目录
一、改造pagebean
二、分页查询
一、改造pagebean
目标需求：
需要新增变量保存上一次查询条件
需要新增变量保存上一次请求地址
需要添加方法：获取最大页的页码
需要添加方法：获取下一页的页码
需要添加方法：获取上一页的页码
需要新增方法：初始化pagebean
pagebean的代码：```
package com.zsx.util;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
public class PageBean {
private int page = 1;// 页码
private int rows = 10;// 页大小
private int total = 0;// 总记录数
//需要新增变量保存上一次请求地址
private String url;
private boolean pagination = true;// 是否分页
//需要新增变量保存上一次查询条件
private Map parameterMap = new HashMap();
//需要添加方法：获取最大页码
public int maxPage() {
return this.total % this.rows==0 ? this.total / this.rows : this.total / this.rows+1;
}
//需要添加方法：获取上一页页码
public int previousPage() {
return this.page >1 ? this.page -1 : this.page;
}
//需要添加方法：获取下一页页码
public int nextPage() {
return this.page < this.maxPage()?this.page+1:this.page;
}
//需要添加方法：初始化pagebean
public void setRequest(HttpServletRequest req) {
this.setPage(req.getParameter("page"));
this.setRows(req.getParameter("rows"));
this.setPagination(req.getParameter("pagination"));
this.setUrl(req.getRequestURL().toString());
this.setParameterMap(req.getParameterMap());
}
private void setPagination(String pagination) {
if(StringUtils.isNotBlank(pagination)) {
this.setPagination((!"false".equals(pagination)));
}
}
private void setRows(String rows) {
if(StringUtils.isNotBlank(rows)) {
this.setPage(Integer.valueOf(rows));
}
}
public 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 getParameterMap() {
return parameterMap;
}
public void setParameterMap(Map parameterMap) {
this.parameterMap = parameterMap;
}
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;
}
public int getStartIndex() {
return (this.page - 1) * this.rows;
}
@Override
public String toString() {
return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", url=" + url + ", pagination="
+ pagination + ", parameterMap=" + parameterMap + "]";
}
}
```
再建一个bookservlet：```
package com.zsx.servlet;
import java.io.IOException;
import java.util.List;
import java.util.Map;
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.zsx.dao.BookDao;
import com.zsx.entity.Book;
import com.zsx.util.EncodingFiter;
import com.zsx.util.PageBean;
@WebServlet("/book.action")
public class BookServlet extends HttpServlet{
@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 {
PageBean pagebean=new PageBean();
pagebean.setRequest(req);
BookDao bookDao=new BookDao();
Book book=new Book();
book.setBname(req.getParameter("bname"));
try {
List books = bookDao.list2(book, pagebean);
req.setAttribute("books", books);
} catch (Exception e) {
e.printStackTrace();
}
req.setAttribute("pagebean", pagebean);
req.getRequestDispatcher("/booklist.jsp").forward(req, resp);
}
}
```
界面bookList.jsp:```
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib prefix="z" uri="http://jsp.zsx.com" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>书籍列表
| 书籍ID | 书籍名 | 价格 |
|---|---|---|
| ${b.bid } | ${b.bname } | ${b.price } |
二、分页查询
以一个书籍的表为例
建一个pageTag类：
```
package com.zsx.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.sun.org.apache.xml.internal.serializer.ToHTMLSAXHandler;
import com.zsx.util.PageBean;
public class PageTag extends BodyTagSupport{
private PageBean pageBean;
public PageBean getPageBean() {
return pageBean;
}
public void setPageBean(PageBean pageBean) {
this.pageBean = pageBean;
}
@Override
public int doStartTag() throws JspException {
JspWriter out = pageContext.getOut();
try {
out.print(toHTML());
} catch (IOException e) {
e.printStackTrace();
}
return super.doStartTag();
}
private String toHTML() {
StringBuffer sb = new StringBuffer();
//隐藏的from表单
sb.append(" ");
//分页条
sb.append("- ");
sb.append("
- 首页 "); sb.append("
- < "); sb.append("
- "+pageBean.getPage()+" "); sb.append("
- > "); sb.append("
- 尾页 "); sb.append("
- 到第页 "); sb.append("
- 确定 "); sb.append("
- 共"+pageBean.getTotal()+"条 "); sb.append("
```
写一个配置文件zsx.tld```
JSTL 1.1 core library JSTL core 1.1 c http://jsp.zsx.com Provides core validation features for JSTL tags. org.apache.taglibs.standard.tlv.JstlCoreTLV page com.zsx.tag.PageTag JSP pageBean true true
```
注意：当发生页数改变时，很多参数不变，但是页数（page）是会改变的
在bookList.jsp中导入标签库
<%@taglib uri="http://cdl.com" prefix="z" %> <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
将数据展示到页面上去```
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib prefix="z" uri="http://jsp.zsx.com" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>书籍列表
| 书籍ID | 书籍名 | 价格 |
|---|---|---|
| ${b.bid } | ${b.bname } | ${b.price } |
最后效果：
