com.topologi.diffx.xml.dom.DOMWriterImpl Maven / Gradle / Ivy
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/*
* This file is part of the DiffX library.
*
* For licensing information please see the file license.txt included in the release.
* A copy of this licence can also be found at
* http://www.opensource.org/licenses/artistic-license-2.0.php
*/
package com.topologi.diffx.xml.dom;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;
import org.docx4j.XmlUtils;
import org.w3c.dom.Attr;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.Text;
import com.topologi.diffx.xml.IllegalCloseElementException;
/**
* A simple implementation of a DOM writer
*
* Provides methods to generate well-formed XML data easily via DOM.
*
* @author Christophe Lauret
* @version 11 December 2011
*/
public final class DOMWriterImpl implements DOMWriter {
// Class attributes
// ----------------------------------------------------------------------------------------------
/**
* The DOM document on which we write.
*/
private final Document document;
/**
* The new line used.
*/
private final Node newline;
/**
* Indicates whether the xml should be indented or not.
*
*
The default is true (indented).
*
*
The indentation is 2 white-spaces.
*/
private boolean indent;
/**
* The default indentation spaces used.
*/
private String indentChars;
// state variables
// ----------------------------------------------------------------------------------------------
/**
* Level of the depth of the xml document currently produced.
*
*
This attribute changes depending on the state of the instance.
*/
private transient int depth;
/**
* Flag to indicate that the element open tag is not finished yet.
*/
private transient boolean isNude;
/**
* The current node being written onto.
*
*
This node should always be an element except before and after writing where it
* is the document node itself.
*/
private transient Node currentElement;
/**
* An array to indicate which elements have children.
*/
private transient List childrenFlags = new ArrayList();
// Constructors
// ----------------------------------------------------------------------------------------------
/**
* Creates a new XML writer for DOM using the default implementation on
* the system.
*
*
Attempts to create the DOM document using:
*
* DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance()
* DocumentBuilder builder = factory.newDocumentBuilder();
* Document document = builder.newDocument();
*
*
* @throws ParserConfigurationException If thrown by the document builder factory.
*/
public DOMWriterImpl() throws ParserConfigurationException {
this(newDocument());
}
/**
* Creates a new XML writer for DOM.
*
* @param document The DOM provided.
*
* @throws NullPointerException If the handler is null.
*/
public DOMWriterImpl(Document document) {
if (document == null)
throw new NullPointerException("The XMLWriter requires a DOM Document to write on.");
this.document = document;
this.currentElement = document;
this.newline = document.createTextNode("\n");
}
// Setup methods
// ----------------------------------------------------------------------------------------------
/**
* Does nothing.
*/
public void xmlDecl() {
}
/**
* {@inheritDoc}
*/
public void setIndentChars(String spaces) {
if (this.depth != 0)
throw new IllegalStateException("To late to set the indentation characters!");
// check that this is a valid indentation string
if (spaces != null) {
for (int i = 0; i < spaces.length(); i++) {
if (!Character.isSpaceChar(spaces.charAt(i)))
throw new IllegalArgumentException("Not a valid indentation string.");
}
}
// update the flags
this.indentChars = spaces;
this.indent = spaces != null;
}
// Write text methods
// ----------------------------------------------------------------------------------------------
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeText(String text) {
if (text == null) return;
deNude();
Text textNode = this.document.createTextNode(text);
this.currentElement.appendChild(textNode);
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeText(char[] text, int off, int len) {
this.writeText(new String(text, off, len));
}
/**
* This method is expensive as the character has to be converted to a String for DOM.
*
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeText(char c) {
this.writeText(new String(new char[]{c}));
}
/**
* Writes the string value of an object.
*
*
Does nothing if the object is null.
*
* @see Object#toString
*
* @param o The object that should be written as text.
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeText(Object o) {
// TODO: what about an XML serializable ???
// TODO: Add to interface ???
if (o != null) {
this.writeText(o.toString());
}
}
/**
* Writes the CDATA section to the DOM.
*
*
Does nothing if the object is null.
*
* @param data The data to write to the section.
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeCDATA(String data) {
if (data == null) return;
this.document.createCDATASection(data);
}
// Write xml methods are not supported
// ----------------------------------------------------------------------------------------------
/**
* {@inheritDoc}
*
* @throws UnsupportedOperationException XML cannot be written to the DOM
*/
public void writeXML(String text) {
throw new UnsupportedOperationException("Cannot use unparsed XML as DOM node.");
}
/**
* {@inheritDoc}
*
* @throws UnsupportedOperationException XML cannot be written to the DOM
*/
public void writeXML(char[] text, int off, int len)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("Cannot use unparsed XML as DOM node.");
}
// PI and comments
// ----------------------------------------------------------------------------------------------
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writeComment(String comment) throws DOMException {
if (comment.indexOf("--") >= 0)
throw new IllegalArgumentException("A comment must not contain '--'.");
deNude();
Node node = this.document.createComment(comment);
this.currentElement.appendChild(node);
if (this.indent) {
newLine();
}
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void writePI(String target, String data) throws DOMException {
deNude();
Node node = this.document.createProcessingInstruction(target, data);
this.currentElement.appendChild(node);
if (this.indent) {
newLine();
}
}
// Attribute methods
// ----------------------------------------------------------------------------------------------
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void attribute(String name, String value) throws DOMException {
if (!this.isNude)
throw new IllegalArgumentException("Cannot write attribute: too late!");
Attr att = this.document.createAttribute(name);
att.setValue(value);
this.currentElement.appendChild(att);
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void attribute(String name, int value) throws DOMException {
attribute(name, Integer.toString(value));
}
// Open/close specific elements
// ----------------------------------------------------------------------------------------------
/**
* Writes a start element tag correctly indented.
