myxmlmemento.java

eclipse开发笔记

        if (attr == null) {
			return null;
		}
        return attr.getValue();
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public String getTextData() {
        Text textNode = getTextNode();
        if (textNode != null) {
            return textNode.getData();
        }
        return null;
    }

    /**
     * Returns the Text node of the memento. Each memento is allowed only 
     * one Text node.
     * 
     * @return the Text node of the memento, or <code>null</code> if
     * the memento has no Text node.
     */
    private Text getTextNode() {
        // Get the nodes.
        NodeList nodes = element.getChildNodes();
        int size = nodes.getLength();
        if (size == 0) {
			return null;
		}
        for (int nX = 0; nX < size; nX++) {
            Node node = nodes.item(nX);
            if (node instanceof Text) {
                return (Text) node;
            }
        }
        // a Text node was not found
        return null;
    }

    /**
     * Places the element's attributes into the document.
     * @param copyText true if the first text node should be copied
     */
    private void putElement(Element element, boolean copyText) {
        NamedNodeMap nodeMap = element.getAttributes();
        int size = nodeMap.getLength();
        for (int i = 0; i < size; i++) {
            Attr attr = (Attr) nodeMap.item(i);
            putString(attr.getName(), attr.getValue());
        }

        NodeList nodes = element.getChildNodes();
        size = nodes.getLength();
        // Copy first text node (fixes bug 113659).
        // Note that text data will be added as the first child (see putTextData)
        boolean needToCopyText = copyText;
        for (int i = 0; i < size; i++) {
            Node node = nodes.item(i);
            if (node instanceof Element) {
                MYXMLMemento child = (MYXMLMemento) createChild(node.getNodeName());
                child.putElement((Element) node, true);
            } else if (node instanceof Text && needToCopyText) {
                putTextData(((Text) node).getData());
                needToCopyText = false;
            }
        }
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public void putFloat(String key, float f) {
        element.setAttribute(key, String.valueOf(f));
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public void putInteger(String key, int n) {
        element.setAttribute(key, String.valueOf(n));
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public void putMemento(IMemento memento) {
    	// Do not copy the element's top level text node (this would overwrite the existing text).
    	// Text nodes of children are copied.
        putElement(((MYXMLMemento) memento).element, false);
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public void putString(String key, String value) {
        if (value == null) {
			return;
		}
        element.setAttribute(key, value);
    }

    /* (non-Javadoc)
     * Method declared in IMemento.
     */
    public void putTextData(String data) {
        Text textNode = getTextNode();
        if (textNode == null) {
            textNode = factory.createTextNode(data);
			// Always add the text node as the first child (fixes bug 93718) 
			element.insertBefore(textNode, element.getFirstChild());
        } else {
            textNode.setData(data);
        }
    }

    /**
     * Saves this memento's document current values to the
     * specified writer. 
     * 
     * @param writer the writer used to save the memento's document
     * @throws IOException if there is a problem serializing the document to the stream.
     */
    public void save(Writer writer) throws IOException {
    	DOMWriter out = new DOMWriter(writer);
        try {
        	out.print(element);
    	} finally {
    		out.close();
    	}
	}

	/**
     * A simple XML writer.  Using this instead of the javax.xml.transform classes allows
     * compilation against JCL Foundation (bug 80053). 
     */
    private static final class DOMWriter extends PrintWriter {
    	
    	private int tab;

    	/* constants */
    	private static final String XML_VERSION = "<?xml version=\"1.0\" encoding=\"GB2312\"?>"; //$NON-NLS-1$

    	/**
    	 * Creates a new DOM writer on the given output writer.
    	 * 
    	 * @param output the output writer
    	 */
    	public DOMWriter(Writer output) {
    		super(output);
    		tab = 0;
    		println(XML_VERSION);
    	}

