课堂作业（新课程添加）

• 创建Maven项目

• 导入依赖

　　　　<dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
      <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.26</version>
    </dependency>

• 建连接数据库及释放的工具类

import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils {
    public static String url = null;
    public static String user = null;
    public static String driver = null;
    public static String password = null;

    static {
        try {
            InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);

            driver = properties.getProperty("driver");
            user = properties.getProperty("user");
            password = properties.getProperty("password");
            url = properties.getProperty("url");

            Class.forName(driver);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, user, password);
    }

    public static void release(Connection conn, PreparedStatement st, ResultSet rs, Statement stt) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (stt != null) {
            try {
                stt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

• 写properties文件

url=jdbc:mysql://localhost:3306/jdbcstudy?&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&useSSL=true
driver=com.mysql.cj.jdbc.Driver
user=root
password=123456

• 编写servlet文件

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.HashSet;
import java.util.Set;

public class servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");

        String classname = req.getParameter("classname");
        String teachername = req.getParameter("teachername");
        String place = req.getParameter("place");

        Set<String> hashSet = new HashSet<String>(8);
        hashSet.add("王建民");
        hashSet.add("刘立嘉");
        hashSet.add("刘丹");
        hashSet.add("杨子光");
        hashSet.add("张云霞");
        hashSet.add("武勇亮");
        hashSet.add("高飞");
        if (!hashSet.contains(teachername)) {
            resp.getWriter().print("<script> alert(\"Teacher name input error\") </script>");
            return;
        }

        Set<String> hashSet2 = new HashSet<String>(5);
        hashSet2.add("一教");
        hashSet2.add("二教");
        hashSet2.add("三教");
        hashSet2.add("四教");
        //System.out.println(classname);
        if (!hashSet2.contains(place)) {
            resp.getWriter().print("<script> alert(\"Classroom location input error\") </script>");
            return;
        }

        Connection conn = null;
        ResultSet rs = null;
        Statement stt = null;
        try {
            conn = JDBCUtils.getConnection();
            stt = conn.createStatement();
            String sql = "select * from lesson";
            rs = stt.executeQuery(sql);

            while (rs.next()) {
                if (rs.getString("ipp").equals(classname)) {
                    resp.getWriter().print("<script> alert(\"Duplicate course name, please re-enter\") </script>");
                    return;
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        try {

            conn = JDBCUtils.getConnection();
            String sql = "insert into `lesson`(`ipp`,`teacher`,`position`) values(?,?,?)";
            PreparedStatement st = null;

            try {
                //创建语句传输对象
                st = conn.prepareStatement(sql);

                st = conn.prepareStatement(sql);
                st.setString(1, classname);
                st.setString(2, teachername);
                st.setString(3, place);
                st.executeUpdate();
                int i = st.executeUpdate(sql);
                if (i > 0) {
                    System.out.println("插入成功");
                }
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                //关闭资源
                JDBCUtils.release(conn, st, rs, stt);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

• 编写jsp代码（抄滴）https://www.cnblogs.com/tianxiayoujiu/p/7911091.html

<%@ page language="java" contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>课程添加页面</title>
</head>
<body>
<form action="${pageContext.request.contextPath}\p" method="get">
    <table align="center" border="1" width="500">
        <tr>
            <td>课程名称 : </td>
            <td>
                <input type="text" name="classname" />
            </td>
        </tr>
        <tr>
            <td>任课教师:</td>
            <td>
                <input type="text" name="teachername" />
            </td>
        </tr>
        <tr>
            <td>上课地点:</td>
            <td>
                <input type="text" name="place" />
            </td>
        </tr>
        <tr align="center">
            <td colspan="2">
                <input type="submit" value="提交" />
                <input type="reset" value="重置" />
            </td>
        </tr>
    </table>
</form>
</body>
</html>

• 在web.xml下注册

<servlet>
    <servlet-name>test</servlet-name>
    <servlet-class>servlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>test</servlet-name>
    <url-pattern>/p</url-pattern>
  </servlet-mapping>

• 项目总体结构

 

•  效果