用Java实现通用分页（2）
通用分页
1，写好web层
2, jsp展示
3, 在PageBean写好分页所需要的参数
4, 自定义好标签在jsp页面调用
我们先导入实体类
package com.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(int bid, String bname, float price) {
super();
this.bid = bid;
this.bname = bname;
this.price = price;
}
public Book() {
super();
}
}
导入判空等下需要用到
package com.zking.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);
}
}
导入防中文乱码工具
package com.zking.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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 中文乱码处理
*
*/
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");// 读取web.xml文件中配置的字符集
if (null != s && !s.trim().equals("")) {
this.encoding = s.trim();
}
}
}
然后我们开始写PageBean，代码如下
package com.zking.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;// 页码
private int rows = 10;// 页大小
private int total = 0;// 总记录数
private boolean pagination = true;// 是否分页
private String url;
private Map paramMap = new HashMap<>();
//提供一个初始化的方法
public void setRequest(HttpServletRequest req) {
this.setPage(req.getParameter("page"));
this.setRows(req.getParameter("rows"));
this.setPagination(req.getParameter("pagination"));
//getRequestURI()获取全路径
this.setUrl(req.getRequestURI().toString());
//getParameterMap获取到一次url请求所携带的所有参数
this.setParamMap(req.getParameterMap());
}
public void setPagination(String pagination) {
if(StringUtils.isNotBlank(pagination)) {
this.setPagination(!"false".equals(pagination));
}
}
//重载rows
public void setRows(String rows) {
if(StringUtils.isNotBlank(rows)) {
this.setPage(Integer.valueOf(rows));
}
}
//重载
public void setPage(String page) {
if(StringUtils.isNotBlank(page)) {
this.setPage(Integer.valueOf(page));
}
}
public PageBean() {
super();
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public Map getParamMap() {
return paramMap;
}
public void setParamMap(Map paramMap) {
this.paramMap = paramMap;
}
public int getPage() {
return page;
}
public void setPage(int page) {
this.page = page;
}
public int getRows() {
return 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 + "]";
}
//获取到总页数
public int getMaxPage() {
return this.total % this.rows ==0 ?
this.total / this.rows :
(this.total / this.rows) +1;
}
//获取下一页
public int getNextPage() {
return this.page < this.getMaxPage() ? this.page+1 : this.getMaxPage();
}
//获取上一页
public int getPreviousPage() {
return this.page > 1 ? this.page-1 : this.page;
}
}
注：
这里有一个重要的核心
这三个方法一定要写，因为我们等下在自定义标签里面需要用到
//获取到总页数
public int getMaxPage() {
return this.total % this.rows ==0 ?
this.total / this.rows :
(this.total / this.rows) +1;
}
//获取下一页
public int getNextPage() {
return this.page < this.getMaxPage() ? this.page+1 : this.getMaxPage();
}
//获取上一页
public int getPreviousPage() {
return this.page > 1 ? this.page-1 : this.page;
}
然后我们开始编写通用分页方法
package com.zking.util;
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.entity.Book;
public class BaseDao {
//通用查询
/**
*
* @param sql 决定查询那张表的数据
* @param clz 查询出来的数据封装到哪里实体类中
* @param pageBean 决定是否分页
* @return
* @throws IllegalAccessException
* @throws InstantiationException
* @throws SQLException
*/
@SuppressWarnings("resource")
public List executeQuery(String sql,Class clz,PageBean pageBean) throws InstantiationException, IllegalAccessException, SQLException{
List list = new ArrayList<>();
Connection con = DBAccess.getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
try {
if (pageBean != null && pageBean.isPagination()) {
//该分页了
String countSql = getCountsql(sql);
ps = con.prepareStatement(countSql);
rs = ps.executeQuery();
if(rs.next()) {
pageBean.setTotal(rs.getLong(1)+"");
}
String pageSql = getPageSql(sql,pageBean);
ps = con.prepareStatement(pageSql);
rs = ps.executeQuery();
} else {
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
}
while (rs.next()) {
// list.add(new Book(rs.getInt("bid"),
// rs.getString("bname"),
// rs.getFloat("price")));
/*
* 1.创建了一个Book对象
* 2.从ResultSet结果集中获取值放入Book对象属性中
* 2.1 获取到book属性对象
* 2.2 给属性对象赋值
* 3.将已经有值的Book对象放入list集合中
* */
//1
T t = (T) clz.newInstance();
//2
Field[] fields = clz.getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
field.set(t, rs.getObject(field.getName()));
}
list.add(t);
}
} finally {
//shift + alt + z
DBAccess.close(con,ps,rs);
}
return list;
}
/**
* 将原生sql拼接出符合条件的某一页的数据查询sql
* @param sql
* @param pageBean
* @return
*/
