mxobjectcodec.java

经典的java图像处理程序源码

	/**
	 * Returns the XML node attribute name for the given Java field name. That
	 * is, it returns the mapping of the field name.
	 */
	protected String getAttributeName(String fieldname)
	{
		if (fieldname != null)
		{
			Object mapped = mapping.get(fieldname);

			if (mapped != null)
			{
				fieldname = mapped.toString();
			}
		}

		return fieldname;
	}

	/**
	 * Returns the Java field name for the given XML attribute name. That is, it
	 * returns the reverse mapping of the attribute name.
	 * 
	 * @param attributename
	 *            The attribute name to be mapped.
	 * @return String that represents the mapped field name.
	 */
	protected String getFieldName(String attributename)
	{
		if (attributename != null)
		{
			Object mapped = reverse.get(attributename);

			if (mapped != null)
			{
				attributename = mapped.toString();
			}
		}

		return attributename;
	}

	/**
	 * Returns the field with the specified name.
	 */
	protected Field getField(Object obj, String fieldname)
	{
		Class type = obj.getClass();

		while (type != null)
		{
			try
			{
				Field field = type.getDeclaredField(fieldname);

				if (field != null)
				{
					return field;
				}
			}
			catch (Exception e)
			{
				// ignore
			}

			type = type.getSuperclass();
		}

		return null;
	}

	/**
	 * Returns the accessor (getter, setter) for the specified field.
	 */
	protected Method getAccessor(Object obj, Field field, boolean isGetter)
	{
		String name = field.getName();
		name = name.substring(0, 1).toUpperCase() + name.substring(1);

		if (!isGetter)
		{
			name = "set" + name;
		}
		else if (boolean.class.isAssignableFrom(field.getType()))
		{
			name = "is" + name;
		}
		else
		{
			name = "get" + name;
		}

		try
		{
			if (isGetter)
			{
				return getMethod(obj, name, null);
			}
			else
			{
				return getMethod(obj, name, new Class[] { field.getType() });
			}
		}
		catch (Exception e1)
		{
			// ignore
		}

		return null;
	}

	/**
	 * Returns the method with the specified signature.
	 */
	protected Method getMethod(Object obj, String methodname, Class[] params)
	{
		Class type = obj.getClass();

		while (type != null)
		{
			try
			{
				Method method = type.getDeclaredMethod(methodname, params);

				if (method != null)
				{
					return method;
				}
			}
			catch (Exception e)
			{
				// ignore
			}

			type = type.getSuperclass();
		}
		return null;
	}

	/**
	 * Returns the value of the field with the specified name in the specified
	 * object instance.
	 */
	protected Object getFieldValue(Object obj, String fieldname)
	{
		Object value = null;

		if (obj != null && fieldname != null)
		{
			Field field = getField(obj, fieldname);

			try
			{
				if (field != null)
				{
					value = field.get(obj);
				}
			}
			catch (IllegalAccessException e1)
			{
				if (field != null)
				{
					try
					{
						Method method = getAccessor(obj, field, true);
						value = method.invoke(obj, (Object[]) null);
					}
					catch (Exception e2)
					{
						// ignore
					}
				}
			}
			catch (Exception e)
			{
				// ignore
			}
		}

		return value;
	}

	/**
	 * Sets the value of the field with the specified name
	 * in the specified object instance.
	 */
	protected void setFieldValue(Object obj, String fieldname, Object value)
	{
		Field field = null;

		try
		{
			field = getField(obj, fieldname);

			if (field.getType() == Boolean.class)
			{
				value = new Boolean(value.equals("1")
						|| String.valueOf(value).equalsIgnoreCase("true"));
			}

			field.set(obj, value);
		}
		catch (IllegalAccessException e1)
		{
			if (field != null)
			{
				try
				{
					Method method = getAccessor(obj, field, false);
					Class type = method.getParameterTypes()[0];
					value = convertValueFromXml(type, value);
					method.invoke(obj, new Object[] { value });
				}
				catch (Exception e2)
				{
					System.err.println("setFieldValue: " + e2 + " on "
							+ obj.getClass().getSimpleName() + "." + fieldname
							+ " (" + field.getType().getSimpleName() + ") = "
							+ value + " (" + value.getClass().getSimpleName()
							+ ")");
				}
			}
		}
		catch (Exception e)
		{
			// ignore
		}
	}

