| // Copyright 2007, 2008 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.tapestry5.grid; |
| |
| import java.util.List; |
| |
| /** |
| * Defines how a {@link org.apache.tapestry5.corelib.components.Grid} component (and its sub-components) gain access to |
| * the row data that is displayed on the page. In many cases, this is just a wrapper around a simple List, but the |
| * abstractions exist to support access to a large data set that is accessible in sections. |
| */ |
| public interface GridDataSource |
| { |
| |
| /** |
| * Return whether the data source is empty, i.e. does not have any rows available. |
| */ |
| default public boolean isEmpty() |
| { |
| return getAvailableRows(1) == 0; |
| } |
| |
| /** |
| * Return the number of rows available in the data source with an upper limit. |
| * If determining the total number of rows is expensive, this method should be overridden to provide a more |
| * efficient implementation. |
| * Please note that the default Grid pager will still determine the total number of rows, so for this to have |
| * an effect, a custom pager should be used. |
| * |
| * @param limit the upper limit |
| * @return the number of rows or {@code limit}, whichever is lower |
| */ |
| default public int getAvailableRows(final int limit) |
| { |
| int availableRows = getAvailableRows(); |
| if (availableRows >= limit) |
| { |
| return limit; |
| } |
| return availableRows; |
| } |
| |
| /** |
| * Returns the number of rows available in the data source. |
| */ |
| int getAvailableRows(); |
| |
| /** |
| * Invoked to allow the source to prepare to present values. This gives the source a chance to pre-fetch data (when |
| * appropriate) and informs the source of the desired sort order. Sorting comes first, then extraction by range. |
| * |
| * @param startIndex the starting index to be retrieved |
| * @param endIndex the ending index to be retrieved |
| * @param sortConstraints identify how data is to be sorted |
| */ |
| void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints); |
| |
| /** |
| * Returns the row value at the provided index. This method will be invoked in sequential order. In rare instances, |
| * {@link #getAvailableRows()} may return a different number of rows than are actually available (i.e., the database |
| * was changed between calls to {@link #getAvailableRows()} and the call to {@link #prepare(int, int, |
| * java.util.List)}). In that case, this method should return null for any out-of-range indexes. |
| */ |
| Object getRowValue(int index); |
| |
| /** |
| * Returns the type of value in the rows, or null if not known. This value is used to create a default {@link |
| * org.apache.tapestry5.beaneditor.BeanModel} when no such model is explicitly provided. |
| * |
| * @return the row type, or null |
| */ |
| Class getRowType(); |
| } |