Question

我想实现此tutorial

中的代码

我用14行数据填充了Oracle表，但是当我每次第二页为空时尝试在JSF页面之间导航时：

enter image description here

这是JSF页面的代码：

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"    
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:ui="http://java.sun.com/jsf/facelets">
    <h:head>
        <ui:insert name="header">           
            <ui:include src="header.xhtml"/>         
        </ui:insert>
    </h:head>
    <h:body>

        <h1><img src="resources/css/images/icon.png" alt="NVIDIA.com" /> History Center</h1>
        <!-- layer for black background of the buttons -->
        <div id="toolbar" style="margin: 0 auto; width:1180px; height:30px; position:relative;  background-color:black">
            <!-- Include page Navigation -->
            <ui:insert name="Navigation">           
                <ui:include src="Navigation.xhtml"/>         
            </ui:insert>

        </div>  

        <div id="greenBand" class="ui-state-default ui-corner-allh" style="position:relative; top:35px; left:0px;"> 
            <h:graphicImage alt="Dashboard"  style="position:relative; top:-20px; left:9px;"  value="resources/images/logo_sessions.png" />
        </div>
        <div id="main" style="margin: 0 auto; width:1190px; height:700px; position:absolute;  background-color:transparent; top:105px">

            <div id="mainpage" style="margin: 0 auto; width:1190px; height:500px; position:absolute;  background-color:transparent; top:80px">

                <div id="settingsHashMap" style="width:750px; height:400px; position:absolute;  background-color:r; top:20px; left:1px">

                    <h:form id="form">

                        <!-- The sortable data table -->
                        <h:dataTable value="#{SessionsController.dataList}" var="item">

                            <h:column>
                                <f:facet name="header">
                                    <h:commandLink value="Account Session ID" actionListener="#{SessionsController.sort}">
                                        <f:attribute name="sortField" value="Account Session ID" />
                                    </h:commandLink>
                                </f:facet>
                                <h:outputText value="#{item.aSessionID}" />
                            </h:column>


                            <h:column>
                                <f:facet name="header">
                                    <h:commandLink value="User ID" actionListener="#{SessionsController.sort}">
                                        <f:attribute name="sortField" value="User ID" />
                                    </h:commandLink>
                                </f:facet>
                                <h:outputText value="#{item.userID}" />
                            </h:column>
                            <h:column>
                                <f:facet name="header">
                                    <h:commandLink value="Activity Start Time" actionListener="#{SessionsController.sort}">
                                        <f:attribute name="sortField" value="Activity Start Time" />
                                    </h:commandLink>
                                </f:facet>
                                <h:outputText value="#{item.activityStart}" />
                            </h:column>
                            <h:column>
                                <f:facet name="header">
                                    <h:commandLink value="Activity End Time" actionListener="#{SessionsController.sort}">
                                        <f:attribute name="sortField" value="Activity End Time" />
                                    </h:commandLink>
                                </f:facet>
                                <h:outputText value="#{item.activityEnd}" />
                            </h:column>
                            <h:column>
                                <f:facet name="header">
                                    <h:commandLink value="Activity" actionListener="#{SessionsController.sort}">
                                        <f:attribute name="sortField" value="Activity" />
                                    </h:commandLink>
                                </f:facet>
                                <h:outputText value="#{item.activity}" />
                            </h:column>
                        </h:dataTable>

                        <!-- The paging buttons -->
                        <h:commandButton value="first" action="#{SessionsController.pageFirst}"
                                         disabled="#{SessionsController.firstRow == 0}" />
                        <h:commandButton value="prev" action="#{SessionsController.pagePrevious}"
                                         disabled="#{SessionsController.firstRow == 0}" />
                        <h:commandButton value="next" action="#{SessionsController.pageNext}"
                                         disabled="#{SessionsController.firstRow + SessionsController.rowsPerPage >= SessionsController.totalRows}" />
                        <h:commandButton value="last" action="#{SessionsController.pageLast}"
                                         disabled="#{SessionsController.firstRow + SessionsController.rowsPerPage >= SessionsController.totalRows}" />
                        <h:outputText value="Page #{SessionsController.currentPage} / #{SessionsController.totalPages}" />
                        <br />

                        <!-- The paging links -->
                        <ui:repeat value="#{SessionsController.pages}" var="page">
                            <h:commandLink value="#{page}" actionListener="#{SessionsController.page}"
                                           rendered="#{page != SessionsController.currentPage}" />
                            <h:outputText value="#{page}" escape="false"
                                          rendered="#{page == SessionsController.currentPage}" />
                        </ui:repeat>
                        <br />

