zoukankan      html  css  js  c++  java

  • 分页技术

    这篇以Java+Oracle为基础，讲解代码层的实现。
    就如平时我们很在分页中看到的，分页的时候返回的不仅包括查询的结果集(List)，而且还包括总的页数(pageNum)、当前第几页(pageNo)等等信息，所以我们封装一个查询结果PageModel类，代码如下： 

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    package kane;
    import java.util.List;
    public class PageModel<E> {
     private List<E> list;
     private int pageNo;
     private int pageSize;
     private int totalNum;
     private int totalPage;
     
     public List<E> getList() {
     return list;
     }
     
     public void setList(List<E> list) {
     this.list = list;
     }
     
     public int getPageNo() {
     return pageNo;
     }
     
     public void setPageNo(int pageNo) {
     this.pageNo = pageNo;
     }
     
     public int getPageSize() {
     return pageSize;
     }
     
     public void setPageSize(int pageSize) {
     this.pageSize = pageSize;
     }
     
     public int getTotalNum() {
     return totalNum;
     }
     
     public void setTotalNum(int totalNum) {
     this.totalNum = totalNum;
     setTotalPage((getTotalNum() % pageSize) == 0 ? (getTotalNum() / pageSize)
     : (getTotalNum() / pageSize + 1));
     }
     
     public int getTotalPage() {
     return totalPage;
     }
     
     public void setTotalPage(int totalPage) {
     this.totalPage = totalPage;
     }
     
     // 获取第一页
     public int getFirstPage() {
     return 1;
     }
     
     // 获取最后页
     public int getLastPage() {
     return totalPage;
     }
     
     // 获取前页
     public int getPrePage() {
     if (pageNo > 1)
     return pageNo - 1;
     return 1;
     }
     
     // 获取后页
     public int getBackPage() {
     if (pageNo < totalPage)
     return pageNo + 1;
     return totalPage;
     }
     
     // 判断'首页'及‘前页'是否可用
     public String isPreable() {
     if (pageNo == 1)
     return "disabled";
     return "";
     }
     
     // 判断'尾页'及‘下页'是否可用
     public String isBackable() {
     if (pageNo == totalPage)
     return "disabled";
     return "";
     }
    }

    其中使用泛型是为了能使的该分页类能进行重用，比如在查询用户时可以封装User对象、在查询财务中的流向单时可以封装流向单FlowCard类。
    我们以查询用户为例，用户选择查询条件，首先调用Servlet获取查询参数，然后请求业务逻辑层取得分页封装结果类。业务逻辑调用Dao层取得结果集、取得中记录数封装成分页类。最后Servlet将结果设置到jsp页面显示。
    首先来讲解Servlet，代码如下：

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    95
    package kane;
    import java.io.*;
    import java.util.*;
     
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
     
    import kane.UserInfo;
    import kane.UserInfoManage;
    import kane.PageModel;
     
    public class UserBasicSearchServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;
     private int pageSize = 0;
     
     @Override
     public void init(ServletConfig config) throws ServletException {
     pageSize = Integer.parseInt(config.getInitParameter("pageSize"));
     }
     
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp)
     throws ServletException, IOException {
     doPost(req, resp);
     }
     
     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp)
     throws ServletException, IOException {
     // 1.取得页面参数并构造参数对象
     int pageNo = Integer.parseInt(req.getParameter("pageNo"));
     String sex = req.getParameter("gender");
     String home = req.getParameter("newlocation");
     String colleage = req.getParameter("colleage");
     String comingyear = req.getParameter("ComingYear");
     
     UserInfo u = new UserInfo();
     u.setSex(sex);
     u.setHome(home);
     u.setColleage(colleage);
     u.setCy(comingyear);
     
     // 2.调用业务逻辑取得结果集
     UserInfoManage userInfoManage = new UserInfoManage();
     PageModel<UserInfo> pagination = userInfoManage.userBasicSearch(u,
     pageNo, pageSize);
     List<UserInfo> userList = pagination.getList();
     
     // 3.封装返回结果
     StringBuffer resultXML = new StringBuffer();
     try {
     resultXML.append("<?xml version='1.0' encoding='gb18030'?>/n");
     resultXML.append("<root>/n");
     for (Iterator<UserInfo> iterator = userList.iterator(); iterator
     .hasNext();) {
     UserInfo userInfo = iterator.next();
     resultXML.append("<data>/n");
     resultXML.append("/t<id>" + userInfo.getId() + "</id>/n");
     resultXML.append("/t<truename>" + userInfo.getTruename()
     + "</ truename >/n");
     resultXML.append("/t<sex>" + userInfo.getSex() + "</sex>/n");
     resultXML.append("/t<home>" + userInfo.getHome() + "</home>/n");
     resultXML.append("</data>/n");
     }
     resultXML.append("<pagination>/n");
     resultXML.append("/t<total>" + pagination.getTotalPage()
     + "</total>/n");
     resultXML.append("/t<start>" + pagination.getFirstPage()
     + "</start>/n");
     resultXML.append("/t<end>" + pagination.getLastPage() + "</end>/n");
     resultXML.append("/t<pageno>" + pagination.getPageNo()
     + "</pageno>/n");
     resultXML.append("</pagination>/n");
     
     resultXML.append("</root>/n");
     } catch (Exception e) {
     e.printStackTrace();
     }
     writeResponse(req, resp, resultXML.toString());
     
