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我正在尝试在我的 primefaces 数据表设置中实现延迟加载。目前，这在没有延迟加载实现的情况下工作，但是在实现延迟加载后我在数据表中没有数据。但是，我可以在我的 LoadData 方法中打印我的列表，以验证数据是否正在加载到我的列表中，但是一旦我的 LazyModel 返回并尝试加载数据表，似乎就会出现问题。这可能只是我忽略的一些简单的事情。任何帮助是极大的赞赏！

这是我的 ScreenshotListProducer 类代码：

    @ManagedBean
    @RequestScoped
    public class ScreenshotListProducer implements Serializable  {
       private static final long serialVersionUID = 1L;
       @Inject
       private EntityManager em;

       private List<Screenshot> screenshots;

       private LazyDataModel<Screenshot> lazyModel = null;

       private int pageSize = 5;

       public void setPageSize(int pageSize) {
           this.pageSize = pageSize;
       }

       public int getPageSize() {
           return pageSize;
       }

       @Produces
       @Named
       public List<Screenshot> getScreenshots() {
          System.out.println("************* getting screenshots list **************");
          return screenshots;
       }

       @PostConstruct
       public void LoadData() {
            lazyModel = new LazyDataModel<Screenshot>() {
                private static final long serialVersionUID = 1L;

                    @Override
                    public List<Screenshot> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String,String> filters) {      
                    int start = first;
                    int end = first + pageSize;

                    try {
                        CriteriaBuilder cb = em.getCriteriaBuilder();
                        CriteriaQuery<Screenshot> criteria = cb.createQuery(Screenshot.class);
                        Root<Screenshot> screenshot = criteria.from(Screenshot.class);
                        criteria.select(screenshot).orderBy(cb.asc(screenshot.get("time")));

                        TypedQuery<Screenshot> s = em.createQuery(criteria);
                        s.setMaxResults(end - start);
                        s.setFirstResult(start);

                        screenshots = s.getResultList();
                        System.out.println("************* lazy screenshot list created **************");
                        for (Screenshot lazylist : screenshots) {
                          System.out.println("id numbers in lazy list: " + lazylist.getId());
                        }
                    } catch (NullPointerException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

                    return screenshots;
                  }
            };
       }

   public LazyDataModel<Screenshot> getLazyModel() {
        return lazyModel;
    }

这是我的截图类：

@Entity
@XmlRootElement
@Table(name="Test2012", uniqueConstraints = @UniqueConstraint(columnNames = "id"))
public class Screenshot implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue
    @Column(name = "id", columnDefinition="INT")
    private Long id;

    private Timestamp time;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Timestamp getTime() {
        return time;
    }

    public void setTime(Timestamp time) {
        this.time = time;
    }   
}

这是我的 xhtml 代码：

    <p:dataTable id="table1" var="scrshot" rowKey="#{scrshot.id}" value="#{screenshotListProducer.lazyModel}" paginator="true" rows="7" paginatorPosition="bottom" 
                 paginatorTemplate="{CurrentPageReport}  {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}"  
                 rowsPerPageTemplate="7,20,50,100" widgetVar="dataTable" currentPageReportTemplate="(Number of Records: {totalRecords})"
                 emptyMessage="No screenshot data found with given criteria" lazy="true" scrollable="true" draggableColumns="true" scrollHeight="217" style="width: 100%;">  
          <f:facet name="header">  
            <p:outputPanel>  
                <h:outputText value="Search all fields: "/>  
                <p:inputText id="globalFilter" onkeyup="dataTable.filter()"/>  
            </p:outputPanel>  
          </f:facet> 
          <p:column selectionMode="multiple"/>  
          <p:column id="time" headerText="Time" sortBy="#{scrshot.time}" filterBy="#{scrshot.time}" filterMatchMode="startsWith">  
            <h:outputText value="#{scrshot.time}"/>  
          </p:column>   
          <p:column id="id" headerText="ID" sortBy="#{scrshot.id}" filterBy="#{scrshot.id}" filterOptions="#{scrshot.id}" filterMatchMode="exact">  
            <h:outputText value="#{scrshot.id}"/>  
          </p:column>  
    </p:dataTable>
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1 回答 1

10

Well in the case of lazy loader you will have to set total count of you records like "this.setRowCount(total_records_that_are_there);" in your "load" method. It is necessary for the lazy loader to determine how much pages there will be so that the next and previous buttons on data table can be determined i.e (Enable/disable). Like [0 is start] and [total/rowsize] is the total number of pages however you fetch using the load method with (first and pagezie => skip and limit);

于 2012-12-03T07:19:10.987 回答