通用分页三

目录

• 改造PageBean
• • 通用类BaseDao
  • 补全Servlet
  • • 封装页面标签自定义Tag

改造PageBean

1.增强PageBean属性

    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

    //上一次查询的urlprivate String url;//上一次查询所携带的查询条件mapprivate Map<String, String[]> parameter = new HashMap<String, String[]>();

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.setParameter(req.getParameterMap());}

//重载setpaginationprivate void setPagination(String pagination) {//只有填写了false才会不分页 ，其他的字符串无效this.setPagination(!"false".equals(pagination));}//重载setRowsprivate void setRows(String rows) {if(StringUtils.isNotBlank(rows))this.setRows(Integer.valueOf(rows));} //重载setpageprivate void setPage(String page) {if(StringUtils.isNotBlank(page)) this.setPage(Integer.valueOf(page));}

//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;}

6.PageBean实体类改造好了

package com.houzhihong.pagebean.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//上一次查询的urlprivate String url;//上一次查询所携带的查询条件mapprivate Map<String, String[]> parameter = 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.setParameter(req.getParameterMap());}//重载setpaginationprivate void setPagination(String pagination) {//只有填写了false才会不分页 ，其他的字符串无效this.setPagination(!"false".equals(pagination));}//重载setRowsprivate void setRows(String rows) {if(StringUtils.isNotBlank(rows))this.setRows(Integer.valueOf(rows));} //重载setpageprivate void setPage(String page) {if(StringUtils.isNotBlank(page)) this.setPage(Integer.valueOf(page));}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public Map<String, String[]> getParameter() {return parameter;}public void setParameter(Map<String, String[]> parameter) {this.parameter = parameter;}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;}@Overridepublic 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;}}

通用类BaseDao

1.使用泛型定义好方法方便子类调用达成通用性

package com.houzhihong.pagebean.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;public class BaseDao<T> {public List<T> executeQuery(String sql, Class clz, PageBean pagebean)throws SQLException, InstantiationException, IllegalAccessException {List<T> list = new ArrayList<>();// 获取连接Connection con = DBAccess.getConnection();// 执行sqlPreparedStatement ps = null;ResultSet rs = null;  if(pagebean !=null && pagebean.isPagination()) {//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(countSql);rs = ps.executeQuery();  if(rs.next()) {//把数据放入pageBeanpagebean.setTotal(rs.getObject(1).toString());}//展示想要看到的数据 ，比如3页的十条数据String pageSql = getPageSql(sql,pagebean);ps = con.prepareStatement(pageSql);rs = ps.executeQuery();  }else {//不分页 ---> 下拉框需求ps = con.prepareStatement(sql);rs = ps.executeQuery();  }while (rs.next()) {// *实例化对象T t = (T) clz.newInstance();for (Field f : clz.getDeclaredFields()) {f.setAccessible(true);// 给这一个空对象的每一个属性赋值f.set(t, rs.getObject(f.getName()));}// 将赋值完的对象添加到list集合中返回list.add(t);}DBAccess.close(con, ps, rs);return list;}private String getPageSql(String sql, PageBean pagebean) {return sql + " limit "+pagebean.getStartIndex()+","+pagebean.getRows();}/*** --原生的带条件的查询语句*	sql =SELECT * FROM t_mvc_book WHERE true and bname like '%斗破%'***--符合条件的记录数有多少条* countsql= SELECT COUNT(1) from  (SELECT * FROM t_mvc_book WHERE TRUE AND bname LIKE '%圣墟%') t;**--查询第几页的数据 LIMIT 起始下标，偏移量 展示的记录数* pagesql=	SELECT * FROM t_mvc_book WHERE TRUE AND bname LIKE '%圣墟%' LIMIT 10,10*  **/private String getCountSql(String sql) {return "select count(1) from ("+sql+") t";}}

2.bookDao直接继承BaseDao的方法executeQuery，直接反射一波

return super.executeQuery(sql, Book.class, pagebean);

while (rs.next()) {// *实例化对象T t = (T) clz.newInstance();for (Field f : clz.getDeclaredFields()) {f.setAccessible(true);// 给这一个空对象的每一个属性赋值f.set(t, rs.getObject(f.getName()));}// 将赋值完的对象添加到list集合中返回list.add(t);}

补全Servlet

1.action业务层
2.注意初始化PageBean不要写到异常里面去了

package com.houzhihong.pagebean.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.houzhihong.pagebean.dao.BookDao;
import com.houzhihong.pagebean.entity.Book;
import com.houzhihong.pagebean.util.PageBean;@WebServlet(name = "book", urlPatterns = "/book.action")
public class BookAction extends HttpServlet {private static final long serialVersionUID = 4591437219474314661L;private BookDao bookDao = new BookDao();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// TODO Auto-generated method stubdoPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 实例化对象Book book = new Book();// 获取表单值book.setBname(req.getParameter("bname"));// 初始化PageBeanPageBean 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 blocke.printStackTrace();}}}

封装页面标签自定义Tag

1.PageTag助手类，将页面的表单，分页条，js拼接代码

package com.houzhihong.pagebean.tag;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.houzhihong.pagebean.util.PageBean;public class PageTag extends BodyTagSupport {private static final long serialVersionUID = 6584001758518399660L;private PageBean pageBean;public PageBean getPageBean() {return pageBean;}public void setPageBean(PageBean pageBean) {this.pageBean = pageBean;}@Overridepublic int doStartTag() throws JspException {// 输出分页条JspWriter out = pageContext.getOut();try {out.println(toHTML());} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}return super.doStartTag();}private String toHTML() {StringBuilder sb = new StringBuilder();// 上一次查询的form表单的html拼接sb.append("
");// 查第几页sb.append("");// 拼接带条件查询Map<String, String[]> parameter = pageBean.getParameter();if (parameter.size() > 0) {Set<Entry<String, String[]>> entrySet = parameter.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页int page = pageBean.getPage();int max = pageBean.getMaxPage();int before = page > 4 ? 4 : page - 1;int after = 10 - 1 - before;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 = max == page;// 拼接分页条sb.append("
");sb.append("
首页
");sb.append("
 + pageBean.getPrevPage() + ")'><
");// 代表了当前页的前4页for (int i = before; i > 0; i--) {sb.append("
 + (page - i) + ")'>"+ (page - i) + "
");}sb.append("
 + pageBean.getPage()+ ")'>" + pageBean.getPage() + "
");// 代表了当前页的后5页for (int i = 1; i <= after; i++) {sb.append("
 + (page + i) + ")'>"+ (page + i) + "
");}sb.append("
 + pageBean.getNextPage() + ")'>>
");sb.append("
 + pageBean.getMaxPage() + ")'>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();}
}

2.配置好自己定义tld标签库

<?xml version="1.0" encoding="UTF-8" ?><taglib xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"version="2.0"><description>JSTL 1.1 core library</description><display-name>JSTL core</display-name><tlib-version>1.1</tlib-version><short-name>h</short-name><uri>/houzhihong</uri><tag><name>page</name><tag-class>com.houzhihong.pagebean.tag.PageTag</tag-class><body-content>JSP</body-content><attribute><name>pageBean</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib>

3.代码贴的差不多了还有些之前有贴，上效果了

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