這近做個學校網站，用struts寫的，所以把其中分頁討論下，在做之前我們的頭腦中要有一個大概的框架：也就是我們怎么樣來劃分各個功能模塊。一般來說一個分頁功能框架至少要包含如下幾個部分(java class)(括號注釋對應本實例中的類)：
1:頁面元素(Order.java)。也就是一個頁面要顯示的一條條的記錄
2:數據(DataCollection.java)。對應一個javaBean,我看有不少前輩將獲取數據與頁面控制放在一起,
我本人認為這樣做不好。一來邏輯不清楚，二來對于一個控制來說應是可重用的，但放在一起就不能重用了。
3:頁面頁面控制（PageController.java）。也就是對一個頁面的定義
4:頁面跳轉的Action(PageAction.java).因為這個頁面跳轉相對來說比較簡單我們可以直接繼承ActionForward
來達到這個目的。
5:用來顯示的View.(page.jsp)
*********************************
注：本實例是從一個客戶定單中取數據
*********************************
下面的我就各個部分作一個簡單的介紹
1:頁面元素。也就是一個頁面要顯示的一條條的記錄(Order.java)
這個Order.java沒有多大意思它只是一個“定單”的定義
private int orderID; 定單編號
private String customerID; 客戶編號
private Date orderDate; 下單日期
***********************************************************
/*
* Created on 2004-9-14
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.toad.pub;
import java.util.Date;
/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class Order {
private int orderID;
private String customerID;
private Date orderDate;
/**
*
*/
public Order() {
// TODO Auto-generated constructor stub
}
/**
* @param orderID
* @param customerID
* @param orderDate
*/
public Order(int orderID, String customerID, Date orderDate) {
this.orderID = orderID;
this.customerID = customerID;
this.orderDate = orderDate;
}
/**
* @return Returns the customerID.
*/
public String getCustomerID() {
return customerID;
}
/**
* @param customerID The customerID to set.
*/
public void setCustomerID(String customerID) {
this.customerID = customerID;
}
/**
* @return Returns the orderDate.
*/
public Date getOrderDate() {
return orderDate;
}
/**
* @param orderDate The orderDate to set.
*/
public void setOrderDate(Date orderDate) {
this.orderDate = orderDate;
}
/**
* @return Returns the orderID.
*/
public int getOrderID() {
return orderID;
}
/**
* @param orderID The orderID to set.
*/
public void setOrderID(int orderID) {
this.orderID = orderID;
}
***********************************************************
2:數據(DataCollection.java).這個部分有您可以依據個人情況來進行
自定義。我已有的環境中是用的連接池.
private ArrayList list; 用來存放所查詢到的數據
private Connection con; 代表一個數據庫連接。這個連接
是通過<jsp:setProperty../>傳過來的。在接下來的view中我會作介紹
***********************************************************
/*
* Created on 2004-9-15
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.toad.pub;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class DataCollection {
private ArrayList list;
private Connection con;
/**
*
*/
public DataCollection() {
list=new ArrayList();
}
/**
* @return Returns the con.
*/
public Connection getCon() {
return con;
}
/**
* @param con The con to set.
*/
public void setCon(Connection con) {
this.con = con;
}
/**
* @return Returns the list.
*/
public ArrayList getList() {
return list;
}
/**
* @param list The list to set.
*/
public void setList() {
if(this.con==null){
System.out.println("con is null!");
return;
}
String syntax="select orderid,customerid,orderdate from orders order by orderid asc";
int orderID=0;
String customerID=null;
Date orderDate=null;
ResultSet rs=null;
PreparedStatement pst=null;
try{
pst=con.prepareStatement(syntax);
rs=pst.executeQuery();
while(rs.next()){
orderID=rs.getInt(1);
customerID=rs.getString(2);
orderDate=rs.getDate(3);
list.add(new Order(orderID,customerID,orderDate));
}
}catch(SQLException e){
System.out.println("SQLException occur at fetch datas !");
}finally{
try{
rs.close();
con.close();
}catch(SQLException e){
System.out.println("SQLException occur at rs and con close() !");
}
}
}
}
***********************************************************
3:頁面頁面控制（PageController.java）
private ArrayList allItems; 保存DataCollection中的list，也就是所有的數據
private int pageNumber; 當前頁的頁號
private int lastIndexOfPage; 當前頁的最后一個item(Order)在allItems中的index
private int itemsPerPage; 每一頁的容量
private int itemsInPage; 當前頁的實際items(orders)
private int lastPageNumber; 為allItems/iemsPerPage or allItems/iemsPerPage+1
private boolean hasPrevious; 是否為第一頁
private boolean hasNext; 是來為最后一頁
***********************************************************
/*
* Created on 2004-9-14
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.toad.pub;
import java.util.ArrayList;
/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class PageController {
private int pageNumber;
private int lastIndexOfPage;
private int itemsPerPage;
private int itemsInPage;
private int lastPageNumber;
private boolean hasPrevious;
private boolean hasNext;
private ArrayList allItems;
/**
* @return Returns the allItems.
