com.topologi.diffx.xml.XMLWriterNSImpl 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;
import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import javax.xml.XMLConstants;
/**
* A Namespace-aware writer for XML data.
*
* Provides methods to generate well-formed XML data easily. wrapping a writer.
*
*
This version only supports utf-8 encoding, if writing to a file make sure that the
* encoding of the file output stream is "utf-8".
*
*
The recommended implementation is to use a BufferedWriter to write.
*
*
* Writer writer =
* new BufferedWriter(new OutputStreamWriter(new FileOutputStream("foo.out"),"utf-8"));
*
*
* This class is not synchronised.
*
* @author Christophe Lauret - Allette Systems (Australia)
* @version 11 December 2011
*/
public final class XMLWriterNSImpl extends XMLWriterBase implements XMLWriter {
/**
* Set to true to show debug info.
*/
private static final boolean DEBUG = false;
/**
* The default namespace mapped to the empty prefix.
*/
private static final PrefixMapping DEFAULT_NS = new PrefixMapping(XMLConstants.NULL_NS_URI, XMLConstants.DEFAULT_NS_PREFIX);
/**
* The root node.
*/
private static final Element ROOT;
static {
List mps = new ArrayList();
mps.add(DEFAULT_NS);
ROOT = new Element("", true, mps);
}
/**
* The current prefix mapping.
*/
private final Map prefixMapping = new HashMap();
/**
* The list of prefix mappings to be associated with the next element.
*/
private List tempMapping;
/**
* A stack of elements to close the elements automatically.
*/
private final List elements = new ArrayList();
// Constructors
// ----------------------------------------------------------------------------------------------
/**
* Creates a new XML writer.
*
*
Sets the depth attribute to 0 and the indentation to true.
*
* @param writer Where this writer should write the XML data.
*
* @throws NullPointerException If the writer is null.
*/
public XMLWriterNSImpl(Writer writer) throws NullPointerException {
this(writer, false);
}
/**
*
Create a new XML writer.
*
* @param writer Where this writer should write the XML data.
* @param indent Set the indentation flag.
*
* @throws NullPointerException If the writer is null.
*/
public XMLWriterNSImpl(Writer writer, boolean indent) throws NullPointerException {
super(writer, indent);
this.elements.add(ROOT);
this.prefixMapping.put(XMLConstants.NULL_NS_URI, XMLConstants.DEFAULT_NS_PREFIX);
this.prefixMapping.put(XMLConstants.XML_NS_URI, XMLConstants.XML_NS_PREFIX);
}
/**
* Writes the angle bracket if the element open tag is not finished.
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
void deNude() throws IOException {
if (this.isNude) {
this.writer.write('>');
if (super.indent && peekElement().hasChildren) {
this.writer.write('\n');
}
this.isNude = false;
}
}
// Open/close specific elements
// ----------------------------------------------------------------------------------------------
/**
* Writes a start element tag correctly indented.
*
*
It is the same as openElement(null, name, false)
*
* @see #openElement(java.lang.String, java.lang.String, boolean)
*
* @param name the name of the element
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void openElement(String name) throws IOException {
openElement(null, name, false);
}
/**
* Write a start element tag correctly indented.
*
*
It is the same as openElement(name, false)
*
* @see #openElement(java.lang.String, boolean)
*
* @param uri The namespace URI of this element.
* @param name The name of the element.
*
* @throws IOException If thrown by the wrapped writer.
*/
public void openElement(String uri, String name) throws IOException {
openElement(uri, 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 IOException If thrown by the wrapped writer.
*/
@Override
public void openElement(String name, boolean hasChildren) throws IOException {
openElement(null, name, hasChildren);
}
/**
* 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 uri The namespace URI of this element.
* @param name The name of the element.
* @param hasChildren true if this element has children.
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void openElement(String uri, String name, boolean hasChildren) throws IOException {
deNude();
indent();
String qName = getQName(uri, name);
this.elements.add(new Element(qName, hasChildren, this.tempMapping));
this.writer.write('<');
this.writer.write(qName);
handleNamespaceDeclaration();
this.isNude = true;
this.depth++;
}
/**
* Write an end element tag.
