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/**
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 *        Name: MetaCatServlet.java
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 *     Purpose: A Class that implements a metadata catalog as a java Servlet
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 *   Copyright: 2000 Regents of the University of California and the
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 *              National Center for Ecological Analysis and Synthesis
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 *     Authors: Matt Jones
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 * 
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 *     Version: '$Id: MetaCatServlet.java 68 2000-05-04 21:44:38Z higgins $'
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 */
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package edu.ucsb.nceas.metacat;
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import java.io.PrintWriter;
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import java.io.IOException;
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import java.io.Reader;
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import java.io.StringReader;
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import java.io.BufferedReader;
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import java.util.Enumeration;
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import java.util.Hashtable;
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import java.net.URL;
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import java.net.MalformedURLException;
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import java.sql.Connection;
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import java.sql.SQLException;
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import javax.servlet.ServletConfig;
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import javax.servlet.ServletContext;
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import javax.servlet.ServletException;
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import javax.servlet.ServletInputStream;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import javax.servlet.http.HttpUtils;
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import oracle.xml.parser.v2.XSLStylesheet;
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import oracle.xml.parser.v2.XSLException;
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import oracle.xml.parser.v2.XMLDocumentFragment;
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import oracle.xml.parser.v2.XSLProcessor;
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import oracle.xml.parser.v2.*;    //Oracle parser - DFH
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/**
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 * A metadata catalog server implemented as a Java Servlet
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   *
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   * <p>Valid parameters are:<br>
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   * action=query -- query the values of all elements and attributes
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   *                     and return a result set of nodes<br>
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   * action=getdocument -- display an XML document in XML or HTML<br>
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   * qformat=xml -- display resultset from query in XML<br>
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   * qformat=html -- display resultset from query in HTML<br>
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   * action=getdocument -- display an XML document in XML or HTML<br>
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   * docid=34 -- display the document with the document ID number 34<br>
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   * action=putdocument -- load an XML document into the database store<br>
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   * doctext -- XML text ofthe document to load into the database<br>
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   * query -- actual query text (to go with 'action=query')<br>
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   * action=validate -- vallidate the xml contained in validatetext<br>
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   * valtext -- XML text to be validated
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 */
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public class MetaCatServlet extends HttpServlet {
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  private ServletConfig		config = null;
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  private ServletContext	context = null;
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  Connection 		conn = null;
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  DBSimpleQuery		queryobj = null;
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  DBReader		docreader = null;
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  static  String 	user = MetaCatUtil.user;
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  static  String 	password = MetaCatUtil.password;
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  static  String 	defaultDB = MetaCatUtil.defaultDB;
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  static  String 	resultStyleURL = "file:///home/httpd/html/xmltodb/resultset.xsl";
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  /**
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   * Initialize the servlet by creating appropriate database connections
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   */
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  public void init( ServletConfig config ) throws ServletException {
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    try {
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      super.init( config );
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      this.config = config;
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      this.context = config.getServletContext();
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    System.out.println("Servlet Initialize");
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      try {
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        // Open a connection to the database
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        conn = MetaCatUtil.openDBConnection(
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                "oracle.jdbc.driver.OracleDriver",
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                defaultDB, user, password);
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        queryobj = new DBSimpleQuery(conn);
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        docreader = new DBReader(conn);
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      } catch (Exception e) {
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      }
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    } catch ( ServletException ex ) {
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      throw ex;
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    }
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  }
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  /** Handle "GET" method requests from HTTP clients */
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  public void doGet (HttpServletRequest request, HttpServletResponse response)
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    throws ServletException, IOException {
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    // Process the data and send back the response
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    handleGetOrPost(request, response);
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  }
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  /** Handle "POST" method requests from HTTP clients */
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  public void doPost( HttpServletRequest request, HttpServletResponse response)
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    throws ServletException, IOException {
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    // Process the data and send back the response
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    handleGetOrPost(request, response);
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  }
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  /**
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   * Control servlet response depending on the action parameter specified
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   */
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  private void handleGetOrPost(HttpServletRequest request, 
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    HttpServletResponse response) 
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    throws ServletException, IOException {
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    // Get a handle to the output stream back to the client
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    PrintWriter out = response.getWriter();
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    String name = null;
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    String[] value = null;
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    Hashtable params = new Hashtable();
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    Enumeration paramlist = request.getParameterNames();
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    while (paramlist.hasMoreElements()) {
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      name = (String)paramlist.nextElement();
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      value = request.getParameterValues(name);
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      params.put(name,value);
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    }
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    String action = ((String[])params.get("action"))[0];
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    if (action.equals("query")) {
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      handleQueryAction(out, params, response);
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    } else if (action.equals("getdocument")) {
