SAX parser servlet help

Greenhorn

Posts: 3

posted 19 years ago

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It seems that Ant won't let me compile this file since it appears to be laden with errors. What this servlet does is that it prompts for a search term provided by the user in order to search within an RSS feed for headlines that contain the search term, and write them out in HTML. The error that I keep getting is "illegal start of expression" in the startElement method. Can someone please see if the syntax is correct as well as point out the mistakes that I have made? Thanks.

import javax.servlet.*;
import javax.servlet.http.*;
import java.net.URL;
import java.io.*;
import java.util.*;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.*;
 
 
public class SearchAndDeliver extends HttpServlet implements ContentHandler {
 
String queryString=null;
 
 
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException
        {
//XMLReader parser=new SAXParser();
boolean inTitleElement;
boolean inLinkElement;
String title=null;
String link=null;
XMLReader parser=XMLReaderFactory.createXMLReader();
parser.setContentHandler(this);
queryString = request.getParameter("query");
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
 
out.println("<html>");
out.println("<head>");
out.println("</head>");
out.println("<body>");
out.println("<h2>Headlines from The New York Times Arts Section.</h2>");
try
{
parser.parse("http://www.nytimes.com/services/xml/rss/nyt/Arts.xml");
}
catch(SAXException e)
{
//System.out.println(args[0]+" is not well formed");
System.out.println(e.getMessage());
}
catch(IOException e)
{
System.out.println("Due to an IOException, the parser could not check"+parser);//I don't know what to make of this as well.
}
 
// do-nothing methods
 
public void startElement(String namespaceURI, String localName, String qualifiedName, Attributes atts)
throws SAXException
{
if(localName.equals("title"))
{
title="";
inTitleElement=true;
}
if(localName.equals("link"))
{
link="";
inLinkElement=true;
}
}
public void endElement(String namespaceURI, String localName, String qualifiedName)
{
if(localName.equals("title"))
{
System.out.println(title);
inTitleElement=false;
}
if(localName.equals("link"))
{
System.out.println(link);
inLinkElement=false;
}
 
try
{
if(queryString.equals(title.indexOf(queryString)))
{
out.println("<a href=\""+link+"\""+">"+title+"</a><br>");
}
else
{
out.println(" Your search of "+queryString+" produced no results.");
}
}
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
public void characters(char[] text, int start, int length)
throws SAXException
{
if(inTitleElement)
{
title+=String.valueOf(text,start,length);
}
if(inLinkElement)
{
link+=String.valueOf(text,start,length);
}
}
public void setDocumentLocator(Locator locator) {}
public void startDocument()
throws SAXException
{
 inTitleElement=false;
 inLinkElement=false;
}
public void endDocument() {}
public void startPrefixMapping(String prefix, String uri) {}
public void endPrefixMapping(String prefix) {}
public void ignorableWhitespace(char[] text, int start,int length) throws SAXException {}
public void processingInstruction(String target, String data){}
public void skippedEntity(String name){}
 
out.println("</body>");
out.println("</html>");
out.close();
         }
 
         public void doGet(HttpServletRequest request, HttpServletResponse response)
         throws ServletException, java.io.IOException
         {
         doPost(request,response);
         }
 
}

[ November 18, 2004: Message edited by: Diego Tori ]
[ November 18, 2004: Message edited by: Diego Tori ]

Madhav Lakkapragada

Ranch Hand

Posts: 5040

posted 19 years ago

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Diego,

Welcome to the ranch.

You code seems to involve a lot of stuff. Generally, its a good ide to seperate stuff and not put too much into one file. Here you have servlet code that seems to output HTML, which is good. But your attempt to stuff it with XML Parsing makes the code rather ugly and difficult to follow / debug.

If you agree that its difficult to debug, I would suggest that you seperate the parsing from the servlet code. Generally this is done inside a Java Bean class of some kind.

Also if you could tell us how familiar you are with Servlets / XML parsing, it would help us to point you in the right direction with some links.
Consider that and then lets see where we go...
regds.

- m

Diego Tori

Greenhorn

Posts: 3

posted 19 years ago

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OK, it seems that I put a method in a method, and that's why it was laden with errors. I made some necessary changes to the code, but it's still throwing me some errors, possibly a syntax error. I just started learning how to write servlets a month ago, thus my knowledge is limited. How would I successfully integrate these classes into one servlet, a.k.a., the standard skeletal syntax for a servlet of this nature.

Here's some updated code:

public class SearchAndDeliver extends HttpServlet implements ContentHandler {
 
String queryString=null;
boolean inTitleElement;
boolean inLinkElement;
String title=null;
String link=null;
String comparison=null;
java.io.PrintWriter out = response.getWriter();
 
public void startElement(String namespaceURI, String localName, String qualifiedName, Attributes atts)
throws SAXException
{
if(localName.equals("title"))
{
title="";
inTitleElement=true;
}
if(localName.equals("link"))
{
link="";
inLinkElement=true;
}
}
public void endElement(String namespaceURI, String localName, String qualifiedName)
{
if(localName.equals("title"))
{
System.out.println(title);
inTitleElement=false;
}
if(localName.equals("link"))
{
System.out.println(link);
inLinkElement=false;
}
comparison=title.indexOf(queryString);
try
{
if(queryString.equals(comparison))
{
out.println("<a href=\""+link+"\""+">"+title+"</a><br>");
}
else
{
out.println(" Your search of "+queryString+" produced no results.");
}
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void characters(char[] text, int start, int length)
throws SAXException
{
if(inTitleElement)
{
title+=String.valueOf(text,start,length);
}
if(inLinkElement)
{
link+=String.valueOf(text,start,length);
}
}
public void setDocumentLocator(Locator locator) {}
public void startDocument()
throws SAXException
{
 inTitleElement=false;
 inLinkElement=false;
}
public void endDocument() {}
public void startPrefixMapping(String prefix, String uri) {}
public void endPrefixMapping(String prefix) {}
public void ignorableWhitespace(char[] text, int start,int length) throws SAXException {}
public void processingInstruction(String target, String data){}
public void skippedEntity(String name){}
 
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException
        {
//XMLReader parser=new SAXParser();
 
XMLReader parser=XMLReaderFactory.createXMLReader();
queryString = request.getParameter("query");
response.setContentType("text/html");

out.println("<html>");
out.println("<head>");
out.println("</head>");
out.println("<body>");
out.println("<h2>Headlines from The New York Times Arts Section.</h2>");
try
{
parser.setContentHandler(this);
parser.parse("http://www.nytimes.com/services/xml/rss/nyt/Arts.xml");
}
catch(SAXException e)
{
//System.out.println(args[0]+" is not well formed");
System.out.println(e.getMessage());
}
catch(IOException e)
{
System.out.println("Due to an IOException, the parser could not check"+parser);//I don't know what to make of this as well.
}
 
// do-nothing methods

out.println("</body>");
out.println("</html>");
out.close();
         }
 
         public void doGet(HttpServletRequest request, HttpServletResponse response)
         throws ServletException, java.io.IOException
         {
         doPost(request,response);
         }
 
}

[ November 19, 2004: Message edited by: Diego Tori ]

Consider Paul's rocket mass heater.