    	/**
    	 * Prints the given element.
    	 * 
    	 * @param element the element to print
    	 */
        public void print(Element element) {
        	// Ensure extra whitespace is not emitted next to a Text node,
        	// as that will result in a situation where the restored text data is not the
        	// same as the saved text data.
        	boolean hasChildren = element.hasChildNodes();
        	startTag(element, hasChildren);
        	if (hasChildren) {
	        	tab++;
	        	boolean prevWasText = false;
	        	NodeList children = element.getChildNodes();
	    		for (int i = 0; i < children.getLength(); i++) {
	    			Node node = children.item(i);
	    			if (node instanceof Element) {
	    				if (!prevWasText) {
	    					println();
	    					printTabulation();
	    				}
	    				print((Element) children.item(i));
	    				prevWasText = false;
	    			}
	    			else if (node instanceof Text) {
	    				print(getEscaped(node.getNodeValue()));
	    				prevWasText = true;
	    			}
	    		}
	    		tab--;
	    		if (!prevWasText) {
	    			println();
	    			printTabulation();
	    		}
	    		endTag(element);
        	}
    	}

    	private void printTabulation() {
        	// Indenting is disabled, as it can affect the result of getTextData().
        	// In 3.0, elements were separated by a newline but not indented.
    		// This causes getTextData() to return "\n" even if no text data had explicitly been set.
        	// The code here emulates that behaviour.
    		
//    		for (int i = 0; i < tab; i++)
//    			super.print("\t"); //$NON-NLS-1$
    	}

    	private void startTag(Element element, boolean hasChildren) {
    		StringBuffer sb = new StringBuffer();
    		sb.append("<"); //$NON-NLS-1$
    		sb.append(element.getTagName());
    		NamedNodeMap attributes = element.getAttributes();
   			for (int i = 0;  i < attributes.getLength(); i++) {
   				Attr attribute = (Attr)attributes.item(i);
				sb.append(" "); //$NON-NLS-1$
				sb.append(attribute.getName());
				sb.append("=\""); //$NON-NLS-1$
				sb.append(getEscaped(String.valueOf(attribute.getValue())));
				sb.append("\""); //$NON-NLS-1$
   			}
   			sb.append(hasChildren ? ">" : "/>"); //$NON-NLS-1$ //$NON-NLS-2$
   			print(sb.toString());
    	}

    	private void endTag(Element element) {
    		StringBuffer sb = new StringBuffer();
    		sb.append("</"); //$NON-NLS-1$
    		sb.append(element.getNodeName());
    		sb.append(">"); //$NON-NLS-1$
   			print(sb.toString());
    	}
    	
    	private static void appendEscapedChar(StringBuffer buffer, char c) {
    		String replacement = getReplacement(c);
    		if (replacement != null) {
    			buffer.append('&');
    			buffer.append(replacement);
    			buffer.append(';');
    		} else {
    			buffer.append(c);
    		}
    	}

    	private static String getEscaped(String s) {
    		StringBuffer result = new StringBuffer(s.length() + 10);
    		for (int i = 0; i < s.length(); ++i) {
				appendEscapedChar(result, s.charAt(i));
			}
    		return result.toString();
    	}

    	private static String getReplacement(char c) {
    		// Encode special XML characters into the equivalent character references.
			// The first five are defined by default for all XML documents.
			// The next three (#xD, #xA, #x9) are encoded to avoid them
			// being converted to spaces on deserialization
			// (fixes bug 93720)
    		switch (c) {
    			case '<' :
    				return "lt"; //$NON-NLS-1$
    			case '>' :
    				return "gt"; //$NON-NLS-1$
    			case '"' :
    				return "quot"; //$NON-NLS-1$
    			case '\'' :
    				return "apos"; //$NON-NLS-1$
    			case '&' :
    				return "amp"; //$NON-NLS-1$
				case '\r':
					return "#x0D"; //$NON-NLS-1$
				case '\n':
					return "#x0A"; //$NON-NLS-1$
				case '\u0009':
					return "#x09"; //$NON-NLS-1$
    		}
    		return null;
    	}
    }

}