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void closeElement() throws IOException {
Element elt = popElement();
// reaching the end of the document
if (elt == ROOT)
throw new IllegalCloseElementException();
this.depth--;
// this is an empty element
if (this.isNude) {
this.writer.write('/');
this.isNude = false;
// the element contains text
} else {
if (elt.hasChildren) {
indent();
}
this.writer.write('<');
this.writer.write('/');
int x = elt.qName.indexOf(' ');
if (x < 0) {
this.writer.write(elt.qName);
} else {
this.writer.write(elt.qName.substring(0, x));
}
}
// restore previous mapping if necessary
restorePrefixMapping(elt);
this.writer.write('>');
// take care of the new line if the indentation is on
if (super.indent) {
Element parent = peekElement();
if (parent.hasChildren && parent != ROOT) {
this.writer.write('\n');
}
}
}
/**
* Same as emptyElement(null, element);.
*
* @param element the name of the element
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void emptyElement(String element) throws IOException {
emptyElement(null, element);
}
/**
* Write an empty element.
*
*
It is possible for the element to contain attributes,
* however, since there is no character escaping, great care
* must be taken not to introduce invalid characters. For
* example:
*
* <example test="yes"/>
*
*
* @param uri The namespace URI for this element.
* @param element The name of the element.
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void emptyElement(String uri, String element) throws IOException {
deNude();
indent();
this.writer.write('<');
this.writer.write(getQName(uri, element));
handleNamespaceDeclaration();
this.writer.write('/');
this.writer.write('>');
if (super.indent) {
this.writer.write('\n');
}
}
/**
* Returns the last element in the list.
*
* @return The current element.
*/
private Element peekElement() {
return this.elements.get(this.elements.size() - 1);
}
/**
* Removes the last element in the list.
*
* @return The current element.
*/
private Element popElement() {
return this.elements.remove(this.elements.size() - 1);
}
/**
* Writes an attribute.
*
* @param uri The namespcae URI this attribute belongs to.
* @param name The name of the attribute.
* @param value The value of the attribute.
*
* @throws IOException If thrown by the wrapped writer.
* @throws IllegalStateException If there is no open element or text has been written.
*/
@Override
public void attribute(String uri, String name, String value)
throws IOException, IllegalStateException {
if (!this.isNude) throw new IllegalArgumentException("Cannot write attribute: too late!");
this.writer.write(' ');
this.writer.write(getQName(uri, name));
this.writer.write("=\"");
this.writerEscape.writeAttValue(value);
this.writer.write('"');
handleNamespaceDeclaration();
}
/**
* Writes an attribute.
*
* This method for number does not require escaping.
*
* @param uri The namespcae URI this attribute belongs to.
* @param name The name of the attribute.
* @param value The value of the attribute.
*
* @throws IOException If thrown by the wrapped writer.
* @throws IllegalStateException If there is no open element or text has been written.
*/
@Override
public void attribute(String uri, String name, int value)
throws IOException, IllegalStateException {
if (!this.isNude) throw new IllegalArgumentException("Cannot write attribute: too late!");
this.writer.write(' ');
this.writer.write(getQName(uri, name));
this.writer.write("=\"");
this.writer.write(Integer.toString(value));
this.writer.write('"');
handleNamespaceDeclaration();
}
// Namespace handling
// ----------------------------------------------------------------------------------------------
/**
* @see com.topologi.diffx.xml.XMLWriter#setPrefixMapping(java.lang.String, java.lang.String)
*
*
This implementation does not keep a history of the prefix mappings so it needs to be
* reset. If a prefix is already being used it is overridden.
*
* @param uri The full namespace URI.
* @param prefix The prefix for the namespace uri.
*
* @throws NullPointerException if the prefix is null.
*/
@Override
public void setPrefixMapping(String uri, String prefix) throws NullPointerException {
//do not declare again if the same mapping already exist
if (!prefix.equals(this.prefixMapping.get(uri))) {
// remove the previous mapping to the prefix
removeIfNeeded(prefix);
// create the new prefix mapping
PrefixMapping pm = new PrefixMapping(prefix, uri);
this.prefixMapping.put(pm.uri, pm.prefix);
if (DEBUG) {
System.err.println(pm.prefix+" -> "+pm.uri);
}
if (this.tempMapping == null) {
this.tempMapping = new ArrayList();
}
this.tempMapping.add(pm);
}
}
/**
* Returns the qualified name for this element using the specified namespace URI.
*
* @param uri The namespace URI for the element.
* @param name The name of the element or attribute.
*
* @return The qualified element name.
*
* @throws UndeclaredNamespaceException If the uri has not being previously declared.
*/
private String getQName(String uri, String name) throws UndeclaredNamespaceException {
String prefix = this.prefixMapping.get(uri != null? uri : "");
if (prefix != null) {
if (!"".equals(prefix))
return this.prefixMapping.get(uri)+":"+name;
else
return name;
} else if (uri == null) return name;
else
throw new UndeclaredNamespaceException(uri);
}
/**
* Handles the namespace declaration and updates the prefix mappings.
