通用分页精装版本（二）
通用分页精装版本
- 前言
- 通用分页的思路及步骤
- 最终实现的效果
- 所需要的所有类结构以及架包
- 代码实践
- 使用的数据库表
- 1.实体类Book.java
- 2.共性部分BaseDao.java
- 3.写dao层（BookDao.java 继承BaseDao）
- 4.写分页工具类(pageBean.java)
- 5.封装分页标签类(PageTag.java)
- 6.处理业务逻辑BookAction.java
- 7.配置字符编码过滤器(EncodingFiter.java)
- 8.展示页面bookList.jsp
- 9.附加StringUtils类
- 总结
前言
小编在前面的博客中已把通用分页细讲解了，今天我们来整理一下前两篇博客中的通用分页，可能很多细节方面在此不会重复啰嗦，所以需要的朋友欢迎去查阅
链接: 通用分页（一）.与通用分页（二）.
本章节重要的是梳理业务逻辑以及全部代码合在一起
通用分页的思路及步骤
准备工作的文字说明前面的通用分页中已说明，去查阅就好，本次直接从代码着手
最终实现的效果
所需要的所有类结构以及架包
代码实践
使用的数据库表
1.实体类Book.java
package com.xiaoqing.entity;
public class Book {
private int bid;
private String bname;
private float price;
@Override
public String toString() {
return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
}
public int getBid() {
return bid;
}
public void setBid(int bid) {
this.bid = bid;
}
public String getBname() {
return bname;
}
public void setBname(String bname) {
this.bname = bname;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public Book() {
}
public Book(int bid, String bname, float price) {
this.bid = bid;
this.bname = bname;
this.price = price;
}
}
2.共性部分BaseDao.java
package com.xiaoqing.dao;
import java.lang.reflect.Field;
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.xiaoqing.util.DBAccess;
import com.xiaoqing.util.PageBean;
public class BaseDao<T> {
/*public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws SQLException, InstantiationException, IllegalAccessException{
List<T> list=new ArrayList<T>();
Connection con=DBAccess.getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
if(pageBean!=null&&!pageBean.isPagination()) {
//想要分页---->列表需求
//查询出符合条件的总记录数
String countSql=getCountSql(sql);
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
if(rs.next()) {
pageBean.setTotal(rs.getLong(1)+ "");
}
//查询出符合条件的结果集
String pageSql=getPageSql(sql,pageBean);
ps=con.prepareStatement(pageSql);
rs=ps.executeQuery();
System.out.println(ps);
//展示想要看到的分页效果
}else {
//不想分页---->下拉框需求
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
System.out.println(ps);
}
T t;//为了节省内存，所以定义在while外面
while(rs.next()) {
//list.add(new k(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
*//**
* Book b=new Book();
* b.setBid(rs.getInt("bid"));
* b.setBname(rs.getString("bname"));
* b.setPrice(rs.getFloat("price"));
* list.add(b);
*
* 实例化了一个对象
* 给这一个空对象的每一个属性赋值
* 将赋值完的对象添加到list集合中返回
*//*
t =(T)clz.newInstance();
for (Field f : clz.getDeclaredFields()) {
f.setAccessible(true);
f.set(t, rs.getObject(f.getName()));
}
}
DBAccess.close(con, ps, rs);
return list;
}
*/
public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws SQLException, InstantiationException, IllegalAccessException{
Connection con = DBAccess.getConnection();
PreparedStatement pst = null;
ResultSet rs = null;
//判断是否分页
if(pageBean!=null&&pageBean.isPagination()) {
//想要分页的-----》列表需求
//查询出符合条件的总记录数
String countSql=getCountSql(sql);
//重新执行countSql
pst=con.prepareStatement(countSql);
rs=pst.executeQuery();
if(rs.next()) {
//设置总记录数
pageBean.setTotal(rs.getLong(1)+ "");
}
//查询出符合条件的结果集
String pageSql=getPageSql(sql,pageBean);
pst=con.prepareStatement(pageSql);
rs=pst.executeQuery();
}else {
//不想要分页的----》下拉框需求
pst=con.prepareStatement(sql);
rs=pst.executeQuery();
}
List<T> list=new ArrayList<T>();
T t;//为了节省内存，所以定义在while外面
while(rs.next()) {
/**
* 1.实例化一个book对象（该对象是空的，不是null）
* 2.取book的所有属性，然后给其赋值
* 2.1 获取所有属性对象
* 2.2 给属性对象赋值
* 3.赋完值的book对象装进list容器中
*/
//反射实例化
t =(T)clz.newInstance();//相当于Book b=new Book();
//反射获取所以属性对象
Field[] fields = clz.getDeclaredFields();
//遍历
for (Field field : fields) {
//打开通道
field.setAccessible(true);
//给属性对象赋值
field.set(t, rs.getObject(field.getName()));
}
//把对象增加到集合
list.add(t);
}
DBAccess.close(con, pst, rs);
return list;
}
public String getCountSql(String sql) {
// TODO Auto-generated method stub
return "select count(1) from ("+sql+") t";
}
/**
* sql=select * from t_mvc_book where true and bname like '%圣墟%'；//原生sql
* countSql=select count(1) from (select * from t_mvc_book where true and bname like '%圣墟%')
* pageSql=select * from t_mvc_book where true and bname like '%圣墟%' limit 10,10;
*/
public String getPageSql(String sql,PageBean pageBean) {
return sql+" limit "+pageBean.getStartIndex()+","+pageBean.getRows();
}
}
3.写dao层（BookDao.java 继承BaseDao）
