我的Struts分页方法
我的Struts分页方法 拜读了bibiye的《一个高效简洁的Struts分页方法(原创)》后，根据bibiye的方法，自己修改了一下，也弄了一个struts下的分页，大家见笑了！
我的方法是，根据用户点击导航条上的页号(offset)，到DB中读取该页的数据(不是一次全部读出)，点到哪页读哪页的数据，JBX + tomcat + oracle下测试通过
********分页类Pager.java，负责生成分页导航条********
package page;
/**
* 分页代码
* <p>Title: 分页</p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: BCS</p>
* @author Alex
* @version 1.0
*/
public class Pager {
private int offset;
private int size;
private int length;
private String url;
private String pageHeader;
public Pager(int offset, int size, int length, String url, String pageHeader) {
this.offset = offset;
this.size = size;
this.length = length;
this.url = url;
this.pageHeader = pageHeader;
}
/**
* 返回分页导航条
* @param offset int 起始记录的位置
* @param size int 总记录数
* @param length int 步长
* @param url String .do的url
* @param pageHeader String 导航条的前缀文字提示
* @return String
*/
public String getPageNavigation() {
String pageNavigation = ''; //最终返回的分页导航条
//记录数超过一页,需要分页
if (size > length) {
String pref; //前缀
if (url.indexOf('?') > -1) {
//如果url中已经包含了其他的参数,就把offset参数接在后面
pref = '&';
}
else {
//如果url中没有别的参数
pref = '?';
}
//如果导航条包含header
if (pageHeader != null && pageHeader.length() > 0) {
pageNavigation = pageHeader + ' : ';
}
//如果不是第一页,导航条将包含“<<”(第一页)和“<”(前一页)
if (offset > 0) {
pageNavigation += '<a href='' + url + pref + 'offset=0'>[<<]</a>\n' +
'<a href='' + url + pref + 'offset=' + (offset - length) +
''>[<]</a>\n';
}
//导航条中,排头的那一页的offset值
int startOffset;
//位于导航条中间的那一页的offset值(半径)
int radius = constants.MAX_PAGE_INDEX / 2 * length;
//如果当前的offset值小于半径
if (offset < radius || this.pageCount() <= constants.MAX_PAGE_INDEX) {
//那么第一页排头
startOffset = 0;
}
else if (offset < size - radius) {
startOffset = offset - radius;
}
else {
startOffset = (size / length - constants.MAX_PAGE_INDEX) * length;
}
for (int i = startOffset;
i < size && i < startOffset + constants.MAX_PAGE_INDEX * length;
i += length) {
if (i == offset) {
//当前页号,加粗显示
pageNavigation += '<b>' + (i / length + 1) + '</b>\n';
}
else {
//其他页号,包含超链接
pageNavigation += '<a href='' + url + pref + 'offset=' + i + ''>' +
(i / length + 1) + '</a>\n';
}
}
//如果不是最后一页,导航条将包含“>”(下一页)和“>>”(最后一页)
if (offset < size - length) {
pageNavigation += '<a href='' + url + pref + 'offset=' +
(offset + length) + ''>[>]</a>\n' +
'<a href='' + url + pref + 'offset=' + lastPageOffset() +
''>[>>]</a>\n';
}
// System.out.println('radius : ' + radius);
// System.out.println('start offset : ' + startOffset);
return pageNavigation;
}
//记录不超过一页,不需要分页
else {
return '';
}
}
/**
* 返回分页后的总页数
* @param size int 总记录数
* @param length int 每页的记录数
* @return int
*/
public int pageCount() {
int pagecount = 0;
if (size % length == 0) {
pagecount = size / length;
}
else {
pagecount = size / length + 1;
}
return pagecount;
}
/**
* 返回最后一页的记录数
* @param size int 总记录数
* @param length int 每页的记录数
* @return int
*/
public int lastPageSize() {
int lastpagesize = 0;
if (size % length == 0) {
lastpagesize = length;
}
else {
lastpagesize = size % length;
}
return lastpagesize;
}
/**
* 返回最后一页的起始记录位置
* @param size int 总记录数
* @param length int 每页的记录数
* @return int
*/
public int lastPageOffset() {
return size - lastPageSize();
}
public int getOffset() {
return offset;
}
public void setOffset(int offset) {
this.offset = offset;
}
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
public int getLength() {
return length;
}
public void setLength(int length) {
this.length = length;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getPageHeader() {
return pageHeader;
}
public void setPageHeader(String pageHeader) {
this.pageHeader = pageHeader;
}
}
********数据处理类empDAO.java，负责访问DB，获取当前页面需要显示的记录********
package page;
import java.sql.*;
import java.util.*;
public class empDAO {
public empDAO() {
}
/**
* 从offset位置起始,返回length条记录
* @param offset int 起始的记录位置
* @param length int 步长
* @param conn Connection 数据库连接
* @return ArrayList
*/
public ArrayList findAllEmp(int offset, int length, Connection conn) throws
SQLException {
PreparedStatement ps = null;
ResultSet rs = null;
ArrayList emps = new ArrayList();
empVO empvo = null;
String strSql = 'select empno, ename from emp where rowid not in (select rowid from emp where rownum <= ?) and rownum <= ?';
try {
ps = conn.prepareStatement(strSql);
ps.setInt(1, offset); //起始记录的位置
ps.setInt(2, length); //步长