*
*
It is the same as openElement("", name, false)
*
* @see #openElement(java.lang.String, java.lang.String, boolean)
*
* @param name the name of the element
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void openElement(String name) throws DOMException {
openElement(name, false);
}
/**
* Writes a start element tag correctly indented.
*
*
Use the hasChildren parameter to specify whether this element is terminal
* node or not, note: this affects the indenting. To produce correctly indented XML, you
* should use the same value for this flag when closing the element.
*
*
The name can contain attributes and should be a valid xml name.
*
* @param name The name of the element.
* @param hasChildren true if this element has children.
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void openElement(String name, boolean hasChildren) throws DOMException {
deNude();
indent();
this.childrenFlags.add(Boolean.valueOf(hasChildren));
Element element = this.document.createElement(name);
this.currentElement.appendChild(element);
this.currentElement = element;
this.isNude = true;
this.depth++;
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void element(String name, String text) throws DOMException {
this.openElement(name);
this.writeText(text);
closeElement();
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void closeElement() throws DOMException, IllegalCloseElementException {
if (this.currentElement.getNodeType() == Node.DOCUMENT_NODE)
throw new IllegalCloseElementException();
this.depth--;
this.isNude = false;
Boolean hasChildren = this.childrenFlags.remove(this.childrenFlags.size() - 1);
if (hasChildren.booleanValue()) {
indent();
}
this.currentElement.normalize();
this.currentElement = (Element)this.currentElement.getParentNode();
// new line if parent has children
if (this.indent) {
Boolean b = this.childrenFlags.get(this.childrenFlags.size() - 1);
if (b.booleanValue()) {
newLine();
}
}
}
/**
* {@inheritDoc}
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
public void emptyElement(String name) throws DOMException {
Element element = this.document.createElement(name);
this.currentElement.appendChild(element);
}
// direct access to the writer ----------------------------------------------------------
/**
* Does nothing.
*
* {@inheritDoc}
*/
public void close() {
// Do nothing
}
/**
* Normalises the current element.
*/
public void flush() {
this.currentElement.normalize();
}
// DOM Writer methods -------------------------------------------------------------------
/**
* {@inheritDoc}
*/
public Document getDocument() {
return this.document;
}
// unsupported operations -------------------------------------------------------------------
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param name This parameter is ignored.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void openElement(String uri, String name) throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces.");
}
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param name This parameter is ignored.
* @param hasChildren This parameter is ignored.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void openElement(String uri, String name, boolean hasChildren)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces.");
}
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param element This parameter is ignored.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void emptyElement(String uri, String element)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces");
}
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param prefix This parameter is ignored.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void setPrefixMapping(String uri, String prefix)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces");
}
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param name The name of the attribute.
* @param value The value of the attribute.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void attribute(String uri, String name, String value)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces");
}
/**
* Not supported.
*
* @param uri This parameter is ignored.
* @param name The name of the attribute.
* @param value The value of the attribute.
*
* @throws UnsupportedOperationException This class does not handle namespaces.
*/
public void attribute(String uri, String name, int value)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces");
}
// private helpers ----------------------------------------------------------------------
/**
* Insert the correct amount of space characterss depending on the depth and if
* the indent flag is set to true.
*/
void indent() {
if (this.indent) {
StringBuffer out = new StringBuffer(this.depth * this.indentChars.length());
for (int i = 0; i < this.depth; i++) {
out.append(this.indentChars);
}
Node node = this.document.createTextNode(out.toString());
this.currentElement.appendChild(node);
}
}
/**
* Writes the angle bracket if the element open tag is not finished.
*/
private void deNude() {
if (this.isNude) {
if (this.indent) { //TODO: hasChildren
newLine();
}
this.isNude = false;
}
}
/**
* Adds a new line to the DOM.
*
* @throws DOMException If thrown by method invoked on the underlying DOM document
*/
private void newLine() {
this.currentElement.appendChild(this.newline.cloneNode(false));
}
/**
* Returns a new DOM document.
*
*
Attempts to create the DOM document using:
*
* DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance()
* DocumentBuilder builder = factory.newDocumentBuilder();
* Document document = builder.newDocument();
*
*
* @return A new DOM document.
*
* @throws ParserConfigurationException If thrown by the document builder factory.
*/
private static Document newDocument() throws ParserConfigurationException {
DocumentBuilder builder = XmlUtils.getNewDocumentBuilder();
return builder.newDocument();
}
}