连接数据库的增删改查

Posted 2021-01-25 ljm-zsy

1.在mysql中新建一个名为course的数据库，并在其中新建一个course数据表，包含四个字段，id，name，teacher，classname如图（注意：将id设为自动递增，否则后面新增会出错。id设为自增，新增时就只需关注course的其它属性。）

 

二.建立Java  web  项目

 1. eclipse新建一个Dynamic Web Project

 

2.将连接mysql的驱动jar包（mysql-connector-java-5.1.7-bin.jar）copy到WEB-INF下的lib目录下

 

3.新建五个包，entity存放实体类(User)，dao存放数据库操作类(UserDao)，servlet存放控制类(addServlet,updateServlet,deleteServlet,listServlet)，util存放开发帮助类service是算法实现(这里是数据库操作帮助类，封装了数据库连接部分代码，避免大量重复代码)

4. 新建类，java类放在对应包中，jsp页面放在WebContent目录下，替换web.xml中内容，结构如图

 

三.代码

//Course.java
package com.hjf.entity;

public class Course {

    private int id;
    private String name;
    private String teacher;
    private String classroom;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getTeacher() {
        return teacher;
    }
    public void setTeacher(String teacher) {
        this.teacher = teacher;
    }
    public String getClassroom() {
        return classroom;
    }
    public void setClassroom(String classroom) {
        this.classroom = classroom;
    }
    
    public Course() {}
    
    public Course(int id, String name, String teacher, String classroom) {
        this.id = id;
        this.name = name;
        this.teacher = teacher;
        this.classroom = classroom;
    }
    
    public Course(String name, String teacher, String classroom) {
        this.name = name;
        this.teacher = teacher;
        this.classroom = classroom;
    }
}

//CourseDao.java
package com.hjf.dao;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.hjf.entity.Course;
import com.hjf.util.DBUtil;

/**
 * 课程Dao
 * Dao层操作数据
 * @author Hu
 *
 */
public class CourseDao {

    /**
     * 添加
     * @param course
     * @return
     */
    public boolean add(Course course) {
        String sql = "insert into course(name, teacher, classroom) values(‘" + course.getName() + "‘,‘" + course.getTeacher() + "‘,‘" + course.getClassroom() + "‘)";
        //创建数据库链接
        Connection conn = DBUtil.getConn();
        Statement state = null;
        boolean f = false;
        int a = 0;
        
        try {
            state = conn.createStatement();
            state.executeUpdate(sql);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //关闭连接
            DBUtil.close(state, conn);
        }
        
        if (a > 0) {
            f = true;
        }
        return f;
    }

    /**
     * 删除
     * 
     * @param id
     * @return
     */
    public boolean delete (int id) {
        boolean f = false;
        String sql = "delete from course where id=‘" + id + "‘";
        
        Connection conn = DBUtil.getConn();
        Statement state = null;
        int a = 0;
        
        try {
            state = conn.createStatement();
            a = state.executeUpdate(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(state, conn);
        }
        
        if (a > 0) {
            f = true;
        }
        return f;
    }

    /**
     * 修改
     * @param name
     * @param pass
     */
    public boolean update(Course course) {
        String sql = "update course set name=‘" + course.getName() + "‘, teacher=‘" + course.getTeacher() + "‘, classroom=‘" + course.getClassroom()
            + "‘ where id=‘" + course.getId() + "‘";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        boolean f = false;
        int a = 0;

        try {
            state = conn.createStatement();
            a = state.executeUpdate(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(state, conn);
        }
        
        if (a > 0) {
            f = true;
        }
        return f;
    }
    
    /**
     * 验证课程名称是否唯一
     * true --- 不唯一
     * @param name
     * @return
     */
    public boolean name(String name) {
        boolean flag = false;
        String sql = "select name from course where name = ‘" + name + "‘";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;
        
        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            while (rs.next()) {
                flag = true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        return flag;
    }
    
    /**
     * 通过ID得到课程信息
     * @param id
     * @return
     */
    public Course getCourseById(int id) {
        String sql = "select * from course where id =‘" + id + "‘";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;
        Course course = null;
        
        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            while (rs.next()) {
                String name = rs.getString("name");
                String teacher = rs.getString("teacher");
                String classroom = rs.getString("classroom");
                course = new Course(id, name, teacher, classroom);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return course;
    }
    
