JavaWeb基础系列（三）Request

其他 2018-06-21 22:14:23 阅读次数: 2

一、HttpServletRequest概述

我们在创建Servlet时会覆盖service()方法，或doGet()/doPost()方法，这些方法都有两个参数，一个代表请求的request和代表响应response
service方法中的request的类型是ServletRequest，而doGet()/doPost()方法的request的类型是HttpServletRequest，HttpServletRequest是ServletRequest的子类接口，功能和方法更加强大。

二、Request的运行流程

这里写图片描述

三、通过Request获得请求信息

Http请求：
这里写图片描述
因为request代表请求，所以我们可以通过该对象分别获得Http请求的请求行，请 求头和请求体。

1、通过request获得请求行

获得客户端的请求方式：String getMethod()
获得请求的资源：
String getRequestURI()
StringBuffer getRequestURL()
String getContextPath() —web应用的名称
String getQueryString() —- get提交url地址后的参数字符串username=zhangsan&password=123
注意：request获得客户机（客户端）的一些信息
request.getRemoteAddr() — 获得访问的客户端IP地址
案例演示：
login.html：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<form action="/Servlet4" method="get">
    用户名:<input type="text" name="username"/><br />
    密码：<input type="password" name="password" /><br />
    <input type="submit" value="登录" />
</form>
</body>
</html>

Servlet4：

@WebServlet(name = "Servlet4",
        urlPatterns = {"/Servlet4"})
public class Servlet4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取请求方式
        String method = request.getMethod();
        System.out.println(method);
        //获得请求的资源
        String requestURI = request.getRequestURI();
        StringBuffer requestURL = request.getRequestURL();
        System.out.println("URI："+requestURI);
        System.out.println("URL："+requestURL);
        //获得WEB应用名称
        String contextPath = request.getContextPath();
        System.out.println("WEB应用："+contextPath);
        //地址后的参数字符串
        String queryString = request.getQueryString();
        System.out.println(queryString);
    }
}

注意：request获得客户机（客户端）的一些信息
request.getRemoteAddr() — 获得访问的客户端IP地址

2、通过request获得请求头

主要方法有：
long getDateHeader(String name)
String getHeader(String name)
Enumeration getHeaderNames()
Enumeration getHeaders(String name)
int getIntHeader(String name)

3、通过request获得请求体

请求体中的内容是通过post提交的请求参数，格式是：
username=zhangsan&password=123&hobby=football&hobby=basketball
key ———————- value
username———- [ zhangsan ]
password —————[ 123 ]
hobby ——— [ football，basketball ]
以上面参数为例，通过一下方法获得请求参数：

String getParameter(String name) 
String[] getParameterValues(String name)
Enumeration getParameterNames()
Map<String,String[]> getParameterMap()

注意：get请求方式的请求参数 上述的方法一样可以获得
解决post提交方式的乱码：request.setCharacterEncoding(“UTF-8”);
解决get提交的方式的乱码：parameter = new String(parameter.getbytes(“iso8859-1”),”utf-8”);
案例演示：
login1.html：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<form action="/Servlet5" method="get">
    用户名:<input type="text" name="username"/><br />
    密码：<input type="password" name="password" /><br />
    <input type="checkbox" name="hobby" value="zq">足球
    <input type="checkbox" name="hobby" value="pq">排球
    <input type="checkbox" name="hobby" value="lq">篮球
    <input type="submit" value="提交" />
</form>
</body>
</html>

Servlet5：

@WebServlet(name = "Servlet5",
        urlPatterns = {"/Servlet5"})
public class Servlet5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获得单个表单值
        String username = request.getParameter("username");
        System.out.println(username);
        String password = request.getParameter("password");
        System.out.println(password);
        //获得多个表单值
        String[] hobbies = request.getParameterValues("hobby");
        for(String hobby:hobbies){
            System.out.println(hobby);
        }
        System.out.println("---------");
        //获得所有的参数，参数封装到一个map中
        Map<String, String[]> parameterMap = request.getParameterMap();
        for(Map.Entry<String,String[]> entry:parameterMap.entrySet()){
            System.out.println(entry.getKey());
            for(String str:entry.getValue()){
                System.out.println(str);
            }
        }
    }
}

