, fieldname, value, true))
		{
			if (isReference(obj, fieldname, value, true))
			{
				Object tmp = enc.getId(value);

				if (tmp == null)
				{
					System.err.println("mxObjectCodec.encode: No ID for "
							+ mxCodecRegistry.getName(obj.getClass()) + "."
							+ fieldname + "=" + value);
					return; // exit
				}

				value = tmp;
			}

			Object defaultValue = getFieldValue(template, fieldname);
			if (fieldname == null || enc.isEncodeDefaults()
					|| defaultValue == null || !defaultValue.equals(value))
			{
				writeAttribute(enc, obj, getAttributeName(fieldname), value,
						node);
			}
		}
	}

	/**
	 * Returns true if the given object is a primitive value.
	 * 
	 * @param value Object that should be checked.
	 * @return Returns true if the given object is a primitive value.
	 */
	protected boolean isPrimitiveValue(Object value)
	{
		return value instanceof String || value instanceof Boolean
				|| value instanceof Character || value instanceof Byte
				|| value instanceof Short || value instanceof Integer
				|| value instanceof Long || value instanceof Float
				|| value instanceof Double || value.getClass().isPrimitive();
	}

	/**
	 * Writes the given value into node using writePrimitiveAttribute
	 * or writeComplexAttribute depending on the type of the value.
	 */
	protected void writeAttribute(mxCodec enc, Object obj, String attr,
			Object value, Node node)
	{
		value = convertValueToXml(value);

		if (isPrimitiveValue(value))
		{
			writePrimitiveAttribute(enc, obj, attr, value, node);
		}
		else
		{
			writeComplexAttribute(enc, obj, attr, value, node);
		}
	}

	/**
	 * Writes the given value as an attribute of the given node.
	 */
	protected void writePrimitiveAttribute(mxCodec enc, Object obj,
			String attr, Object value, Node node)
	{
		if (attr == null || obj instanceof Map)
		{
			Node child = enc.document.createElement("add");

			if (attr != null)
			{
				mxCodec.setAttribute(child, "as", attr);
			}

			mxCodec.setAttribute(child, "value", value);
			node.appendChild(child);
		}
		else
		{
			mxCodec.setAttribute(node, attr, value);
		}
	}

	/**
	 * Writes the given value as a child node of the given node.
	 */
	protected void writeComplexAttribute(mxCodec enc, Object obj, String attr,
			Object value, Node node)
	{
		Node child = enc.encode(value);

		if (child != null)
		{
			if (attr != null)
			{
				mxCodec.setAttribute(child, "as", attr);
			}

			node.appendChild(child);
		}
		else
		{
			System.err.println("mxObjectCodec.encode: No node for "
					+ mxCodecRegistry.getName(obj.getClass()) + "." + attr
					+ ": " + value);
		}
	}

	/**
	 * Converts true to "1" and false to "0". All other values are ignored.
	 */
	protected Object convertValueToXml(Object value)
	{
		if (value instanceof Boolean)
		{
			value = ((Boolean) value).booleanValue() ? "1" : "0";
		}

		return value;
	}

	/**
	 * Converts XML attribute values to object of the given type.
	 */
	protected Object convertValueFromXml(Class type, Object value)
	{
		if (value instanceof String && type.isPrimitive())
		{
			String tmp = (String) value;

			if (type.equals(boolean.class))
			{
				if (tmp.equals("1") || tmp.equals("0"))
				{
					tmp = (tmp.equals("1")) ? "true" : "false";
				}

				value = new Boolean(tmp);
			}
			else if (type.equals(char.class))
			{
				value = new Character(tmp.charAt(0));
			}
			else if (type.equals(byte.class))
			{
				value = new Byte(tmp);
			}
			else if (type.equals(short.class))
			{
				value = new Short(tmp);
			}
			else if (type.equals(int.class))
			{
				value = new Integer(tmp);
			}
			else if (type.equals(long.class))
			{
				value = new Long(tmp);
			}
			else if (type.equals(float.class))
			{
				value = new Float(tmp);
			}
			else if (type.equals(double.class))
			{
				value = new Double(tmp);
			}
		}

		return value;
	}