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Oracle下的Java分页功能_动力节点Java学院整理

时间：2021-01-09 11:16:24 | 栏目：Oracle | 点击：次

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：

package com.bjpowernode.test; 
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：

package com.bjpowernode.test; 
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：

package com.bjpowernode.test; 
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：

package com.bjpowernode.test; 
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： 

package com.bjpowernode.test; 
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.package com.bjpowernode.test;    

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。

总结

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