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      handleGetDocumentAction(out, params, response);
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    } else if (action.equals("putdocument")) {
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      handlePutDocumentAction(out, params, response);
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    } else if (action.equals("validate")) {
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      handleValidateAction(out, params, response);  
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    } else {
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      out.println("Error: action not registered.  Please report this error.");
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    }
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    // Close the stream to the client
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    out.close();
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  }
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  /** 
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   * Handle the database query request and return a result set, possibly
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   * transformed from XML into HTML
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   */
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  private void handleQueryAction(PrintWriter out, Hashtable params, 
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               HttpServletResponse response) {
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      // Run the query
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      String query = ((String[])params.get("query"))[0]; 
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      Hashtable nodelist = queryobj.findRootNodes(query);
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      // Create a buffer to hold the xml result
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      StringBuffer resultset = new StringBuffer();
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      // Print the resulting root nodes
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      long nodeid;
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      resultset.append("<?xml version=\"1.0\"?>\n");
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      resultset.append("<resultset>\n");
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      resultset.append("  <query>" + query + "</query>");
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      Enumeration rootlist = nodelist.keys(); 
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      while (rootlist.hasMoreElements()) {
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        nodeid = ((Long)rootlist.nextElement()).longValue();
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        resultset.append("  <nodeid>" + nodeid + "</nodeid>");
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      }
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      resultset.append("</resultset>");
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      String qformat = ((String[])params.get("qformat"))[0]; 
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      if (qformat.equals("xml")) {
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        // set content type and other response header fields first
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        response.setContentType("text/xml");
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        out.println(resultset.toString());
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      } else if (qformat.equals("html")) {
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        // set content type and other response header fields first
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        response.setContentType("text/html");
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        //out.println("Converting to HTML...");
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        XMLDocumentFragment htmldoc = null;
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        try {
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          XSLStylesheet style = new XSLStylesheet(new URL(resultStyleURL), null);
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          htmldoc = (new XSLProcessor()).processXSL(style, 
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                     (Reader)(new StringReader(resultset.toString())),null);
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          htmldoc.print(out);
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        } catch (Exception e) {
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          out.println("Error transforming document:\n" + e.getMessage());
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        }
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      }
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  }
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  /** 
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   * Handle the database getdocument request and return a XML document, 
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   * possibly transformed from XML into HTML
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   */
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  private void handleGetDocumentAction(PrintWriter out, Hashtable params, 
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               HttpServletResponse response) {
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      // Get the document indicated
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      String docid = ((String[])params.get("docid"))[0]; 
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      String doc = docreader.readXMLDocument((new Long(docid)).longValue());
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      // set content type and other response header fields first
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      response.setContentType("text/xml");
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      out.println(doc);
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  }
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  /** 
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   * Handle the database putdocument request and write an XML document 
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   * to the database connection
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   */
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  private void handlePutDocumentAction(PrintWriter out, Hashtable params, 
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               HttpServletResponse response) {
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      // Get the document indicated
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      String[] doctext = (String[])params.get("doctext");
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      StringReader xml = new StringReader(doctext[0]);
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      // write the document to the database
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      try {
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        DBSAXWriter dbw = new DBSAXWriter(xml, conn);
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      } catch (SQLException e1) {
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          out.println("Error 1 loading document:<p>\n" + e1.getMessage());
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      }catch (IOException e2) {
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          out.println("Error 2 loading document:<p>\n" + e2.getMessage());
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      }catch (ClassNotFoundException e3) {
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          out.println("Error 3 loading document:<p>\n" + e3.getMessage());
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      }
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      // set content type and other response header fields first
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      response.setContentType("text/xml");
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      out.println(doctext[0]);
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  }
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  /** 
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   * Handle the validtion request and return the results 
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   * to the requestor - DFH
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   */
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  private void handleValidateAction(PrintWriter out, Hashtable params, HttpServletResponse response) {
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      // Get the document indicated
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      String[] valtext = (String[])params.get("valtext");
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      SAXParser parser = new SAXParser();           // works for both Xerces and Oracle
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      parser.setValidationMode(true);               // Oracle
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      GenericXMLValidate gxv = new GenericXMLValidate(parser);
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      boolean valid = gxv.validateString(valtext[0]);
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      // set content type and other response header fields first
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      response.setContentType("text/plain");
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      if (valid) {
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        out.println("The input XML is VALID!");
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      }
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      else {
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        out.println("The input XML is NOT VALID\n" + gxv.returnErrors());
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      } 
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    }
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}
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