JSP 分页

Oracle大记录数分页借助rownum
select * from ( select a.*, rownum num from (select * from
guestbook order by name desc) a where rownum <= 20 )
where num >=10;

Mysql大记录数分页借助rownum
select * from (select * from guestbook ) aa limit 0,10

借助Pager标签实现分页功能
<dependency>
<groupId>jsptags</groupId>
<artifactId>pager-taglib</artifactId>
<version>2.0</version>
</dependency>

使用方法：
1.MysqlPagination.java

import java.sql.ResultSet;import java.sql.SQLException;import java.util.List;import java.util.regex.Pattern;import org.apache.commons.dbutils.ResultSetHandler;import org.apache.commons.dbutils.handlers.MapListHandler;public class MysqlPagination implements Pagination {private int pageSize = 3;private int pageNumber = 1;private int maxPages;private int maxElements;private String sql;private MysqlUtil db;public MysqlPagination(String sql) {this.sql = sql;init();}public MysqlPagination(String sql, int pageSize, int pageNumber) {this.sql = sql;this.pageSize = pageSize;this.pageNumber = pageNumber;init();this.setPageNumber(pageNumber);}private void init() {db = MysqlUtil.getInstance();setMaxElements();setMaxPages();}private void setMaxElements() {// select * from xxx order by desc// select count(1) from xxx order by descString regex = "select((.)+)from";Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);String[] s = p.split(this.sql);String newSql = "select count(1) as total from " + s[1];ResultSetHandler handler = new ResultSetHandler() {public Object handle(ResultSet rs) throws SQLException {if (rs.next()) {return new Integer(rs.getInt("total"));} else {return null;}}};this.maxElements = (Integer) db.query(newSql, null, handler);}private void setMaxPages() {if (maxElements != 0 && (maxElements % pageSize == 0)) {maxPages = maxElements / pageSize;} else {maxPages = maxElements / pageSize + 1;}}private String sqlModify(String source,int begin, int size){System.out.println(begin+", " + size);StringBuffer target = new StringBuffer(200);target.append("select * from (");target.append(sql);target.append(") aa limit ");target.append(begin);target.append(", ");target.append(size);return target.toString();}private int getEndElement() {int endElement = pageNumber * pageSize;if (endElement >= maxElements) {return maxElements;} else {return endElement;}}private int getBeginElement() {return (pageNumber - 1) * pageSize;}@Overridepublic List<Object> getList() {String newSql = this.sqlModify(this.sql, this.getBeginElement(), this.pageSize);return (List) db.query(newSql, null, new MapListHandler());}@Overridepublic int getMaxElements() {return maxElements;}@Overridepublic int getMaxPages() {return maxPages;}@Overridepublic int getNext() {if (pageNumber + 1 >= this.getMaxPages()) {return getMaxPages();}return pageNumber + 1;}@Overridepublic int getPageNumber() {return pageNumber;}@Overridepublic int getPageSize() {return pageSize;}@Overridepublic int getPrevious() {if(pageNumber-1<=1){return 1;}else{return pageNumber-1;}}@Overridepublic boolean hasNext() {return pageNumber<this.getMaxPages();}@Overridepublic boolean hasPrevious() {return pageNumber>1;}@Overridepublic boolean isFirst() {return pageNumber==1;}@Overridepublic boolean isLast() {return pageNumber>=this.getMaxPages();}@Overridepublic void setPageNumber(int pageNumber) {if(pageNumber>maxPages){this.pageNumber=maxPages;}else if(pageNumber<1){this.pageNumber=1;}else{this.pageNumber=pageNumber;}}@Overridepublic void setPageSize(int pageSize) {this.pageSize=pageSize;}// Pagination p = new OraclePagination(sql,20,3);   //List list=p.getList();}

2. GuestbookDAOJdbc.java

        private static final String SELECT_GUESTBOOKS_SQL="select * from guestbook order by id desc";@Overridepublic Pagination getGuestbookByPage(int pageSize, int pageNumber) {Pagination p = new MysqlPagination(SELECT_GUESTBOOKS_SQL,pageSize,pageNumber);return p;}

3.GetMessagesServlet.java

public class GetMessagesServlet extends HttpServlet {private static final long serialVersionUID = 5964428201228635704L;private int pageSize;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {int pageNumber;try {pageNumber = Integer.parseInt(request.getParameter("p"));} catch (Exception e) {pageNumber = 1;}GuestbookDAO dao = new GuestbookDAOJdbc();Pagination pager=dao.getGuestbookByPage(pageSize, pageNumber);request.setAttribute("guestbook.pager", pager);request.getRequestDispatcher("/getMessages.jsp").forward(request, response);}public void init(ServletConfig config)throws ServletException{super.init(config);try{this.pageSize=Integer.parseInt(config.getServletContext().getInitParameter("pageSize"));}catch(Exception e){this.pageSize=10;}}}

4.getMessages.jsp

<%@ taglib uri="http://jsptags.com/tags/navigation/pager" prefix="pg"%><pg:pager url="${ctx}/servlet/getMessages"items="${requestScope['guestbook.pager'].maxElements}"maxPageItems="${initParam.pageSize}"  maxIndexPages="5"><pg:index><pg:first unless="current"><a href="${pageUrl}&p=${pageNumber}">首页</a></pg:first><pg:prev><a href="${pageUrl}&p=${pageNumber}">上一页(${pageNumber})</a></pg:prev><pg:pages><a href="${pageUrl}&p=${pageNumber}">${pageNumber}</a></pg:pages><pg:next><a href="${pageUrl}&p=${pageNumber}">下一页(${pageNumber})</a></pg:next><pg:last unless="current"><a href="${pageUrl}&p=${pageNumber}">尾页</a></pg:last></pg:index></pg:pager>