运行结果：
tom
123
zq
lq
~~~~~~~~~~~~~
username
tom
password
123
hobby
zq
lq

四、Request其他功能

4.1、request是一个域对象

request对象也是一个存储数据的区域对象，所以也具有如下方法：
setAttribute(String name, Object o)
getAttribute(String name)
removeAttribute(String name)
注意：request域的作用范围：一次请求中

4.2、request完成请求转发

获得请求转发器—-path是转发的地址
RequestDispatcher getRequestDispatcher(String path)
通过转发器对象转发
requestDispathcer.forward(ServletRequest request, ServletResponse response)
注意：ServletContext域与Request域的生命周期比较？
ServletContext：
    创建：服务器启动
    销毁：服务器关闭
    域的作用范围：整个web应用
request：
    创建：访问时创建request
    销毁：响应结束request销毁
    域的作用范围：一次请求中
注意：转发与重定向的区别？
    1）重定向两次请求，转发一次请求
    2）重定向地址栏的地址变化，转发地址不变
    3）重新定向可以访问外部网站 转发只能访问内部资源
    4）转发的性能要优于重定向
注意：客户端地址与服务器端地址的写法？
客户端地址：
    是客户端去访问服务器的地址，服务器外部的地址，特点：写上web应用名称
服务器端地址：
    服务器内部资源的跳转的地址，特点：不需要写web应用的名称

@WebServlet(name = "Servlet6",
        urlPatterns = {"/Servlet6"})
public class Servlet6 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //转发到Servlet3
        RequestDispatcher dispatcher = request.getRequestDispatcher("/Servlet3");
        dispatcher.forward(request,response);
    }
}

五、案例：用户注册功能

前端代码：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>龙心商城首页</title>
        <link rel="stylesheet" href="css/bootstrap.min.css" type="text/css" />
        <script src="js/jquery-1.11.3.min.js" type="text/javascript"></script>
        <script src="js/bootstrap.min.js" type="text/javascript"></script>
    </head>

    <body>
        <div class="container-fluid">

            <!-- 引入header.jsp -->
            <jsp:include page="/header.jsp"></jsp:include>

            <!-- 轮播图 -->
            <div class="container-fluid">
                <div id="carousel-example-generic" class="carousel slide" data-ride="carousel">
                    <!-- 轮播图的中的小点 -->
                    <ol class="carousel-indicators">
                        <li data-target="#carousel-example-generic" data-slide-to="0" class="active"></li>
                        <li data-target="#carousel-example-generic" data-slide-to="1"></li>
                        <li data-target="#carousel-example-generic" data-slide-to="2"></li>
                    </ol>
                    <!-- 轮播图的轮播图片 -->
                    <div class="carousel-inner" role="listbox">
                        <div class="item active">
                            <img src="img/1.jpg">
                            <div class="carousel-caption">
                                <!-- 轮播图上的文字 -->
                            </div>
                        </div>
                        <div class="item">
                            <img src="img/2.jpg">
                            <div class="carousel-caption">
                                <!-- 轮播图上的文字 -->
                            </div>
                        </div>
                        <div class="item">
                            <img src="img/3.jpg">
                            <div class="carousel-caption">
                                <!-- 轮播图上的文字 -->
                            </div>
                        </div>
                    </div>

                    <!-- 上一张 下一张按钮 -->
                    <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
                        <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
                        <span class="sr-only">Previous</span>
                    </a>
                    <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
                        <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
                        <span class="sr-only">Next</span>
                    </a>
                </div>
            </div>

            <!-- 热门商品 -->
            <div class="container-fluid">
                <div class="col-md-12">
                    <h2>热门商品&nbsp;&nbsp;<img src="img/title2.jpg"/></h2>
                </div>
                <div class="col-md-2" style="border:1px solid #E7E7E7;border-right:0;padding:0;">
                    <img src="products/hao/big01.jpg" width="205" height="404" style="display: inline-block;"/>
                </div>
                <div class="col-md-10">
                    <div class="col-md-6" style="text-align:center;height:200px;padding:0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/middle01.jpg" width="516px" height="200px" style="display: inline-block;">
                        </a>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2 yes-right-border" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2 yes-right-border" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>
                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>
                </div>
            </div>

            <!-- 广告条 -->
            <div class="container-fluid">
                <img src="products/hao/ad.jpg" width="100%"/>
            </div>

            <!-- 最新商品 -->
            <div class="container-fluid">
                <div class="col-md-12">
                    <h2>最新商品&nbsp;&nbsp;<img src="img/title2.jpg"/></h2>
                </div>