rs = ps.executeQuery();
while (rs != null && rs.next()) {
empvo = new empVO();
empvo.setEmpno(rs.getInt('empno'));
empvo.setEname(rs.getString('ename'));
emps.add(empvo);
}
}
catch (SQLException ex) {
ex.printStackTrace();
throw ex;
}
return emps;
}
/**
* 返回总的记录数
* @param conn Connection
* @throws SQLException
* @return int
*/
public int getRsTotalCount(Connection conn) throws SQLException {
PreparedStatement ps = null;
ResultSet rs = null;
int rsCount = 0;
String strSql = 'select count(empno) as empCount from emp';
try {
ps = conn.prepareStatement(strSql);
rs = ps.executeQuery();
if (rs != null && rs.next()) {
rsCount = rs.getInt('empCount');
}
}
catch (SQLException ex) {
ex.printStackTrace();
throw ex;
}
return rsCount;
}
}
********业务类empBO.java，调用empDAO类********
package page;
import java.util.*;
/**
* BO类
* <p>Title: 分页</p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: BCS</p>
* @author Alex
* @version 1.0
*/
public class empBO {
private DBPool db = DBPool.newInstance();
private empDAO empdao = new empDAO();
public empBO() {
}
/**
* 从offset位置起始,返回length条记录
* @param offset int 起始
* @param length int 步长
* @throws Exception
* @return ArrayList
*/
public ArrayList findAllEmp(int offset, int length) throws Exception {
ArrayList emps = new ArrayList();
try {
emps = empdao.findAllEmp(offset, length, db.getConnection());
}
catch (Exception ex) {
throw ex;
}
finally {
db.release();
}
return emps;
}
/**
* 返回总的记录数
* @throws Exception
* @return int
*/
public int getRsTotalCount() throws Exception {
int rsCount = 0;
try {
rsCount = empdao.getRsTotalCount(db.getConnection());
}
catch (Exception ex) {
throw ex;
}
finally {
db.release();
}
return rsCount;
}
}
********ActionForm类empForm.java********
package page;
import javax.servlet.http.*;
import org.apache.struts.action.*;
public class empForm
extends ActionForm {
private int offset; //起始记录的位置//每页显示的记录数
public ActionErrors validate(ActionMapping actionMapping,
HttpServletRequest httpServletRequest) {
/**@todo: finish this method, this is just the skeleton.*/
return null;
}
public void reset(ActionMapping actionMapping,
HttpServletRequest httpServletRequest) {
this.offset = 0; //记录默认从第一条开始显示
}
public int getOffset() {
return offset;
}
public void setOffset(int offset) {
this.offset = offset;
}
}
********Action类empAction.java，控制器，调用BO类，Pager类********
package page;
import java.util.*;
import javax.servlet.http.*;
import org.apache.struts.action.*;
/**
* 分页测试的Action
* <p>Title: 分页</p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: BCS</p>
* @author Alex
* @version 1.0
*/
public class empAction
extends Action {
public ActionForward execute(ActionMapping actionMapping,
ActionForm actionForm,
HttpServletRequest httpServletRequest,
HttpServletResponse httpServletResponse) {
empForm empform = (empForm) actionForm;
return performList(actionMapping, actionForm, httpServletRequest,
httpServletResponse);
}
private ActionForward performList(ActionMapping actionMapping,
ActionForm actionForm,
HttpServletRequest request,
HttpServletResponse response) {
try {
empBO empbo = new empBO();
//获取外部传进来的起始记录号
int offset = ( (empForm) actionForm).getOffset();
//获取每页的记录数
int pagesize = constants.PAGE_SIZE;
//获取记录集合,从offset开始,取length条记录
ArrayList emps = empbo.findAllEmp(offset, pagesize);
//计算所有记录的条数(总记录数)
int size = empbo.getRsTotalCount();
//外部url地址,得到形如: http://localhost:8088/bugMIS/showlist.do 的String
String url = request.getContextPath() + actionMapping.getPath() + '.do';
//实例化分页类
Pager p = new Pager(offset, size, pagesize, url, 'Page Navigation');
//获取分页导航条
//String pageNavigation = p.getPageNavigation();
//将url字符串和记录集合,存入request中
request.setAttribute('pager', p);
request.setAttribute('emps', emps);
}
catch (Exception e) {
e.printStackTrace();
return actionMapping.findForward('failure');
}
return actionMapping.findForward('success');
}
}
********数据库连接池类DBPool.java，可以使用tomcat的连接池，也可以不用，这里关闭了********
package page;
import java.sql.*;
import javax.naming.*;
import javax.sql.*;
import org.apache.commons.logging.*;
/**
* 系统连接池类
* <p>Title: Gantoo@91.com</p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: BCS</p>
* @author Alex
* @version 1.0
*/
public class DBPool {
Log log = LogFactory.getLog('DBPool'); //日志机
private DBPool() {
}
private Connection conn = null;
/* true:使用连接池
false:不使用连接池,采用JDBC直接连接 */
