Metacat

/**

 *        Name: MetaCatServlet.java

 *     Purpose: A Class that implements a metadata catalog as a java Servlet

 *   Copyright: 2000 Regents of the University of California and the

 *              National Center for Ecological Analysis and Synthesis

 *     Authors: Matt Jones

 *

 *     Version: '$Id$'

 */

package edu.ucsb.nceas.metacat;

import java.io.IOException;

import java.io.StringReader;

import java.util.Hashtable;

import java.net.MalformedURLException;

import java.sql.Connection;

import javax.servlet.ServletConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import oracle.xml.parser.v2.XSLException;

import oracle.xml.parser.v2.XMLDocumentFragment;

import oracle.xml.parser.v2.XSLProcessor;

 * A metadata catalog server implemented as a Java Servlet

   * <p>Valid parameters are:<br>

   * action=query -- query the values of all elements and attributes

   *                     and return a result set of nodes<br>

   * action=getdocument -- display an XML document in XML or HTML<br>

   * qformat=xml -- display resultset from query in XML<br>

   * qformat=html -- display resultset from query in HTML<br>

   * action=getdocument -- display an XML document in XML or HTML<br>

   * docid=34 -- display the document with the document ID number 34<br>

   * doctext -- XML text ofthe document to load into the database<br>

   * action=validate -- vallidate the xml contained in validatetext<br>

   * valtext -- XML text to be validated

public class MetaCatServlet extends HttpServlet {

  private ServletConfig		config = null;

  private ServletContext	context = null;

  static  String 	password = MetaCatUtil.password;

  static  String 	defaultDB = MetaCatUtil.defaultDB;

  static  String 	resultStyleURL = "file:///home/httpd/html/xmltodb/resultset.xsl";

   * Initialize the servlet by creating appropriate database connections

   */

    try {

      super.init( config );

      this.config = config;

      this.context = config.getServletContext();

                defaultDB, user, password);

        docreader = new DBReader(conn);

      }

    } catch ( ServletException ex ) {

      throw ex;

    }

  }

    throws ServletException, IOException {

    throws ServletException, IOException {

    // Process the data and send back the response

    HttpServletResponse response)

    String[] value = null;

    Hashtable params = new Hashtable();

    Enumeration paramlist = request.getParameterNames();

    while (paramlist.hasMoreElements()) {

      name = (String)paramlist.nextElement();

      value = request.getParameterValues(name);

      params.put(name,value);

    }

      handleQueryAction(out, params, response);

    } else if (action.equals("getdocument")) {

      handleGetDocumentAction(out, params, response);

      handlePutDocumentAction(out, params, response);

      handleValidateAction(out, params, response);

      out.println("Error: action not registered.  Please report this error.");

  }

   * Handle the database query request and return a result set, possibly

   * transformed from XML into HTML

   */

               HttpServletResponse response) {

      // Run the query

      String query = ((String[])params.get("query"))[0];

      Hashtable nodelist = queryobj.findRootNodes(query);

      // Create a buffer to hold the xml result

      StringBuffer resultset = new StringBuffer();

      long nodeid;

      resultset.append("<resultset>\n");

      resultset.append("  <query>" + query + "</query>");

      while (rootlist.hasMoreElements()) {

        nodeid = ((Long)rootlist.nextElement()).longValue();

      String qformat = ((String[])params.get("qformat"))[0];

      if (qformat.equals("xml")) {

        // set content type and other response header fields first

        response.setContentType("text/xml");

        out.println(resultset.toString());

      } else if (qformat.equals("html")) {

        // set content type and other response header fields first

        response.setContentType("text/html");

        //out.println("Converting to HTML...");

        XMLDocumentFragment htmldoc = null;

        try {

          XSLStylesheet style = new XSLStylesheet(new URL(resultStyleURL), null);

          htmldoc = (new XSLProcessor()).processXSL(style,

                     (Reader)(new StringReader(resultset.toString())),null);

          htmldoc.print(out);

        } catch (Exception e) {

          out.println("Error transforming document:\n" + e.getMessage());

        }

      }

   * Handle the database getdocument request and return a XML document,

   * possibly transformed from XML into HTML

   */

               HttpServletResponse response) {

      // Get the document indicated

      String docid = ((String[])params.get("docid"))[0];

      String doc = docreader.readXMLDocument((new Long(docid)).longValue());

      // set content type and other response header fields first

      response.setContentType("text/xml");

      out.println(doc);

  }

  /**

   * Handle the database putdocument request and write an XML document

   * to the database connection

   */

  private void handlePutDocumentAction(PrintWriter out, Hashtable params,

               HttpServletResponse response) {

      StringReader xml = new StringReader(doctext[0]);

      // write the document to the database

      // set content type and other response header fields first

  /**

   * Handle the validtion request and return the results

   * to the requestor - DFH

   */

  private void handleValidateAction(PrintWriter out, Hashtable params, HttpServletResponse response) {

      // Get the document indicated

      String[] valtext = (String[])params.get("valtext");

      SAXParser parser = new SAXParser();           // works for both Xerces and Oracle

      parser.setValidationMode(true);               // Oracle

      GenericXMLValidate gxv = new GenericXMLValidate(parser);

      boolean valid = gxv.validateString(valtext[0]);

      // set content type and other response header fields first

      response.setContentType("text/plain");

      if (valid) {

        out.println("The input XML is VALID!");

      }

      else {

        out.println("The input XML is NOT VALID\n" + gxv.returnErrors());

      }

    }