	/**
	 * Hook for subclassers to pre-process the object before encoding. This
	 * returns the input object. The return value of this function is used in
	 * encode to perform the default encoding into the given node.
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object to be encoded.
	 * @param node XML node to encode the object into.
	 * @return Returns the object to be encoded by the default encoding.
	 */
	public Object beforeEncode(mxCodec enc, Object obj, Node node)
	{
		return obj;
	}

	/**
	 * Hook for subclassers to post-process the node for the given object after
	 * encoding and return the post-processed node. This implementation returns
	 * the input node. The return value of this method is returned to the
	 * encoder from <encode>.
	 * 
	 * Parameters:
	 * 
	 * @param enc Codec that controls the encoding process.
	 * @param obj Object to be encoded.
	 * @param node XML node that represents the default encoding.
	 * @return Returns the resulting node of the encoding.
	 */
	public Node afterEncode(mxCodec enc, Object obj, Node node)
	{
		return node;
	}

	/**
	 * Parses the given node into the object or returns a new object
	 * representing the given node.
	 * 
	 * @param dec Codec that controls the encoding process.
	 * @param node XML node to be decoded.
	 * @return Returns the resulting object that represents the given XML node.
	 */
	public Object decode(mxCodec dec, Node node)
	{
		return decode(dec, node, null);
	}

	/**
	 * Parses the given node into the object or returns a new object
	 * representing the given node.
	 * 
	 * Dec is a reference to the calling decoder. It is used to decode complex
	 * objects and resolve references.
	 * 
	 * If a node has an id attribute then the object cache is checked for the
	 * object. If the object is not yet in the cache then it is constructed
	 * using the constructor of <template> and cached in <mxCodec.objects>.
	 * 
	 * This implementation decodes all attributes and childs of a node according
	 * to the following rules:
	 *  - If the variable name is in <exclude> or if the attribute name is "id"
	 * or "as" then it is ignored. - If the variable name is in <idrefs> then
	 * <mxCodec.getObject> is used to replace the reference with an object. -
	 * The variable name is mapped using a reverse <mapping>. - If the value has
	 * a child node, then the codec is used to create a child object with the
	 * variable name taken from the "as" attribute. - If the object is an array
	 * and the variable name is empty then the value or child object is appended
	 * to the array. - If an add child has no value or the object is not an
	 * array then the child text content is evaluated using <mxUtils.eval>.
	 * 
	 * If no object exists for an ID in <idrefs> a warning is issued using
	 * <mxLog.warn>.
	 * 
	 * @param dec Codec that controls the encoding process.
	 * @param node XML node to be decoded.
	 * @param into Optional objec to encode the node into.
	 * @return Returns the resulting object that represents the given XML node
	 * or the object given to the method as the into parameter.
	 */
	public Object decode(mxCodec dec, Node node, Object into)
	{
		Object obj = null;

		if (node instanceof Element)
		{
			String id = ((Element) node).getAttribute("id");
			obj = dec.objects.get(id);

			if (obj == null)
			{
				obj = into;

				if (obj == null)
				{
					obj = cloneTemplate(node);
				}

				if (id != null && id.length() > 0)
				{
					dec.putObject(id, obj);
				}
			}

			node = beforeDecode(dec, node, obj);
			decodeNode(dec, node, obj);
			obj = afterDecode(dec, node, obj);
		}

		return obj;
	}

	/**
	 * Calls decodeAttributes and decodeChildren for the given node.
	 */
	protected void decodeNode(mxCodec dec, Node node, Object obj)
	{
		if (node != null)
		{
			decodeAttributes(dec, node, obj);
			decodeChildren(dec, node, obj);
		}
	}

	/**
	 * Decodes all attributes of the given node using decodeAttribute.
	 */
	protected void decodeAttributes(mxCodec dec, Node node, Object obj)
	{
		NamedNodeMap attrs = node.getAttributes();

		if (attrs != null)
		{
			for (int i = 0; i < attrs.getLength(); i++)
			{
				Node attr = attrs.item(i);
				decodeAttribute(dec, attr, obj);
			}
		}
	}

	/**
	 * Reads the given attribute into the specified object.
	 */
	protected void decodeAttribute(mxCodec dec, Node attr, Object obj)
	{
		String name = attr.getNodeName();

		if (!name.equalsIgnoreCase("as") && !name.equalsIgnoreCase("id"))
		{
			Object value = attr.getNodeValue();
			String fieldname = getFieldName(name);

			if (isReference(obj, fieldname, value, false))
			{
				Object tmp = dec.getObject(String.valueOf(value));