                <div class="col-md-2" style="border:1px solid #E7E7E7;border-right:0;padding:0;">
                    <img src="products/hao/big01.jpg" width="205" height="404" style="display: inline-block;"/>
                </div>
                <div class="col-md-10">
                    <div class="col-md-6" style="text-align:center;height:200px;padding:0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/middle01.jpg" width="516px" height="200px" style="display: inline-block;">
                        </a>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2 yes-right-border" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2 yes-right-border" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>
                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small03.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small04.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>

                    <div class="col-md-2 yes-right-border" style="text-align:center;height:200px;padding:10px 0px;">
                        <a href="product_info.htm">
                            <img src="products/hao/small05.jpg" width="130" height="130" style="display: inline-block;">
                        </a>
                        <p><a href="product_info.html" style='color:#666'>冬瓜</a></p>
                        <p><font color="#E4393C" style="font-size:16px">&yen;299.00</font></p>
                    </div>
                </div>
            </div>          

            <!-- 引入footer.jsp -->
            <jsp:include page="/footer.jsp"></jsp:include>

        </div>
    </body>

</html>

后端代码：

package com.servlet;

import com.naruto.domain.User;
import com.naruto.utils.DataSourceUtils;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.dbutils.QueryRunner;

import javax.servlet.RequestDispatcher;
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.sql.SQLException;
import java.util.Map;
import java.util.UUID;

/**
 * Created by long on 2018/6/19.
 */
@WebServlet(name = "Register",
        urlPatterns = {"/Register"})
public class Register extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、获取数据
        //String username = request.getParameter("username");
        //String password = request.getParameter("password");
        //使用BeanUtils包进行自动映射封装
        //BeanUtils工作原理：将map中的数据根据key和实体的属性的对应关系封装的
        //只要key的名字与实体的属性的名字一样，就自动的封装到实体中
        Map<String, String[]> parameterMap = request.getParameterMap();
        User user = new User();
        try {
            BeanUtils.populate(user,parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        //现在这个位置user对象已经封装好了
        //手动封装uid--uuid--随机不重复的字符串32位--java代码生成后是36位
        user.setUid(UUID.randomUUID().toString());
        //2、将参数传递给一个业务操作方法
        try {
            register(user);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    public void register(User user) throws SQLException {
        //操作数据库
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "insert into user values(?,?,?,?,?,?,?,?,?,?)";
        runner.update(sql,user.getUid(),user.getUsername(),user.getPassword(),user.getName(),user.getEmail(),null,user.getBirthday(),user.getSex(),null,null);
    }
}

运行结果：
这里写图片描述
点击注册按钮，到注册页面：
这里写图片描述
注册完成后，查看数据库：
这里写图片描述
解决中文乱码问题：

//设置request的编码
request.setCharacterEncoding("UTF-8");

乱码产生的原因：
页面将中文采用UTF-8编码，然后Servlet采用ISO8859-1解码
乱码解决：
将中文使用IOS8859-1编码，然后使用UTF-8解码

//get方式乱码解决（也适用于POST）
String username = request.getParameter("username");
//先用ISO8859-1编码，再使用UTF-8解码
username = new String(username.getBytes("ISO8859-1"),"UTF-8");

运行结果：
这里写图片描述

六、用户登陆失败的信息回显

注册成功之后重定向到登录界面：

@WebServlet(name = "Register",
        urlPatterns = {"/Register"})
public class Register extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置request的编码--只适合POST方式
        request.setCharacterEncoding("UTF-8");
        Map<String, String[]> parameterMap = request.getParameterMap();
        User user = new User();
        try {
            BeanUtils.populate(user,parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        //现在这个位置user对象已经封装好了
        //手动封装uid--uuid--随机不重复的字符串32位--java代码生成后是36位
        user.setUid(UUID.randomUUID().toString());
        //2、将参数传递给一个业务操作方法
        try {
            register(user);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //3、认为注册成功跳转到登录页面
        response.sendRedirect(request.getContextPath()+"/login.jsp");
        //request.getRequestDispatcher("/login.jsp").forward(request,response);
    }
    public void register(User user) throws SQLException {
        //操作数据库
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "insert into user values(?,?,?,?,?,?,?,?,?,?)";
        runner.update(sql,user.getUid(),user.getUsername(),user.getPassword(),user.getName(),user.getEmail(),null,user.getBirthday(),user.getSex(),null,null);
    }
}

完成登录功能

前端代码：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>会员登录</title>
<link rel="stylesheet" href="css/bootstrap.min.css" type="text/css" />
<script src="js/jquery-1.11.3.min.js" type="text/javascript"></script>
