XMLInstance2Schema

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 * $Id$
 */

package org.exolab.castor.xml.schema.util;

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;

import org.castor.xml.BackwardCompatibilityContext;
import org.castor.xml.InternalContext;
import org.exolab.castor.util.NestedIOException;
import org.exolab.castor.xml.schema.Order;
import org.exolab.castor.xml.schema.Schema;
import org.exolab.castor.xml.schema.writer.SchemaWriter;
import org.xml.sax.InputSource;
import org.xml.sax.Parser;
import org.xml.sax.SAXException;

/**
 * A class for reading XML Schemas.
 *
 * To generate an XML schema from a given XML document instance and write it to a file, please use
 * code similar to the following:
 *
 * InputSource inputSource = ...; XMLInstance2Schema xi2s = new XMLInstance2Schema(); Schema schema
 * = xi2s.createSchema(inputSource);
 *
 * Writer dstWriter = new FileWriter(...); xi2s.serializeSchema(dstWriter, schema);
 * dstWriter.close();
 *
 * @author <a href="mailto:kvisco@intalio.com">Keith Visco</a>
 * @version $Revision$ $Date: 2006-01-16 13:22:58 -0700 (Mon, 16 Jan 2006) $
 */
public class XMLInstance2Schema {

  /**
   * The {@link InternalContext} used to get Parser from.
   */
  private InternalContext _internalContext;

  private Order _defaultGroup = Order.sequence;

  /**
   * Creates a new XMLInstance2Schema
   *
   */
  public XMLInstance2Schema() {
    super();
    _internalContext = new BackwardCompatibilityContext();
  }

  /**
   * Creates an XML Schema using the given XML instance filename. The XML Schema created will be
   * based on the specific XML instance document.
   *
   * @param filename the filename for the XML document
   */
  public Schema createSchema(String filename) throws IOException {
    return createSchema(new InputSource(filename));
  }

  /**
   * Creates an XML Schema using the given Reader. The reader must be for an XML instance document.
   * The XML Schema created will be based on the specific XML instance document.
   *
   * @param reader the Reader for the XML document
   */
  public Schema createSchema(Reader reader) throws IOException {
    return createSchema(new InputSource(reader));
  }

  /**
   * Creates an XML Schema using the given InputSource. The InputSource must be for an XML instance
   * document. The XML Schema created will be based on the specific XML instance document.
   *
   * @param source the InputSource for the XML document
   */
  public Schema createSchema(InputSource source) throws IOException {
    XMLInstance2SchemaHandler handler = new XMLInstance2SchemaHandler();
    handler.setDefaultGroupOrder(_defaultGroup);

    try {
      Parser parser = _internalContext.getParser();
      if (parser == null) {
        throw new IOException("fatal error: unable to create SAX parser.");
      }
      parser.setDocumentHandler(handler);
      parser.setErrorHandler(handler);
      parser.parse(source);
    } catch (org.xml.sax.SAXException sx) {
      throw new NestedIOException(sx);
    }
    return handler.getSchema();
  }

  /**
   * Sets the default grouping as "all". By default groups will be treated as "sequence".
   */
  public void setDefaultGroupingAsAll() {
    _defaultGroup = Order.all;
  }

  /**
   * Serializes a {@link Schema} instance to the given {@link Writer} instance.
   *
   * @param dstWriter The {@link Writer} instance to output the XML schema to.
   * @param schema The XML {@link Schema} instance to be output.
   * @throws IOException If there's a problem related to writing to the given {@link Writer}
   *         instance.
   * @throws SAXException If there's a problem related to SAX streaming.
   */
  public void serializeSchema(Writer dstWriter, Schema schema) throws IOException, SAXException {
    SchemaWriter schemaWriter = new SchemaWriter(dstWriter);
    schemaWriter.write(schema);
  }

  /**
   * For testing purposes only.
   *
   * @deprecate Please see class documentation for an example of how to use this class. Or consider
   *            using the Ant task for the schema generator.
   */
  public static void main(String args[]) {

    if (args.length == 0) {
      System.out.println("Missing filename");
      System.out.println();
      System.out.println("usage: java XMLInstance2Schema <input-file> [<output-file> (optional)]");
      return;
    }

    try {
      XMLInstance2Schema xi2s = new XMLInstance2Schema();
      Schema schema = xi2s.createSchema(args[0]);

      Writer dstWriter = null;
      if (args.length > 1) {
        dstWriter = new FileWriter(args[1]);
      } else {
        dstWriter = new PrintWriter(System.out, true);
      }

      xi2s.serializeSchema(dstWriter, schema);
      dstWriter.flush();
    } catch (Exception ex) {
      ex.printStackTrace();
    }

  }

}