简封为HttpServlet的用户登录例子、结合jdbc的用户登录例子

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我们先看简封为HttpServlet的用户登录例子

这个小例子对servlet、request进行了小小的封装
需求是：在web.xml中进行配置用户名、密码，然后通过html进行登录，跳转到servlet，通过getServletContext().getInitParameter获取配置信息，然后通过req.getParameter获取请求信息，如果用户名、密码配对正确那么就输出成功即可

首先看配置文件：

    <!-- 配置servlet -->    <context-param>        <param-name>user</param-name>        <param-value>wyf</param-value>    </context-param>    <context-param>        <param-name>password</param-name>        <param-value>123456</param-value>    </context-param>   <servlet>    <servlet-name>loginServlet</servlet-name>    <servlet-class>com.safly.LoginServlet2</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>loginServlet</servlet-name>    <url-pattern>/loginServlet</url-pattern>  </servlet-mapping>

然后看一个简单的html界面login.html

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body>    <form action="loginServlet" method="post">        user:<input type="text" name="user" />         password:<input type="text"        <input type="submit" value="Submit" />    </form></body></html>

MyGenericServlet

package com.safly;import java.io.IOException;import java.util.Enumeration;import javax.servlet.Servlet;import javax.servlet.ServletConfig;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public abstract class MyGenericServlet implements Servlet, ServletConfig {    public void destroy() {    }    public ServletConfig getServletConfig() {        return servletConfig;    }    public String getServletInfo() {        return null;    }    private ServletConfig servletConfig;    public void init(ServletConfig config) throws ServletException {        this.servletConfig = config;        init();    }    private void init() throws ServletException {    }    public abstract void service(ServletRequest req, ServletResponse res)            throws ServletException, IOException;    //以下是ServletConfig的实现方法    public String getInitParameter(String arg0) {        return servletConfig.getInitParameter(arg0);    }    public Enumeration getInitParameterNames() {        return servletConfig.getInitParameterNames();    }    public ServletContext getServletContext() {        return servletConfig.getServletContext();    }    public String getServletName() {        return servletConfig.getServletName();    }}

MyHttpServlet

package com.safly;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class MyHttpServlet extends MyGenericServlet {    public void service(ServletRequest req, ServletResponse res)            throws ServletException, IOException {        if (req instanceof HttpServletRequest) {            HttpServletRequest request = (HttpServletRequest) req;            if (res instanceof HttpServletResponse) {                HttpServletResponse response = (HttpServletResponse) res;                service(request, response);            }        }    }    public void service(HttpServletRequest req, HttpServletResponse res)            throws ServletException, IOException {        String method = req.getMethod();        if ("GET".equalsIgnoreCase(method)) {            doGet(req, res);        } else if ("POST".equalsIgnoreCase(method)) {            doPost(req, res);        }    }    public void doPost(HttpServletRequest req, HttpServletResponse res)            throws IOException {    }    public void doGet(HttpServletRequest req, HttpServletResponse res)            throws IOException {    }}

LoginServlet2

package com.safly;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServlet2 extends MyHttpServlet {    public void doPost(HttpServletRequest req, HttpServletResponse res)            throws IOException {        String username = req.getParameter("user");        String password = req.getParameter("password");        String initUser = getServletContext().getInitParameter("user");        String initPassword = getServletContext().getInitParameter("password");        PrintWriter pw = res.getWriter();        if (initUser.equals(username) && initPassword.equals(password)) {            pw.print("Helloo:" + username);        } else {            pw.print("Sorryy:" + username);        }    }}

进行调试：
http://localhost:8080/day01/login.html
输入wyf,123456
然后浏览器输出 Helloo:wyf 说明校验正确
如果输出错误输出 Sorryy:www（用户名输入的是www）
http://localhost:8080/day01/loginServlet

结合jdbc的用户登录例子
总体流程就是创建一个user数据库，里面存有用户登录的姓名、密码
然后通过html页面进行登录，跳转到servlet，通过req.getParameter获取对应的值，构建sql语句，jdbc进行数据库链接，去查询数据库是否有用户信息，如果有的话，就输出登录成功即可

这里写图片描述
以上就是创建mydatabase数据库，然后创建user表，字段有username、password

再看代码之前，由于jdbc是数据库连接池，所以有些方法需要用到mysql-connector-java-5.1.7-bin.jar
直接丢在WEB-INF-lib下即可

我们还是先来看web.xml配置信息：

    <!-- 配置servlet -->    <servlet>        <servlet-name>loginServlet</servlet-name>        <servlet-class>com.safly.LoginServelt3</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>loginServlet</servlet-name>        <url-pattern>/loginServlet</url-pattern>    </servlet-mapping>

接下来就就看html界面的东东，就一个用户名，密码框

<form action="loginServlet" method="post">        user:<input type="text" name="username" /> password:<input type="text"            name="password" /><br> <input type="submit" value="Submit" />    </form>

然后就是servlet了

package com.safly;import java.io.IOException;import java.io.PrintWriter;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServelt3 extends HttpServlet {    public void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        String username = req.getParameter("username");        String password = req.getParameter("password");        System.out.println("username:"+username+",password:"+password);        java.sql.Connection connection = null;        java.sql.PreparedStatement statement = null;        ResultSet resultSet = null;        PrintWriter pw = resp.getWriter();        try {            Class.forName("com.mysql.jdbc.Driver");            String url = "jdbc:mysql://127.0.0.1:3306/mydatabase";            String user = "root";            String password2 = "root";            connection = DriverManager.getConnection(url, user, password2);            String sql = "select count(id) from user where username=? and password=?";            statement = connection.prepareStatement(sql);            statement.setString(1, username);            statement.setString(2, password);            resultSet = statement.executeQuery();            if (resultSet.next()) {                int count = resultSet.getInt(1);                System.out.println("resultSet.count1:"+count);                if (count == 1) {                    pw.print("hello" + username);                } else {                    pw.print("sorry" + username);                }            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if (resultSet != null) {                try {                    resultSet.close();                } catch (SQLException e) {                    e.printStackTrace();                }            }            if (statement != null) {                try {                    statement.close();                } catch (SQLException e) {                    e.printStackTrace();                }            }            if (connection != null) {                try {                    connection.close();                } catch (SQLException e) {                    e.printStackTrace();                }            }        }    }}

浏览器调试：
http://localhost:8080/day01/login.html
输入wyff、wyf
这里写图片描述

这说明wyff、wyf在数据库中存在2条记录
这里判断的不严禁

if (count == 1) {                    pw.print("hello" + username);                } else {                    pw.print("sorry" + username);                }

就输出 sorrywyff

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