如何在我的代码中实现 primefaces 延迟加载

Question

我需要一些帮助来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;
} // ...

道：

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，但不知道是否可行。 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，或者我应该一次 return 所有行。我需要一些帮助和建议，谢谢

Answer 1

我考虑到您想实施分页。

先把<p:dataTable>修改成下面这样:

<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<p:column>字段中添加filterBy、sortBy（根据您的需要）。

然后，在托管 Bean class 中，创建私有字段： private LazyDataModel<Logger> lazyDataModel;

为托管 bean 中的 LazyDataModel<Logger> lazyDataModel 创建适当的 getter 和 setter。

现在在 getAll() 方法中，但将 return 类型设为 void，添加：

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

创建 LazyLoggerDataModel class 其中 extends LazyDataModel<Logger>。它看起来像这样：

public class LazyLoggerDataModel extends LazyDataModel<Logger> {

    private List<Logger> loggerList;

    public LazyLoggerDataModel(List<Logger> loggerList) {
        this.loggerList = loggerList;
    }

    @Override
    public Logger getRowData(String rowKey) {
        ....
    }

    @Override
    public Object getRowKey(Logger logger) {
        return ...;
    }

    @Override
    public List<Logger> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String,Object> filters) {
       ... put here the main logic..
    }
}

更多请参考Primefaces官方的懒加载示例:

Link 这里：Primefaces Lazy Loading Example

希望这对您有所帮助:)

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;
}

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