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@@ -0,0 +1,427 @@
+# 考勤系统
+
+### 工具类
+
+```java
+package tool;
+
+import java.sql.*;
+
+public class DbUTIl {
+    //数据块的主机名，端口号，数据库名
+    private String url="jdbc:mysql:///attdb?useSSL=false&useUnicode=true&characterEncoding=utf8";
+    private String user="root";
+    private String password="root";
+
+    //注册驱动
+    static {
+        try {
+            Class.forName("com.mysql.jdbc.Driver");
+        } catch (ClassNotFoundException e) {
+            System.out.println("注册驱动异常");
+            e.printStackTrace();
+        }
+    }
+    //获取连接对象
+    public static Connection getConn(){
+        Connection conn = null;
+        try {
+            conn = DriverManager.getConnection("url", "user", "password");
+        } catch (SQLException e) {
+            e.printStackTrace();
+            System.out.println("连接对象失败");
+        }
+        return conn;
+    }
+    //通用查询方法
+    public static ResultSet query(String sql,Object... keys){
+        ResultSet res =null;
+        try {
+            //获取连接对象
+            Connection conn = getConn();
+            //预编译对象
+            PreparedStatement pre= conn.prepareStatement(sql);
+            for (int i = 0; i < keys.length; i++) {
+                pre.setObject((i+1),keys[i]);
+            }
+            //执行SQL语句
+            res = pre.executeQuery();
+        } catch (SQLException e) {
+            e.printStackTrace();//打印错误
+            System.out.println("通用查询方法发生错误");
+        }
+        return res;
+    }
+
+    //通用增加、删除、修改方法
+    public static int update(String sql,Object... keys){
+        int num =0;
+        try {
+            //获取连接对象
+            Connection conn = getConn();
+            //预编译对象
+            PreparedStatement pre= conn.prepareStatement(sql);
+            for (int i = 0; i < keys.length; i++) {
+                pre.setObject((i+1),keys[i]);
+            }
+            //执行SQL语句
+           num = pre.executeUpdate();
+        } catch (SQLException e) {
+            e.printStackTrace();//打印错误
+            System.out.println("通用查询方法发生错误");
+        }
+        return num;
+    }
+}
+
+```
+
+###  Student
+
+```java
+package dao;
+
+public class Student {
+    int sid;
+    String sname;
+
+    public Student() {
+    }
+
+    public Student(int sid, String sname) {
+        this.sid = sid;
+        this.sname = sname;
+    }
+
+    public int getSid() {
+        return sid;
+    }
+
+    public void setSid(int sid) {
+        this.sid = sid;
+    }
+
+    public String getSname() {
+        return sname;
+    }
+
+    public void setSname(String sname) {
+        this.sname = sname;
+    }
+
+    @Override
+    public String toString() {
+        return "Student{" +
+                "sid=" + sid +
+                ", sname='" + sname + '\'' +
+                '}';
+    }
+}
+
+```
+
+### Attence
+
+````java
+package dao;
+
+public class Attence {
+    int aid;//考勤编号
+    int sid;//学生编号
+    String sname;//学生姓名
+    String time;//出勤时间
+    int type;//出勤状况
+
+    public Attence() {
+    }
+
+    public Attence(int aid, int sid, String sname, String time, int type) {
+        this.aid = aid;
+        this.sid = sid;
+        this.sname = sname;
+        this.time = time;
+        this.type = type;
+    }
+
+    public int getAid() {
+        return aid;
+    }
+
+    public void setAid(int aid) {
+        this.aid = aid;
+    }
+
+    public int getSid() {
+        return sid;
+    }
+
+    public void setSid(int sid) {
+        this.sid = sid;
+    }
+
+    public String getSname() {
+        return sname;
+    }
+
+    public void setSname(String sname) {
+        this.sname = sname;
+    }
+
+    public String getTime() {
+        return time;
+    }
+
+    public void setTime(String time) {
+        this.time = time;
+    }
+
+    public int getType() {
+        return type;
+    }
+
+    public void setType(int type) {
+        this.type = type;
+    }
+
+    @Override
+    public String toString() {
+        return "Attence{" +
+                "aid=" + aid +
+                ", sid=" + sid +
+                ", sname='" + sname + '\'' +
+                ", time='" + time + '\'' +
+                ", type=" + type +
+                '}';
+    }
+}
+
+````
+
+###
+
+```java
+package all;
+
+import dao.Attence;
+import dao.Student;
+import tool.DbUTIl;
+
+import javax.servlet.*;
+import javax.servlet.http.*;
+import javax.servlet.annotation.*;
+import java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+
+@WebServlet("/AddServlet")
+public class AddServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        //定义SQL语句
+        String sql ="select * from student";
+        //执行SQL语句
+        ResultSet re = DbUTIl.query(sql);
+        ArrayList<Student> list = new ArrayList<>();
+        try {
+            while (re.next()){
+                int sid = re.getInt(sid);
+                String sname = re.getString(sname);
+                Student stu = new Student(sid, sname);
+                list.add(stu);
+            }
+        } catch (SQLException e) {
+            e.getStackTrace();//打印错误
+            System.out.println("addserviet发生错误");
+        }
+        System.out.println(list);//输出结果
+        //将集合转发给all.jsp
+        request.setAttribute("stuList",list);//将集合放在请求域中
+       //跳到一个JSP中
+        request.getRequestDispatcher("/WEB-INF/add.jsp").forward(request,response);
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+//接受表单数据，做处理后，添加到数据库的attence
+        //处理乱码问题
+        request.setCharacterEncoding("utf-8");
+        //通过表单的name参数取得表单项的值
+        String sid =request.getParameter("sid");
+        String time =request.getParameter("time");
+        String type =request.getParameter("type");
+        //编写SQL语句
+        String sql ="insert into attence values (?,?,?,?)";
+        int i = DbUTIl.update(sql, null, time, type);
+        if (i >0) {
+            request.setAttribute("msg","添加成功");
+            request.getRequestDispatcher("/WEB-INF/msg.jsp").forward(request,response);
+        }else {
+            request.setAttribute("msg","添加失败");
+            request.getRequestDispatcher("/WEB-INF/msg.jsp").forward(request,response);
+
+        }
+    }
+}
+
+```
+
+### 
+
+```java
+package all;
+
+import dao.Attence;
+import tool.DbUTIl;
+
+import javax.servlet.*;
+import javax.servlet.http.*;
+import javax.servlet.annotation.*;
+import java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+
+@WebServlet("/stu")
+public class SelectServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        ArrayList<Attence> list = new ArrayList<>();
+        //定义SQL语句
+        String sql ="select * from attence a ,student s where a.sid=s.sid";
+        //执行SQL语句
+        ResultSet re = DbUTIl.query(sql);
+        try {
+            while (re.next()){
+                int aid = re.getInt(1);
+                int sid = re.getInt(2);
+                String name = re.getString(3);
+                String time = re.getString(4);
+                int type = re.getInt(5);
+                Attence att = new Attence(aid,sid , name, time, type);
+                list.add(att);
+            }
+        } catch (SQLException e) {
+            e.getStackTrace();//打印错误
+            System.out.println("selectserviet发生错误");
+        }
+        System.out.println(list);//输出结果
+        //将集合转发给all.jsp
+        request.setAttribute("stuList",list);//将集合放在请求域中
+        request.getRequestDispatcher("/WEB-INF/all.jsp").forward(request,response);
+
+
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+
+    }
+}
+
+```
+
+### 
+
+```java
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
+<%@ page contentType="text/html;charset=UTF-8" language="java" %>
+<html>
+<head>
+    <title>Title</title>
+</head>
+<body>
+<h1><a href="/stu/add">添加</a></h1>
+<hr>
+<table border="1" width="200">
+    <tr>
+        <th>考勤编号</th>
+        <th>学生编号</th>
+        <th>学生姓名</th>
+        <th>出勤时间</th>
+        <th>出勤状况</th>
+    </tr>
+<%-- list集合要遍历，需要attence库--%>
+    <c:forEach items="${stuList}" var="student">
+        <tr>
+            <td>${student.aid}</td>
+            <td>${student.sid}</td>
+            <td>${student.name}</td>
+            <td>${student.time}</td>
+            <td>
+                <c:if test="${student.type == 1}" >
+                    已到
+                </c:if>
+                <c:if test="${student.type == 2}" >
+                    迟到
+                </c:if>
+                <c:if test="${student.type == 3}" >
+                    早退
+                </c:if>
+            </td>
+        </tr>
+    </c:forEach>
+</table>
+</body>
+</html>
+
+```
+
+### 
+
+```java
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
+<%@ page contentType="text/html;charset=UTF-8" language="java" %>
+<html>
+<head>
+    <title>添加考勤</title>
+<%--    表单--%>
+</head>
+<body>
+<center><h1>学生考勤系统</h1></center>
+<table border="1">
+    <tr>
+        <td>学生姓名</td>
+<%--        遍历--%>
+        <td><select name="sid" id="">
+          <c:forEach items="${stu}" var="list">
+              <option value="${list.sid}">${stu.sname}</option>
+          </c:forEach>
+        </select></td>
+    </tr>
+    <tr>
+        <td>添加时间</td>
+        <td><input type="date" name="time"></td>
+    </tr>
+    <tr>
+        <td>考勤状态</td>
+        <td>
+            已到 <input type="radio" value="1" name="type">
+            迟到 <input type="radio" value="2" name="type">
+            旷课 <input type="radio" value="3" name="type">
+        </td>
+    </tr>
+    <tr>
+        <td colspan="2"><input type="submit" value="添加"></td>
+    </tr>
+</table>
+</body>
+</html>
+
+```
+
+### 
+
+```java
+<%@ page contentType="text/html;charset=UTF-8" language="java" %>
+<html>
+<head>
+    <title>提示信息</title>
+</head>
+<body>
+<h1>${msg}</h1>
+</body>
+</html>
+
+```
+