                        <!-- Set rows per page -->
                        <h:outputLabel for="rowsPerPage" value="Rows per page" />
                        <h:inputText id="rowsPerPage" value="#{SessionsController.rowsPerPage}" size="3" maxlength="3" />
                        <h:commandButton value="Set" action="#{SessionsController.pageFirst}" />
                        <h:message for="rowsPerPage" errorStyle="color: red;" />

                    </h:form>

                </div>   

                <div id="settingsdiva" style="width:350px; height:400px; position:absolute;  background-color:transparent; top:20px; left:400px">

                </div>   

                <div id="settingsdivb" style="width:350px; height:400px; position:absolute;  background-color:transparent; top:20px; left:800px">

                </div>   
            </div>  
        </div>

    </h:body>
</html>

会话：

   import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
// or import javax.faces.bean.SessionScoped;
import javax.inject.Named;
/* include SQL Packages */
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.annotation.PostConstruct;
import javax.sql.DataSource;
import javax.annotation.Resource;
import javax.faces.bean.ViewScoped;
import javax.faces.component.UICommand;
import javax.faces.context.FacesContext;
import javax.inject.Inject;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
// or import javax.faces.bean.ManagedBean; 
import javax.faces.event.ActionEvent;

import org.glassfish.osgicdi.OSGiService;

// source http://balusc.blogspot.com/2008/10/effective-datatable-paging-and-sorting.html
@Named("SessionsController")
@ViewScoped
public class Sessions implements Serializable {

    /* Call the Oracle JDBC Connection driver */
    @Resource(name = "jdbc/Oracle")
    private DataSource ds;
    // Data.
    private List<ActiveSessionObj> dataList;
    // Rows
    private int totalRows;
    // Paging.
    private int firstRow;
    private int rowsPerPage;
    private int totalPages;
    private int pageRange;
    private Integer[] pages;
    private int currentPage;
    // Sorting.
    private String sortField;
    private boolean sortAscending;

    /* Constructor */
    public Sessions() {
        /* Set default properties */
        rowsPerPage = 10; // Default rows per page (max amount of rows to be displayed at once).
        pageRange = 10; // Default page range (max amount of page links to be displayed at once).
        sortField = "ASESSIONID"; // Default sort field.
        sortAscending = true; // Default sort direction.
    }

    public static class ActiveSessionObj {

        /* Oracle table structure
        CREATE TABLE ACTIVESESSIONSLOG(
        ASESSIONID VARCHAR2(30 ) NOT NULL,
        USERID VARCHAR2(30 ),
        ACTIVITYSTART TIMESTAMP(6),
        ACTIVITYEND TIMESTAMP(6),
        ACTIVITY CLOB
        )
         */
        private String aSessionID;
        private String userID;
        private Date activityStart;
        private Date activityEnd;
        private String activity;

        public ActiveSessionObj(String aSessionID, String userID, Date activityStart, Date activityEnd, String activity) {
            this.aSessionID = aSessionID;
            this.userID = userID;
            this.activityStart = activityStart;
            this.activityEnd = activityEnd;
            this.activity = activity;
        }

        public String getaSessionID() {
            return aSessionID;
        }

        public void setaSessionID(String aSessionID) {
            this.aSessionID = aSessionID;
        }

        public String getactivity() {
            return activity;
        }

        public void setactivity(String activity) {
            this.activity = activity;
        }

        public Date getactivityEnd() {
            return activityEnd;
        }

        public void setactivityEnd(Date activityEnd) {
            this.activityEnd = activityEnd;
        }

        public Date getactivityStart() {
            return activityStart;
        }

        public void setactivityStart(Date activityStart) {
            this.activityStart = activityStart;
        }

        public String getuserID() {
            return userID;
        }

        public void setuserID(String userID) {
            this.userID = userID;
        }

        private ActiveSessionObj() {
            throw new UnsupportedOperationException("Not yet implemented");
        }
    }

    // Paging actions -----------------------------------------------------------------------------
    public void pageFirst() {
        page(0);
    }

    public void pageNext() {
        page(firstRow + rowsPerPage);
    }

    public void pagePrevious() {
        page(firstRow - rowsPerPage);
    }

    public void pageLast() {
        page(totalRows - ((totalRows % rowsPerPage != 0) ? totalRows % rowsPerPage : rowsPerPage));
    }

    public void page(ActionEvent event) {
        page(((Integer) ((UICommand) event.getComponent()).getValue() - 1) * rowsPerPage);
    }

    private void page(int firstRow) {
        this.firstRow = firstRow;
        loadDataList(); // Load requested page.
    }

    // Sorting actions ----------------------------------------------------------------------------
    public void sort(ActionEvent event) {
        String sortFieldAttribute = (String) event.getComponent().getAttributes().get("sortField");