    /**
     * 通过name得到Course
     * @param name
     * @return
     */
    public Course getCourseByName(String name) {
        String sql = "select * from course where name =‘" + name + "‘";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;
        Course course = null;
        
        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            while (rs.next()) {
                int id = rs.getInt("id");
                String teacher = rs.getString("teacher");
                String classroom = rs.getString("classroom");
                course = new Course(id, name, teacher, classroom);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return course;
    }
    
    /**
     * 查找
     * @param name
     * @param teacher
     * @param classroom
     * @return
     */
    public List<Course> search(String name, String teacher, String classroom) {
        String sql = "select * from course where ";
        if (name != "") {
            sql += "name like ‘%" + name + "%‘";
        }
        if (teacher != "") {
            sql += "teacher like ‘%" + teacher + "%‘";
        }
        if (classroom != "") {
            sql += "classroom like ‘%" + classroom + "%‘";
        }
        List<Course> list = new ArrayList<>();
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;

        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            Course bean = null;
            while (rs.next()) {
                int id = rs.getInt("id");
                String name2 = rs.getString("name");
                String teacher2 = rs.getString("teacher");
                String classroom2 = rs.getString("classroom");
                bean = new Course(id, name2, teacher2, classroom2);
                list.add(bean);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return list;
    }
    
    /**
     * 全部数据
     * @param name
     * @param teacher
     * @param classroom
     * @return
     */
    public List<Course> list() {
        String sql = "select * from course";
        List<Course> list = new ArrayList<>();
        Connection conn = DBUtil.getConn();
        Statement state = null;
        ResultSet rs = null;

        try {
            state = conn.createStatement();
            rs = state.executeQuery(sql);
            Course bean = null;
            while (rs.next()) {
                int id = rs.getInt("id");
                String name2 = rs.getString("name");
                String teacher2 = rs.getString("teacher");
                String classroom2 = rs.getString("classroom");
                bean = new Course(id, name2, teacher2, classroom2);
                list.add(bean);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, state, conn);
        }
        
        return list;
    }

}

//CourseService.java
package com.hjf.service;

import java.util.List;

import com.hjf.dao.CourseDao;
import com.hjf.entity.Course;

/**
 * CourseService
 * 服务层
 * @author Hu
 *
 */
public class CourseService {

    CourseDao cDao = new CourseDao();
    
    /**
     * 添加
     * @param course
     * @return
     */
    public boolean add(Course course) {
        boolean f = false;
        if(!cDao.name(course.getName())) {
            cDao.add(course);
            f = true;
        }
        return f;
    }
    
    /**
     * 删除
     */
    public void del(int id) {
        cDao.delete(id);
    }
    
    /**
     * 修改
     * @return 
     */
    public void update(Course course) {
        cDao.update(course);
    }
    
    /**
     * 通过ID得到一个Course
     * @return 
     */
    public Course getCourseById(int id) {
        return cDao.getCourseById(id);
    }

    /**
     * 通过Name得到一个Course
     * @return 
     */
    public Course getCourseByName(String name) {
        return cDao.getCourseByName(name);
    }
    
    /**
     * 查找
     * @return 
     */
    public List<Course> search(String name, String teacher, String classroom) {
        return cDao.search(name, teacher, classroom);
    }
    
    /**
     * 全部数据
     * @return 
     */
    public List<Course> list() {
        return cDao.list();
    }
}

//CourseServlet.java
package com.hjf.servlet;

import java.io.IOException;
import java.util.List;

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.hjf.entity.Course;
import com.hjf.service.CourseService;

@WebServlet("/CourseServlet")
public class CourseServlet extends HttpServlet {
    
    private static final long serialVersionUID = 1L;

    CourseService service = new CourseService();
    
    /**
     * 方法选择
     */
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String method = req.getParameter("method");
        
        if ("add".equals(method)) {
            add(req, resp);
        } else if ("del".equals(method)) {
            del(req, resp);
        } else if ("update".equals(method)) {
            update(req, resp);
        } else if ("search".equals(method)) {
            search(req, resp);
        } else if ("getcoursebyid".equals(method)) {
            getCourseById(req, resp);
        } else if ("getcoursebyname".equals(method)) {
            getCourseByName(req, resp);
        } else if ("list".equals(method)) {
            list(req, resp);
        }
    }