*
* @throws IOException If thrown by the wrapped writer.
*/
private void handleNamespaceDeclaration() throws IOException {
if (this.tempMapping != null) {
PrefixMapping pm = null;
for (int i = 0; i < this.tempMapping.size(); i++) {
pm = this.tempMapping.get(i);
if (!XMLConstants.XML_NS_PREFIX.equals(pm.prefix)) {
this.writer.write(" xmlns");
// specify a prefix if different from ""
if (!"".equals(pm.prefix)) {
this.writer.write(':');
this.writer.write(pm.prefix);
}
this.writer.write("=\"");
this.writer.write(pm.uri);
this.writer.write("\"");
}
}
this.tempMapping = null;
}
}
/**
* Restores the prefix mapping after closing an element.
*
* This costly operation need only to be done if the method
* {@link XMLWriterNSImpl#setPrefixMapping(String, String)} have been used
* immediately before, therefore it should not happen often.
*
* @param elt The element that had some new mappings.
*/
private void restorePrefixMapping(Element elt) {
if (elt.mappings != null) {
// for each mapping of this element
for (int i = 0; i < elt.mappings.size(); i++) {
PrefixMapping mpi = elt.mappings.get(i);
if (DEBUG) {
System.err.print(mpi.prefix+" -< ");
}
// find the first previous namespace mapping amongst the parents
// that defines namespace mappings
for (int j = this.elements.size() - 1; j > 0; j--) {
if (this.elements.get(j).mappings != null) {
List mps = this.elements.get(j).mappings;
// iterate through the define namespace mappings of the parent
for (int k = 0; k < mps.size(); k++) {
PrefixMapping mpk = mps.get(k);
// if we found a namespace prefix for the namespace
if (mpk.prefix.equals(mpi.prefix)) {
removeIfNeeded(mpk.prefix);
this.prefixMapping.put(mpk.uri, mpk.prefix);
if (DEBUG) {
System.err.println(mpk.uri+" [R]");
}
j = 0; // exit from the previous loop
break; // exit from this one
}
}
}
}
}
}
}
/**
* Removes the mapping associated to the specified prefix.
*
* @param prefix The prefix which mapping should be removed.
*/
private void removeIfNeeded(String prefix) {
// remove the previous mapping to the prefix
if (this.prefixMapping.containsValue(prefix)) {
Entry remove = null;
for (Entry e : this.prefixMapping.entrySet()) {
if (e.getValue().equals(prefix)) {
remove = e;
break;
}
}
// we know key should have a value
this.prefixMapping.remove(remove.getKey());
}
}
/**
* Close the writer.
*
* @throws IOException If thrown by the wrapped writer.
* @throws UnclosedElementException If an element has been left open.
*/
@Override
public void close() throws IOException, UnclosedElementException {
Element open = peekElement();
if (open != XMLWriterNSImpl.ROOT)
throw new UnclosedElementException(open.qName);
this.writer.close();
}
// Inner class: Element
// ----------------------------------------------------------------------------------------------
/**
* A light object to keep track of the elements
*
* @author Christophe Lauret (Allette Systems)
* @version 31 August 2004
*/
private static final class Element {
/**
* The fully qualified name of the element.
*/
private final String qName;
/**
* Indicates whether the element has children.
*/
private final boolean hasChildren;
/**
* A list of prefix mappings for this element.
*
* Can be null.
*/
private final List mappings;
/**
* Creates a new Element.
*
* @param qName The qualified name of the element.
* @param hasChildren Whether the element has children.
* @param mappings The list of prefix mapping if any.
*/
public Element(String qName, boolean hasChildren, List mappings) {
this.qName = qName;
this.hasChildren = hasChildren;
this.mappings = mappings;
}
}
// Inner class: Prefix Mapping
// ----------------------------------------------------------------------------------------------
/**
* Light-weight class to represent a prefix mapping.
*
* The class attributes cannot be null.
*
* @author Christophe Lauret (Allette Systems)
* @version 31 August 2004
*/
private static final class PrefixMapping {
/**
* The prefix associated to the URI.
*/
private final String prefix;
/**
* The namespace URI.
*/
private final String uri;
/**
* Creates a new prefix mapping.
*
* @param prefix The prefix for the URI.
* @param uri The full namespace URI.
*/
public PrefixMapping(String prefix, String uri) {
this.prefix = prefix != null? prefix : "";
this.uri = uri != null? uri : "";
}
}
}