pageiterator.java~1~

用JBuilder+Jboos+mysql实现的EJB项目

package com.jdon.estore.catalog.dao;

import java.util.*;


public class PageIterator  implements Iterator {

    private Integer [] elements;
    private int currentIndex = -1;
    private Object nextElement = null;

    private DatabaseObjectFactory objectFactory;

    private ServiceLocator serviceLocator = ServiceLocator.getInstance();

    /**
     * Creates a new DatabaseObjectIterator. The type must be one of the
     * following:
     */
    public PageIterator(int type, Integer [] elements,
            final Object extraObject)
    {
        this.elements = elements;

        // Load the appropriate proxy factory depending on the type of object
        // that we're iterating through.
        switch (type) {
            case SiteDefs.USER:
                // Create an objectFactory to load users.
                this.objectFactory = new DatabaseObjectFactory() {
                   ReaderDAO reader = (ReaderDAO)extraObject;

                    public Object loadObject(Integer id) {
                        try {
                            mysite.ejb.dao.model.User user = reader.getUser(id.intValue());
                            return user;
                        }catch (Exception unfe) { }
                        return null;
                    }
                };
                break;
            // Otherwise, an invalid value was passed in so throw an exception.
            default:
                throw new IllegalArgumentException("Illegal type specified");
        }
    }

    /**
     * Returns true if there are more elements in the iteration.
     *
     * @return true if the iterator has more elements.
     */
    public boolean hasNext() {
        // If we are at the end of the list, there can't be any more elements
        // to iterate through.
        if (currentIndex+1 >= elements.length && nextElement == null) {
            return false;
        }
        // Otherwise, see if nextElement is null. If so, try to load the next
        // element to make sure it exists.
        if (nextElement == null) {
            nextElement = getNextElement();
            if (nextElement == null) {
                return false;
            }
        }
        return true;
    }

    /**
     * Returns the next element.
     *
     * @return the next element.
     * @throws NoSuchElementException if there are no more elements.
     */
    public Object next() throws java.util.NoSuchElementException {
        Object element = null;
        if (nextElement != null) {
            element = nextElement;
            nextElement = null;
        }
        else {
            element = getNextElement();
            if (element == null) {
                throw new java.util.NoSuchElementException();
            }
        }
        return element;
    }

    /**
     * Not supported for security reasons.
     */
    public void remove() throws UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    /**
     * Returns the next available element, or null if there are no more
     * elements to return.
     *
     * @return the next available element.
     */
    public Object getNextElement() {
        while (currentIndex+1 < elements.length) {
            currentIndex++;
            Object element = objectFactory.loadObject(elements[currentIndex]);
            if (element != null) {
                return element;
            }
        }
        return null;
    }
}

/**
 * An interface for loading Jive database objects.
 */
interface DatabaseObjectFactory {

    /**
     * Returns the object associated with <code>id</code> or null if the
     * object could not be loaded.
     *
     * @param id the id of the object to load.
     * @return the object specified by <code>id</code> or null if it could not
     *      be loaded.
     */
    public Object loadObject(Integer id);
}