    /**
     * 添加
     * @param req
     * @param resp
     * @throws IOException 
     * @throws ServletException 
     */
    private void add(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        req.setCharacterEncoding("utf-8");
        //获取数据
        String name = req.getParameter("name");
        String teacher = req.getParameter("teacher");
        String classroom = req.getParameter("classroom");
        Course course = new Course(name, teacher, classroom);
        
        //添加后消息显示
        if(service.add(course)) {
            req.setAttribute("message", "添加成功");
            req.getRequestDispatcher("add.jsp").forward(req,resp);
        } else {
            req.setAttribute("message", "课程名称重复，请重新录入");
            req.getRequestDispatcher("add.jsp").forward(req,resp);
        }
    }
    
    /**
     * 全部
     * @param req
     * @param resp
     * @throws ServletException 
     */
    private void list(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        
        List<Course> courses = service.list();
        req.setAttribute("courses", courses);
        req.getRequestDispatcher("list.jsp").forward(req,resp);
    }

    /**
     * 通过ID得到Course
     * @param req
     * @param resp
     * @throws ServletException 
     */
    private void getCourseById(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(req.getParameter("id"));
        Course course = service.getCourseById(id);
        req.setAttribute("course", course);
        req.getRequestDispatcher("detail2.jsp").forward(req,resp);
    }

    /**
     * 通过名字查找
     * 跳转至删除
     * @param req
     * @param resp
     * @throws IOException
     * @throws ServletException 
     */
    private void getCourseByName(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        String name = req.getParameter("name");
        Course course = service.getCourseByName(name);
        if(course == null) {
            req.setAttribute("message", "查无此课程！");
            req.getRequestDispatcher("del.jsp").forward(req,resp);
        } else {
            req.setAttribute("course", course);
            req.getRequestDispatcher("detail.jsp").forward(req,resp);
        }
    }
    
    /**
     * 删除
     * @param req
     * @param resp
     * @throws IOException
     * @throws ServletException 
     */
    private void del(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(req.getParameter("id"));
        service.del(id);
        req.setAttribute("message", "删除成功！");
        req.getRequestDispatcher("del.jsp").forward(req,resp);
    }
    
    /**
     * 修改
     * @param req
     * @param resp
     * @throws IOException
     * @throws ServletException 
     */
    private void update(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(req.getParameter("id"));
        String name = req.getParameter("name");
        String teacher = req.getParameter("teacher");
        String classroom = req.getParameter("classroom");
        Course course = new Course(id, name, teacher, classroom);
        
        service.update(course);
        req.setAttribute("message", "修改成功");
        req.getRequestDispatcher("CourseServlet?method=list").forward(req,resp);
    }
    
    /**
     * 查找
     * @param req
     * @param resp
     * @throws ServletException 
     */
    private void search(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
        req.setCharacterEncoding("utf-8");
        String name = req.getParameter("name");
        String teacher = req.getParameter("teacher");
        String classroom = req.getParameter("classroom");
        List<Course> courses = service.search(name, teacher, classroom);
        req.setAttribute("courses", courses);
        req.getRequestDispatcher("searchlist.jsp").forward(req,resp);
    }
}

//DBUtil.java
package com.hjf.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 数据库连接工具
 * @author Hu
 *
 */
public class DBUtil {
    
    public static String db_url = "jdbc:mysql://localhost:3306/course";
    public static String db_user = "root";
    public static String db_pass = "root";
    
    public static Connection getConn () {
        Connection conn = null;
        
        try {
            Class.forName("com.mysql.jdbc.Driver");//加载驱动
            conn = DriverManager.getConnection(db_url, db_user, db_pass);
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return conn;
    }
    
    /**
     * 关闭连接
     * @param state
     * @param conn
     */
    public static void close (Statement state, Connection conn) {
        if (state != null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    public static void close (ResultSet rs, Statement state, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (state != null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws SQLException {
        Connection conn = getConn();
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        String sql ="select * from course";
        pstmt = conn.prepareStatement(sql);
        rs = pstmt.executeQuery();
        if(rs.next()){
            System.out.println("空");
        }else{
            System.out.println("不空");
        }
    }
}

