1.删除：href=“javascript:void(0);”
如下绿色第一行不走，走第二行。QueryListServlet会自动跳转到list.jsp。
package com.itheima.manager.web;
import com.itheima.manager.service.UserService;
import com.itheima.manager.service.impl.UserServiceImpl;
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 java.io.IOException;
@WebServlet(urlPatterns = "/DeteleServlet")
public class DeteleServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String id = request.getParameter("id"); //先写=号右边.val回车，自动左边
//list.jsp中href="/DeteleServlet?id=${user.id} 的id
UserService service = new UserServiceImpl();
service.deleteUser(id); //不需要返回值
//request.getRequestDispatcher("/QueryListServlet").forward(request,response);
request.getRequestDispatcher("/QueryPageServlet ").forward(request,response);
}
}
2.添加：主键自增设为null，BeanUtils
name，value自动拼接，表单提交和文件上传常用post。
//add.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!-- HTML5文档-->
<!DOCTYPE html>
<!-- 网页使用的语言 -->
<html lang="zh-CN">
<head>
<!-- 指定字符集 -->
<meta charset="utf-8">
<!-- 使用Edge最新的浏览器的渲染方式 -->
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<!-- viewport视口：网页可以根据设置的宽度自动进行适配，在浏览器的内部虚拟一个容器，容器的宽度与设备的宽度相同。
width: 默认宽度与设备的宽度相同
initial-scale: 初始的缩放比，为1:1 -->
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- 上述3个meta标签*必须*放在最前面，任何其他内容都*必须*跟随其后！ -->
<title>添加用户</title>
<!-- 1. 导入CSS的全局样式 -->
<link href="css/bootstrap.min.css" rel="stylesheet">
<!-- 2. jQuery导入，建议使用1.9以上的版本 -->
<script src="js/jquery-2.1.0.min.js"></script>
<!-- 3. 导入bootstrap的js文件 -->
<script src="js/bootstrap.min.js"></script>
</head>
<!--1111111111111111111111111111111111111111111111111111111111111111111111111111111111-->
<body>
<div class="container text-left">
<center><h3>添加联系人页面</h3></center>
<form action="/AddServlet" method="post" class="form-horizontal"> <!--这行最重要-->
<div class="form-group">
<label class="col-lg-2 control-label" for="name">姓名：</label>
<div class="col-lg-8">
<input type="text" class="form-control" id="name" name="name" placeholder="请输入姓名">
</div>
<label class="col-lg-2 control-label" id="nameMsg"></label>
</div>
<div class="form-group">
<label class="col-lg-2 control-label">性别：</label>
<div class="col-lg-3">
<input type="radio" name="sex" value="男" checked="checked"/>男
</div>
<div class="col-lg-3">
<input type="radio" name="sex" value="女"/>女
</div>
<label class="col-lg-2 control-label" id="sexMsg"></label>
</div>
<div class="form-group">
<label for="age" class="control-label col-lg-2">年龄：</label>
<div class="col-lg-8">
<input type="text" class="form-control" id="age" name="age" placeholder="请输入年龄">
</div>
</div>
<div class="form-group">
<label for="jiguan" class="col-lg-2 control-label">籍贯：</label>
<div class="col-lg-8">
<select name="address" class="form-control" id="jiguan">
<option value="广东">广东</option>
<option value="广西">广西</option>
<option value="湖南">湖南</option>
</select>
</div>
</div>
<div class="form-group">
<label for="qq" class="control-label col-lg-2">QQ：</label>
<div class="col-lg-8">
<input type="text" class="form-control" id="qq" name="qq" placeholder="请输入QQ号码"/>
</div>
</div>
<div class="form-group">
<label for="email" class="col-lg-2 control-label">Email：</label>
<div class="col-lg-8">
<input type="text" class="form-control" id="email" name="email" placeholder="请输入邮箱地址"/>
</div>
</div>
<div class="form-group" style="text-align: center">
<input class="btn btn-primary" type="submit" value="提交" />
<input class="btn btn-default" type="reset" value="重置" />
<input class="btn btn-default" type="button" value="返回" />
</div>
</form>
</div>
</body>
</html>
package com.itheima.manager.web;
import com.itheima.manager.entity.User;
import com.itheima.manager.service.UserService;
import com.itheima.manager.service.impl.UserServiceImpl;
import org.apache.commons.beanutils.BeanUtils;
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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Arrays;
import java.util.Map;
import java.util.Set;
@WebServlet(urlPatterns = "/AddServlet")
public class AddServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8"); //post请求中文乱码
/* //获取请求参数
Integer age = Integer.parseInt(request.getParameter("age")); // ()里返回string类型
String name = request.getParameter("name");
String sex = request.getParameter("sex");
String address = request.getParameter("address");
String qq = request.getParameter("qq");
String email = request.getParameter("email");
//传到service层，参数太多，封装到JavaBean
User user = new User();
user.setAge(age);
user.setName(name);
user.setAddress(address);