package com.xiaoqing.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.xiaoqing.entity.Book;
import com.xiaoqing.util.DBAccess;
import com.xiaoqing.util.PageBean;
import com.xiaoqing.util.StringUtils;
public class BookDao extends BaseDao<Book> {
//通过反射改装后的通用查询方法
public List<Book> list(Book book,PageBean pageBean) throws InstantiationException, IllegalAccessException, SQLException{
String sql="select * from t_mvc_book where 1=1";
String bname=book.getBname();
if(StringUtils.isNotBlank(bname)) {
sql+=" and bname like '%"+bname+"%'";
}
return super.executeQuery(sql, Book.class, pageBean);
}
}
4.写分页工具类(pageBean.java)
package com.xiaoqing.util;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
/**
* 分页工具类
*
*/
public class PageBean {
private int page = 1;// 当前页码
private int rows = 10;// 页大小
private int total = 0;//总记录数
//上一次查询的url
private String url;
//上一次查询所携带的查询条件
private Map<String, String[]> parameterMap=new HashMap<String, String[]>();
//对pagebean进行初始化
public void setRequest(HttpServletRequest req) {
//初始化jsp页面传递过来的当前页
this.setPage(req.getParameter("page"));
//初始化jsp页面传递过来的页大小
this.setRows(req.getParameter("rows"));
//初始化jsp页面 传递过来是否分页
this.setPagination(req.getParameter("pagination"));
//保留上一次的查询请求
this.setUrl(req.getRequestURL().toString());
//保留上一次的查询条件
this.setParameterMap(req.getParameterMap());
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public Map<String, String[]> getParameterMap() {
return parameterMap;
}
public void setParameterMap(Map<String, String[]> parameterMap) {
this.parameterMap = parameterMap;
}
private void setPage(String page) {
if(StringUtils.isNotBlank(page)) {
this.setPage(Integer.valueOf(page));
}
}
private void setRows(String rows) {
if(StringUtils.isNotBlank(rows)) {
this.setRows(Integer.valueOf(rows));
}
}
private void setPagination(String pagination) {
//只有填了false字符串，才代表不分页
this.setPagination(!"false".equals(pagination));;
}
private boolean pagination = true;// 是否分页
public PageBean() {
super();
}
public int getPage() {
return page;
}
public void setPage(int page) {
this.page = page;
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
this.rows = rows;
}
public int getTotal() {
return total;
}
public void setTotal(int total) {
this.total = total;
}
public void setTotal(String total) {
this.total = Integer.parseInt(total);
}
public boolean isPagination() {
return pagination;
}
public void setPagination(boolean pagination) {
this.pagination = pagination;
}
/**
* 获得起始记录的下标
*
* @return
*/
public int getStartIndex() {
return (this.page - 1) * this.rows;
}
@Override
public String toString() {
return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
}
//上一页
public int getPrevPage() {
return this.page>1?this.page-1:this.page;
}
//下一页
public int getNextPage() {
return this.page<this.getMaxPage()?this.page+1:this.page;
}
//最大页
public int getMaxPage() {
return this.total%this.rows==0?this.total/this.rows:(this.total/this.rows)+1;
}
}
5.封装分页标签类(PageTag.java)
package com.xiaoqing.tag;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;
import com.xiaoqing.util.PageBean;
public class PageTag extends BodyTagSupport{
private static final long serialVersionUID = -258029245678348536L;
private PageBean pageBean;
public PageBean getPageBean() {
return pageBean;
}
public void setPageBean(PageBean pageBean) {
this.pageBean = pageBean;
}
@Override
public int doStartTag() throws JspException {
// TODO Auto-generated method stub
JspWriter out = pageContext.getOut();
try {
out.print(toHTML());
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
return super.doStartTag();
}
private String toHTML() {
// TODO Auto-generated method stub
StringBuilder sb=new StringBuilder();
//上一次查询的form表单的HTML拼接
sb.append(" );
//查第几页的数据
sb.append(" ");
Map<String, String[]> parameterMap = pageBean.getParameterMap();
if(parameterMap.size()>0) {
Set<Entry<String,String[]>> entrySet = parameterMap.entrySet();
for (Entry<String, String[]> entry : entrySet) {
if(!"page".equals(entry.getKey())) {
for (String val : entry.getValue()) {
sb.append("");
}
}
}
}
sb.append(" ");
//默认展示前面4页，当前页 ，后面5也
int page=pageBean.getPage();
int max=pageBean.getMaxPage();
int before=page>4?4:page-1;
int after=10-1-before;//5
after=max-page>after?after:max-page;
//用来控制上一页的点击按钮特效的
boolean startFlag=page>1;
//用来控制下一页的点击按钮特效的
boolean endFlag=page<max;
//拼接分页条