     }
     
     public void writeResponse(HttpServletRequest request,
     HttpServletResponse response, String result) throws IOException {
     response.setContentType("text/xml");
     response.setHeader("Cache-Control", "no-cache");
     response.setHeader("Content-Type", "text/xml; charset=gb18030");
     PrintWriter pw = response.getWriter();
     pw.write(result);
     pw.close();
     }
    }

    其中User对象代码如下：

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    package kane;
    import java.util.Date;
    public class UserInfo {
     private int id;
     private String username;
     private String password;
     private String truename;
     private String sex;
     private Date birthday;
     private String home;
     private String colleage;
     private String comingYear;
     
     public int getId() {
     return id;
     }
     
     public void setId(int id) {
     this.id = id;
     }
     
     public String getUsername() {
     return username;
     }
     
     public void setUsername(String username) {
     this.username = username;
     }
     
     public String getPassword() {
     return password;
     }
     
     public void setPassword(String password) {
     this.password = password;
     }
     
     public String getTruename() {
     return truename;
     }
     
     public void setTruename(String truename) {
     this.truename = truename;
     }
     
     public String getSex() {
     return sex;
     }
     
     public void setSex(String sex) {
     this.sex = sex;
     }
     
     public Date getBirthday() {
     return birthday;
     }
     
     public void setBirthday(Date birthday) {
     this.birthday = birthday;
     }
     
     public String getHome() {
     return home;
     }
     
     public void setHome(String home) {
     this.home = home;
     }
     
     public String getColleage() {
     return colleage;
     }
     
     public void setColleage(String colleage) {
     this.colleage = colleage;
     }
     
     public String getCy() {
     return comingYear;
     }
     
     public void setCy(String cy) {
     this. comingYear= cy;
     }
    }

    接着是业务逻辑层代码，代码如下：

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    package kane;
    import java.sql.Connection;
     
    import kane.DBUtility;
    import kane.PageModel;
     
    public class UserInfoManage {
     private UserInfoDao userInfoDao = null;
     
     public UserInfoManage () {
     userInfoDao = new UserInfoDao();
     }
     
     public PageModel<UserInfo> userBasicSearch(UserInfo u, int pageNo,
     int pageSize) throws Exception {
     Connection connection = null;
     PageModel<UserInfo> pagination = new PageModel<UserInfo>();
     try {
     connection = DBUtility.getConnection();
     DBUtility.setAutoCommit(connection, false);
     pagination.setList(userInfoDao.getUserList(u, pageNo, pageSize));
     pagination.setPageNo(pageNo);
     pagination.setPageSize(pageSize);
     pagination.setTotalNum(userInfoDao.getTotalNum(u));
     DBUtility.commit(connection);
     } catch (Exception e) {
     DBUtility.rollBack(connection);
     e.printStackTrace();
     throw new Exception();
     } finally {
     DBUtility.closeConnection();
     }
     return pagination;
     }
    }

    其中DBUtility为数据库的连接封装类。
    最后是Dao层代码实现，代码如下： 

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    package kane;
     
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.List;
     
    import kane.UserInfo;
    import kane.DBUtility;
     
    public class UserInfoDao {
     
     public List<UserInfo> getUserList(UserInfo userInfo, int pageNo,
     int pageSize) throws Exception {
     PreparedStatement pstmt = null;
     ResultSet rs = null;
     List<UserInfo> userList = null;
     try {
     String sql = "select * from(select rownum num,u.* from(select * from user_info where sex = ? and home like '"
     + userInfo.getHome()
     + "%"
     + "' and colleage like '"
     + userInfo.getColleage()
     + "%"
     + "' and comingyear like '"
     + userInfo.getCy()
     + "%"
     + "' order by id) u where rownum<=?) where num>=?";
     userList = new ArrayList<UserInfo>();
     Connection conn = DBUtility.getConnection();
     pstmt = conn.prepareStatement(sql);
     pstmt.setString(1, userInfo.getSex());
     pstmt.setInt(2, pageNo * pageSize);
     pstmt.setInt(3, (pageNo - 1) * pageSize + 1);
     rs = pstmt.executeQuery();
     while (rs.next()) {
     UserInfo user = new UserInfo();
     user.setId(rs.getInt("id"));
     user.setTruename(rs.getString("truename"));
     user.setSex(rs.getString("sex"));
     user.setHome(rs.getString("home"));
     userList.add(user);
     }
     } catch (SQLException e) {
     e.printStackTrace();
     throw new Exception(e);
     } finally {
     DBUtility.closeResultSet(rs);
     DBUtility.closePreparedStatement(pstmt);
     }
     return userList;
     }
     
