tapestry-examples/Vlib/src/org/apache/tapestry/vlib/pages/ViewBook.java

//  Copyright 2004 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry.vlib.pages;

import java.rmi.RemoteException;
import java.text.DateFormat;

import javax.ejb.FinderException;

import org.apache.tapestry.IExternalPage;
import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.event.PageEvent;
import org.apache.tapestry.event.PageRenderListener;
import org.apache.tapestry.html.BasePage;
import org.apache.tapestry.vlib.VirtualLibraryEngine;
import org.apache.tapestry.vlib.ejb.Book;
import org.apache.tapestry.vlib.ejb.IOperations;

/**
 *  Shows the details of a book, and allows the user to borrow it.
 *
 *  @author Howard Lewis Ship
 *  @version $Id$
 * 
 **/

public abstract class ViewBook extends BasePage implements IExternalPage, PageRenderListener
{
    private DateFormat _dateFormat;

    public abstract Integer getBookId();

    public abstract void setBookId(Integer bookId);

    public abstract Book getBook();

    public abstract void setBook(Book value);

    public void activateExternalPage(Object[] parameters, IRequestCycle cycle)
    {
        Integer bookId = (Integer) parameters[0];

        setBookId(bookId);
    }

    private void readBook()
    {
        VirtualLibraryEngine vengine = (VirtualLibraryEngine) getEngine();
        Integer bookId = getBookId();

        int i = 0;
        while (true)
        {
            IOperations bean = vengine.getOperations();

            try
            {
                setBook(bean.getBook(bookId));

                return;
            }
            catch (FinderException ex)
            {
                vengine.presentError("Book not found in database.", getRequestCycle());
                return;
            }
            catch (RemoteException ex)
            {
                vengine.rmiFailure(
                    "Remote exception obtaining information for book #" + bookId + ".",
                    ex,
                    i++);
            }
        }

    }

    public DateFormat getDateFormat()
    {
        if (_dateFormat == null)
            _dateFormat =
                DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT, getLocale());

        return _dateFormat;
    }

    public void pageBeginRender(PageEvent event)
    {
        if (getBook() == null)
            readBook();
    }

}