sb.append(""
);
sb.append("首页 ");
sb.append("< ");
//代表了当前页的前4页
for (int i = before; i > 0 ; i--) {
sb.append("" +(page-i)+"");
}
sb.append("" +pageBean.getPage()+"");
//代表了当前页的后5页
for (int i = 1; i <= after; i++) {
sb.append("" +(page+i)+"");
}
sb.append("> ");
sb.append("尾页 ");
sb.append("到第页 ");
sb.append("确定 ");
sb.append("共" +pageBean.getTotal()+"条");
sb.append("");
//拼接分页的js代码
sb.append("");
return sb.toString();
}
}
6.处理业务逻辑BookAction.java
package com.xiaoqing.web;
import java.io.IOException;
import java.sql.SQLException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.xiaoqing.dao.BookDao;
import com.xiaoqing.entity.Book;
import com.xiaoqing.util.PageBean;
@WebServlet(name="book",urlPatterns="/book.action")
public class BookAction extends HttpServlet{
private static final long serialVersionUID = 6817006004626927502L;
private BookDao bookDao=new BookDao();
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
Book book=new Book();
book.setBname(req.getParameter("bname"));
PageBean pageBean=new PageBean();
pageBean.setRequest(req);
try {
List<Book> list = this.bookDao.list(book, pageBean);
req.setAttribute("bookList", list);
req.setAttribute("pageBean", pageBean);
req.getRequestDispatcher("bookList.jsp").forward(req, resp);
} catch (InstantiationException | IllegalAccessException | SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
7.配置字符编码过滤器(EncodingFiter.java)
package com.xiaoqing.util;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.ws.WebFault;
/**
* 中文乱码处理
*
*/
@WebFilter(filterName="encodingFiter",urlPatterns="*.action")
public class EncodingFiter implements Filter {
private String encoding = "UTF-8";// 默认字符集
public EncodingFiter() {
super();
}
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
// 中文处理必须放到 chain.doFilter(request, response)方法前面
res.setContentType("text/html;charset=" + this.encoding);
if (req.getMethod().equalsIgnoreCase("post")) {
req.setCharacterEncoding(this.encoding);
} else {
Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
Set set = map.keySet();// 取出所有参数名
Iterator it = set.iterator();
while (it.hasNext()) {
String name = (String) it.next();
String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
for (int i = 0; i < values.length; i++) {
values[i] = new String(values[i].getBytes("ISO-8859-1"),
this.encoding);
}
}
}
chain.doFilter(request, response);
}
public void init(FilterConfig filterConfig) throws ServletException {
String s = filterConfig.getInitParameter("encoding");// 璇诲彇web.xml鏂囦欢涓厤缃殑瀛楃闆�
if (null != s && !s.trim().equals("")) {
this.encoding = s.trim();
}
}
}
8.展示页面bookList.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@taglib uri="/xiaoqing" prefix="z" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.js"></script>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>书籍展示</title>
<style type="text/css">
.page-item input {
padding: 0;
width: 40px;
height: 100%;
text-align: center;
margin: 0 6px;
}
.page-item input,
.page-item b {
line-height: 38px;
float: left;
font-weight: 400;
}
.page-item.go-input {
margin: 0 10px;
}
</style>
</head>
<body>
<form class="form-inline" action="${pageContext.request.contextPath }/book.action" method="post">
<div class="form-group mb-2">
<input type="text" name="bname" class="form-control-plaintext" id="staticEmail2" placeholder="请输入书籍名称">
</div>
<button type="submit" class="btn btn-primary mb-2">查询</button>
</form>
<table class="table table-striped">
<thead>
<tr>
<th scope="col">书籍编号</th>
<th scope="col">书籍名字</th>
<th scope="col">书籍价格</th>
</tr>
</thead>
<tbody>
<c:forEach var="b" items="${bookList }">
<tr>
<td>${b.bid }</td>
<td>${b.bname }</td>
<td>${b.price }</td>
</tr>
</c:forEach>
</tbody>
</table>
<z:page pageBean="${pageBean }"></z:page>
</body>
</html>
9.附加StringUtils类
package com.xiaoqing.util;
public class StringUtils{
// 私有的构造方法，保护此类不能在外部实例化
private StringUtils() {
}
/**
* 如果字符串等于null或去空格后等于""，则返回true，否则返回false
*
* @param s
* @return
*/
public static boolean isBlank(String s) {
boolean b = false;
if (null == s || s.trim().equals("")) {
b = true;
}
return b;
}
/**
* 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
*
* @param s
* @return
*/
public static boolean isNotBlank(String s) {
return !isBlank(s);
}
}
总结
OK了，整个通用分页的流程就是这样，本篇博客讲的不是很详细，需要详细的通用分页讲解在小编前面的博客中有记录，不懂的欢迎大家评论！！！
谢谢！！