user.setQq(qq);
user.setEmail(email);
user.setSex(sex);*/
//如上想到反射，行映射器：下面用BeanUtils，原理一样。
//11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
/* Map<String, String[]> parameterMap = request.getParameterMap(); //获取所有的请求参数
Set<String> set = parameterMap.keySet();
for (String name : set) { //name单例集合
String[] value = parameterMap.get(name);
System.out.println(name + "->" + Arrays.toString(value));
}*/
Map<String, String[]> parameterMap = request.getParameterMap();
User user = new User();
try {
/*
* void populate(Object bean, Map properties) : map中的数据填充到bean中
* 原理: 反射
* 1. 遍历map
* name = 瘪三
* 2. 反射
* clazz = user.getClass();
* setName = clazz.getMethod("set" + "Name",String.class);
* setName.invoke(user,"瘪三"); //set进user里，如【Mysql5】第3章
*
* 注意: BeanUtils
* 1. 类必须是javaBean（规范必须有set方法）
* 2. 属性名和参数的key必须一致
* */
BeanUtils.populate(user,parameterMap);
}catch (Exception e) {
e.printStackTrace();
}
//111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
UserService service = new UserServiceImpl();
service.addUser(user);
request.getRequestDispatcher("/QueryListServlet").forward(request,response); //刷新数据
}
}
如下是name单例集合遍历
3.修改：${user.id}
如下list.jsp修改按钮。
package com.itheima.manager.web;
import com.itheima.manager.entity.User;
import com.itheima.manager.service.UserService;
import com.itheima.manager.service.impl.UserServiceImpl;
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 java.io.IOException;
@WebServlet(urlPatterns = "/QuerySingleServlet")
public class QuerySingleServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String id = request.getParameter("id");
UserService service = new UserServiceImpl();
User user = service.querySingleUser(id);
System.out.println("user:" + user);
request.setAttribute("user",user);
request.getRequestDispatcher("/update.jsp").forward(request,response);
}
}
点击前端修改按钮，idea打印如下。
如下进行回显。
//update.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html>
<!-- 网页使用的语言 -->
<html lang="zh-CN">
<head>
<base href="<%=basePath%>"/>
<!-- 指定字符集 -->
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>修改用户</title>
<link href="css/bootstrap.min.css" rel="stylesheet">
<script src="js/jquery-2.1.0.min.js"></script>
<script src="js/bootstrap.min.js"></script>
</head>
<!--11111111111111111111111111111111111111111111111111111111111111111111111111111-->
<body>
<div class="container" style="width: 400px;">
<h3 style="text-align: center;">修改联系人</h3>
<form action="/UpdateServlet" method="post">
<%--TODO: --%>
<input type="hidden" name="id" value="${user.id}">
<div class="form-group">
<label for="name">姓名：</label>
<input type="text" class="form-control" id="name" name="name" value="${user.name}"
readonly="readonly" placeholder="请输入姓名" />
</div>
<div class="form-group">
<label>性别：</label>
<%--
逻辑: ${user.sex == '男' ? "checked" : ""}
--%>
<input type="radio" name="sex" value="男" ${user.sex == '男' ? "checked" : ""}/>男
<input type="radio" name="sex" value="女" ${user.sex == '女' ? "checked" : ""} />女
</div>
<div class="form-group">
<label for="age">年龄：</label>
<input type="text" class="form-control" id="age" name="age" placeholder="请输入年龄" value="${user.age}"/>
</div>
<div class="form-group">
<label for="address">籍贯：</label>
<select name="address" id="address" class="form-control" >
<option value="广东" ${user.address == '广东' ? "selected" : ""} >广东</option>
<option value="广西" ${user.address == '广西' ? "selected" : ""} >广西</option>
<option value="湖南" ${user.address == '湖南' ? "selected" : ""} >湖南</option>
</select>
</div>
<div class="form-group">
<label for="qq">QQ：</label>
<input type="text" id="qq" class="form-control" name="qq" placeholder="请输入QQ号码" value="${user.qq}"/>
</div>
<div class="form-group">
<label for="email">Email：</label>
<input type="text" id="email" class="form-control" name="email" placeholder="请输入邮箱地址" value="${user.email}"/>
</div>
<div class="form-group" style="text-align: center">
<input class="btn btn-primary" type="submit" value="提交" />
<input class="btn btn-default" type="reset" value="重置" />
<input class="btn btn-default" type="button" value="返回"/>
</div>
</form>
</div>
</body>
</html>
如下id设为hidden，即用户不可见，但服务器知道。
package com.itheima.manager.web;
import com.itheima.manager.entity.User;
import com.itheima.manager.service.UserService;
import com.itheima.manager.service.impl.UserServiceImpl;
import org.apache.commons.beanutils.BeanUtils;
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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;
