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Scala example source code file (XIncludeFilter.scala)

This example Scala source code file (XIncludeFilter.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

array, document, int, int, io, malformedurlexception, net, network, sax, saxexception, saxexception, stack, string, string, unresolvable, url, url, util, xinclude

The Scala XIncludeFilter.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


package scala.xml
package include.sax

import scala.xml.include._

import org.xml.sax.{ Attributes, XMLReader, Locator }
import org.xml.sax.helpers.{ XMLReaderFactory, XMLFilterImpl, NamespaceSupport, AttributesImpl }

import java.io.{ InputStream, BufferedInputStream, InputStreamReader, IOException, UnsupportedEncodingException }
import java.util.Stack
import java.net.{ URL, MalformedURLException }

/**
 * <p>
 *  This is a SAX filter which resolves all XInclude include elements
 *  before passing them on to the client application. Currently this
 *  class has the following known deviation from the XInclude specification:
 * </p>
 *  <ol>
 *   <li>XPointer is not supported.
 *  </ol>
 *
 *  <p>
 *    Furthermore, I would definitely use a new instance of this class
 *    for each document you want to process. I doubt it can be used
 *    successfully on multiple documents. Furthermore, I can virtually
 *    guarantee that this class is not thread safe. You have been
 *    warned.
 *  </p>
 *
 *  <p>
 *    Since this class is not designed to be subclassed, and since
 *    I have not yet considered how that might affect the methods 
 *    herein or what other protected methods might be needed to support 
 *    subclasses, I have declared this class final. I may remove this 
 *    restriction later, though the use-case for subclassing is weak.
 *    This class is designed to have its functionality extended via a
 *    a horizontal chain of filters, not a 
 *    vertical hierarchy of sub and superclasses.
 *  </p>
 *
 *  <p>
 *    To use this class: 
 *  </p>
 *  <ol>
 *   <li>Construct an XIncludeFilter object with a known base URL
 *   <li>Pass the XMLReader object from which the raw document will 
 *       be read to the <code>setParent() method of this object. 
 *   <li>Pass your own ContentHandler object to the 
 *       <code>setContentHandler() method of this object. This is the 
 *       object which will receive events from the parsed and included
 *       document.
 *   </li>
 *   <li>Optional: if you wish to receive comments, set your own 
 *       <code>LexicalHandler object as the value of this object's
 *       http://xml.org/sax/properties/lexical-handler property.
 *       Also make sure your <code>LexicalHandler asks this object 
 *       for the status of each comment using <code>insideIncludeElement
 *       before doing anything with the comment. 
 *   </li>
 *   <li>Pass the URL of the document to read to this object's 
 *       <code>parse() method
 *  </ol>
 * 
 *  <p> e.g.

