struts2实现简单分页显示

在开发web程序时，从数据库中取出来的数据一般都要分页显示在页面上，分页显示的方法非常多，有人写自定义标签，用自己写的标签进行分页显示，我个人觉得这是一种比较好的方法。下面是我用Struts2做的一个分页显示实例，基本的思路是：把数据库表中的每一行数据封装成一个对象，用一个返回类型为List的方法返回这些对象，接着在Struts2的action里面定义一个List属性，用这个List来接收从数据库中查询出来并进行了封装的那些对象，然后通过Struts2的标签遍历List里的每个对象，并把这些对象里所包含的属性取出来展现在页面上。下面是具体的步骤：
所用工具：JDK1.6 + MyEclipse9.0 + Tomcat6.0 + MySQL5.0 + struts 2.2

1、新建一个web工程,导入struts2中相应的jar包和mysql数据驱动包。
2、编写web.xml文件，其代码如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
 http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name></display-name> 
   <filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>
                 
3、建一个数据库表，用于保存学员信息：
drop database if exists page;
create database page ;
use page;
create table student (
   stu_id integer auto_increment,
   stuName varchar(255) not null,
   address varchar(255) not null,
   stuPhone varchar(255)not null,
   primary key(stu_id)
);
insert into student(stuName,address,stuPhone) values('杨华林','长沙','13787825190');
insert into student(stuName,address,stuPhone) values('李明清','天津','13787525190');
insert into student(stuName,address,stuPhone) values('李小华','大连','13788451190');
insert into student(stuName,address,stuPhone) values('郑小明','苏州','13787052188');
insert into student(stuName,address,stuPhone) values('杨一新','西安','13787851190');
insert into student(stuName,address,stuPhone) values('王新任','广州','13787056460');
insert into student(stuName,address,stuPhone) values('谢小华','深圳','13787075550');
insert into student(stuName,address,stuPhone) values('王建明','厦门','13788853690');
insert into student(stuName,address,stuPhone) values('秦一生','北京','13788689236');
insert into student(stuName,address,stuPhone) values('田翠林','杭州','13787655150');
insert into student(stuName,address,stuPhone) values('陈小明','广州','13787623668');
4、编写PageDAO类，该类用于从数据库中取出所有的学员信息，把这些学员信息封装成一个Student对象并将
   其放入List中。
package net.fygk.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import net.fygk.model.Student;
public class PageDAO
{
  private Connection conn ;
  private PreparedStatement pstmt ;
  private ResultSet rs ;
  private static final String DRIVER = "com.mysql.jdbc.Driver" ;
  private static final String URL = "jdbc:mysql://192.168.15.161:9736/page" ;
  private static final String USERNAME = "root" ;
  private static final String PASSWORD = "mysql" ;
  
  private Student student ;
  
  //数据库连接
  public synchronized Connection getConnection () {
   try {
    Class.forName (DRIVER) ;
    conn = DriverManager.getConnection (URL,USERNAME,PASSWORD) ;
   } catch (ClassNotFoundException e) {
    e.printStackTrace () ;
    return null ;
   } catch (SQLException e) {
    e.printStackTrace () ;
    return null ;
   }
   return conn ;
  }
  
   //分页查询
   public List<Student> queryByPage (int pageSize, int pageNow) {
    List<Student> list = new ArrayList<Student> () ;
    try {
      if (this.getConnection()!=null && pageSize>0 && pageNow>0) {
       pstmt = this.getConnection().prepareStatement(
         "select * from student order by stu_id limit "+(pageNow*pageSize-pageSize)+","+pageSize);
       rs = pstmt.executeQuery () ;
       while (rs.next()) {
        student = new Student () ;
        student.setStu_id (rs.getInt(1)) ;
        student.setStuName (rs.getString(2)) ;
        student.setAddress (rs.getString(3)) ;
        student.setStuPhone (rs.getString(4)) ;
        list.add (student) ;
       }
      }
    } catch(SQLException e) {
     e.printStackTrace() ;
    }
    return list ;
   }
  
   //获取总的记录数
   public int getAllCount()
   {
    int return_size = 0;
    try
    {
     if (this.getConnection()!=null)
     {
      pstmt = this.getConnection().prepareStatement("select stu_id from student");
      rs = pstmt.executeQuery();
      while(rs.next())
      {
       return_size++;
      }
     }
    }catch(Exception e)
    {
     e.printStackTrace();
    }
    return return_size;
   }
  
   //计算总页数
   public int getAllPage(int pageSize,int allCount)
   {
    int allPage = 0;
    if(allCount==0||pageSize==0)
    {
     allPage = 1;
    }
    else
    {
     allPage = allCount/pageSize;
     if(allCount%pageSize!=0)
     {
      allPage = allPage+1;
     }
    }
    return allPage;
   }
   public static void main(String[] args) {
  System.out.println(new PageDAO().getAllCount());
 }
}
                 
