struts2--操作数据库（数据分页）

很多时候，数据库中存在大量数据，一个jsp页面肯定无法全部显示出来，这时，数据分页就显示其强大了。

设计思路：数据分页总是围绕着三个量（总的记录数，当前页数，每页多少条记录），使用了两个Acton，PageAction和AllGoods，分别实现分页功能和获取当前页面信息（保持到list集合，以便在jsp页面输出）。使用了一个DAO类（PageDao）用于数据层的操作（如：从数据库中获取当前页面的记录，查询数据库中的总记录数）。接下来就是数据源的使用了：配置context.xml文件（WebRoot/META-INF下），自定义工具类连接数据库。

1、实体类bean：Goods.java

package com.bean;

public class Goods {
private Integer id;
private String goodsName;
private Double price;
private Integer num;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getGoodsName() {
return goodsName;
}

public void setGoodsName(String goodsName) {
this.goodsName = goodsName;
}

public Double getPrice() {
return price;
}

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

public Integer getNum() {
return num;
}

public void setNum(Integer num) {
this.num = num;
}

}
2、Action
PageAction.java:

package com.action;

import com.dao.PageDao;
import com.opensymphony.xwork2.ActionSupport;

public class PageAction extends ActionSupport{
private int pageNum; //当前页
private int totalPage; //总页数
private int pageSize; //每页显示记录数

public String execute(){
PageDao pageDao = new PageDao();
int goodAmount = pageDao.getGoodsAmount();
pageSize = 4;
totalPage = (goodAmount%pageSize == 0) ? (goodAmount/pageSize) : (goodAmount/pageSize + 1);
if(pageNum <= 0){
pageNum = 1; //如果pageName小于1将其赋值为1
}
if(pageNum > totalPage){
pageNum = totalPage;
}
return SUCCESS;
}

public int getPageNum() {
return pageNum;
}

public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}

public int getTotalPage() {
return totalPage;
}

public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}

public int getPageSize() {
return pageSize;
}

public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}

}
AllGoods.java
package com.action;

import java.util.List;

import com.bean.Goods;
import com.dao.PageDao;
import com.opensymphony.xwork2.ActionSupport;
import com.tools.DbPool;

public class AllGoods extends ActionSupport{
private int pageNum;
private int totalPage;
private int pageSize;
private List<Goods> list;

public String execute(){
PageDao pageDao = new PageDao();
list = pageDao.getGoods(pageNum, pageSize);
return SUCCESS;
}

public int getPageNum() {
return pageNum;
}

public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}

public int getTotalPage() {
return totalPage;
}

public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}

public int getPageSize() {
return pageSize;
}

public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}

public List<Goods> getList() {
return list;
}

public void setList(List<Goods> list) {
this.list = list;
}

}其实这两个Action可以合并，可以减少很多代码，这里为了练习就分开写了。
3、DAO

PageDao.java:

package com.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.bean.Goods;
import com.tools.DbPool;

public class PageDao {
private DbPool pool = new DbPool();
public List<Goods> getGoods(int pageNum,int pageSize) { //获取当前页的商品
List<Goods> list = new ArrayList<Goods>();
if(pool.getConnection() == null){ //如果连接不可用，则重新创建连接
pool.getConn();
}

String sql = "select * from goods order by id limit ?,?";
PreparedStatement ps = null;
try {
ps = pool.getConnection().prepareStatement(sql);
ps.setInt(1, (pageNum-1)*pageSize);
ps.setInt(2, pageSize);
ResultSet rs = ps.executeQuery();
while(rs.next()){
Goods good = new Goods();
good.setId(rs.getInt(1));
good.setGoodsName(rs.getString(2));
good.setPrice(rs.getDouble(3));
good.setNum(rs.getInt(4));
list.add(good);
}
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}

public int getGoodsAmount() { //获取总记录数
int all = 0;
if(pool.getConnection() == null){
pool.getConn();
}