//add.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <%
         Object message = request.getAttribute("message");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>
    <div align="center">
        <h1 style="color: black;">课程信息录入</h1>
        <a href="index.jsp">返回主页</a>
        <form action="CourseServlet?method=add" method="post" onsubmit="return check()">
            <div class="a">
                课程名称<input type="text" id="name" name="name"/>
            </div>
            <div class="a">
                任课教师<input type="text" id="teacher" name="teacher" />
            </div>
            <div class="a">
                上课地点<input type="text" id="classroom" name="classroom" />
            </div>
            <div class="a">
                <button type="submit" class="b">保&nbsp;&nbsp;&nbsp;存</button>
            </div>
        </form>
    </div>
    <script type="text/javascript">
        function check() {
            var name = document.getElementById("name");;
            var teacher = document.getElementById("teacher");
            var classroom = document.getElementById("classroom");
            
            //非空
            if(name.value == ‘‘) {
                alert(‘课程名称为空‘);
                name.focus();
                return false;
            }
            if(teacher.value == ‘‘) {
                alert(‘教师为空‘);
                teacher.focus();
                return false;
            }
            if(classroom.value == ‘‘) {
                alert(‘上课地点为空‘);
                classroom.focus();
                return false;
            }
            
            //教师
            if(teacher.value != ‘王建民‘ && teacher.value != ‘王辉‘ && teacher.value != ‘刘丹‘ && teacher.value != ‘刘立嘉‘ && teacher.value != ‘杨子光‘){
                alert(‘教师名称错误‘);
                return false;
            }
            
            //教室
            if(!/^基教/.test(classroom.value) && !/^一教/.test(classroom.value) && !/^二教/.test(classroom.value) && !/^三教/.test(classroom.value)) {
                alert(‘上课地点错误‘);
                return false;
            }
        }
    </script>
</body>
</html>

//del.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <%
         Object message = request.getAttribute("message");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>
    <div align="center">
        <h1 style="color: black;">课程信息删除</h1>
        <a href="index.jsp">返回主页</a>
        <form action="deleteservlet" method="post" onsubmit="return check()">
            <div class="a">
                课程名称<input type="text" id="classname" name="classname"/>
            </div>
            <div class="a">
                <button type="submit" class="b">查&nbsp;&nbsp;&nbsp;找</button>
            </div>
        </form>
    </div>
    <script type="text/javascript">
        function check() {
            var name = document.getElementById("classname");;
            
            //非空
            if(name.value == ‘‘) {
                alert(‘课程名称为空‘);
                name.focus();
                return false;
            }
        }
    </script>
</body>
</html>

//detail.jap
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style>
    .a{
        margin-top: 20px;
    }
    .b{
        font-size: 20px;
        width: 160px;
        color: white;
        background-color: greenyellow;
    }
    .tb, td {
        border: 1px solid black;
        font-size: 22px;
    }
</style>
</head>
<body>
    <div align="center">
        <h1 style="color: black;">课程信息删除</h1>
        <a href="index.jsp">返回主页</a>
        <table class="tb">
            <tr>
                <td>课程名称</td>
                <td>${list.classname}</td>
            </tr>
            <tr>
                <td>任课教师</td>
                <td>${list.teachnamr}</td>
            </tr>
            <tr>
                <td>上课地点</td>
                <td>${list.site}</td>
            </tr>
        </table>
        <div class="a">
            <a onclick="return check()" href="deleteservlet?method=post">删&nbsp;&nbsp;&nbsp;除</a>
        </div>
    </div>
    <script type="text/javascript">
        function check() {
            if (confirm("真的要删除吗？")){
                return true;
            }else{
                return false;
            }
        }
    </script>
</body>
</html>

//detail2.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <%
         Object message = request.getAttribute("message");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>
    <div align="center">
        <h1 style="color: black;">课程信息修改</h1>
        <a href="index.jsp">返回主页</a>
        <form action="CourseServlet?method=update" method="post" onsubmit="return check()">
            <div class="a">
                课程名称<input type="text" id="name" name="name" value="${course.name}"/>
            </div>
            <div class="a">
                任课教师<input type="text" id="teacher" name="teacher" value="${course.teacher}"/>
            </div>
            <div class="a">
                上课地点<input type="text" id="classroom" name="classroom" value="${course.classroom}"/>
            </div>
            <input type="hidden" id="id" name="id" value="${course.id}"/>
            <div class="a">
                <button type="submit" class="b">修&nbsp;&nbsp;&nbsp;改</button>
            </div>
        </form>
    </div>
    <script type="text/javascript">
        function check() {
            var name = document.getElementById("name");;
            var teacher = document.getElementById("teacher");
            var classroom = document.getElementById("classroom");
            