private final static boolean USE_DB_POOL = false;
private final static String jndi_DataSource = 'jdbc/BugMIS_ora';
private final static String jdbcdriver =
'oracle.jdbc.driver.OracleDriver';
private final static String url =
'jdbc:oracle:thin:@localhost:1521:myo9';
private final static String user = 'scott';
private final static String pass = 'tiger';
public static DBPool newInstance() {
return new DBPool();
}
/**
* 切换是否使用连接池
* */
public Connection getConnection() {
if (USE_DB_POOL) {
conn = getConnectionByDBPool();
}
else {
conn = getConnectionDirect();
}
return conn;
}
/**
* 直接采用JDBC连接数据库
* */
private Connection getConnectionDirect() {
try {
Class.forName(jdbcdriver).newInstance();
conn = DriverManager.getConnection(url, user, pass);
}
catch (SQLException ex) {
log.error('Error Connection! ' + ex.getMessage());
}
catch (ClassNotFoundException ex) {
log.error('Driver Not Found! ' + ex.getMessage());
}
catch (IllegalAccessException ex) {
log.error(ex.getMessage());
}
catch (InstantiationException ex) {
log.error(ex.getMessage());
}
return conn;
}
/**
* 采用连接池
* */
private Connection getConnectionByDBPool() {
try {
Context initCtx = new InitialContext();
Context ctx = (Context) initCtx.lookup('java:/comp/env');
DataSource ds = (DataSource) ctx.lookup(jndi_DataSource);
conn = ds.getConnection();
}
catch (NamingException ex) {
log.error('Data Source Not Found! ' + ex.getMessage());
//System.out.println('未找到数据源' + ex.getMessage());
}
catch (SQLException ex1) {
log.error('Error Connection! ' + ex1.getMessage());
//System.out.println('错误的数据连接' + ex1.getMessage());
}
return conn;
}
/**
* 释放连接
* */
public void release() {
try {
if (!conn.isClosed()) {
conn.close();
}
}
catch (SQLException ex) {
log.error('Connection Closing Error! ' + ex.getMessage());
//System.out.println('连接关闭失败' + ex.getMessage());
}
}
}
********包含常量的类constants.java，常量********
package page;
/**
* 定义工程中公用的常量
* <p>Title: 分页</p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: BCS</p>
* @author Alex
* @version 1.0
*/
public final class constants {
public static final int MAX_PAGE_INDEX = 5; //页脚显示多少页
public static final int PAGE_SIZE = 2; //每页的记录数
}
********测试jsp页面index.jsp，为了方便测试，嵌入了java代码，能显示就行
<%@ taglib uri='/WEB-INF/struts-logic.tld' prefix='logic' %>
<%@ taglib uri='/WEB-INF/struts-bean.tld' prefix='bean' %>
<%@ taglib uri='/WEB-INF/struts-html.tld' prefix='html' %>
<%@ page contentType='text/html; charset=GBK' import='java.util.*,page.*'%>
<html:html>
<head>
<title></title>
<style type='text/css'>
.pt9 { font: 10pt '宋体'}
body { font: 10pt '宋体' ; margin: 15px}
td { font-size: 10pt}
a:hover { font-size: 10pt; color: red; text-decoration: underline}
a:link { font-size: 10pt; color: blue; text-decoration: underline}
a:active { font-size: 10pt; color: blue; text-decoration: underline}
a:visited { font-size: 10pt; color: blue; text-decoration: underline }
</style>
</head>
<body bgcolor='#ffffff'>
<p><a href='http://localhost:8088/page/showEmp.do?offset=0'>Show Me All Of The Emps</a></p>
<logic:present name='emps'>
<%
ArrayList emps = (ArrayList)request.getAttribute('emps');
Iterator it = emps.iterator();
empVO empvo;
while(it!=null && it.hasNext()){
empvo = (empVO)it.next();
out.print(empvo.getEmpno() + ' ');
out.print(empvo.getEname() + '<br>');
}
out.print('当前页有 ' + emps.size() + ' 条记录<br>');
out.print('<p>');
%>
</logic:present>
<logic:present name='pager'>
<%
Pager pager = (Pager)request.getAttribute('pager');
out.print(pager.getPageNavigation() + '<p>');
out.print('共有记录 ' + pager.getSize() + ' 条<br>');
out.print('每页有 ' + pager.getLength() + ' 条记录<br>');
out.print('共分 ' + pager.pageCount() + ' 页<br>');
%>
</logic:present>
</body>
</html:html>
********配置文件struts-config.xml********
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE struts-config PUBLIC '-//Apache Software Foundation//DTD Struts Configuration 1.1//EN' 'http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd'>
<struts-config>
<form-beans>
<form-bean name='empForm' type='page.empForm' />
</form-beans>
<action-mappings>
<action input='/index.jsp' name='empForm' path='/showEmp' scope='request' type='page.empAction' validate='false'>
<forward name='faiure' path='/index.jsp' />
<forward name='success' path='/index.jsp' />
</action>
</action-mappings>
</struts-config>
