incrementalsaxsource_xerces.java

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/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: IncrementalSAXSource_Xerces.java,v 1.2.4.1 2005/09/15 08:15:08 suresh_emailid Exp $
 */

package com.sun.org.apache.xml.internal.dtm.ref;

import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

import com.sun.org.apache.xerces.internal.parsers.SAXParser;
import com.sun.org.apache.xml.internal.res.XMLErrorResources;
import com.sun.org.apache.xml.internal.res.XMLMessages;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;


/** <p>IncrementalSAXSource_Xerces takes advantage of the fact that Xerces1
 * incremental mode is already a coroutine of sorts, and just wraps our
 * IncrementalSAXSource API around it.</p>
 *
 * <p>Usage example: See main().</p>
 *
 * <p>Status: Passes simple main() unit-test. NEEDS JAVADOC.</p>
 * */
public class IncrementalSAXSource_Xerces
  implements IncrementalSAXSource
{
  //
  // Reflection. To allow this to compile with both Xerces1 and Xerces2, which
  // require very different methods and objects, we need to avoid static 
  // references to those APIs. So until Xerces2 is pervasive and we're willing 
  // to make it a prerequisite, we will rely upon relection.
  //
  Method fParseSomeSetup=null; // Xerces1 method
  Method fParseSome=null; // Xerces1 method
  Object fPullParserConfig=null; // Xerces2 pull control object
  Method fConfigSetInput=null; // Xerces2 method
  Method fConfigParse=null; // Xerces2 method
  Method fSetInputSource=null; // Xerces2 pull control method
  Constructor fConfigInputSourceCtor=null; // Xerces2 initialization method
  Method fConfigSetByteStream=null; // Xerces2 initialization method
  Method fConfigSetCharStream=null; // Xerces2 initialization method
  Method fConfigSetEncoding=null; // Xerces2 initialization method
  Method fReset=null; // Both Xerces1 and Xerces2, but diff. signatures
  
  //
  // Data
  //
  SAXParser fIncrementalParser;
  private boolean fParseInProgress=false;

  //
  // Constructors
  //

  /** Create a IncrementalSAXSource_Xerces, and create a SAXParser
   * to go with it. Xerces2 incremental parsing is only supported if
   * this constructor is used, due to limitations in the Xerces2 API (as of
   * Beta 3). If you don't like that restriction, tell the Xerces folks that
   * there should be a simpler way to request incremental SAX parsing.
   * */
  public IncrementalSAXSource_Xerces() 
		throws NoSuchMethodException
	{
		try
		{
			// Xerces-2 incremental parsing support (as of Beta 3)
			// ContentHandlers still get set on fIncrementalParser (to get
			// conversion from XNI events to SAX events), but
			// _control_ for incremental parsing must be exercised via the config.
			// 
			// At this time there's no way to read the existing config, only 
			// to assert a new one... and only when creating a brand-new parser.
			//
			// Reflection is used to allow us to continue to compile against
			// Xerces1. If/when we can abandon the older versions of the parser,
			// this will simplify significantly.
			
			// If we can't get the magic constructor, no need to look further.
			Class xniConfigClass=ObjectFactory.findProviderClass(
                            "com.sun.org.apache.xerces.internal.xni.parser.XMLParserConfiguration",
                            ObjectFactory.findClassLoader(), true);
			Class[] args1={xniConfigClass};
			Constructor ctor=SAXParser.class.getConstructor(args1);
			
			// Build the parser configuration object. StandardParserConfiguration
			// happens to implement XMLPullParserConfiguration, which is the API
			// we're going to want to use.
			Class xniStdConfigClass=ObjectFactory.findProviderClass(
                            "com.sun.org.apache.xerces.internal.parsers.StandardParserConfiguration",
                            ObjectFactory.findClassLoader(), true);
			fPullParserConfig=xniStdConfigClass.newInstance();
			Object[] args2={fPullParserConfig};
			fIncrementalParser = (SAXParser)ctor.newInstance(args2);
			
			// Preload all the needed the configuration methods... I want to know they're
			// all here before we commit to trying to use them, just in case the
			// API changes again.
			Class fXniInputSourceClass=ObjectFactory.findProviderClass(
                            "com.sun.org.apache.xerces.internal.xni.parser.XMLInputSource",
                            ObjectFactory.findClassLoader(), true);
			Class[] args3={fXniInputSourceClass};
			fConfigSetInput=xniStdConfigClass.getMethod("setInputSource",args3);