            //非空
            if(name.value == ‘‘) {
                alert(‘课程名称为空‘);
                name.focus();
                return false;
            }
            if(teacher.value == ‘‘) {
                alert(‘教师为空‘);
                teacher.focus();
                return false;
            }
            if(classroom.value == ‘‘) {
                alert(‘上课地点为空‘);
                classroom.focus();
                return false;
            }
            
            //教师
            if(teacher.value != ‘王建民‘ && teacher.value != ‘王辉‘ && teacher.value != ‘刘丹‘ && teacher.value != ‘刘立嘉‘ && teacher.value != ‘杨子光‘){
                alert(‘教师名称错误‘);
                return false;
            }
            
            //教室
            if(!/^基教/.test(classroom.value) && !/^一教/.test(classroom.value) && !/^二教/.test(classroom.value) && !/^三教/.test(classroom.value)) {
                alert(‘上课地点错误‘);
                return false;
            }
        }
    </script>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>首页</title>

</head>
<body>
    <div align="center">
        
        <div class="a">
            <a href="add.jsp">课程信息添加</a>
        </div>
        <div class="a">
            <a href="CourseServlet?method=list">课程信息修改</a>
        </div>
        <div class="a">
            <a href="del.jsp">课程信息删除</a>
        </div>
        <div class="a">
            <a href="search.jsp">课程信息查询</a>
        </div>
    </div>
</body>
</html>

//list.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <%
         Object message = request.getAttribute("message");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>
    <div align="center">
        <h1 style="color: black;">课程信息列表</h1>
        <a href="index.jsp">返回主页</a>
        <table class="tb">
            <tr>
                <td>id</td>
                <td>课程名称</td>
                <td>任课教师</td>
                <td>上课地点</td>
                <td align="center" colspan="2">操作</td>
            </tr>
            <c:forEach items="${courses}" var="item">
                <tr>
                    <td>${item.id}</td>
                    <td>${item.name}</td>
                    <td>${item.teacher}</td>
                    <td>${item.classroom}</td>
                    <td><a href="CourseServlet?method=getcoursebyid&id=${item.id}">修改</a></td>
                </tr>
            </c:forEach>
        </table>
    </div>
</body>
</html>

//search.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <div align="center">
        <h1 style="color: black;">课程信息查询</h1>
        <a href="index.jsp">返回主页</a>
        <form action="CourseServlet?method=search" method="post" onsubmit="return check()">
            <div class="a">
                课程名称<input type="text" id="name" name="name"/>
            </div>
            <div class="a">
                任课教师<input type="text" id="teacher" name="teacher" />
            </div>
            <div class="a">
                上课地点<input type="text" id="classroom" name="classroom" />
            </div>
            <div class="a">
                <button type="submit" class="b">查&nbsp;&nbsp;&nbsp;询</button>
            </div>
        </form>
    </div>
    <script type="text/javascript">
        function check() {
            var name = document.getElementById("name");;
            var teacher = document.getElementById("teacher");
            var classroom = document.getElementById("classroom");
            
            //非空
            if(name.value == ‘‘ && teacher.value == ‘‘ && classroom.value == ‘‘) {
                alert(‘请填写一个条件‘);
                return false;
            }
        }
    </script>
</body>
</html>

//searchlist.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

</head>
<body>
    <div align="center">
        <h1 style="color: black;">课程信息列表</h1>
        <a href="index.jsp">返回主页</a>
        <table class="tb">
            <tr>
                <td>id</td>
                <td>课程名称</td>
                <td>任课教师</td>
                <td>上课地点</td>
            </tr>
            <!-- forEach遍历出adminBeans -->
            <c:forEach items="${courses}" var="item" varStatus="status">
                <tr>
                    <td>${item.id}</td>
                    <td><a>${item.name}</a></td>
                    <td>${item.teacher}</td>
                    <td>${item.classroom}</td>
                </tr>
            </c:forEach>
        </table>
    </div>
</body>
</html>