@WebServlet(urlPatterns = "/UpdateServlet")
public class UpdateServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
Map<String, String[]> map = request.getParameterMap();
User user = new User();
try {
BeanUtils.populate(user,map); //是apache里，不是spring里
} catch (Exception e) {
e.printStackTrace();
}
UserService service = new UserServiceImpl();
service.updateUser(user);
request.getRequestDispatcher("/QueryListServlet").forward(request,response);
}
}
4.分页：this.value，index=offset
如下count每页都一样，index=offset。
如下方案A不行，因为list.jsp不是同一个，B覆盖A（刷新页面）。背景色在bootstrap中就是class=“active”。
如下按钮个数要动态显示。count是每页显示的个数，btncount是按钮数量，/是整除。
onchange: 当选项改变时触发，省级联动。
4.1 前端
https://v3.bootcss.com/components/#pagination 找到分页组件，复制到最后面，nav就是div占满整个区域。
如下在list.jsp中，QueryPageServlet传来page，如下第一行是EL表达式写法，第二行往后是JSTL标签写法，两种方法都一样。下面page==1,2,3,4,5都要删除，因为没有动态显示。
//list.jsp，前面不变，尾部添加
<nav aria-label="Page navigation" class="text-center" >
<ul class="pagination pagination-lg">
<c:if test="${page == 1}">
<li class="disabled"> <!-- 上一页 《 按钮disabled变灰色-->
<a href="javascript:;" aria-label="Previous"> <!--点击事件禁了-->
<span aria-hidden="true">«</span>
</a>
</li>
</c:if>
//没有上一块内容，当page<=1时就被隐藏了
<!--1111111111111111111111111111111111111111111111111111111111111111111111111111111111-->
<c:if test="${page > 1}"> <!--page不能为0，offset为负索引了-->
<li>
<a href="/QueryPageServlet?page=${page-1}&count=${count}" aria-label="Previous">
<span aria-hidden="true">«</span>
</a>
</li>
</c:if>
//上面两块内容都为 《 按钮 显示
<!--111111111111111111111111111111111111111111111111111111111111111111111111111111111-->
<%--TODO:
1. 问题: 我们发现按钮数量太多了
2. 解决: 参照百度,总共10个按钮, (前5后4)
3. 逻辑
1. pageCount <= 10
1. begin = 1
2. end = pageCount
2. pageCount > 10
1. begin = page - 5
2. end = page + 4
3. 越界
1. begin < 1
1. begin = 1
2. end = 10
2. end > pageCount
1. end = pageCount
2. begin = pageCount-9
--%>
<c:forEach var="i" begin="1" end="${btnCount}"> <!--按钮个数动态显示-->
<li <c:if test="${page == i}">class='active' </c:if> ><a href="/QueryPageServlet?page=${i}&count=${count}">${i}</a></li>
</c:forEach>
<!--11111111111111111111111111111111111111111111111111111111111111111111111111111111111-->
//下面内容是 》 按钮
<c:if test="${page < count}"> <!--每页显示数量动态化-->
<li>
<a href="/QueryPageServlet?page=${page+1}&count=${count}" aria-label="Next">
<span aria-hidden="true">»</span>
</a>
</li>
</c:if>
<!--11111111111111111111111111111111111111111111111111111111111111111111111111111111111-->
<li>
<select onchange="method02(this.value)" class="btn-lg btn-success">
<option value="5" ${count == 5? "selected" : ""}>每页显示5条数据</option>
<option value="10" ${count == 10? "selected" : ""} >每页显示10条数据</option>
<option value="15" ${count == 15? "selected" : ""} >每页显示15条数据</option>
</select>
</li>
</ul>
</nav>
</div>
</body>
</html>
<script>
function method02(value) {
location.href = "/QueryPageServlet?page=1&count=" + value
}
</script>
//index.jsp 前面不变，这里修改原因是一进来只要显示5页就行，其他增删改也要改一下。
<div align="center">
<%--<a
href="/QueryListServlet" style="text-decoration:none;font-size:33px">查询所有用户信息
</a>--%>
<a
href="/QueryPageServlet?page=1&count=5" style="text-decoration:none;font-size:33px">查询所有用户信息
</a>
</div>
</body>
</html>
4.2 web
package com.itheima.manager.web;
import com.itheima.manager.entity.User;
import com.itheima.manager.service.UserService;
import com.itheima.manager.service.impl.UserServiceImpl;
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 java.io.IOException;
import java.util.List;
@WebServlet(urlPatterns = "/QueryPageServlet")
public class QueryPageServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1. 接收请求
int page = 1;
int count = 5;
String pageStr = request.getParameter("page"); //传参就用你传来的参数，不传参默认第一页，每页显示5条
String countStr = request.getParameter("count");
if(pageStr != null && countStr != null){
page = Integer.parseInt(pageStr); //前端传来字符串，因为要计算，所以转为int
count = Integer.parseInt(countStr);
}
int offset = (page-1) * count;
UserService service = new UserServiceImpl();
List<User> list = service.pageQuery(offset,count); //查询用户数据,不需要page了，用到上面得到的offset
int sum = service.findUserSum();
int btnCount = sum%count==0? sum/count : sum/count+1;
request.setAttribute("list",list);
request.setAttribute("page",page); //按钮点击显示效果
request.setAttribute("btnCount",btnCount); //按钮个数
request.setAttribute("count",count); //每页显示的数量
request.getRequestDispatcher("/list.jsp").forward(request,response);
}
}
转载：https://blog.csdn.net/weixin_43435675/article/details/113829359
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