			Class[] args4={String.class,String.class,String.class};
			fConfigInputSourceCtor=fXniInputSourceClass.getConstructor(args4);
			Class[] args5={java.io.InputStream.class};
			fConfigSetByteStream=fXniInputSourceClass.getMethod("setByteStream",args5);
			Class[] args6={java.io.Reader.class};
			fConfigSetCharStream=fXniInputSourceClass.getMethod("setCharacterStream",args6);
			Class[] args7={String.class};
			fConfigSetEncoding=fXniInputSourceClass.getMethod("setEncoding",args7);

			Class[] argsb={Boolean.TYPE};
			fConfigParse=xniStdConfigClass.getMethod("parse",argsb);			
			Class[] noargs=new Class[0];
			fReset=fIncrementalParser.getClass().getMethod("reset",noargs);
		}
		catch(Exception e)
		{
	    // Fallback if this fails (implemented in createIncrementalSAXSource) is
			// to attempt Xerces-1 incremental setup. Can't do tail-call in
			// constructor, so create new, copy Xerces-1 initialization, 
			// then throw it away... Ugh.
			IncrementalSAXSource_Xerces dummy=new IncrementalSAXSource_Xerces(new SAXParser());
			this.fParseSomeSetup=dummy.fParseSomeSetup;
			this.fParseSome=dummy.fParseSome;
			this.fIncrementalParser=dummy.fIncrementalParser;
		}
  }

  /** Create a IncrementalSAXSource_Xerces wrapped around
   * an existing SAXParser. Currently this works only for recent
   * releases of Xerces-1.  Xerces-2 incremental is currently possible
   * only if we are allowed to create the parser instance, due to
   * limitations in the API exposed by Xerces-2 Beta 3; see the
   * no-args constructor for that code.
   * 
   * @exception if the SAXParser class doesn't support the Xerces
   * incremental parse operations. In that case, caller should
   * fall back upon the IncrementalSAXSource_Filter approach.
   * */
  public IncrementalSAXSource_Xerces(SAXParser parser) 
    throws NoSuchMethodException  
  {
		// Reflection is used to allow us to compile against
		// Xerces2. If/when we can abandon the older versions of the parser,
		// this constructor will simply have to fail until/unless the
		// Xerces2 incremental support is made available on previously
		// constructed SAXParser instances.
    fIncrementalParser=parser;
		Class me=parser.getClass();
    Class[] parms={InputSource.class};
    fParseSomeSetup=me.getMethod("parseSomeSetup",parms);
    parms=new Class[0];
    fParseSome=me.getMethod("parseSome",parms);
    // Fallback if this fails (implemented in createIncrementalSAXSource) is
    // to use IncrementalSAXSource_Filter rather than Xerces-specific code.
  }

  //
  // Factories
  //
  static public IncrementalSAXSource createIncrementalSAXSource() 
	{
		try
		{
			return new IncrementalSAXSource_Xerces();
		}
		catch(NoSuchMethodException e)
		{
			// Xerces version mismatch; neither Xerces1 nor Xerces2 succeeded.
			// Fall back on filtering solution.
			IncrementalSAXSource_Filter iss=new IncrementalSAXSource_Filter();
			iss.setXMLReader(new SAXParser());
			return iss;
		}
  }
	
  static public IncrementalSAXSource
  createIncrementalSAXSource(SAXParser parser) {
		try
		{
			return new IncrementalSAXSource_Xerces(parser);
		}
		catch(NoSuchMethodException e)
		{
			// Xerces version mismatch; neither Xerces1 nor Xerces2 succeeded.
			// Fall back on filtering solution.
			IncrementalSAXSource_Filter iss=new IncrementalSAXSource_Filter();
			iss.setXMLReader(parser);
			return iss;
		}
  }

  //
  // Public methods
  //

  // Register handler directly with the incremental parser
  public void setContentHandler(org.xml.sax.ContentHandler handler)
  {
    // Typecast required in Xerces2; SAXParser doesn't inheret XMLReader
    // %OPT% Cast at asignment?
    ((XMLReader)fIncrementalParser).setContentHandler(handler);
  }

  // Register handler directly with the incremental parser
  public void setLexicalHandler(org.xml.sax.ext.LexicalHandler handler)