在網(wǎng)上看了幾個(gè)Structs分頁(yè)，感覺(jué)不是很完善，于是根據(jù)自己的經(jīng)驗(yàn)，寫了一個(gè)相對(duì)高效簡(jiǎn)潔的分頁(yè)方法。由于本人水平有限，如果大家有什么更好的想法，歡迎不吝賜教。

一、 開(kāi)發(fā)環(huán)境
我的開(kāi)發(fā)環(huán)境是：JBuilder x + Weblogic 8.1 + Oracle 9i + Windows 2003 ，如果朋友們的開(kāi)發(fā)環(huán)境不一樣亦無(wú)妨。

二、開(kāi)發(fā)思路
既然講的是Struts，那自然離不了MVC，分頁(yè)顯示也是如此。
1、 建立數(shù)據(jù)庫(kù)和對(duì)應(yīng)的表，本例的表是TCertificate。
2、 建立適當(dāng)?shù)哪Ｐ徒M件，對(duì)應(yīng)你要查詢數(shù)據(jù)庫(kù)中的表。這部分由DAO數(shù)據(jù)訪問(wèn)層來(lái)實(shí)現(xiàn)，如果有的朋友對(duì)DAO不熟悉可以查詢一下相關(guān)資料。本例由CertificateDAO.java來(lái)實(shí)現(xiàn)。
3 、建立分頁(yè)所需要的模型組件，由javaBean來(lái)充當(dāng)，并與CertificateDAO實(shí)現(xiàn)分離。網(wǎng)上介紹的很多方法，都存在著數(shù)據(jù)與分頁(yè)組件藕合的現(xiàn)象，這也是本方法與其它分頁(yè)方法的主要不同之處。

4、建立控制器組件，這部分由Struts 中的Action來(lái)實(shí)現(xiàn)。主要負(fù)責(zé)將實(shí)例化CertificateDAO，只取要顯示的數(shù)據(jù)記錄，存入ArrayList對(duì)象然后返回，并放到request中。而分頁(yè)部分則根據(jù)分頁(yè)條件，單獨(dú)進(jìn)行構(gòu)造，避免了與DAO混在一起的情況發(fā)生。網(wǎng)上其它介紹的一些分頁(yè)方法中，基本上都是一次性讀出所有查詢的數(shù)據(jù)，然后再由分頁(yè)相關(guān)組件進(jìn)行構(gòu)造。這樣，如果數(shù)據(jù)量大的話，很容易形成瓶頸。在本例中由于不是一次性地讀出查詢的所有數(shù)據(jù)，而只是讀出一個(gè)頁(yè)面要顯示的數(shù)據(jù)記錄，這就節(jié)省了很多不必要的數(shù)據(jù)傳輸，提高了效率。本例中為CertificateAction.java。

5、建立視圖組件，這部分由jsp來(lái)充當(dāng)，為了不出現(xiàn)java 代碼，我們使用Struts提供的標(biāo)簽庫(kù)，主要負(fù)責(zé)從request中取出剛剛放入的對(duì)象，通過(guò)反復(fù)調(diào)用CertificateAction以及action參數(shù)，而實(shí)現(xiàn)分頁(yè)顯示。本例中為listcertificate.jsp。
6、 建立并配置struts-config.xml。

三、實(shí)例代碼
確定好上面的開(kāi)發(fā)思路后，代碼的實(shí)現(xiàn)就有單可循了。
1、建數(shù)據(jù)庫(kù)和相應(yīng)的表。
2、數(shù)據(jù)邏輯層的相關(guān)代碼。
1）、通用的DAO類：CommonDAO.java
這是一個(gè)很多DAO都要繼承到的通用DAO類，是我根據(jù)實(shí)踐總結(jié)出來(lái)的，為了減少篇幅，這里只顯示和本例相關(guān)的代碼。

java代碼:

package com.xindeco.business ; import java.io.*; import java.sql.*; import java.util.*; import javax.sql.*; import java.lang.IllegalAccessException; import java.lang.reflect.InvocationTargetException; import org.apache.commons.beanutils.BeanUtils; public class DAO {   protected DataSource ds; /**   * 說(shuō)明:取得當(dāng)前查詢的總記錄數(shù)   */ public int getRows () {   return this.count; }   public void rsHandler (ResultSet rs, int offset, int limit)   {    try    {     count = 0;     rs.absolute ( -1) ;     count = rs.getRow () ;     if (offset <= 0)     {      rs.beforeFirst () ;     }     else     {      rs.absolute (offset) ;     }    }    catch (Exception e)    {     e.printStackTrace () ;    }   }   public DAO(DataSource ds) {           this.ds = ds;   }   public void setDataSource(DataSource ds) {     this.ds = ds;   }   protected void close(ResultSet rs) {     if (rs != null) {             try {                     rs.close();             } catch (SQLException e) {             }             rs = null;     }   }   protected void close(PreparedStatement pstmt) {     if (pstmt != null) {             try {                     pstmt.close();             } catch (SQLException e) {             }             pstmt = null;     }   }   protected void close(Connection conn) {     if (conn != null) {             try {                     conn.close();             } catch (SQLException e) {                     e.printStackTrace();             }             conn = null;     }   }   protected void rollback(Connection conn) {     if (conn != null) {             try {                     conn.rollback();             } catch (SQLException e) {                     e.printStackTrace();             }             conn = null;     }   } }

這個(gè)類主要是通過(guò)子類傳進(jìn)來(lái)的先進(jìn)結(jié)果集，取得查詢的記錄總數(shù)，并對(duì)數(shù)據(jù)庫(kù)連接進(jìn)行簡(jiǎn)單的管理。
2）、對(duì)數(shù)據(jù)庫(kù)進(jìn)行訪問(wèn)：CertificateDAO.java

java代碼:

package com.xindeco.business; import java.io.*; import java.sql.*; import java.util.*; import javax.sql.*; import com.xindeco.common.dbconn.DbConn; public class CertificateDAO extends DAO {   public NationDAO(DataSource ds) {     super(ds);   } public List findCertificateList(int offset,int limit) throws SQLException         {         int countRows = 0 ;         ArrayList list = null ;     Connection conn = null;     PreparedStatement pstmt = null; ResultSet rs = null; try         {              conn = ds.getConnection();                 String sql =                                 "SELECT certificateID, certificateCode,certificateName,photoURL,"                                 + "description,graduateID FROM TCertificate " ;       pstmt = conn.prepareStatement(sql);       rs = pstmt.executeQuery();                         /*對(duì)游標(biāo)進(jìn)行處理，rsHandler 方法在父類DAO中*/                         this.rsHandler(rs,offset,limit);                         if (rs != null && rs.next ())                         {                                 list = new ArrayList () ;                                 do                                 {                                         countRows++ ;                                         list.add (rs2VO (rs)) ;                                 }                                 while ( (countRows++ < limit) && rs.next ()) ;                         }       close(rs);       close(pstmt);           } catch (SQLException e) {       close(rs);       close(pstmt);       rollback(conn);                 e.printStackTrace();                   } finally {             close(conn);     }         return list ;         }         private CertificateVO rs2VO (ResultSet rs)         {                 try                 {                         CertificateVO certificateVO = new CertificateVO () ;                         certificateVO.setCertificateID (rs.getInt ("certificateID")) ;                         certificateVO.setCertificateCode (rs.getString ("certificateCode")) ;                         certificateVO.setCertificateName (rs.getString ("certificateName")) ;                         certificateVO.setPhotoURL (rs.getString ("photoURL")) ;                         certificateVO.setDescription (rs.getString ("description")) ;                         certificateVO.setGraduateID (rs.getInt ("graduateID")) ;                         return certificateVO ;                 }                 catch (Exception ex)                 {                         ex.printStackTrace () ;                         return null ;                 }         } }

findCertificateList(int offset,int limit)是查得所有要顯示的數(shù)據(jù)，并放入ArrayList中。看過(guò)網(wǎng)上有些例子，把數(shù)據(jù)記錄放入ArrayList的動(dòng)作過(guò)程直接在while循環(huán)體里完成，如果字段多的話，會(huì)造成方法過(guò)于寵大，又不美觀。 這里，數(shù)據(jù)記錄放入ArrayList的動(dòng)作過(guò)程由rs2VO方法完成，就比較整潔了。另外，if (rs != null && rs.next ()) 配合while ( (countRows++ < limit) && rs.next ()) 是為了程序的健壯性考慮的，稍分析一下不難得出結(jié)論。

3、建立控制器組件：CertificateAction.java

java代碼:

package com.xindeco.presentation; import javax.sql.* ; import java.util.* ; import javax.servlet.http.* ; import javax.servlet.* ; import org.apache.struts.action.* ; import org.apache.struts.util.* ; import com.xindeco.common.Pager; import com.xindeco.business.graduatedata.CertificateDAO ; public class CertificateAction         extends Action {         private static final int PAGE_LENGTH = 5 ; //每頁(yè)顯示5條記錄         public ActionForward execute (ActionMapping mapping, ActionForm form,                                                                   HttpServletRequest request,                                                                   HttpServletResponse response)         {                 ActionForward myforward = null ;                 String myaction = mapping.getParameter () ;                 if (isCancelled (request))                 {                         return mapping.findForward ("failure") ;                 }                 if ("".equalsIgnoreCase (myaction))                 {                         myforward = mapping.findForward ("failure") ;                 }                 else if        ("LIST".equalsIgnoreCase (myaction))                 {                         myforward = performList (mapping, form, request, response) ;                 }                 else                 {                         myforward = mapping.findForward ("failure") ;                 }                 return myforward ;         }         private ActionForward performList (ActionMapping mapping,                                                                            ActionForm actionForm,                                                                            HttpServletRequest request,                                                                            HttpServletResponse response)         {                      try                 {         DataSource ds = (DataSource) servlet.getServletContext().getAttribute(Action.DATA_SOURCE_KEY);                 CertificateDAO   certificateDAO  = new CertificateDAO  (ds) ;                         int offset = 0;   //翻頁(yè)時(shí)的起始記錄所在游標(biāo)                         int length = PAGE_LENGTH;                           String pageOffset = request.getParameter("pager.offset");                 if (pageOffset == null || pageOffset.equals("")) {         offset = 0;       } else {         offset = Integer.parseInt(pageOffset);       }                         List certificateList = certificateDAO .findCertificateList (offset,length) ;                         int size = certificateDAO.getRows(); //  取得總記錄數(shù)                         String url = request.getContextPath()+"/"+mapping.getPath()+".do";                         String pagerHeader = Pager.generate(offset, size, length, url); //分頁(yè)處理                         request.setAttribute ("pager", pagerHeader) ;                         request.setAttribute ("list", certificateList) ;                 }                 catch (Exception e)                 {                         e.printStackTrace();                         return mapping.findForward ("error") ;                 }                 return mapping.findForward ("success") ;         } }

CertificateAction.java主要是把數(shù)據(jù)從DAO中取出，并放入一個(gè)ArrayList 中，然后通過(guò)配置文件再軟件View的JSP頁(yè)。

5、建立視圖listcertificate.jsp文件。

java代碼:

<%@ page contentType="text/html; charset=GBK" %> <%@ taglib uri="/WEB-INF/struts-template.tld" prefix="template" %> <%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %> <%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %> <%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %> <table bgcolor="#666666" cellpadding="1" cellspacing="0" border="0" width="500"> <tr> <td> <table cellpadding="0" cellspacing="0" border="0" width="500"> <tr> <td bgcolor="#fecc51">&</td> </tr> </table> </td> </tr> <tr> <td> <table cellpadding="0" cellspacing="0" border="0" width="500">   <tr> <td bgcolor="#d6e0ed">     &&<bean:message key="label.list4certificate"/>   </td> </tr> <tr bgcolor="#FFFFFF"> <td width="5%"></td><td width="19%"></td><td width="76%"></td> </tr>     <tr> <td> <table bgcolor="#f2f2f2" width="500" cellspacing="0" border="0">       <tr bgcolor="#bacce1">         <td><b><bean:message key="Certificate.select"/> </b></td>         <td><b><bean:message key="Certificate.certificateID"/> </b></td>         <td><b><bean:message key="Certificate.certificateCode"/></b></td>         <td><b><bean:message key="Certificate.certificateName"/></b></td>         <td><b><bean:message key="Certificate.view"/></b></td>     ?/tr> <bean:write name="pager" property="description"/>   <logic:equal name="pager" property="hasPrevious" value="true">               <a href="/graduatedata/list.do?viewPage=<bean:write name="pager" property="previousPage"/>" class="a02">            Previous         </a>   </logic:equal>   <logic:equal name="pager" property="hasNext" value="true">     ?a href="/graduatedata/list.do?viewPage=<bean:write name="pager" property="nextPage"/>" class="a02">      Next     ?/a>   </logic:equal> <logic:notEmpty name="list" scope="request"> <logic:iterate id="certificate" name="list" type="com.xindeco.business.graduatedata.CertificateVO"scope="request"> <tr bgcolor="#FFFFFF">     ?td><html:text property="name" value="<bean:write name="certificate" property="certificateID" scope="page"/>"/>                 </td>     ?td> <bean:write name="certificate" property="certificateID" scope="page"/></td>     ?td> <bean:write name="certificate" property="certificateCode" scope="page"/></td>     ?td> <bean:write name="certificate" property="certificateName" scope="page"/></td>     ?td> <bean:write name="certificate" property="photoURL" scope="page"/></td> </tr> </logic:iterate> </logic:notEmpty> </table> </td> </tr> </table> </td> </tr> </table>

6、對(duì)應(yīng)的配置文件struts-config.xml。

java代碼:

<?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="certificateForm" type="com.xindeco.presentation.graduatedata.CertificateForm" />   </form-beans>   <global-forwards>     <forward name="error" path="/error/error.jsp" />   </global-forwards>   <action-mappings>       <action name="certificateForm" parameter="LIST" path="/graduatedata/list" scope="request" type="com.xindeco.presentation.graduatedata.CertificateAction" validate="true">       <forward name="success" path="/graduatedata/listcertificate.jsp" />     </action>   </action-mappings> …… </struts-config>

7、最后當(dāng)然是最重要的分頁(yè)代碼了：Pager.java

java代碼:

package com.xindeco.common; import java.util.* ; public class Pager {   private static int MAX_PAGE_INDEX = 10; //頁(yè)腳顯示多少頁(yè)   private static String HEADER = "Result page";      public static String generate(int offset, int length, int size, String url) {         if (length > size) {           String pref;           if (url.indexOf("?") > -1) {                 pref = "&";           } else {                 pref = "?";           }           String header = "<font face='Helvetica' size='-1'>"+HEADER+": ";           if (offset > 0) {                 header += "&<a href=\""+url+pref+"pager.offset="+(offset-size)+"\">[<< Prev]</a>\n";           }           int start;           int radius = MAX_PAGE_INDEX/2*size;           if (offset < radius) {                 start = 0;           } else if(offset < length-radius) {                 start = offset - radius;           } else {                 start = (length/size-MAX_PAGE_INDEX)*size;           }           for(int i=start;i<length && i < start + MAX_PAGE_INDEX*size;i+=size) {                 if (i == offset) {                   header += "<b>"+(i/size+1)+"</b>\n";                 } else {                   header += "&<a href=\""+url+pref+"pager.offset="+i+"\">"+(i/size+1)+"</a>\n";                 }           }           if(offset < length - size) {                 header += "&<a href=\""+url+pref+"pager.offset="+((int)offset+(int)size)+"\">[Next >>]</a>\n";           }           header += "</font>";           return header;         } else {           return "";         }   } }

這部分代碼的實(shí)現(xiàn)相當(dāng)簡(jiǎn)潔，但已經(jīng)足夠完成所需了。