之前第一版有個問題，就是如果進行了刪除等操作并立即返回列表頁，被刪除的項還在那，但其實數據庫已經被刪除了，需要做一個刷新列表操作才可以，本版就是修正此問題的。
如果要修正此問題，就需要將分頁的擴展代碼也就是第一版中TestBean中的代碼放入業(yè)務相關管理Bean中。
頁面代碼（其中testBean已經變成業(yè)務Managed-bean user了）：
<f:view>
<h:form id="formlist">
<rich:dataTable id="carList" width="483" columnClasses="col" rows="#{user.pageSize}"
value="#{user.dataModel}" var="car">
<f:facet name="header">
<rich:columnGroup>
<h:column>
<h:outputText styleClass="headerText" value="Name" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Decription" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Base Price" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Time" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="操作" />
</h:column>
</rich:columnGroup>
</f:facet>
<h:column>
<h:outputText value="#{car.name}" />
</h:column>
<h:column>
<h:outputText value="#{car.description}" />
</h:column>
<h:column>
<h:outputText value="#{car.baseprice}" />
</h:column>
<h:column>
<h:outputText value="#{car.timestamp}" />
</h:column>
<h:column>
<h:commandLink action="#{user.delete}" value="刪除" >
<f:param name="id" value="#{car.id}"/>
</h:commandLink>
</h:column>
</rich:dataTable>
<rich:datascroller for="carList" id="dc1"
style="width:483px" page="#{user.scrollerPage}"/>
</h:form>
</f:view>
import java.util.List;
public class DataPage
{
/** *//**
* 將需要的頁的數據封裝到一個DataPage中去， 這個類表示了我們需要的一頁的數據，<br>
* 里面包含有三個元素：datasetSize，startRow，和一個用于表示具體數據的List。<br>
* datasetSize表示了這個記錄集的總條數，查詢數據的時候，使用同樣的條件取count即可，<br>
* startRow表示該頁的起始行在數據庫中所有記錄集中的位置
*/
private int datasetSize;
private int startRow;
private List data;
/** *//**
*
* @param datasetSize
* 數據集大小
* @param startRow
* 起始行
* @param data
* 數據list
*/
public DataPage(int datasetSize, int startRow, List data)
{
this.datasetSize = datasetSize;
this.startRow = startRow;
this.data = data;
}
/** *//**
*
* @return
*/
public int getDatasetSize()
{
return datasetSize;
}
public int getStartRow()
{
return startRow;
}
/** *//**
*
* @return 已填充好的數據集
*/
public List getData()
{
return data;
}
}
PagedListDataModel.java（添加了一些注釋）:
import java.util.List;
import javax.faces.model.DataModel;
/** *//**
*
* TODO 分頁所使用的類
* @author <a href="mailto:tianlu@jsecode.com">TianLu</a>
* @version $Rev$ <br>
* $Id$
*/
/**//* 使用方法：
* 前臺的功能模塊Bean(例如User)中加入類似下面的代碼，可根據您的需要進行相應修改
* private PagedListDataModel dataModel;
private int pageSize = 10;
public int getPageSize()
{
return pageSize;
}
public PagedListDataModel getDataModel()
{
if ( dataModel == null ) {
dataModel = new PagedListDataModel(pageSize)
{
//查詢分頁函數
public DataPage fetchPage(int startRow, int pageSize)
{
// call enclosing managed bean method to fetch the data
CarBeanDAO dao = new CarBeanDAO();
String sql = "from CarBean model order by model.id desc";
Query query = EntityManagerHelper.createQuery(sql);
query.setFirstResult(startRow);
query.setMaxResults(pageSize);
List list = query.getResultList();
System.out.println("current row count = " + list.size());
Query q = EntityManagerHelper.createQuery("select count(*) from CarBean");
return new DataPage(Integer.parseInt(q.getSingleResult().toString()), startRow, list);
}
};
}
return dataModel;
}*/
/**//* 前臺控件像這樣使用
* <rich:dataTable id="carList" width="483" columnClasses="col" rows="#{user.pageSize}"
value="#{user.dataModel}" var="car">
<f:facet name="header">
<rich:columnGroup>
<h:column>
<h:outputText styleClass="headerText" value="Name" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Decription" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Base Price" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="Time" />
</h:column>
<h:column>
<h:outputText styleClass="headerText" value="操作" />
</h:column>
</rich:columnGroup>
</f:facet>
<h:column>
<h:outputText value="#{car.name}" />
</h:column>
<h:column>
<h:outputText value="#{car.description}" />
</h:column>
<h:column>
<h:outputText value="#{car.baseprice}" />
</h:column>
<h:column>
<h:outputText value="#{car.timestamp}" />
</h:column>
<h:column>
<h:commandLink action="#{user.delete}" value="刪除" >
<f:param name="id" value="#{car.id}"/>
</h:commandLink>
</h:column>
</rich:dataTable>
<rich:datascroller for="carList" id="dc1"
style="width:483px" page="#{user.scrollerPage}"/>*/
/**//*
* 進行刪除等操作后會立即改變列表項并且返回列表頁的，請調用本類的refresh方法刷新當前頁面
* 使用方法：
* dao.delete(bean);
* dataModel.refresh();
*/
public abstract class PagedListDataModel extends DataModel {
int pageSize;
int rowIndex;
DataPage page;
/** *//**
* Create a datamodel that pages through the data showing the specified
* number of rows on each page.
*/
public PagedListDataModel(int pageSize) {
super();
this.pageSize = pageSize;
this.rowIndex = -1;
this.page = null;
}
/** *//**
* Not used in this class; data is fetched via a callback to the fetchData
* method rather than by explicitly assigning a list.
*/
public void setWrappedData(Object o) {
if (o instanceof DataPage) {
this.page = (DataPage) o;
} else {
throw new UnsupportedOperationException(" setWrappedData ");
}
}
public int getRowIndex() {
return rowIndex;
}
/** *//**
* Specify what the "current row" within the dataset is. Note that the
* UIData component will repeatedly call this method followed by getRowData
* to obtain the objects to render in the table.
*/
public void setRowIndex(int index) {
rowIndex = index;
}
/** *//**
* Return the total number of rows of data available (not just the number of
* rows in the current page!).
*/
public int getRowCount() {
return getPage().getDatasetSize();
}
/** *//**
* Return a DataPage object; if one is not currently available then fetch
* one. Note that this doesn't ensure that the datapage returned includes
* the current rowIndex row; see getRowData.
*/
private DataPage getPage() {
if (page != null) {
return page;
}
int rowIndex = getRowIndex();
int startRow = rowIndex;
if (rowIndex == -1) {
// even when no row is selected, we still need a page
// object so that we know the amount of data available.
startRow = 0;
} // invoke method on enclosing class
page = fetchPage(startRow, pageSize);
return page;
}
/** *//**
* Return the object corresponding to the current rowIndex. If the DataPage
* object currently cached doesn't include that index then fetchPage is
* called to retrieve the appropriate page.
*/
public Object getRowData() {
if (rowIndex < 0) {
throw new IllegalArgumentException(
" Invalid rowIndex for PagedListDataModel; not within page ");
} // ensure page exists; if rowIndex is beyond dataset size, then
// we should still get back a DataPage object with the dataset size
// in it
if (page == null) {
page = fetchPage(rowIndex, pageSize);
}
int datasetSize = page.getDatasetSize();
int startRow = page.getStartRow();
int nRows = page.getData().size();
int endRow = startRow + nRows;
if (rowIndex >= datasetSize) {
throw new IllegalArgumentException(" Invalid rowIndex ");
}
if (rowIndex < startRow) {
page = fetchPage(rowIndex, pageSize);
startRow = page.getStartRow();
} else if (rowIndex >= endRow) {
page = fetchPage(rowIndex, pageSize);
startRow = page.getStartRow();
}
return page.getData().get(rowIndex - startRow);
}
public Object getWrappedData() {
return page.getData();
}
/** *//**
* Return true if the rowIndex value is currently set to a value that
* matches some element in the dataset. Note that it may match a row that is
* not in the currently cached DataPage; if so then when getRowData is
* called the required DataPage will be fetched by calling fetchData.
*/
public boolean isRowAvailable() {
DataPage page = getPage();
if (page == null) {
return false;
}
int rowIndex = getRowIndex();
if (rowIndex < 0) {
return false;
} else if (rowIndex >= page.getDatasetSize()) {
return false;
} else {
return true;
}
}
/** *//**
* Method which must be implemented in cooperation with the managed bean
* class to fetch data on demand.
*/
public abstract DataPage fetchPage(int startRow, int pageSize);
/** *//**
* 進行刪除等操作后會立即改變列表項并且返回列表頁的，請調用此方法，用于刷新列表。
*/
public void refresh() {
if (this.page != null) {
this.page = null;
getPage();
}
}
}
public String delete()
{
FacesContext ctx = FacesContext.getCurrentInstance();
int id = Integer.parseInt(ctx.getExternalContext().getRequestParameterMap().get("id"));
EntityManagerHelper.beginTransaction();
CarBeanDAO dao = new CarBeanDAO();
CarBean bean = dao.findById(id);
if(bean != null)
{
dao.delete(bean);
dataModel.refresh();
}
EntityManagerHelper.commit();
return null;
}
User中scrollerPage的相關代碼：
private int scrollerPage = 1;
public int getScrollerPage()
{
return scrollerPage;
}
public void setScrollerPage(int scrollerPage)
{
this.scrollerPage = scrollerPage;
System.out.println("current page = " + scrollerPage);
}
Faces-config.xml:
<managed-bean>
<managed-bean-name>user</managed-bean-name>
<managed-bean-class>com.gcoresoft.jsfdemo.bean.User</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope>
</managed-bean>
有人反映會出現(xiàn)獲取兩次DataModel的情況,為什么呢？
經過我的測試，是因為設置的datatable的rows屬性的值大于了程序中pageSize的值，比如你設置rows="12"，而你的pageSize設置的是10，那么JSF為了滿足顯示12條得條件，就會取兩次數據集組成一個12跳得數據集顯示出來，所以給定的rows屬性最好可以使用相關管理bean的pageSize變量，這樣前后臺統(tǒng)一數據條目，提高性能和可操作性。
為了方便大家JSF的項目開發(fā)，后面我會推出一套我自己寫的一個基于JSF的框架，當然此框架是基于實際項目成功實施后提取出來的，主要是簡化了對表單的操作，增加一些常用的工具套件，例如分頁，驗證器等等。對表單操作部分的簡化主要體現(xiàn)在：每種控件都可以和固定的模型綁定，這樣操作模型就可以做到對前臺控件的控制，比如后臺取值可以使用attributes.get("username")，設置前臺控件值可以使用attributes.put("username","admin")，對選擇控件操作也更加簡便，當使用put的方法的時候，前臺會自動選擇到那項，更重要的是這些簡化不需要你寫程序代碼，寫一些簡單的配置文件即可，而且選擇項不僅可以設置在配置文件中，還可以通過數據庫等其他數據源獲取，大大提高開發(fā)效率。
posted on 2008-11-23 01:00
Vincent-chen 閱讀(557)
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