解决struts分页显示
作者：李敏强 email: mill_lmq@tom.com
学习struts已经有2个多月了，前几天群里的朋友问我struts分页显示的问题，觉得好像与在jsp中的差不多，但还是遇到了这样那样的问题，好不容易花了几天时间把问题都搞清楚，觉得还是写点东西跟大家分享一下的好！
至于struts的语法这里就不多介绍了，不懂的朋友可以先看网上的其他文章。
一 开发环境
elicpse+struts studio+sqlserver2000+tomcat。
二 开发思路
既然讲的是struts，那自然离不了mvc，分页显示也是如此。
1 建立适当的模型组件，对应你要查询数据库中的表。这部分由我们熟悉的javabean来充当。并在其中建立数据库查询方法，该方法需要一个java.sql.conntection类型的参数，并返回一个arraylist。在本例中为 book.java
2 建立分页所需要的模型组件，也是由javabean来充当，通过由book中提供的arraylist来构造。本例中为 pagebean.java.。
3建立控制器组件，这部分由struts 中的action来实现。主要负责将实例化book，并利用返回的arraylist对象，构造pagebean。以及接收由视图传递而来的action参数。从而在pagebean对象中调用不同的方法，该方法返回book[] 对象。最后将 book[]和pagebean放入request中。本例中为pagelistaction.java。
4建立视图组件，这部分由jsp来充当，为了不出现java 代码，我们使用struts提供的标签库，主要负责从request中取出刚刚放入的对象，通过反复调用pagelistaction以及action参数，而实现分页显示。本例中为pagetest.jsp.
5 建立并配置struts-config.xml。
6 建立数据库。
三 实例代码
1 book.java
package bean;
import java.sql.*;
import java.util.arraylist;
/**
* @作者 李敏强
* struts分页显示数据bean，对应数据库中book表
*/
public class book {
private string bookname; //书名
private string author; //作者
private string price; //价格
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 数据查询已完成！");
while(resultset.next())
{
string name = resultset.getstring("name");
string author = resultset.getstring("author");
string price = resultset.getstring("price");
system.out.println("开始数据封装：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("数据库异常"+e.tostring());
}
return arraylist;
}
}
2 pagebean.java
package page;
import bean.book;
import java.util.*;
/**
* @作者 李敏强
* struts分页显示逻辑bean
*/
public class pagebean {
int currentpage=1; //当前页
public int totalpages=0; //总页数
int pagerecorders=5;//每页5条数据
int totalrows=0; //总数据数
int pagestartrow=0;//每页的起始数
int pageendrow=0; //每页显示数据的终止数
boolean hasnextpage=false; //是否有下一页
boolean haspreviouspage=false; //是否有前一页
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()正在执行；");
system.out.println("参数currentpage="+currentpage);
if((currentpage-1)>0)
{
haspreviouspage=true;
}
else
{
haspreviouspage=false;
}
if(currentpage>=totalpages)
{
hasnextpage=false;
}
else
{
hasnextpage=true;
}
system.out.println("参数hasnextpage="+hasnextpage);
system.out.println("准备执行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（）开始执行；");
if(currentpage*pagerecorders<totalrows){//判断是否为最后一页
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("要显示的页面数据已经封装,具体信息如下：");
this.description();
return books;
}
public string tostring(int temp)
{
string str=integer.tostring(temp);
return str;
}
public void description()
{
string description="共有数据数:"+this.gettotalrows()+
"共有页数: "+this.gettotalpages() +
"当前页数为:"+this.getcurrentpage()+
" 是否有前一页: "+this.ishaspreviouspage() +
" 是否有下一页:"+this.ishasnextpage()+
" 开始行数:"+this.getpagestartrow()+
" 终止行数:"+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;
/**
* @author 李敏强
* struts分页显示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")){ //第一次读取数据
try{
datasource datasource=this.getdatasource(request,constants.datasource_key);
arraylist=book.getallbook(datasource.getconnection());
system.out.println("第一步，数据已经成功传递到action，action="+action);
}catch(exception e){
e.printstacktrace();
system.out.println("数据库连接出现异常");
}
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("参数action="+action);
system.out.println("函数pb.getnextpage()准备执行");
book[]books=pb.getnextpage();
request.setattribute("page",pb);
request.setattribute("result",books);
}
if(action=="previouspage" action.equals("previouspage"))
{
system.out.println("参数action="+action);
system.out.println("函数pb.getpreviouspage()准备执行");
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>书名</th><th>作者</th><th>价格</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>
共有数据总数<bean:write name="page" property="totalrows"/>;
共分<bean:write name="page" property="totalpages"/>页,当前是第
<bean:write name="page" property="currentpage"/>页
</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"
"http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">
<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数据库，以及表book（name,author,parce）;其中数据的配置可以根据你的不同情况在struts-config.xml中而定。
7 constants.java
package comm;
/**
* this interface provides the constant string for applicator constant
*/
public class constants {
/**
* name of the user object in httpsession
*/
public static string user_key="user";
/**
* datasource name
*/
public static string datasource_key="datasource";
}
好了，全部代码我已经贴完了，难免有不妥的地方，如果您有好的意见或者建议请跟我联系，在下将感激不尽！！ mill_lmq@tom.com
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