cvs commit: jakarta-commons/digester/src/examples/api/catalog BookFactory.java

[rd...@apache.org]

rdonkin     2003/09/25 13:04:55

  Added:       digester/src/examples/api/catalog BookFactory.java
  Log:
  Example of a catalog. Submitted by Simon Kitching.
  
  Revision  Changes    Path
  1.1                  jakarta-commons/digester/src/examples/api/catalog/BookFactory.java
  
  Index: BookFactory.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/digester/src/examples/api/catalog/BookFactory.java,v 1.1 2003/09/25 20:04:55 rdonkin Exp $
   * $Revision: 1.1 $
   * $Date: 2003/09/25 20:04:55 $
   *
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 1999-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Group.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  import org.apache.commons.digester.AbstractObjectCreationFactory;
  
  /**
   * The Book class doesn't have a no-argument constructor, so the
   * standard digester ObjectCreateRule can't be used to create instances
   * of it.
   * <p>
   * To resolve this issue, the FactoryCreateRule can be used in 
   * conjunction with an appropriate factory class, like this one.
   * The "createObject" method of the factory is invoked to generate
   * object instances when required.
   * <p>
   * The factory object can access any xml attributes, plus of course
   * any values set up within it before digester parsing starts (like
   * JNDI references, database connections, etc) that it may in the
   * process of generating an appropriate object.
   * <p>
   * Note that it is <i>not</i> possible for any data to be extracted
   * from the body or subelements of the xml element that caused the
   * createObject method on this factory to be invoked. For example:
   * <pre>
   *  [book isdn="12345"]
   * </pre>
   * is fine; the isdn value can be accessed during the createObject method.
   * However, given the xml:
   * <pre>
   * [book]
   *   [isdn]12345[/isdn]
   *   ...
   * </pre>
   * it is not possible to access the isdn number until after the
   * Book instance has been created.
   * <p>
   * Note that even if the class to be created does have a default constructor,
   * you may wish to use a factory class, in order to initialise the created
   * object in specific ways, or insert created objects into a central
   * register, etc.
   * <p>
   * And don't forget, either, that factories may be implemented as
   * inner classes or anonymous classes if appropriate, reducing the
   * overhead of using this functionality in many cases. 
   */
  public class BookFactory extends AbstractObjectCreationFactory {
  	
  	public Object createObject(org.xml.sax.Attributes attributes) 
      throws Exception {
          String isbn = attributes.getValue("isbn");
          
          if (isbn == null) {
              throw new Exception(
                  "Mandatory isbn attribute not present on book tag.");
          }
          
          return new Book(isbn);
  	}
  }
  
  
  

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