<script src="js/bootstrap.min.js" type="text/javascript"></script>
<!-- 引入自定义css文件 style.css -->
<link rel="stylesheet" href="css/style.css" type="text/css" />

<style>
body {
    margin-top: 20px;
    margin: 0 auto;
}

.carousel-inner .item img {
    width: 100%;
    height: 300px;
}

.container .row div {
    /* position:relative;
                 float:left; */

}

font {
    color: #666;
    font-size: 22px;
    font-weight: normal;
    padding-right: 17px;
}
</style>
</head>
<body>
    <!-- 引入header.jsp -->
    <jsp:include page="/header.jsp"></jsp:include>

    <div class="container"
        style="width: 100%; height: 460px; background: #FF2C4C url('images/loginbg.jpg') no-repeat;">
        <div class="row">
            <div class="col-md-7">
                <!--<img src="./image/login.jpg" width="500" height="330" alt="会员登录" title="会员登录">-->
            </div>

            <div class="col-md-5">
                <div
                    style="width: 440px; border: 1px solid #E7E7E7; padding: 20px 0 20px 30px; border-radius: 5px; margin-top: 60px; background: #fff;">
                    <font>会员登录</font>USER LOGIN
                    <div><%=request.getAttribute("loginInfo")==null?"":request.getAttribute("loginInfo")%></div>
                    <form class="form-horizontal" action="/Login" method="post">
                        <div class="form-group">
                            <label for="username" class="col-sm-2 control-label">用户名</label>
                            <div class="col-sm-6">
                                <input type="text" class="form-control" id="username" name="username"
                                    placeholder="请输入用户名">
                            </div>
                        </div>
                        <div class="form-group">
                            <label for="inputPassword3" class="col-sm-2 control-label">密码</label>
                            <div class="col-sm-6">
                                <input type="password" class="form-control" id="inputPassword3" name="password"
                                    placeholder="请输入密码">
                            </div>
                        </div>
                        <div class="form-group">
                            <label for="inputPassword3" class="col-sm-2 control-label">验证码</label>
                            <div class="col-sm-3">
                                <input type="text" class="form-control" id="inputPassword3"
                                    placeholder="请输入验证码">
                            </div>
                            <div class="col-sm-3">
                                <img src="./image/captcha.jhtml" />
                            </div>
                        </div>
                        <div class="form-group">
                            <div class="col-sm-offset-2 col-sm-10">
                                <div class="checkbox">
                                    <label> <input type="checkbox"> 自动登录
                                    </label>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <label> <input
                                        type="checkbox"> 记住用户名
                                    </label>
                                </div>
                            </div>
                        </div>
                        <div class="form-group">
                            <div class="col-sm-offset-2 col-sm-10">
                                <input type="submit" width="100" value="登录" name="submit"
                                    style="background: url('./images/login.gif') no-repeat scroll 0 0 rgba(0, 0, 0, 0); height: 35px; width: 100px; color: white;">
                            </div>
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>

    <!-- 引入footer.jsp -->
    <jsp:include page="/footer.jsp"></jsp:include>

</body>
</html>

后端代码Login：

@WebServlet(name = "Login",
        urlPatterns = {"/Login"})
public class Login extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        //1、获得用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //2、调用一个业务方法进行该用户查询
        User login1 = null;
        try {
            login1 = login(username,password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //3、通过user是否为null判断用户名和密码是否正确
        if(login1!=null){
            //用户名和密码正确
            //登录成功 跳转到网站的首页
            response.sendRedirect(request.getContextPath()+"/index.jsp");
        }else
        {
            //用户名或密码错误
            //跳回当前login.jsp
            request.setAttribute("loginInfo","用户名或密码错误");
            request.getRequestDispatcher("login.jsp").forward(request,response);
        }
    }
    public User login(String username,String password) throws SQLException {
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "select * from user where username=? and password=?";
        User user = runner.query(sql,new BeanHandler<User>(User.class),username,password);
        return user;
    }
}

运行结果：当用户名或密码错误的时候，回显信息
这里写图片描述

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