【DRP】表格—分页查询（1）—表格加载数据

首次进入页面默认显示2条记录：

<%@ page import="java.util.*" %>  
<%@ page import="java.text.*" %>  
<%@ page import="com.bjpowernode.drp.sysmgr.domain.*" %>
<%@ page import="com.bjpowernode.drp.sysmgr.manager.*" %>   
<%@ page import="com.bjpowernode.drp.util.*" %> 
<%
    int pageNo = 1;
    int pageSize = 2;
    String pageNoString = request.getParameter("pageNo");
    if (pageNoString != null) {
        pageNo = Integer.parseInt(pageNoString);
    }
    PageModel pageModel = UserManager.getInstance().findUserList(pageNo, pageSize);    
%>  

调用后台分页查询方法：

/**
     * 分页查询
     * @param pageNo 第几页
     * @param pageSize 每页多少条数据
     * @return pageModel
     */
    public PageModel findUserList(int pageNo, int pageSize) {
        StringBuffer sbSql = new StringBuffer();    
        sbSql.append("select user_id, user_name, password, contact_tel, email, create_date ")
            .append("from ")
            .append("( ")
            .append("select rownum rn, user_id, user_name, password, contact_tel, email, create_date ")
            .append("from ")
            .append("( ")
            .append("select user_id, user_name, password, contact_tel, email, create_date from t_user where user_id <> 'root' order by user_id ")
            .append(")  where rownum <= ? ")
            .append(")  where rn > ? ");
        Connection conn = null;
        //JDBC数据库连接API之一
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        //封装的分页实体
        PageModel pageModel = null;
        try {
            conn = DbUtil.getConnection();
            pstmt = conn.prepareStatement(sbSql.toString());
            pstmt.setInt(1, pageNo * pageSize);
            pstmt.setInt(2, (pageNo - 1) * pageSize);
            rs = pstmt.executeQuery();
            List userList = new ArrayList();
            while (rs.next()) {
                User user = new User();
                user.setUserId(rs.getString("user_id"));
                user.setUserName(rs.getString("user_name"));
                user.setPassword(rs.getString("password"));
                user.setContactTel(rs.getString("contact_tel"));
                user.setEmail(rs.getString("email"));
                user.setCreateDate(rs.getTimestamp("create_date"));
                userList.add(user);
            }
            pageModel = new PageModel();
            pageModel.setList(userList);
            pageModel.setTotalRecords(getTotalRecords(conn));
            pageModel.setPageSize(pageSize);
            pageModel.setPageNo(pageNo);
        }catch(SQLException e) {
            e.printStackTrace();
        }finally {
            DbUtil.close(rs);
            DbUtil.close(pstmt);
            DbUtil.close(conn);
        }
        return pageModel;
    }

前台显示：

<%
     List userList = pageModel.getList();
       for (Iterator iter=userList.iterator(); iter.hasNext();) 
          
     {
                        User user = (User)iter.next();
                 %>
                <tr>
                    <td class="rd8">
                        <input type="checkbox" name="selectFlag" class="checkbox1"
                            value="<%=user.getUserId() %>">
                    </td>
                    <td class="rd8">
                        <%=user.getUserId() %>
                    </td>
                    <td class="rd8">
                        <%=user.getUserName() %>
                    </td>
                    <td class="rd8">
                        <%=user.getContactTel()%>
                    </td>
                    <td class="rd8">
                        <%=user.getEmail() %>
                    </td>
                    <td class="rd8">
                        <%=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(user.getCreateDate()) %>
                    </td>
                </tr>
                <%
      }
 %>

关于 PreparedStatement  对象。

 JDBC使用PreparedStatement的好处   

 JDBC使用PreparedStatement的好处 

PreparedStatement

PageModel 实体

import java.util.List;

/**
 * 封装分页信息
 * @author Administrator
 *
 */
public class PageModel {

    //结果集
    private List list;
    
    //查询记录数
    private int totalRecords;
    
    //每页多少条数据
    private int pageSize;
    
    //第几页
    private int pageNo;
    
    /**
     * 总页数
     * @return
     */
    public int getTotalPages() {
        return (totalRecords + pageSize - 1) / pageSize;
    }
    
    /**
     * 取得首页
     * @return
     */
    public int getTopPageNo() {
        return 1;
    }
    
    /**
     * 上一页
     * @return
     */
    public int getPreviousPageNo() {
        if (pageNo <= 1) {
            return 1;
        }
        return pageNo - 1;
    }
    
    /**
     * 下一页
     * @return
     */
    public int getNextPageNo() {
        if (pageNo >= getBottomPageNo()) {
            return getBottomPageNo();
        }
        return pageNo + 1;    
    }
    
    /**
     * 取得尾页
     * @return
     */
    public int getBottomPageNo() {
        return getTotalPages();
    }
    
    public List getList() {
        return list;
    }

    public void setList(List list) {
        this.list = list;
    }

    public int getTotalRecords() {
        return totalRecords;
    }

    public void setTotalRecords(int totalRecords) {
        this.totalRecords = totalRecords;
    }

    public int getPageSize() {
        return pageSize;
    }

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

    public int getPageNo() {
        return pageNo;
    }

    public void setPageNo(int pageNo) {
        this.pageNo = pageNo;
    }
}

编程小技巧：

1、遍历的应用：

List userList = pageModel.getList();
   for (Iterator iter=userList.iterator(); iter.hasNext();) 
{     

}

2、日期格式化：

<%=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(user.getCreateDate()) %>

3、三目运算

表格中的联系电话个email数据库中是null，如果数据库为null显示空。

       //这里用到了三目运算
    public String getContactTel() {
        return contactTel == null ? "" : contactTel;
    }

    //这里用到了三目运算
    public String getEmail() {
        return email == null ? "" : email;
    }

总结：不断提高自己的编程效率！