*/
public ArrayList getAllItems() {
return allItems;
}
/**
* @param allItems The allItems to set.
*/
public void setAllItems(ArrayList allItems) {
this.allItems = allItems;
}
/**
* @return Returns the hasNext.
*/
public boolean isHasNext() {
return hasNext;
}
/**
* @param hasNext The hasNext to set.
*/
public void setHasNext() {
int items=pageNumber*itemsPerPage;
if(items>=allItems.size()){
this.hasNext =false;
}else{
this.hasNext=true;
}
}
/**
* @return Returns the hasPrevious.
*/
public boolean isHasPrevious() {
return hasPrevious;
}
/**
* @param hasPrevious The hasPrevious to set.
*/
public void setHasPrevious() {
if(pageNumber==1){
this.hasPrevious=false;
}else{
this.hasPrevious=true;
}
}
/**
* @return Returns the itemsInPage.
*/
public int getItemsInPage() {
return this.itemsInPage;
}
/**
* @param itemsInPage The itemsInPage to set.
*/
public void setItemsInPage() {
int temp=pageNumber*itemsPerPage;
if(temp<=allItems.size()){
this.itemsInPage=itemsPerPage;
}else{
this.itemsInPage=( allItems.size() - ((pageNumber-1)*itemsPerPage ));
}
}
/**
* @return Returns the itemsPerPage.
*/
public int getItemsPerPage() {
return itemsPerPage;
}
/**
* @param itemsPerPage The itemsPerPage to set.
*/
public void setItemsPerPage(int itemsPerPage) {
this.itemsPerPage = itemsPerPage;
}
/**
* @return Returns the pageNumber.
*/
public int getPageNumber() {
return pageNumber;
}
/**
* @param pageNumber The pageNumber to set.
*/
public void setPageNumber(int pageNumber) {
this.pageNumber = pageNumber;
}
/**
* @return Returns the lastIndexOfPage.
*/
public int getLastIndexOfPage() {
return lastIndexOfPage;
}
/**
* @param lastIndexOfPage The lastIndexOfPage to set.
*/
public void setLastIndexOfPage() {
this.lastIndexOfPage =(pageNumber -1)*itemsPerPage;
}
/**
* @return Returns the lastPageNumber.
*/
public int getLastPageNumber() {
return lastPageNumber;
}
/**
* @param lastPageNumber The lastPageNumber to set.
*/
public void setLastPageNumber() {
if(allItems.size()%itemsPerPage==0){
this.lastPageNumber =allItems.size()/itemsPerPage;
}else{
this.lastPageNumber =allItems.size()/itemsPerPage+1;
}
}
}
***********************************************************
4:頁面跳轉的Action(PageAction.java).
