Question

我需要一些帮助才能在我的应用中实现延迟加载。

数据表：

<p:dataTable var="log" value="#{logger.getAll()}"
        widgetVar="loggerTable"
        emptyMessage="No logs found with given criteria"
        rowStyleClass="#{log.status eq 'uspesno' ? 'old' : null}">
        <!-- //Main 
        <f:facet name="header">
            <p:outputPanel>
                <h:outputText value="Search all fields:" />
                <p:inputText id="globalFilter" onkeyup="PF('loggerTable').filter()"
                    style="width:150px" placeholder="Enter keyword" />
            </p:outputPanel>
        </f:facet>  -->

        <p:column filterBy="#{log.mdmId}" headerText="Id"
            footerText="contains" filterMatchMode="contains">
            <h:outputText style="display: block; width:100%; "
                value="#{log.mdmId}" />
        </p:column>
        <p:column filterBy="#{log.pib}" headerText="pib"
            footerText="contains" filterMatchMode="contains">
            <h:outputText value="#{log.pib}" />
        </p:column>

        <!-- // poruka 
        <p:column filterBy="#{log.poruka}" headerText="message"
            footerText="contains" filterMatchMode="contains">
            <h:outputText value="#{log.poruka}" />
        </p:column> -->
        <p:column filterBy="#{log.status}" headerText="status"
            footerText="contains" filterMatchMode="contains">
            <h:outputText value="#{log.status}" />
        </p:column>
        <p:column filterBy="#{log.mbr}" headerText="mbr"
            footerText="contains" filterMatchMode="contains">
            <h:outputText value="#{log.mbr}" />
        </p:column>
        <p:column filterBy="#{log.datumUpisa}" headerText="datumupisa"
            footerText="contains" filterMatchMode="contains">
            <h:outputText value="#{log.datumUpisa}" />
        </p:column>
        <p:column style="width:40px;text-align: center">
            <p:commandButton update=":form:logDetail"
                oncomplete="PF('logDialog').initPosition();PF('logDialog').show()"
                icon="fa fa-search" title="View">
                <f:setPropertyActionListener value="#{log}"
                    target="#{logger.selectedLog}" />
            </p:commandButton>
        </p:column>
    </p:dataTable>

ManagedBean：

private static final long serialVersionUID = 1L;

private Integer mdmId;


private String pib;


private String mbr;


private Date datumUpisa;


private String status;


private String poruka;

private Logger selectedLog;

public Logger getSelectedLog() {
    return selectedLog;
}

public static List<Logger> getAll(){
    List<Logger> lista = LoggerDAO.getAll();
    return lista;
} // ...

DAO：

public static List<Logger> getAll() {
    Connection con = null;
    PreparedStatement ps = null;
    List<Logger> lista = new ArrayList<>();
    try {
        con = DataConnect.getConnection();
        ps = con.prepareStatement("Select * from log");

        ResultSet resultSet = ps.executeQuery();

        while (resultSet.next()) {

            int mdm_id = resultSet.getInt(1);
            String pib = resultSet.getString(2);
            String mbr = resultSet.getString(3);
            Date datumUpisa = resultSet.getDate(4);
            String status = resultSet.getString(5);
            String poruka = resultSet.getString(6);

            Logger log = new Logger();
            log.setMbr(mbr);
            log.setMdmId(mdm_id);
            log.setDatumUpisa(datumUpisa);
            log.setPib(pib);
            log.setPoruka(poruka);
            log.setStatus(status);
            lista.add(log);

        }

    } catch (SQLException ex) {
        System.out.println("Login error -->" + ex.getMessage());
        return null;
    } finally {
        DataConnect.close(con);
    }
    return lista;
}

我想实现延迟加载，但是我不知道是否可能。 primefaces提供的数据库没有示例。我是否需要编写查询来获取几行，还是应该一次返回所有行？我需要一些帮助和建议，谢谢

Answer 1

我考虑到您要实现分页。

首先将<p:dataTable>修改为以下内容：

<p:dataTable lazy="true" rows="8" paginator="true" paginatorTemplate="{CurrentPageReport} {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}" rowsPerPageTemplate="2,4,6,8"></p:dataTable>

然后在每个filterBy字段中添加sortBy，<p:column>（根据需要）。

然后，在Managed Bean类中，创建私有字段： private LazyDataModel<Logger> lazyDataModel;

在托管bean中为 LazyDataModel<Logger> lazyDataModel创建合适的吸气剂和吸气剂。

现在使用getAll()方法，但是将返回类型设为void，添加以下内容：

public static void getAll(){
    lazyDataModel = new LazyLoggerDataModel(LoggerDAO.getAll());
}

创建一个LazyLoggerDataModel的{{1}}类。看起来像这样：

extends LazyDataModel<Logger>

请参阅Primefaces Official的Lazy-加载示例以获取更多信息：

链接此处： Primefaces Lazy Loading Example

希望这会对您有所帮助：）

Answer 2

This文章解决了我的问题：

getAll()在DAO中：

public static List<Logger> getAll(int from , int to) {
    Connection con = null;
    PreparedStatement ps = null;
    List<Logger> lista = new ArrayList<>();
    try {
        con = DataConnect.getConnection();
        int upper = from + to;
        ps = con.prepareStatement("Select * from log limit ?,?");
        ps.setInt(1, from);
        ps.setInt(2, upper);

        ResultSet resultSet = ps.executeQuery();

        while (resultSet.next()) {

            int mdm_id = resultSet.getInt(1);
            String pib = resultSet.getString(2);
            String mbr = resultSet.getString(3);
            Date datumUpisa = resultSet.getDate(4);
            String status = resultSet.getString(5);
            String poruka = resultSet.getString(6);

            Logger log = new Logger();
            log.setMbr(mbr);
            log.setMdmId(mdm_id);
            log.setDatumUpisa(datumUpisa);
            log.setPib(pib);
            log.setPoruka(poruka);
            log.setStatus(status);
            lista.add(log);

        }

    } catch (SQLException ex) {
        System.out.println("Login error -->" + ex.getMessage());
        return null;
    } finally {
        DataConnect.close(con);
    }
    return lista;
}

如何在我的代码中实现primefaces延迟加载

2 个答案: