靈魂-放水

漫談解決Struts分頁顯示??

方案<一>

?? ChinaITLab 收集整理???? 2004-9-24??
學習Struts已經有2個多月了，前幾天群里的朋友問我Struts分頁顯示的問題，覺得好像與在jsp中的差不多，但還是遇到了這樣那樣的問題，好不容易花了幾天時間把問題都搞清楚，覺得還是寫點東西跟大家分享一下的好！
至于Struts的語法這里就不多介紹了，不懂的朋友可以先看網上的其他文章。
一 開發環境
Elicpse+Struts Studio+SqlServer2000+Tomcat。
二 開發思路
既然講的是Struts，那自然離不了MVC，分頁顯示也是如此。
1 建立適當的模型組件，對應你要查詢數據庫中的表。這部分由我們熟悉的javaBean來充當。并在其中建立數據庫查詢方法，該方法需要一個java.sql.Conntection類型的參數，并返回一個ArrayList。在本例中為 Book.java
2 建立分頁所需要的模型組件，也是由javaBean來充當，通過由Book中提供的ArrayList來構造。本例中為 PageBean.java.。
3建立控制器組件，這部分由Struts 中的Action來實現。主要負責將實例化Book，并利用返回的ArrayList對象，構造PageBean。以及接收由視圖傳遞而來的action參數。從而在PageBean對象中調用不同的方法，該方法返回Book[] 對象。最后將 Book[]和PageBean放入request中。本例中為PageListAction.java。
4建立視圖組件，這部分由jsp來充當，為了不出現java 代碼，我們使用Struts提供的標簽庫，主要負責從request中取出剛剛放入的對象，通過反復調用PageListAction以及action參數，而實現分頁顯示。本例中為pagetest.jsp.
5 建立并配置struts-config.xml。
6 建立數據庫。
三 實例代碼
1 Book.java
package bean;
import java.sql.*;
import java.util.ArrayList;
/**
* Struts分頁顯示數據Bean，對應數據庫中Book表
*/
public class Book {
private String bookname; //書名
private String author;　 //作者
private String price;　　//價格

public Book(String name,String author,String price){
this.bookname=name;
this.author=author;
this.price=price;
}

public String getAuthor() {
return author;
}

public void setAuthor(String author) {
this.author = author;
}

public String getBookname() {
return bookname;
}

public void setBookname(String bookname) {
this.bookname = bookname;
}

public String getPrice(){
return this.price;
}

public void setPrice(String price){
this.price=price;
}

public static ArrayList getAllBook(Connection connection){
String sql="select * from book";
ArrayList arrayList = new ArrayList();
try{
Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
ResultSet resultSet = statement.executeQuery(sql);
System.out.println("BookBean 數據查詢已完成！");
while(resultSet.next())
{
String name = resultSet.getString("name");
String author = resultSet.getString("author");
String price = resultSet.getString("price");
System.out.println("開始數據封裝：name="+name+"author="+author+"price="+price);
Book book = new Book(name,author,price);
arrayList.add(book);
}
connection.close();
resultSet.close();
}catch(SQLException e)
{
System.out.println("數據庫異常"+e.toString());
}

return arrayList;
}
}

2 PageBean.java
package page;
import bean.Book;
import java.util.*;
/**
* Struts分頁顯示邏輯Bean
*/
public class PageBean {

int currentPage=1;　//當前頁
public int totalPages=0;　//總頁數
int pageRecorders=5;//每頁5條數據
int totalRows=0;　//總數據數
int pageStartRow=0;//每頁的起始數
int pageEndRow=0;　//每頁顯示數據的終止數
boolean hasNextPage=false; //是否有下一頁
boolean hasPreviousPage=false; //是否有前一頁
ArrayList arrayList;
Iterator it;
public PageBean(){}

public PageBean(ArrayList arrayList){
this.arrayList=arrayList;
totalRows=arrayList.size();
it=arrayList.iterator();
hasPreviousPage=false;
currentPage=1;
if((totalRows%pageRecorders)==0)
{
totalPages=totalRows/pageRecorders;
}
else
{
totalPages=totalRows/pageRecorders+1;
}

if(currentPage>=totalPages)
{
hasNextPage=false;
}
else
{
hasNextPage=true;
}

if(totalRows<pageRecorders)
{
this.pageStartRow=0;
this.pageEndRow=totalRows;
}
else
{
this.pageStartRow=0;
this.pageEndRow=pageRecorders;
}

}

/**
* @return Returns the currentPage.
*/
public String getCurrentPage() {
return this.toString(currentPage);
}
/**
* @param currentPage The currentPage to set.
*/
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
/**
* @return Returns the pageRecorders.
*/
public int getPageRecorders() {
return pageRecorders;
}
/**
* @param pageRecorders The pageRecorders to set.
*/
public void setPageRecorders(int pageRecorders) {
this.pageRecorders = pageRecorders;
}
/**
* @return Returns the pageEndRow.
*/
public int getPageEndRow() {
return pageEndRow;
}
/**
* @return Returns the pageStartRow.
*/
public int getPageStartRow() {
return pageStartRow;
}
/**
* @return Returns the totalPages.
*/
public String getTotalPages() {

return this.toString(totalPages);
}
/**
* @return Returns the totalRows.
*/
public String getTotalRows() {
return this.toString(totalRows);
}
/**
* @return Returns the hasNextPage.
*/
public boolean isHasNextPage() {
return hasNextPage;
}
/**
* @param hasNextPage The hasNextPage to set.
*/
public void setHasNextPage(boolean hasNextPage) {
this.hasNextPage = hasNextPage;
}
/**
* @return Returns the hasPreviousPage.
*/
public boolean isHasPreviousPage() {
return hasPreviousPage;
}
/**
* @param hasPreviousPage The hasPreviousPage to set.
*/
public void setHasPreviousPage(boolean hasPreviousPage) {
this.hasPreviousPage = hasPreviousPage;
}
public Book[] getNextPage(){

currentPage=currentPage+1;
System.out.println("PageBean.getNextPage()正在執行；");
System.out.println("參數currentPage="+currentPage);

if((currentPage-1)>0)
{
hasPreviousPage=true;
}
else
{
hasPreviousPage=false;
}
if(currentPage>=totalPages)
{
hasNextPage=false;
}
else
{
hasNextPage=true;
}
System.out.println("參數hasNextPage="+hasNextPage);
System.out.println("準備執行PageBean.getBooks()");
Book[] books=getBooks();
this.description();
return books;
}

public Book[] getPreviouspage(){
currentPage=currentPage-1;

if(currentPage==0){currentPage=1;}

if(currentPage>=totalPages)
{
hasNextPage=false;
}
else
{
hasNextPage=true;
}
if((currentPage-1)>0)
{
hasPreviousPage=true;
}
else
{
hasPreviousPage=false;
}
Book[] books=getBooks();
this.description();
return books;
}

public Book[] getBooks(){
System.out.println("pageBean.getBooks（）開始執行；");
if(currentPage*pageRecorders<totalRows){//判斷是否為最后一頁
pageEndRow=currentPage*pageRecorders;
pageStartRow=pageEndRow-pageRecorders;
}
else{
pageEndRow=totalRows;
pageStartRow=pageRecorders*(totalPages-1);
}
Book[] books=new Book[pageEndRow-pageStartRow+1];

System.out.println("pageStartRow="+pageStartRow);
System.out.println("pageEndRow="+pageEndRow);
int j=0;
for(int i=pageStartRow;i<pageEndRow;i++)
{
Book book=(Book)arrayList.get(i);
books[j++]=book;

}
System.out.println("要顯示的頁面數據已經封裝,具體信息如下：");
this.description();
return books;
}

public String toString(int temp)
{
String str=Integer.toString(temp);
return str;
}

public void description()
{
String description="共有數據數:"+this.getTotalRows()+"共有頁數: "+this.getTotalPages() +"當前頁數為:"+this.getCurrentPage()+" 是否有前一頁: "+this.isHasPreviousPage() +" 是否有下一頁:"+this.isHasNextPage()+" 開始行數:"+this.getPageStartRow()+" 終止行數:"+this.getPageEndRow();
System.out.println(description);
}
}
3　PageListAction.java
package page;
import org.apache.struts.action.*;
import javax.servlet.http.*;
import comm.Constants;
import bean.Book;
import java.util.*;
import javax.sql.DataSource;
/**
* Struts分頁顯示Action
*/
public class PageListAction extends Action {

public PageListAction(){}
ArrayList arrayList=new ArrayList();
PageBean pb;

public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception {
String action;
action=request.getParameter("action");
if(action==null || action.equals("null")){ //第一次讀取數據
try{
DataSource datasource=this.getDataSource(request,Constants.DATASOURCE_KEY);
arrayList=Book.getAllBook(datasource.getConnection());
System.out.println("第一步，數據已經成功傳遞到Action，action="+action);
}catch(Exception e){
e.printStackTrace();
System.out.println("數據庫連接出現異常");
}
pb=new PageBean(arrayList);
Book[] books=pb.getBooks();
pb.description();
request.setAttribute("result",books);
request.setAttribute("page",pb);
}
else
{
if(action=="nextPage" || action.equals("nextPage"))
{
System.out.println("參數action="+action);
System.out.println("函數pb.getNextPage()準備執行");
Book[]books=pb.getNextPage();
request.setAttribute("page",pb);
request.setAttribute("result",books);
}
if(action=="previousPage" || action.equals("previousPage"))
{
System.out.println("參數action="+action);
System.out.println("函數pb.getPreviouspage()準備執行");
Book[] books=pb.getPreviouspage();
request.setAttribute("page",pb);
request.setAttribute("result",books);
}
}
return (mapping.findForward("success"));
}
}
4 pagetest.jsp
<%@ 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=gb2312" language="java"%>
<html:html locale="true">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body>
<table border="1">
<tr><th>書名</th><th>作者</th><th>價格</th></tr>
<logic:present name="result">
<logic:iterate id="book" name="result"　type="bean.Book" >
<logic:present name="book">
<tr>
<td><bean:write name="book" property="bookname" /></td>
<td> <bean:write name="book" property="author" /></td>
<td><bean:write name="book" property="price" /></td>
</tr>
</logic:present>
</logic:iterate>
</logic:present>
</table>
<logic:equal name="page" property="hasNextPage" value="true">
<html:link page="/page.do?action=nextPage">nextPage</html:link>
</logic:equal>
<logic:equal name="page" property="hasPreviousPage" value="true">
<html:link page="/page.do?action=previousPage">PreviousPage</html:link>
</logic:equal>
共有數據總數<bean:write name="page" property="totalRows"/>;
共分<bean:write name="page" property="totalPages"/>頁,當前是第
<bean:write name="page" property="currentPage"/>頁
</body>
</html:html>
5 struts-config.xml
<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
"

<struts-config>
<data-sources>
<data-source key="dataSource" type="org.apache.commons.dbcp.BasicDataSource">
<set-property property="driverClassName" value="com.microsoft.jdbc.sqlserver.SQLServerDriver"/>
<set-property property="url" value="jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=eBookStore;SelectMethod=cursor"/>
<set-property property="username" value="limq"/>
<set-property property="password" value="1"/>
<set-property property="maxActive" value="10"/>
<set-property property="maxWait" value="5000"/>
<set-property property="defaultAutoCommit" value="true"/>
<set-property property="defaultReadOnly" value="false"/>
</data-source>
</data-sources>
<form-beans>
</form-beans>
<global-forwards>
</global-forwards>
<action-mappings>
<action path="/page" type="page.PageListAction" scope="request">
<forward name="success" path="/pagetest.jsp"/>
</action>
</action-mappings>
<controller>
</controller>
</struts-config>
6 建立eBookStore數據庫，以及表book（name,author,parce）;其中數據的配置可以根據你的不同情況在struts-config.xml中而定。
7 Constants.java
package comm;

這僅是一個入門實例，簡潔實用，從網上整理而來，供參考。這里僅列出部分文件，其它文件、數據庫及目錄結構請從本站下載。下載源文件

一、struts-config.xml配置，主要是配數據庫,這里用access。
<?xml?version="1.0"?encoding="ISO-8859-1"??>

<!DOCTYPE?struts-config?PUBLIC
??????????"-//Apache?Software?Foundation//DTD?Struts?Configuration?1.2//EN"
??????????"http://jakarta.apache.org/struts/dtds/struts-config_1_2.dtd">


<struts-config>
<data-sources>
???<data-source?key="dataSource"?type="org.apache.commons.dbcp.BasicDataSource">
????????????<set-property?property="driverClassName"?value="sun.jdbc.odbc.JdbcOdbcDriver"?/>
????????????<set-property?property="url"?value="jdbc:odbc:page"?/>
????????????<set-property?property="username"?value="admin"?/>
????????????<set-property?property="password"?value=""?/>
????????????<set-property?property="maxActive"?value="20"?/>
????????????<set-property?property="maxWait"?value="5000"?/>
????????????<set-property?property="defaultAutoCommit"?value="true"?/>
????????????<set-property?property="defaultReadOnly"?value="false"?/>
????????????<set-property?property="validationQuery"?value="SELECT?1"?/>
????????????<set-property?property="removeAbandoned"?value="true"?/>
????????????<set-property?property="removeAbandonedTimeout"?value="120"?/>????????????
????????????<set-property?property="encoding"?value="false"?/>????????????
????????</data-source>

?</data-sources>
??<form-beans>
??</form-beans>
??<global-forwards>
??</global-forwards>

??<action-mappings>
??<action?path="/page"?type="page.DataSourceAction"?scope="request">
??<forward?name="success"?path="/pagetest.jsp"/>
??</action>
??</action-mappings>

??<controller>
??</controller>
</struts-config>

二、Action類
用?page.do?start=1?來顯示第一個頁面?
參數說明：?
??list：信息列表?
??start：開始位置?
??page：每頁顯示的信息數目?
??pages:?總頁數
??previous：上頁開始位置?
??next：下頁開始位置?

package?page;
import?org.apache.struts.action.*;
import?javax.servlet.http.*;

import?java.util.*;
import?javax.sql.*;
import?java.sql.*;
import?bean.*;

public?class?DataSourceAction?extends?Action?{

?public?DataSourceAction(){}
?
?public?ActionForward?execute(ActionMapping?mapping,?ActionForm?form,?HttpServletRequest?request,?HttpServletResponse?response)?throws?Exception?{???
??try{
??????DataSource?ds=this.getDataSource(request,"dataSource");???
??????Connection?con?=?ds.getConnection();
??????Statement?stmt?=?con.createStatement();
??????ResultSet?resultSet?=?stmt.executeQuery("select?count(*)?from?book"?);?
??????resultSet.next();?
??????int?data_num=resultSet.getInt(1);?
??????int?start=1;
??????int?page?=?4;?//每頁的記錄數。
??????int?pages=data_num/page;
??????if(data_num%page!=0)
?????????pages++;
??????if(request.getParameter("start")!=null)
??????????start?=?Integer.parseInt(request.getParameter("start"));?
??????if(request.getParameter("go")!=null){
????????????????int?go?=?Integer.parseInt(request.getParameter("go"));?
????????????????if(go<=1)
??????????????????start=1;
????????????????else?if(go>pages)
??????????????????start=(pages-1)*page+1;
????????????????else?
???????????????????start=(go-1)*page+1;
???????}?
?????
??????String?sql?=?"SELECT?*?FROM?book?where?id>="+start+"?and?id<"+(start+page);
??????resultSet?=?stmt.executeQuery(sql);??
??????ArrayList?list?=?new?java.util.ArrayList();?
??????while(resultSet.next())
??????{??
????????int?id=resultSet.getInt("id");
????????String?name?=?resultSet.getString("name");
????????String?author?=?resultSet.getString("author");
????????String?price?=?resultSet.getString("price");
????????System.out.println("開始數據封裝：name="+name+"author="+author+"price="+price);
????????Book?book=?new?Book(id,name,author,price);???????
????????list.add(book);
??????}
????con.close();
????request.setAttribute("pages",new?Integer(pages));
????request.setAttribute("list",list);
????//request.setAttribute("start",?new?Integer(start));?
????request.setAttribute("page",?new?Integer(page));?

????????//?if?there?is?a?previous?page,?set?the?previous?variable?
????????int?previous?=?start-page;?
????????if?(?previous>=0?){?
????????????request.setAttribute("previous",?new?Integer(previous));?
????????????System.out.println?("previous:"?+?previous);?
????????}?

????????//?if?there?is?a?next?page,?set?the?next?variable?
????????int?next?=?start+page;?
????????if?(?next<=data_num?){?
????????????request.setAttribute("next",?new?Integer(next));?
????????????System.out.println?("next:"?+?next);?
????????}?

???}catch(SQLException?e){
??????????e.printStackTrace();
??????????System.out.println("數據庫連接出現異常");
??????}?
???
?????????????return?(mapping.findForward("success"));
??}?
}


三、bean類Book.java
package?bean;
import?java.sql.*;
import?java.util.ArrayList;
public?class?Book?{
?int?id;
?private?String?bookname;?//書名
?private?String?author;???//作者
?private?String?price;????//價格
?
public?Book(int?id,String?name,String?author,String?price){
?this.id=id;
?this.bookname=name;
?this.author=author;
?this.price=price;
}

public?int?getId(){?
????????return?id;?
????}?

?public?String?getAuthor()?{
??return?author;
?}

?public?void?setAuthor(String?author)?{
??this.author?=?author;
?}

?public?String?getBookname()?{
??return?bookname;
?}

?public?void?setBookname(String?bookname)?{
??this.bookname?=?bookname;
?}
?
?public?String?getPrice(){
?????return?this.price;?
?}
?
?public?void?setPrice(String?price){
?????this.price=price;?
?}
?
}
四、分頁的jsp頁面pagetest.jsp,用了jstl中的c標記。
<%@?page?contentType="text/html;?charset=gb2312"?language="java"%>
<%@?page?import="java.util.*"?%>
<%@?page?import="bean.*"?%>
<%@?taglib?prefix="c"?uri="http://java.sun.com/jstl/core"?%>
<%@?taglib?uri="/tags/struts-bean"?prefix="bean"?%>
<%@?taglib?uri="/tags/struts-html"?prefix="html"?%>
<%@?taglib?uri="/tags/struts-logic"?prefix="logic"?%>

<logic:iterate?id="book"?name="list"?type="bean.Book">?
????????????<br><html:link??
????????????????????paramId="id"?paramName="book"?paramProperty="id"?
????????????????????page="/messagedetail.do">?
????????????????????<bean:write?name="book"?property="bookname"?/>?
????????????????</html:link>?
</logic:iterate>?

<form?action="/TestPage/page.do">
???<logic:present?name="previous">?
????????????<html:link??
????????????????????paramId="start"?paramName="previous"?
????????????????????page="/page.do">?
????????????????????上一頁?
????????????????</html:link>?
???</logic:present>?

???<logic:present?name="next">?
??????????????<html:link??
????????????????????paramId="start"?paramName="next"?
????????????????????page="/page.do">?
????????????????????下一頁?
????????????????</html:link>?
???</logic:present>?

每頁<c:out?value="${page}"/>條記錄,共<c:out?value="${pages}"/>頁??跳到<input?type="text"??name="go"?size="3"?maxlength="30"?>
<input?type="submit"?value="go"?>
</form>
?????????



OK!!!!
五、測試，請下載本實例的目錄結構TestPage,放入tomcat的webapps下，在瀏覽器中輸入：
????http://127.0.0.1:8080/TestPage/page.do