* <pre>XIncludeFilter includer = new XIncludeFilter(base); * includer.setParent(parser); * includer.setContentHandler(new SAXXIncluder(System.out)); * includer.parse(args[i]);</code> * </pre> * </p> * translated from Elliotte Rusty Harold's Java source * @author Burak Emir */ class XIncludeFilter extends XMLFilterImpl { final val XINCLUDE_NAMESPACE = "http://www.w3.org/2001/XInclude"; private val bases = new Stack[URL](); private val locators = new Stack[Locator](); /* private EntityResolver resolver; public XIncludeFilter() { this(null); } public XIncludeFilter(EntityResolver resolver) { this.resolver = resolver; } */ // what if this isn't called???? // do I need to check this in startDocument() and push something // there???? override def setDocumentLocator(locator: Locator) { locators.push(locator) val base = locator.getSystemId() try { bases.push(new URL(base)) } catch { case e:MalformedURLException => throw new UnsupportedOperationException("Unrecognized SYSTEM ID: " + base) } super.setDocumentLocator(locator) } // necessary to throw away contents of non-empty XInclude elements private var level = 0 /** * <p> * This utility method returns true if and only if this reader is * currently inside a non-empty include element. (This is <strong> * not</strong> the same as being inside the node set which replaces * the include element.) This is primarily needed for comments * inside include elements. It must be checked by the actual * LexicalHandler to see whether a comment is passed or not. * </p> * * @return boolean */ def insideIncludeElement(): Boolean = level != 0 override def startElement(uri: String, localName: String, qName: String, atts1: Attributes) { var atts = atts1 if (level == 0) { // We're not inside an xi:include element // Adjust bases stack by pushing either the new // value of xml:base or the base of the parent val base = atts.getValue(NamespaceSupport.XMLNS, "base") val parentBase = bases.peek().asInstanceOf[URL] var currentBase = parentBase if (base != null) { try { currentBase = new URL(parentBase, base) } catch { case e: MalformedURLException => throw new SAXException("Malformed base URL: " + currentBase, e) } } bases.push(currentBase); if (uri.equals(XINCLUDE_NAMESPACE) && localName.equals("include")) { // include external document val href = atts.getValue("href") // Verify that there is an href attribute if (href==null) { throw new SAXException("Missing href attribute") } var parse = atts.getValue("parse") if (parse == null) parse = "xml" if (parse.equals("text")) { val encoding = atts.getValue("encoding"); includeTextDocument(href, encoding); } else if (parse.equals("xml")) { includeXMLDocument(href); } // Need to check this also in DOM and JDOM???? else { throw new SAXException( "Illegal value for parse attribute: " + parse); } level += 1 } else { if (atRoot) { // add xml:base attribute if necessary val attsImpl = new AttributesImpl(atts) attsImpl.addAttribute(NamespaceSupport.XMLNS, "base", "xml:base", "CDATA", currentBase.toExternalForm()) atts = attsImpl atRoot = false } super.startElement(uri, localName, qName, atts) } } } override def endElement(uri: String, localName: String, qName: String) { if (uri.equals(XINCLUDE_NAMESPACE) && localName.equals("include")) { level -= 1; } else if (level == 0) { bases.pop() super.endElement(uri, localName, qName) } } private var depth = 0; override def startDocument() { level = 0 if (depth == 0) super.startDocument() depth += 1 } override def endDocument() { locators.pop() bases.pop(); // pop the URL for the document itself depth -= 1 if (depth == 0) super.endDocument() } // how do prefix mappings move across documents???? override def startPrefixMapping(prefix: String , uri: String) { if (level == 0) super.startPrefixMapping(prefix, uri) } override def endPrefixMapping(prefix: String) { if (level == 0) super.endPrefixMapping(prefix) } override def characters(ch: Array[Char], start: Int, length: Int) { if (level == 0) super.characters(ch, start, length) } override def ignorableWhitespace(ch: Array[Char], start: Int, length: Int) { if (level == 0) super.ignorableWhitespace(ch, start, length) } override def processingInstruction(target: String, data: String) { if (level == 0) super.processingInstruction(target, data) } override def skippedEntity(name: String) { if (level == 0) super.skippedEntity(name) } // convenience method for error messages private def getLocation(): String = { var locationString = "" val locator = locators.peek().asInstanceOf[Locator] var publicID = "" var systemID = "" var column = -1 var line = -1 if (locator != null) { publicID = locator.getPublicId() systemID = locator.getSystemId() line = locator.getLineNumber() column = locator.getColumnNumber() } locationString = (" in document included from " + publicID + " at " + systemID + " at line " + line + ", column " + column); locationString } /** * <p> * This utility method reads a document at a specified URL * and fires off calls to <code>characters(). * It's used to include files with <code>parse="text" * </p> * * @param url URL of the document that will be read * @param encoding Encoding of the document; e.g. UTF-8, * ISO-8859-1, etc. * @return void * @throws SAXException if the requested document cannot be downloaded from the specified URL or if the encoding is not recognized */ private def includeTextDocument(url: String, encoding1: String) { var encoding = encoding1 if (encoding == null || encoding.trim().equals("")) encoding = "UTF-8"; var source: URL = null try { val base = bases.peek().asInstanceOf[URL] source = new URL(base, url) } catch { case e: MalformedURLException => val ex = new UnavailableResourceException("Unresolvable URL " + url + getLocation()); ex.setRootCause(e); throw new SAXException("Unresolvable URL " + url + getLocation(), ex); } try { val uc = source.openConnection() val in = new BufferedInputStream(uc.getInputStream()) var encodingFromHeader = uc.getContentEncoding() var contentType = uc.getContentType() if (encodingFromHeader != null) encoding = encodingFromHeader else { // What if file does not have a MIME type but name ends in .xml???? // MIME types are case-insensitive // Java may be picking this up from file URL if (contentType != null) { contentType = contentType.toLowerCase(); if (contentType.equals("text/xml") || contentType.equals("application/xml") || (contentType.startsWith("text/") && contentType.endsWith("+xml") ) || (contentType.startsWith("application/") && contentType.endsWith("+xml"))) { encoding = EncodingHeuristics.readEncodingFromStream(in); } } } val reader = new InputStreamReader(in, encoding) val c = new Array[Char](1024) var charsRead: Int = 0 // bogus init value do { charsRead = reader.read(c, 0, 1024); if (charsRead > 0) this.characters(c, 0, charsRead); } while (charsRead != -1) ; } catch { case e: UnsupportedEncodingException => throw new SAXException("Unsupported encoding: " + encoding + getLocation(), e); case e: IOException => throw new SAXException("Document not found: " + source.toExternalForm() + getLocation(), e); } } private var atRoot = false /** * <p> * This utility method reads a document at a specified URL * and fires off calls to various <code>ContentHandler methods. * It's used to include files with <code>parse="xml" * </p> * * @param url URL of the document that will be read * @return void * @throws SAXException if the requested document cannot be downloaded from the specified URL. */ private def includeXMLDocument(url: String) { val source = try new URL(bases.peek(), url) catch { case e: MalformedURLException => val ex = new UnavailableResourceException("Unresolvable URL " + url + getLocation()) ex setRootCause e throw new SAXException("Unresolvable URL " + url + getLocation(), ex) } try { val parser: XMLReader = try XMLReaderFactory.createXMLReader() catch { case e: SAXException => try XMLReaderFactory.createXMLReader(XercesClassName) catch { case _: SAXException => return System.err.println("Could not find an XML parser") } } parser setContentHandler this val resolver = this.getEntityResolver() if (resolver != null) parser setEntityResolver resolver // save old level and base val previousLevel = level this.level = 0 if (bases contains source) throw new SAXException( "Circular XInclude Reference", new CircularIncludeException("Circular XInclude Reference to " + source + getLocation()) ) bases push source atRoot = true parser parse source.toExternalForm() // restore old level and base this.level = previousLevel bases.pop() } catch { case e: IOException => throw new SAXException("Document not found: " + source.toExternalForm() + getLocation(), e) } } }

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