     public int getTotalNum(UserInfo userInfo) throws Exception {
     PreparedStatement pstmt = null;
     ResultSet rs = null;
     int count = 0;
     try {
     String sql = "select count(*) from user_info where sex=? and home like '"
     + userInfo.getHome()
     + "%"
     + "' and colleage like '"
     + userInfo.getColleage()
     + "%"
     + "' and comingyear like '"
     + userInfo.getCy()+ "%" + "'";
     Connection conn = DBUtility.getConnection();
     pstmt = conn.prepareStatement(sql);
     pstmt.setString(1, userInfo.getSex());
     rs = pstmt.executeQuery();
     if (rs.next()) {
     count = rs.getInt(1);
     }
     } catch (SQLException e) {
     e.printStackTrace();
     throw new Exception(e);
     } finally {
     DBUtility.closeResultSet(rs);
     DBUtility.closePreparedStatement(pstmt);
     }
     return count;
     }
    }

    最后就是servlet将得到的结果返回给jsp页面显示出来。
    注：其中DBUtility代码是封装数据库连接操作的代码，如下：

    ?
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    package kane;
     
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
     
    public class DBUtility {
     private static ThreadLocal<Connection> threadLocal = new ThreadLocal<Connection>();
     
     public static Connection getConnection() {
     Connection conn = null;
     conn = threadLocal.get();
     if (conn == null) {
     try {
     Class.forName("oracle.jdbc.driver.OracleDriver");
     conn = DriverManager.getConnection(
     "jdbc:oracle:thin:@localhost:1521:oracle", "admin",
     "admin");
     threadLocal.set(conn);
     } catch (ClassNotFoundException e) {
     e.printStackTrace();
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
     return conn;
     }
     
     // 封装设置Connection自动提交
     public static void setAutoCommit(Connection conn, Boolean flag) {
     try {
     conn.setAutoCommit(flag);
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
     
     // 设置事务提交
     public static void commit(Connection conn) {
     try {
     conn.commit();
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
     
     // 封装设置Connection回滚
     public static void rollBack(Connection conn) {
     try {
     conn.rollback();
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
     
     // 封装关闭Connection、PreparedStatement、ResultSet的函数
     public static void closeConnection() {
     Connection conn = threadLocal.get();
     try {
     if (conn != null) {
     conn.close();
     conn = null;
     threadLocal.remove();
     }
     } catch (SQLException e) {
     e.printStackTrace();
     }
     
     }
     
     public static void closePreparedStatement(PreparedStatement pstmt) {
     try {
     if (pstmt != null) {
     pstmt.close();
     pstmt = null;
     }
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
     
     public static void closeResultSet(ResultSet rs) {
     try {
     if (rs != null) {
     rs.close();
     rs = null;
     }
     } catch (SQLException e) {
     e.printStackTrace();
     }
     }
    }

    使用ThreadLocal是为了保证事务的一致，使得同一个线程的所有数据库操作使用同一个Connection。
    到此一个简单的代码实现就完成了。
  • 相关阅读:
    Qt单元测试工具 QTestlib（QVERIFY, QFETCH, QCOMPARE等）
    再续FPGA初心，京微齐力脱胎京微雅格重新起航（700万元天使轮，泰有基金领投，水木基金、臻云创投、泰科源跟投。数千万元Pre-A轮融资，领投方为海康基金）
    为何放弃 C++ 的工作（开发慢，难度高。完全不适应互联网的快速迭代的思想）
    c++ try catch 问题（没有throw就会被删除，加上/EHa这样就不会被删除）
    西方教育骗局，终于明白精英和普通人的残酷差别！（该校流传着一个数字——4。即“4小时睡眠、4杯咖啡、GPA4.0”——要想获得满分为4分的成绩，每天只睡4个小时，困了就喝4大杯咖啡）
    分析Net 内存对象
    Dynamic Routing Based On Redis
    词云
    vim与sublime
    ASP.NET Core 2.0 源代码
  • 原文地址：https://www.cnblogs.com/zqyanywn/p/5857559.html
Copyright © 2011-2022 走看看