Oracle下的Java分页功能_动力节点Java学院整理

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

以上所述是小编给大家介绍的Oracle下的Java分页功能网站的支持！