DVNOAIFilterHandler.java

/*
   Copyright (C) 2005-2012, by the President and Fellows of Harvard College.

   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.

   Dataverse Network - A web application to share, preserve and analyze research data.
   Developed at the Institute for Quantitative Social Science, Harvard University.
   Version 3.0.
*/
package edu.harvard.iq.dvn.lockss.plugin;

import java.io.PrintWriter; 
import org.xml.sax.SAXException; 
import org.xml.sax.SAXParseException; 
import org.xml.sax.helpers.DefaultHandler; 
import org.xml.sax.Attributes; 
import org.lockss.util.*;

// This filter does a super-minimalistic processing of the incoming
// XML stream stripping pretty much everything except for the tags and 
// attributes that we are specifically interested in. 
// 
// It ain't pretty but it works. 

public class DVNOAIFilterHandler extends DefaultHandler {

    private int printflag = 1;
    private int textprintflag = 1;
    private int idflag = 0; 
    private int deletedflag = 0; 
    private String currentIdentifier = null; 
    private String lastIdentifier = null; 

    private PrintWriter myout = null; 


    public DVNOAIFilterHandler (PrintWriter out) {
	myout = out; 
    }

    public void startDocument() throws SAXException {
	//myout.println ("<?xml version='1.0'?>\n"); 
    }
    public void endDocument() throws SAXException {
	myout.flush(); 
	myout.close(); 
    }

    public void startElement (String uri, String localName,
			      String qName, Attributes attributes) throws SAXException {

	String attString = ""; 
	
	if (qName.equals("dataDscr") ||
	    qName.equals("docDscr") ||
	    qName.equals("stdyDscr")) {
	    printflag = 0; 
	} else {
	    if (qName.equals("metadata")) {
		textprintflag = 0; 
	    }


	    // These are the sections that contains the URLs; 
	    // the URLs are stored in the XML attribute "URI", so 
	    // it is the only attribute we need:
	    
	    if (qName.equals("fileDscr") || 
		qName.equals("otherMat")) {
		attString = attributes.getValue ("URI"); 
		attString = minimallyEncodeString(attString);
		if ( attString != null && attString.length() > 0 ) {
		    attString = " URI=\"" + attString + "\""; 
		}
	    }

	    // We want to preserve all the attributes in the <OAI-PMH> and
	    // <codeBook> and a few other xml tags; 
	    // these may be needed for processing:

	    if (qName.equals("OAI-PMH") ||
		qName.equals("error") ||
		qName.equals("request") ||
		qName.equals("resumptionToken") ||
		qName.equals("notes") ||
                qName.equals("header") ||
		qName.equals("codeBook")) {
		int i = attributes.getLength(); 

		for ( int j = 0; j < i; j++ ) {
		    String aQName = attributes.getQName (j); 
		    String aValue = attributes.getValue (j); 

		    attString =  attString + " " + aQName + "=\"" + aValue + "\"";
		    // We are also specifically interested in access restriction
		    // text inside the special <notes> tags: 

		    if (qName.equals("notes") &&
			aQName.equals("type") &&
			aValue.equals("LOCKSS:CRAWLING")) {
			textprintflag = 1;
		    }
                    
                    if (qName.equals("header") &&
                        aQName.equals("status") &&
                        aValue.equals("deleted")) {
                        deletedflag = 1;
                    }
		}
	    }

	    if ( printflag != 0 ) {
		if ( attString != null && attString.length() > 0 ) {
		    myout.println("<" + qName + attString + ">"); 
		} else {
		    myout.print("<" + qName + ">"); 
		}
	    }
            
            // If this is the OAI <identifier> tag, we want to cache it.
            
            if (qName.equals("identifier") && printflag != 0) {
                idflag = 1;
                if (deletedflag != 0) {
                    textprintflag = 0;
                }
            }
          
	}   
    }
	
    public void endElement (String uri, String localName,
			      String qName) throws SAXException {
	
	if ( printflag != 0 ) {
	    myout.println("</" + qName + ">"); 
	}

	if (qName.equals("dataDscr") ||
	    qName.equals("docDscr") ||
	    qName.equals("stdyDscr")) {
	    printflag = 1; 
	}

	if (qName.equals("metadata")) {
            textprintflag = 1;
        }

	if (qName.equals("notes")) {
            textprintflag = 0;
        }
        
        if (qName.equals("record")) {
            lastIdentifier = currentIdentifier; 
            currentIdentifier = null; 
        }

        if (qName.equals("header")) {
            deletedflag = 0; 
        }
        
        if (qName.equals("identifier") && printflag != 0) {
            textprintflag = 1;
        }
    }
       
    public void characters(char buf[], int offset, int len) throws SAXException {
	String output = new String(buf, offset, len); 
	if ( printflag != 0 
	     && 
	     textprintflag != 0
	     &&
	     output.length() != 0) {
	    myout.print(output); 
	}
        
        if (idflag == 1) {
            currentIdentifier = output; 
            idflag = 0;
        }
    }
    
    public void fatalError (SAXParseException spx) throws SAXException {
        if (currentIdentifier != null) {
            throw new SAXException ("Can't parse ListRecords stream; offending record: " + currentIdentifier + "; " + spx.getMessage());
        }
        
        if (lastIdentifier != null) {
            throw new SAXException ("Can't parse ListRecords stream; last successfully processed record: " + lastIdentifier + "; " + spx.getMessage());
        }
        
        throw new SAXException ("Can't parse ListRecords stream; " + spx.getMessage()); 
        
    }

    private static String minimallyEncodeString(String textString) {
        textString = StringUtil.replaceString(textString, "&", "&");
        return textString;
    }

}