        // If the same field is sorted, then reverse order, else sort the new field ascending.
        if (sortField.equals(sortFieldAttribute)) {
            sortAscending = !sortAscending;
        } else {
            sortField = sortFieldAttribute;
            sortAscending = true;
        }

        pageFirst(); // Go to first page and load requested page.
    }

    // Loaders ------------------------------------------------------------------------------------
    private void loadDataList() {

        // Load list and totalCount.
        try {
            dataList = list(firstRow, rowsPerPage, sortField, sortAscending);
            totalRows = countDBRowNum(); //count the tablerows
        } catch (Exception e) {
            throw new RuntimeException(e); 
        }

        // Set currentPage, totalPages and pages.
        currentPage = (totalRows / rowsPerPage) - ((totalRows - firstRow) / rowsPerPage) + 1;
        totalPages = (totalRows / rowsPerPage) + ((totalRows % rowsPerPage != 0) ? 1 : 0);
        int pagesLength = Math.min(pageRange, totalPages);
        pages = new Integer[pagesLength];

        // firstPage must be greater than 0 and lesser than totalPages-pageLength.
        int firstPage = Math.min(Math.max(0, currentPage - (pageRange / 2)), totalPages - pagesLength);

        // Create pages (page numbers for page links).
        for (int i = 0; i < pagesLength; i++) {
            pages[i] = ++firstPage;
        }
    }

    // Getters ------------------------------------------------------------------------------------
    public List<ActiveSessionObj> getdataList() {
        if (dataList == null) {
            loadDataList(); // Preload page for the 1st view.
        }
        return dataList;
    }

    public int getTotalRows() {
        return totalRows;
    }

    public int getFirstRow() {
        return firstRow;
    }

    public int getRowsPerPage() {
        return rowsPerPage;
    }

    public Integer[] getPages() {
        return pages;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public int getTotalPages() {
        return totalPages;
    }

    // Setters ------------------------------------------------------------------------------------
    public void setRowsPerPage(int rowsPerPage) {
        this.rowsPerPage = rowsPerPage;
    }

    // Actions ------------------------------------------------------------------------------------
    /**
     * Returns list of ActiveSessionObj items starting at the given first index with the given row count,
     * sorted by the given sort field and sort order.
     * @param firstRow First index of rows to be returned.
     * @param rowCount Amount of rows to be returned.
     * @param sortField Field to sort the data on.
     * @param sortAscending Whether to sort data ascending or not.
     * @return list of ActiveSessionObj items starting at the given first index with the given row count,
     * sorted by the given sort field and sort order.
     * @throws DAOException If something fails at DAO level.
     */
    public List<ActiveSessionObj> list(int firstRow, int rowCount, String sortField, boolean sortAscending) throws SQLException {

        String SqlStatement = null;

        if (ds == null) {
            throw new SQLException();
        }

        Connection conn = ds.getConnection();
        if (conn == null) {
            throw new SQLException();
        }

        String sortDirection = sortAscending ? "ASC" : "DESC";

        SqlStatement = "SELECT c.*" +
                          " FROM (SELECT b.*, rownum rn" +
                                 " FROM (SELECT a.*" +
                                          " FROM activeSessionsLog a" +
                                         " ORDER BY %s %s) b" +
                                 " WHERE rownum <= ?) c" +
                       " WHERE rn >= ?";

        String sql = String.format(SqlStatement, sortField, sortDirection);

        PreparedStatement ps = null;
        ResultSet resultSet = null;
        List<ActiveSessionObj> dataList = new ArrayList<ActiveSessionObj>();

        try {
            conn.setAutoCommit(false);
            boolean committed = false;
            try {
                ps = conn.prepareStatement(sql);
                ps.setInt(1, firstRow);
                ps.setInt(2, rowCount);


                resultSet = ps.executeQuery();
                /* take the result from the SQL query and insert it into Array List collection */
                dataList = ActiveSessionsArrayList(resultSet);

                conn.commit();
                committed = true;

            } finally {
                if (!committed) {
                    conn.rollback();
                }
            }

        } finally {
            ps.close();
            conn.close();
        }

        return dataList;
    }

    /**
     * Returns total amount of rows in table.
     * @return Total amount of rows in table.
     * @throws DAOException If something fails at DAO level.
     */
    public int countDBRowNum() throws Exception {

        String SqlStatement = null;

        if (ds == null) {
            throw new SQLException();
        }

        Connection conn = ds.getConnection();
        if (conn == null) {
            throw new SQLException();
        }

        SqlStatement = "SELECT count(*) FROM ACTIVESESSIONSLOG";

