diff --git "a/42 \345\210\230\351\253\230\347\247\221/zuoye03.md" "b/42 \345\210\230\351\253\230\347\247\221/zuoye03.md"
new file mode 100644
index 0000000000000000000000000000000000000000..9ad05ddcfbf978597b202241f648276df0c98a23
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@@ -0,0 +1,149 @@
+```java
+import javax.servlet.*;
+import javax.servlet.http.*;
+import javax.servlet.annotation.*;
+import java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+@WebServlet("/Servlet")
+public class Servlet extends HttpServlet {
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        String sql="SELECT * FROM student; ";
+        response.setContentType("text/html;charset=utf-8");
+
+        try {
+            ResultSet rs = DBUtil.select(sql);
+            while (rs.next()){
+                int id =rs.getInt("id");
+                String name= rs.getString("name");
+                String sex= rs.getString("sex");
+                System.out.println(id+name+sex);
+                response.getWriter().write(id+name+sex);
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        request.setCharacterEncoding("utf-8");
+    String id =request.getParameter("id");
+    String name = request.getParameter("name");
+    String sex = request.getParameter("sex");
+
+
+    System.out.println("id="+id);
+    System.out.println("name="+name);
+    System.out.println("sex="+sex);
+    String sql="insert into student VALUES (?,?,?)";
+    response.setContentType("text/html;charset=utf-8");
+        try {
+         int i = DBUtil.Update(sql,id,name,sex);
+         if(i>0){
+             response.getWriter().write("成功");
+         }else {
+             response.getWriter().write("失败");
+         }
+        } catch (SQLException e) {
+          e.printStackTrace();
+        }
+    }
+
+    @Override
+    protected void doHead(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        req.setCharacterEncoding("utf-8");
+        resp.setContentType("text/html;charset=utf-8");
+        String sql="SELECT * FROM student WHERE id=?";
+        try {
+            String id =req.getParameter("id");
+            int rs = DBUtil.Update(sql,id);
+            if(rs>0){
+                resp.getWriter().write("成功");
+            }else {
+                resp.getWriter().write("失败");
+            }
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+    }
+    
+}
+```
+
+```java
+import java.sql.*;
+import java.sql.SQLException;
+
+public class DBUtil {
+    private final static String url ="jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+    private final static String name = "root";
+    private final static String password = "root";
+    static {
+        try{
+            Class.forName("com.mysql.jdbc.Driver");
+        }
+        catch (ClassNotFoundException e){
+            e.printStackTrace();
+        }
+    }
+    public static Connection getCon() throws SQLException{
+        Connection conn =   DriverManager.getConnection(url,name,password);
+        return conn;
+
+    }
+    public static ResultSet select(String sql,String ...key) throws SQLException{
+        Connection conn =getCon();
+        PreparedStatement state = conn.prepareStatement(sql);
+        for (int i = 0; i < key.length; i++) {
+            state.setString(i,key[i]);
+        }
+        ResultSet res = state.executeQuery();
+        return res;
+    }
+    public static int Update(String url,String ...key) throws SQLException{
+        Connection conn = getCon();
+        PreparedStatement state = conn.prepareStatement(url);
+        for (int i = 0; i < key.length; i++) {
+            state.setString(i+1,key[i]);
+        }
+        int res = state.executeUpdate();
+        return res;
+    }
+}
+```
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>添加学生</title>
+</head>
+<body>
+    <h1>添加学生</h1>
+    <form  action="./Servlet" method="post">
+        编号<input type="text" name="id"><br>
+        姓名<input type="text" name="name"><br>
+        性别<input type="text" name="sex"><br>
+        <input type="submit" value="添加">
+    </form>
+    <form action="./Servlet" method="post">
+        要删除的学生的编号：<input type="text" name="id"><br>
+       <input type="submit" name="提交">
+</form>
+<h1>修改学生</h1>
+<form action="http://localhost:8080/untitled_war_exploded/update" method="post">
+    需要修改学生的id: <input type="text" name="changeID"><br>
+    新的学生id：<input type="text" name="id"><br>
+    姓名：<input type="text" name="name"><br>
+    性别:<input type="text" name="sex"><br>
+    <input type="submit" name="提交">
+		</form>
+	</body>
+</html>
+```
+