refreshablepagedlistholder.java

该源码包括了基于J2EE的数据持久层设计,设计中使用了DAO,Service,等模式,并在Struts下进行了测试．

package org.conference.pagination;
import java.util.Locale;
import org.conference.pagination.BeanUtils;
/**
 * <p><strong>PagedListSourceProvider</strong> ,
 * RefreshablePagedListHolder is a PagedListHolder subclass with reloading capabilities.
 * It automatically re-requests the List from the source provider, in case of Locale or
 * filter changes.
 *
 * <p>It works just like with PagedListHolder. The locale can be specified in
 * Locale's toString syntax, e.g. "locale=en_US". The filter object is of any
 * custom class. An instance will simply get passed through to
 * PagedListSourceProvider.loadList. A filter property can be specified via
 * "filter.myFilterProperty", for example.
 *
 * <p>The scenario in the action could be:
 * <code>
 * RefreshablePagedListHolder holder = request.getSession("mySessionAttr");<br>
 * if (holder == null) {<br>
 *   holder = new RefreshablePagedListHolder();<br>
 *   holder.setSourceProvider(new MyAnonymousOrEmbeddedSourceProvider());<br>
 *   holder.setFilter(new MyAnonymousOrEmbeddedFilter());<br>
 *   request.getSession().setAttribute("mySessionAttr", holder);<br>
 * }<br>
 * holder.refresh(false);
 * return ModelAndView("myViewName", ex.getModel());<br>
 * <br>
 * ...<br>
 * <br>
 * private class MyAnonymousOrEmbeddedSourceProvider implements PagedListSourceProvider {<br>
 *   public List loadList(Locale locale, Object filter) {<br>
 *     MyAnonymousOrEmbeddedFilter filter = (MyAnonymousOrEmbeddedFilter) filter;<br<
 *     // an empty name mask should lead to all objects being loaded
 *     return myBusinessService.loadMyObjectsByNameMask(filter.getName());<br>
 * }<br>
 * <br>
 * private class MyAnonymousOrEmbeddedFilter {<br>
 *   private String name = "";<br>
 *   public String getName() {<br>
 *     return name;<br<
 *   }<br>
 *   public void setName(String name) {<br>
 *     this.name = name;<br>
 *   }<br>
 * }<br>
 * </code>
 *
 * @see org.javawing.component.paging.PagedListSourceProvider
 * @see org.javawing.ioc.gems.propertyconverters.LocaleConverter
 *
 * @author   zxm
 * @version  $Id: PagedListSourceProvider.java,v 2.0 2005/11/26 $
 * @package  gov.cd.gzcx.pagination
 * @since 4.0
 */
public class RefreshablePagedListHolder
    extends PagedListHolder {

  private PagedListSourceProvider sourceProvider;

  private Locale locale;

  private Locale localeUsed;

  private Object filter;

  private Object filterUsed;

  /**
   * Create a new list holder.
   * You'll need to set a source provider to be able to use the holder.
   * @see #setSourceProvider
   */
  public RefreshablePagedListHolder() {
    super();
  }

  /**
   * Create a new list holder with the given source provider.
   *
   * @param sourceProvider PagedListSourceProvider
   */
  public RefreshablePagedListHolder(PagedListSourceProvider sourceProvider) {
    super();
    this.sourceProvider = sourceProvider;
  }

  /**
   * Set the callback class for reloading the List when necessary. If the list
   * is definitely not modifiable, i.e. not locale aware and no filtering, use
   * PagedListHolder.
   *
   * @see org.javawing.component.paging.PagedListHolder
   * @param sourceProvider PagedListSourceProvider
   */
  public void setSourceProvider(PagedListSourceProvider sourceProvider) {
    this.sourceProvider = sourceProvider;
  }

  /**
   * Return the callback class for reloading the List when necessary.
   *
   * @return PagedListSourceProvider
   */
  public PagedListSourceProvider getSourceProvider() {
    return sourceProvider;
  }

  /**
   * Set the Locale that the source provider should use for loading the list.
   * This can either be populated programmatically (e.g. with the request locale),
   * or via binding (using Locale's toString syntax, e.g. "locale=en_US").
   * @param locale the current Locale, or <code>null</code>
   */
  public void setLocale(Locale locale) {
    this.locale = locale;
  }

  /**
   * Return the Locale that the source provider should use for loading the list.
   * @return the current Locale, or <code>null</code>
   */
  public Locale getLocale() {
    return locale;
  }

  /**
   * Set the filter object that the source provider should use for loading the list.
   * This will typically be a bean, for easy accessing.
   * @param filter the filter object, or <code>null</code>
   */
  public void setFilter(Object filter) {
    this.filter = filter;
  }

  /**
   * Return the filter that the source provider should use for loading the list.
   * @return the current filter, or <code>null</code>
   */
  public Object getFilter() {
    return filter;
  }

  /**
   * Reload the underlying list from the source provider if necessary
   * (i.e. if the locale and/or the filter has changed), and resort it.
   * @param force whether a reload should be performed in any case
   */
  public void refresh(boolean force) {
    if (this.sourceProvider != null &&
        (force || (this.locale != null && !this.locale.equals(this.localeUsed)) ||
         (this.filter != null && !this.filter.equals(this.filterUsed)))) {
      setSource(this.sourceProvider.loadList(this.locale, this.filter));
      if (this.filter != null && !this.filter.equals(this.filterUsed)) {
    	 // System.out.println("pppppppppppppppp: "+(this.filter != null)+" : "+!this.filter.equals(this.filterUsed));
        this.setPage(0);
      }
      this.localeUsed = this.locale;
      if (null != this.filter) {
        try {
			this.filterUsed = filter.getClass().newInstance();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        BeanUtils.copyProperties(this.filter, this.filterUsed, null);
      }
    }
    //resort();
  }

}