关于自定义分页的Loop组件：PagedLoop实现
我根据Grid的实现方式，写了一个pagedloop组件，设计了一个LoopDataSource接口作为pagedloop的source，主要是希望从数据库中抓取每页所需的记录，而不是所有记录。?
LoopDataSource.java:?
public interface LoopDataSource extends Iterable<Object>{int getTotalRowCount();void prepare(int startIndex, int endIndex, String propertyName);}?
public class HibernateLoopDataSource implements LoopDataSource {private final Session session; private final Class<?> entityType; private int startIndex; private List<Object> preparedResults; public HibernateLoopDataSource(Session session, Class<?> entityType){ assert session != null; assert entityType != null; this.session = session; this.entityType = entityType; } public int getTotalRowCount(){ Criteria criteria = session.createCriteria(entityType); criteria.setProjection(Projections.rowCount()); Number result = (Number) criteria.uniqueResult(); return result.intValue(); } @SuppressWarnings("unchecked")public void prepare(int startIndex, int endIndex, String propertyName){ Criteria crit = session.createCriteria(entityType); crit.setFirstResult(startIndex).setMaxResults(endIndex - startIndex + 1); if(propertyName!=null){ crit.addOrder(Order.desc(propertyName)); } this.startIndex = startIndex; preparedResults = crit.list(); } @Overridepublic Iterator<Object> iterator() {// TODO Auto-generated method stubreturn preparedResults.iterator();}}?
public class PagedLoop implements ClientElement { //@Parameter(value = "prop:componentResources.id", defaultPrefix = "literal") //private String clientId; /** * The element to render. If not null, then the loop will render the * indicated element around its body (on each pass through the loop). The * default is derived from the component template. */ @Parameter(value = "prop:componentResources.elementName", defaultPrefix = "literal") private String elementName;/** * The element to render. If not null, then the loop will render the * indicated element around its body (on each pass through the loop). The * default is derived from the component template. */ @Parameter(required = true, principal = true, autoconnect = true) private LoopDataSource source;/** * A wrapper around the provided Data Source that caches access to the * availableRows property. This is the source provided to sub-components. */private LoopDataSource cachingSource;/** * Defines where the pager (used to navigate within the "pages" of results) * should be displayed: "top", "bottom", "both" or "none". */@Parameter(value = "bottom", defaultPrefix = "literal" )private String pagerPosition;private GridPagerPosition internalPagerPosition;/** * The number of rows of data displayed on each page. If there are more rows * than will fit, the Grid will divide up the rows into "pages" and * (normally) provide a pager to allow the user to navigate within the * overall result set. */@Parameter("25")private int rowsPerPage;@Persistprivate int currentPage;/** * The current value, set before the component renders its body. */@SuppressWarnings("unused")@Parameterprivate Object value;/** *If true and the Loop is enclosed by a Form, then the normal state saving logic is turned off. * Defaults to false, enabling state saving logic within Forms. */@SuppressWarnings("unused")@Parameter(name = "volatile")private boolean volatileState;/** * The index into the source items. */@SuppressWarnings("unused")@Parameterprivate int index;/** * Optional primary key converter; if provided and inside a form and not * volatile, then each iterated value is converted and stored into the form. */@SuppressWarnings("unused")@Parameterprivate ValueEncoder<?> encoder;@SuppressWarnings("unused")@Component(parameters = { "source=dataSource","elementName=prop:elementName", "value=inherit:value","volatile=inherit:volatileState", "encoder=inherit:encoder","index=inherit:index" })private Loop loop;@Component(parameters = { "source=dataSource", "rowsPerPage=rowsPerPage","currentPage=currentPage" })private Pager pager;@SuppressWarnings("unused")@Component(parameters = "to=pagerTop")private Delegate pagerTop;@SuppressWarnings("unused")@Component(parameters = "to=pagerBottom")private Delegate pagerBottom;/** * A Block to render instead of the table (and pager, etc.) when the source * is empty. The default is simply the text "There is no data to display". * This parameter is used to customize that message, possibly including * components to allow the user to create new objects. */@Parameter(value = "block:empty")private Block empty;private String assignedClientId; @Parameter(name="OrderBy", defaultPrefix="literal") private String propertyName; /** * A version of LoopDataSource that caches the availableRows property. */ static class CachingDataSource implements LoopDataSource { private final LoopDataSource delegate; private boolean availableRowsCached; private int availableRows; CachingDataSource(LoopDataSource delegate) { this.delegate = delegate; } public int getTotalRowCount() { if (!availableRowsCached) { availableRows = delegate.getTotalRowCount(); availableRowsCached = true; } return availableRows; } public void prepare(int startIndex, int endIndex, String propertyName) { delegate.prepare(startIndex, endIndex, propertyName); } @Overridepublic Iterator<Object> iterator() {return delegate.iterator();} }public String getElementName() {return elementName;}public Object getPagerTop() {return internalPagerPosition.isMatchTop() ? pager : null;}public Object getPagerBottom() {return internalPagerPosition.isMatchBottom() ? pager : null;}public int getRowsPerPage() {return rowsPerPage;}public void setRowsPerPage(int rowsPerPage) {this.rowsPerPage = rowsPerPage;}public int getCurrentPage() {return currentPage;}public void setCurrentPage(int currentPage) {this.currentPage = currentPage;}void setupDataSource() { cachingSource = new CachingDataSource(source); int availableRows = cachingSource.getTotalRowCount(); if (availableRows == 0) return; int maxPage = ((availableRows - 1) / rowsPerPage) + 1; // This captures when the number of rows has decreased, typically due to deletions. int effectiveCurrentPage = getCurrentPage(); if (effectiveCurrentPage > maxPage) effectiveCurrentPage = maxPage; int startIndex = (effectiveCurrentPage - 1) * rowsPerPage; int endIndex = Math.min(startIndex + rowsPerPage - 1, availableRows - 1); cachingSource.prepare(startIndex, endIndex, propertyName); }Object setupRender() {if (currentPage == 0)currentPage = 1;internalPagerPosition = new StringToEnumCoercion<GridPagerPosition>( GridPagerPosition.class).coerce(pagerPosition);setupDataSource(); // If there's no rows, display the empty block placeholder. return cachingSource.getTotalRowCount() == 0 ? empty : null;}Object beginRender() {// Skip rendering of component (template, body, etc.) when there's// nothing to display.// The empty placeholder will already have rendered.return (cachingSource.getTotalRowCount() != 0);}void onAction(int newPage){currentPage = newPage;}/** * Returns a unique id for the element. This value will be unique for any given rendering of a * page. This value is intended for use as the id attribute of the client-side element, and will * be used with any DHTML/Ajax related JavaScript. */ @Overridepublic String getClientId() { return assignedClientId; } public LoopDataSource getDataSource(){ return cachingSource; } public String getPropertyName(){ return propertyName; }}?
@Propertyprivate Blog blog;@Injectprivate Session session;public LoopDataSource getList(){return new HibernateLoopDataSource(session, Blog.class);}?