5、由于要对数据库中的学员信息进行封装，所以需要编写一个JavaBean,即Student类：
package org.hnylj.util;
public class Student {
 private int stu_id ;
 private String stuName ;
 private String address ;
 private String stuPhone ;
 
 public Student () {
 }
 
 public int getStu_id () {
  return stu_id ;
 }
 
 public void setStu_id (int stu_id) {
  this.stu_id = stu_id ;
 }
 
 public String getStuName () {
  return stuName ;
 }
 
 public void setStuName (String stuName) {
  this.stuName = stuName ;
 }
 
 public String getAddress () {
  return address ;
 }
 
 public void setAddress (String address) {
  this.address = address ;
 }
 
 public String getStuPhone () {
  return stuPhone ;
 }
 
 public void setStuPhone (String stuPhone) {
  this.stuPhone = stuPhone ;
 }
}
至此底层的代码就写好了。接下来我们需要编写web层的代码。
6、编写web层的jsp文件，分别有index.jsp,show.jsp和error.jsp，其代码分别如下：
Index.jsp:
<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
  <title>Struts2实现分页显示</title>
 </head>
 <body>
    <div align="center">
       <s:a href="show.action">进入查看学员列表</s:a>
    </div>
 </body>
</html>
Show.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
   
    <title>My JSP 'index.jsp' starting page</title>
   
 <meta http-equiv="pragma" content="no-cache">
 <meta http-equiv="cache-control" content="no-cache">
 <meta http-equiv="expires" content="0">   
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 <!--
 <link rel="stylesheet" type="text/css" href="styles.css">
 -->

  </head>
 
  <body>
    <table border="1">
     <tr>
      <td>学号</td>
      <td>姓名</td>
      <td>地址</td>
      <td>电话</td>
     </tr>
     <s:iterator var="student" value="studentList">
      <tr>
       <td><s:property value="stu_id"/></td>
       <td><s:property value="stuName"/></td>
       <td><s:property value="address"/></td>
       <td><s:property value="stuPhone"/></td>
      </tr>
     </s:iterator>
    </table>
   
     <s:url var="begin" value="show!getAllStudent">
      <s:param name="currentPage" value="1" />
     </s:url>
     
     <s:url var="pre_url" value="show!getAllStudent">
      <s:param name="currentPage" value="currentPage-1==0?1:currentPage-1" />
     </s:url>
     
     <s:url var="pre_nex" value="show!getAllStudent">
      <s:param name="currentPage" value="currentPage+1>allPage?allPage:currentPage+1" />
     </s:url>
     
     <s:url var="end" value="show!getAllStudent">
      <s:param name="currentPage" value="allPage" />
     </s:url>
  
     <s:a href="%{begin}">首页</s:a>
     <s:a href="%{pre_url}">上一页</s:a>
     <s:a href="%{pre_nex}">下一页</s:a>
      <s:a href="%{end}">最后页</s:a>
      
  </body>
</html>
error.jsp
<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>发生错误</title>
  </head>
 
  <body>
      业务逻辑发生异常,请稍候再试。。。。。。
  </body>
</html>

7、编写struts2的action来拦截用户的请求：
 
package org.hnylj.web;
import java.util.List;
import org.hnylj.util.PageDAO;
import org.hnylj.util.Student;
import com.opensymphony.xwork2.ActionSupport;
public class ShowAction extends ActionSupport {
 private List<Student> students ;
 private int pageNow = 1 ; //初始化为1,默认从第一页开始显示
    private int pageSize = 5 ; //每页显示5条记录
   
 private PageDAO pageDAO = new PageDAO () ;
 
 public List<Student> getStudents() {
  return students;
 }
 public void setStudents(List<Student> students) {
  this.students = students;
 }
 
 public int getPageNow() {
  return pageNow;
 }
 public void setPageNow(int pageNow) {
  this.pageNow = pageNow;
 }
 public int getPageSize() {
  return pageSize;
 }
 public void setPageSize(int pageSize) {
  this.pageSize = pageSize;
 }
 public String execute() throws Exception {
  students = pageDAO.queryByPage(pageSize, pageNow) ;
  return SUCCESS ;
 }
}
8、配置struts.xml文件，即action和响应结果页面之间的映射：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
    <!-- <constant name="struts.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="false" />
    <include file="example.xml"/> -->
   
     <package name="default" namespace="/" extends="struts-default">
        <action name="show" class="net.fygk.action.ShowAction">
           <result name="success">/show.jsp</result>
     <result name="error">/error.jsp</result>
        </action>
    </package>
    <!-- Add packages here -->
</struts>