private String getPageSql(String sql, PageBean pageBean) {
return sql + " limit "+pageBean.getStartIndex()+ "," +pageBean.getRows();
}
/**
* 用原生sql拼接出查询符合条件的记录数
* @param sql
* @return
*/
private String getCountsql(String sql) {
// t为别名随便取
return "select count(1) from ("+sql+") t";
}
}
写完之后我们就建立一个dao方法，
dao继承通用方法
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.entity.Book;
import com.zking.util.BaseDao;
import com.zking.util.DBAccess;
import com.zking.util.PageBean;
import com.zking.util.StringUtils;
/**
* 操作数据库中的t_mvc_book表
* 1.加载驱动
* 2.建立链接
* 3.获取预定义处理对象
* 4.执行sql语句
* 5.处理结果集
* 6.关闭连接
* @author lqx
*
*/
public class BookDao extends BaseDao{
/**
*
* @param book 是从jsp传递过来的参数封装成对象的作为参数查询并执行sql
* @param pageBean 决定是否分页
* @return
* @throws SQLException
* @throws IllegalAccessException
* @throws InstantiationException
*/
public List list(Book book,PageBean pageBean) throws SQLException, InstantiationException, IllegalAccessException{
String sql = "select * from t_mvc_book where 1=1";
if(StringUtils.isNotBlank(book.getBname())) {
sql += " and bname like '%"+book.getBname()+"%'";
}
return super.executeQuery(sql, Book.class, pageBean);
}
public static void main(String[] args) {
BookDao bookDao = new BookDao();
try {
Book b = new Book();
PageBean pageBean = new PageBean();
//false代表不想分页 反之
// pageBean.setPagination(false);
//代表想从第几页开始查 默认第一页
// pageBean.setPage(2);
//代表想要查询的内容 如果去掉就是查看所有
// b.setBname("圣墟");
List list = bookDao.list(b, pageBean);
for (Book book : list) {
System.out.println(book);
}
} catch (SQLException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
然后后我们就可以开始写自定义标签
package com.tags;
import java.io.IOException;
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.zking.util.PageBean;
public class PageTag extends BodyTagSupport {
private static final long serialVersionUID = 5701619331560886989L;
private PageBean pageBean;
@Override
public int doStartTag() throws JspException {
JspWriter out = pageContext.getOut();
try {
out.write(toHTML());
} catch (IOException e) {
e.printStackTrace();
}
return super.doStartTag();
}
private String toHTML() {
StringBuffer sb = new StringBuffer();
//下一次请求提交到后台的表单html代码拼接
sb.append("");
//分页条html代码拼接
//注意一定要空格不然会跟其他标签在一起
sb.append("");
sb.append(" 每页"+pageBean.getRows()+"条，共"+pageBean.getTotal()+"条，第"+pageBean.getPage()+"页,共"+pageBean.getMaxPage()+"页 首页 上一页 下一页 尾页 ");
sb.append(" href='javascript:skipPage()'>Go");
sb.append(" ");
//分页所需要调用的js代码
sb.append(" ");
return sb.toString();
}
public PageBean getPageBean() {
return pageBean;
}
public void setPageBean(PageBean pageBean) {
this.pageBean = pageBean;
}
}
然后我们建立一个自定义标签库然后进行配置
aaa1.1 core library
aaacore
1.1
c
/aaa
page
com.tags.PageTag
JSP
pageBean
true
true
然后我们写web层
package com.web;
import java.io.IOException;
import java.sql.SQLException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.dao.BookDao;
import com.entity.Book;
import com.zking.util.PageBean;
//controler web
public class BookServlet extends HttpServlet{
private BookDao bookDao = new BookDao();
private static final long serialVersionUID = 2447438096754154253L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String bname = req.getParameter("bname");
// String page = req.getParameter("page");
Book book = new Book();
book.setBname(bname);
PageBean pageBean = new PageBean();
pageBean.setRequest(req);
try {
//查询出符合条件的某一页的记录数 默认为第一页
List list = bookDao.list(book, pageBean);
req.setAttribute("bookList", list);
req.setAttribute("pagebean", pageBean );
req.getRequestDispatcher("bookList.jsp").forward(req, resp);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
然后我们进行配置
其中有过滤器的配置
过滤器用于防止中文乱码，然后就是servlet的配置
Pagebean
bookServlet
com.web.BookServlet
bookServlet
/bookServlet
encodingFiter
com.zking.util.EncodingFiter
encodingFiter
/*
这些配置完成后我们就可以在jsp页面进行展示，我们需要调用自己的自定义标签库
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="z" uri="/aaa" %>
Insert title here
小说目录
编号
名称
价格
${b.bid}
${b.bname}
${b.price}
需要用到的jar包为：
反射所需要的jar包
commons-beanutils-1.8.0
commons-logging
标签库的jar包
jstl-1.2
standard-1.1.2
mysql 连接mysql的jar包
mysql-connector-java-5.1.44-bin
思路总结：
1.需要分页的实体类
2.PageBean
1.1需要初始化
1.2重载
1.3重要的参数方法
3.通用分页方法
3.1要编写总条数sql
3.2要编写分页sql
4.dao方法继承通用方法
4.1定义sql语句,用上面的判空进行拼接
5.web层
6.自定义标签
6.1编译属性
6.2 自定标签的doStartTag()方法,
7.配置自定义标签
8.配置web层
9.jsp页面展示