String sql = "select count(*) from goods";
PreparedStatement ps = null;
try {
ps = pool.getConnection().prepareStatement(sql);
ResultSet rs = ps.executeQuery();
if(rs.next()){
all = rs.getInt(1);
}
} catch (SQLException e) {
e.printStackTrace();
}

return all;
}

}
4、struts.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-/
f95d
/Apache Software Foundation//DTD Struts Configuration 2.1.7//EN"
"http://struts.apache.org/dtds/struts-2.1.7.dtd">

<struts>
<package name="default" namespace = "/" extends = "struts-default">
<action name = "goods" class = "com.action.AllGoods">
<result>/page.jsp</result>
</action>

<action name="page" class = "com.action.PageAction">
<result type = "redirectAction">
<param name="actionName">goods</param>
<param name="pageNum">${pageNum}</param>
<param name="totalPage">${totalPage}</param>
<param name="pageSize">${pageSize}</param>
</result>
</action>
</package>
</struts>

5、page.jsp页面：
<%@ 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 'page.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>
<div align="center">
<table border="1">
<tr>
<td>商品编号</td>
<td>商品名称</td>
<td>商品价格</td>
<td>商品数目</td>
</tr>

<s:iterator value="list" var="good" status = "ss">
<tr>
<td><s:property value="#good.id" /></td>
<td><s:property value="#good.goodsName" /></td>
<td><s:property value="#good.price" /></td>
<td><s:property value="#good.num" /></td>
</tr>
</s:iterator>
</table>

<ul>
<li><s:property value="pageNum" />/<s:property value="totalPage" />

<s:url action="page" id="firstPage">
<s:param name="pageNum">1</s:param>
</s:url> <s:a href="%{firstPage}">首页</s:a>

<s:url action = "page" id = "prePage">
<s:param name = "pageNum">
<s:property value = "pageNum-1"/>
</s:param>
</s:url><s:a href = "%{prePage}">上一页</s:a>

<s:url action = "page" id = "nextPage">
<s:param name = "pageNum">
<s:property value = "pageNum + 1"/>
</s:param>
</s:url><s:a href = "%{nextPage}">下一页</s:a>

<s:url action = "page" id ="lastPage">
<s:param name = "pageNum">
<s:property value = "totalPage"/>
</s:param>
</s:url><s:a href = "%{lastPage}">末页</s:a>
</li>
</ul>
</div>
</body>
</html>

6、context.xml配置：

<?xml version="1.0" encoding="UTF-8"?>
<Context path = "/dbtom" docBase = "dbtom" reloadable = "true" crossContext = "true">
<Resource
name = "jdbc/dbtom"
type = "javax.sql.DataSource"
username = "root"
password = "root"
driverClassName = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost:3306/user"
/>
</Context>7、DBPool.java工具类：（这里需要注意！写完程序找了很久的bug出现在这里 private Connection connection属性要设置为static的，避免每次都通过数据源连接数据库。当时没写，结果点击几次上下页，就陷入了无限制的请求状态！！）
package com.tools;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

public class DbPool {
private static Connection connection; //这里必须设置为静态属性！！！
public void getConn() {
try {
Context initcContext = new InitialContext(); //初始化context对象
Context envContext = (Context) initcContext.lookup("java:comp/env");
DataSource dSource = (DataSource) envContext.lookup("jdbc/dbtom"); //获取数据源

connection = dSource.getConnection();
System.out.println("获取连接成功");
} catch (Exception e) {
System.out.println("获取连接失败");
}
}

public ResultSet query(String sql) {
ResultSet rs = null;
if(connection == null){
getConn();//如果为空，则获取连接
}

PreparedStatement ps;
try {
ps = connection.prepareStatement(sql);
rs = ps.executeQuery();
} catch (Exception e) {
System.out.println("query is failed!");
}
return rs;
}

public Connection getConnection() {
if(connection == null){
getConn();
}
return connection;
}

}


实现效果：


首页显示


末页显示