        PreparedStatement ps = null;
        ResultSet resultSet = null;
        int count = 0;

        try {
            conn.setAutoCommit(false);
            boolean committed = false;
            try {
                SqlStatement = "SELECT count(*) FROM ACTIVESESSIONSLOG";

                ps = conn.prepareStatement(SqlStatement);
                resultSet = ps.executeQuery();

                if (resultSet.next()) {
                    count = resultSet.getInt(1);
                }

                conn.commit();
                committed = true;
            } finally {
                if (!committed) {
                    conn.rollback();
                }
            }
        } finally {
            ps.close();
            conn.close();
        }

        return count;
    }

    /**
     * Map the current row of the given ResultSet to ActiveSessionObj.
     * @param resultSet The ResultSet of which the current row is to be mapped to ActiveSessionObj.
     * @return The mapped ActiveSessionObj from the current row of the given ResultSet.
     * @throws SQLException If something fails at database level.
     */
    private static ArrayList<ActiveSessionObj> ActiveSessionsArrayList(ResultSet rs) throws SQLException {
        ArrayList<ActiveSessionObj> list = new ArrayList<>();


        try {
            while (rs.next()) {
                list.add(new ActiveSessionObj(
                        rs.getString("ASESSIONID"),
                        rs.getString("USERID"),
                        timestampToDate(rs.getTimestamp("ACTIVITYSTART")),
                        timestampToDate(rs.getTimestamp("ACTIVITYEND")),
                        rs.getString("ACTIVITY")));
            }
        } catch (Exception x) {
            x.printStackTrace();
        }

        return list;


        /*
        CREATE TABLE ACTIVESESSIONSLOG(
        ASESSIONID VARCHAR2(30 ) NOT NULL,
        USERID VARCHAR2(30 ),
        ACTIVITYSTART TIMESTAMP(6),
        ACTIVITYEND TIMESTAMP(6),
        ACTIVITY CLOB
        )
         */
    }
    // select all button handle
    private Map<Long, Boolean> selectedIds = new HashMap<Long, Boolean>();

    // get the list from the JSF page
    public Map<Long, Boolean> getSelectedIds() {
        return selectedIds;
    }

    // call this method from the JSF page to delete the selected rows
    public String deleteAction() {

        // do something with the selected rows
        return null;
    }

    private static Date timestampToDate(java.sql.Timestamp ts) {
        Date d = null;
        try {
            d = new Date(ts.getTime());
        } catch (Exception e) {
            e.printStackTrace();
        }

        return d;
    }
}

也许分页算法错误或SQL查询未修正？我还没有从原始代码中触及分页算法。

祝福

修改

SQL查询错误。

编辑2 我更新了SQL代码，但现在第一页错了，第二页等显示数据。问题出在某处：

编辑3工作代码

public List list（int firstRow，int rowCount，String sortField，boolean sortAscending）抛出SQLException {

String SqlStatement = null;

if (ds == null) {
    throw new SQLException();
}

Connection conn = ds.getConnection();
if (conn == null) {
    throw new SQLException();
}

int countrow = firstRow + rowCount;
String sortDirection = sortAscending ? "ASC" : "DESC";

SqlStatement = "SELECT c.*" +
                  " FROM (SELECT b.*, rownum rn" +
                         " FROM (SELECT a.*" +
                                  " FROM activeSessionsLog a" +
                                 " ORDER BY %s %s) b" +
                         " WHERE rownum <= ?) c" +
               " WHERE rn > ?";

String sql = String.format(SqlStatement, sortField, sortDirection);

PreparedStatement ps = null;
ResultSet resultSet = null;
List<ActiveSessionObj> dataList = new ArrayList<ActiveSessionObj>();

try {
    conn.setAutoCommit(false);
    boolean committed = false;
    try {
        ps = conn.prepareStatement(sql);
        ps.setInt(1, countrow);
        ps.setInt(2, firstRow);


        resultSet = ps.executeQuery();
        /* take the result from the SQL query and insert it into Array List collection */
        dataList = ActiveSessionsArrayList(resultSet);

        conn.commit();
        committed = true;

    } finally {
        if (!committed) {
            conn.rollback();
        }
    }

} finally {
    ps.close();
    conn.close();
}

return dataList;

}

Answer 1

我认为您的查询参数错误，第一个参数为rownum <= ?，因此必须为rownum < firstRow + rowCount，而第二个参数为rn >= firstRow

您遵循的教程使用MySQL LIMIT，正如您在此处所见MySQL 5.0 Reference Manual（寻找LIMIT），教程使用的参数是第一行和每页行数。在您的查询中，您使用＆gt;和＆lt; =，然后你必须提供第一个结果和最后一个结果。

没有正确计算到JSF页面的分页

1 个答案: