com.topologi.diffx.xml.XMLWriterImpl 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.List;
/**
* A simple writer for XML data that does not support namespaces.
*
* 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 and does not support namespaces, and will therefore
* throw an unsupported operation exception for each call to a method that uses namespaces.
*
* @author Christophe Lauret
* @version 6 December 2008
*/
public final class XMLWriterImpl extends XMLWriterBase implements XMLWriter {
/**
* The root node.
*/
private static final Element ROOT;
static {
ROOT = new Element("", true);
}
/**
* 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 XMLWriterImpl(Writer writer) throws NullPointerException {
super(writer, false);
this.elements.add(ROOT);
}
/**
*
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 XMLWriterImpl(Writer writer, boolean indent) throws NullPointerException {
super(writer, indent);
this.elements.add(ROOT);
}
// Writing text
// ----------------------------------------------------------------------------------------------
/**
* 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 (peekElement().hasChildren && this.indent) {
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(name, false);
}
/**
* Writes a start element tag correctly indented.
*
*
Use the hasChildren parameter to specify whether this element is
* terminal node or not, which affects the indenting.
*
*
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 {
deNude();
indent();
this.elements.add(new Element(name, hasChildren));
this.writer.write('<');
this.writer.write(name);
this.isNude = true;
this.depth++;
}
/**
* Write the end element tag.
*
* @throws IOException If thrown by the wrapped writer.
* @throws IllegalCloseElementException If there is no element to close
*/
@Override
public void closeElement() throws IOException, IllegalCloseElementException {
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.name.indexOf(' ');
if (x < 0) {
this.writer.write(elt.name);
} else {
this.writer.write(elt.name.substring(0, x));
}
}
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);.
*
*
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 element the name of the element
*
* @throws IOException If thrown by the wrapped writer.
*/
@Override
public void emptyElement(String element) throws IOException {
deNude();
indent();
this.writer.write('<');
this.writer.write(element);
this.writer.write('/');
this.writer.write('>');
if (this.indent) {
Element parent = peekElement();
if (parent.hasChildren && parent != ROOT) {
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);
}
// 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.
*/
@Override
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.
*/
@Override
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.
*/
@Override
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.
*/
@Override
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.
*/
@Override
public void attribute(String uri, String name, int value)
throws UnsupportedOperationException {
throw new UnsupportedOperationException("This class does not handle namespaces");
}
/**
* 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 != ROOT)
throw new UnclosedElementException(open.name);
this.writer.close();
}
// Inner class: Element
// ----------------------------------------------------------------------------------------------
/**
* A light object to keep track of the element.
*
* This object does not support namespaces.
*
* @author Christophe Lauret
* @version 7 March 2005
*/
private static final class Element {
/**
* The fully qualified name of the element.
*/
private final String name;
/**
* Indicates whether the element has children.
*/
private final boolean hasChildren;
/**
* Creates a new Element.
*
* @param name The qualified name of the element.
* @param hasChildren Whether the element has children.
*/
public Element(String name, boolean hasChildren) {
this.name = name;
this.hasChildren = hasChildren;
}
}
}