請注意PageAction是直接繼承于ActionForward
很簡單：就是根據action=arg2.getParameter("action").trim();
的返回值來設定pageNubmer和與之相就的設定。
一定不能忘了調用 return super.execute(arg0, arg1, arg2, arg3);
***********************************************************
/*
* Created on 2004-9-14
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.toad.pub;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.actions.ForwardAction;
import com.toad.pub.PageController;
/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class PageAction extends ForwardAction {
/* (non-Javadoc)
* @see org.apache.struts.action.Action#execute(org.apache.struts.action.ActionMapping, org.apache.struts.action.ActionForm, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
*/
public ActionForward execute(ActionMapping arg0, ActionForm arg1,
HttpServletRequest arg2, HttpServletResponse arg3) throws Exception {
// TODO Auto-generated method stub
String action=null;
HttpSession session=arg2.getSession(true);
action=arg2.getParameter("action").trim();
PageController controller=(PageController)session.getAttribute("controller");
int pageNumber=controller.getPageNumber();
if(action.compareToIgnoreCase("next")==0){
++pageNumber;
}else if(action.compareToIgnoreCase("pervious")==0){
--pageNumber;
}else if(action.compareToIgnoreCase("first")==0){
pageNumber=1;
}else if(action.compareToIgnoreCase("last")==0){
pageNumber=controller.getLastPageNumber();
}
controller.setPageNumber(pageNumber);
controller.setHasNext();
controller.setHasPrevious();
controller.setItemsInPage();
controller.setLastIndexOfPage();
return super.execute(arg0, arg1, arg2, arg3);
}
}
***********************************************************
5:用來顯示的View.(page.jsp)
***********************************************************
<%@ page language="java" %>
<%@ taglib prefix="html" uri="/WEB-INF/struts-html.tld"%>
<%@ taglib prefix="bean" uri="/WEB-INF/struts-bean.tld"%>
<%@ taglib prefix="logic" uri="/WEB-INF/struts-logic.tld"%>
//得到連接池對象
<bean:define id="conpool" name="pool" type="com.toad.util.ConnectionPool"></bean:define>
//定義一個javaBean同時設定數據(<% Data.setList();%>)
<jsp:useBean id="Data" class="com.toad.pub.DataCollection" scope="session">
<jsp:setProperty name="Data" property="con" value="<%=conpool.getcon()%>"/>
<% Data.setList();%>
</jsp:useBean>
//定義一個PageController同時進行初始化請注意調用順序!
<logic:notEmpty name="Data" property="list">
<jsp:useBean id="controller" class="com.toad.pub.PageController" scope="session">
<jsp:setProperty name="controller" property="allItems" value="<%=Data.getList()%>"/>
<jsp:setProperty name="controller" property="itemsPerPage" value="20"/>
<jsp:setProperty name="controller" property="pageNumber" value="1"/>
<%
controller.setHasNext();
controller.setHasPrevious();
controller.setItemsInPage();
controller.setLastIndexOfPage();
controller.setLastPageNumber();
%>
</jsp:useBean>
</logic:notEmpty>
<!DOCTYPE HTML PUBLIC "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<title>Lomboz JSP</title>
</head>
<body bgcolor="#FFFFFF">
<%int i=0;%>
Page Number:<bean:write name="controller" property="pageNumber" />
<table width="100%">
<tr>
<th align='left'>Row Number</th>
<th align='left'>Order ID</th>
<th align='left'>Customer ID</th>
<th align='left'>Order Date</th>
</tr>
<logic:present name="controller" scope="session">
<bean:define id="offset" name="controller" property="lastIndexOfPage" type="Integer"></bean:define>
<bean:define id="length" name="controller" property="itemsInPage" type="Integer"></bean:define>
<logic:iterate id="order" name="controller" property="allItems" offset="<%=offset.toString()%>" length="<%=length.toString()%>" type="com.toad.pub.Order">
<tr>
<td><%=++i%></td>
<td><bean:write name="order" property="orderID" /></td>
<td><bean:write name="order" property="customerID" /></td>
<td><bean:write name="order" property="orderDate" /></td>
</tr>
</logic:iterate>
<tr>
<logic:notEqual name="controller" value="1" property="pageNumber" >
<td><html:link page="/pageaction.do?action=first">First</html:link></td>
</logic:notEqual>
<logic:equal name="controller" property="hasPrevious" value="true">
<td><html:link page="/pageaction.do?action=pervious">Previous</html:link></td>
</logic:equal>
<logic:equal name="controller" property="hasNext" value="true">
<td><html:link page="/pageaction.do?action=next">Next</html:link></td>
</logic:equal>
<bean:define id="lastpagenumber" name="controller" property="lastPageNumber" type="Integer"></bean:define>
<logic:notEqual name="controller" property="pageNumber" value="<%=lastpagenumber.toString()%>" >
<td><html:link page="/pageaction.do?action=last">Last</html:link></td>
</logic:notEqual>
</tr>
</logic:present>
</table>
</body>
</html>
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