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

				value = tmp;
			}

			if (!isExcluded(obj, fieldname, value, false))
			{
				setFieldValue(obj, fieldname, value);
				// mxLog.debug(type+"."+name+"="+value);
			}
		}
	}

	/**
	 * Decodec all children of the given node using decodeChild.
	 */
	protected void decodeChildren(mxCodec dec, Node node, Object obj)
	{
		Node child = node.getFirstChild();

		while (child != null)
		{
			if (child.getNodeType() == Node.ELEMENT_NODE
					&& !this.processInclude(dec, child, obj))
			{
				decodeChild(dec, child, obj);
			}

			child = child.getNextSibling();
		}
	}

	/**
	 * Reads the specified child into the given object.
	 */
	protected void decodeChild(mxCodec dec, Node child, Object obj)
	{
		String fieldname = getFieldName(((Element) child).getAttribute("as"));

		if (fieldname == null || !isExcluded(obj, fieldname, child, false))
		{
			Object value = null;
			Object template = getFieldValue(obj, fieldname);

			if (child.getNodeName().equals("add"))
			{
				value = ((Element) child).getAttribute("value");

				if (value == null)
				{
					value = child.getTextContent();
					// mxLog.debug("Decoded "+role+"
					// "+mxUtils.getTextContent(child));
				}
			}
			else
			{
				value = dec.decode(child, template);
				// System.out.println("Decoded " + child.getNodeName() + "."
				// + fieldname + "=" + value);
			}

			if (value != null && !value.equals(template))
			{
				if (fieldname != null && obj instanceof Map)
				{
					((Map) obj).put(fieldname, value);
				}
				else if (fieldname != null && fieldname.length() > 0)
				{
					setFieldValue(obj, fieldname, value);
				}
				else if (obj instanceof Collection)
				{
					((Collection) obj).add(value);
				}
				else if (obj.getClass().isArray())
				{
					// FIXME: add to array
				}
				// mxLog.debug("Decoded "+type+"."+role+": "+tmp);
			}
		}
	}

	/**
	 * Returns true if the given node is an include directive and executes the
	 * include by decoding the XML document. Returns false if the given node is
	 * not an include directive.
	 * 
	 * @param dec Codec that controls the encoding/decoding process.
	 * @param node XML node to be checked.
	 * @param into Optional object to pass-thru to the codec.
	 * @return Returns true if the given node was processed as an include.
	 */
	public boolean processInclude(mxCodec dec, Node node, Object into)
	{
		if (node.getNodeType() == Node.ELEMENT_NODE
				&& node.getNodeName().equalsIgnoreCase("include"))
		{
			String name = ((Element) node).getAttribute("name");

			if (name != null)
			{
				try
				{
					Node xml = mxUtils.loadDocument(
							mxObjectCodec.class.getResource(name).toString())
							.getDocumentElement();

					if (xml != null)
					{
						dec.decode(xml, into);
					}
				}
				catch (Exception e)
				{
					System.err.println("Cannot process include: " + name);
				}
			}

			return true;
		}

		return false;
	}

	/**
	 * Hook for subclassers to pre-process the node for the specified object
	 * and return the node to be used for further processing by
	 * {@link #decode(mxCodec, Node)}. The object is created based on the
	 * template in the calling method and is never null.
	 * 
	 * This implementation returns the input node. The return value of this
	 * function is used in {@link #decode(mxCodec, Node)} to perform the
	 * default decoding into the given object.
	 * 
	 * @param dec Codec that controls the decoding process.
	 * @param node XML node to be decoded.
	 * @param obj Object to encode the node into.
	 * @return Returns the node used for the default decoding.
	 */
	public Node beforeDecode(mxCodec dec, Node node, Object obj)
	{
		return node;
	}

	/**
	 * Hook for subclassers to post-process the object after decoding. This
	 * implementation returns the given object without any changes. The return
	 * value of this method is returned to the decoder from
	 * {@link #decode(mxCodec, Node)}.
	 * 
	 * @param dec Codec that controls the decoding process.
	 * @param node XML node to be decoded.
	 * @param obj Object that represents the default decoding.
	 * @return Returns the result of the decoding process.
	 */
	public Object afterDecode(mxCodec dec, Node node, Object obj)
	{
		return obj;
	}

}