From 421e82c1ae30b85b1cff3cbe55b72f1c14b5b926 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9D=8E=E6=AC=A3?= <3188923799@qq.com>
Date: Sat, 27 May 2023 02:51:10 +0800
Subject: [PATCH] tree

---
 .../20230526 \344\275\234\344\270\232.md"     | 240 ++++++++++++++++++
 1 file changed, 240 insertions(+)
 create mode 100644 "31 \346\235\216\346\254\243/20230526 \344\275\234\344\270\232.md"

diff --git "a/31 \346\235\216\346\254\243/20230526 \344\275\234\344\270\232.md" "b/31 \346\235\216\346\254\243/20230526 \344\275\234\344\270\232.md"
new file mode 100644
index 0000000..5509487
--- /dev/null
+++ "b/31 \346\235\216\346\254\243/20230526 \344\275\234\344\270\232.md"	
@@ -0,0 +1,240 @@
+```java
+import java.sql.*;
+public class DBUtil {
+    private static final String url="jdbc:mysql://localhost:3306/student_db?useSSL=false&useUnicode=true&characterEncoding=utf8";
+    private static final String name="root";
+    private static final String pwd = "root";
+    static {
+        try {
+            Class.forName("com.mysql.jdbc.Driver");
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException(e);
+        }
+    }
+    public static Connection getConn() throws SQLException {
+        Connection conn = DriverManager.getConnection(url, name, pwd);
+        return conn;
+    }
+    public static ResultSet query(String sql,String ...keys) throws SQLException {
+        Connection conn = getConn();
+        PreparedStatement pr = conn.prepareStatement(sql);
+        for (int i = 0; i < keys.length; i++) {
+            pr.setString((i+1),keys[i]);
+        }
+        ResultSet re = pr.executeQuery();
+        return re;
+    }
+    public static int update(String sql,String ...keys) throws SQLException {
+        Connection conn = getConn();
+        PreparedStatement pr = conn.prepareStatement(sql);
+        for (int i = 0; i < keys.length; i++) {
+            pr.setString((i+1),keys[i]);
+        }
+        int i = pr.executeUpdate();
+        return i;
+    }
+    public static void close(Connection conn,PreparedStatement pst,ResultSet rst) throws SQLException {
+        if (rst!=null){
+            rst.close();
+        }
+        if (pst!=null){
+            pst.close();
+        }
+        if (conn!=null){
+            conn.close();
+        }
+    }
+}
+
+```
+
+```java
+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 java.io.IOException;
+import java.sql.SQLException;
+@WebServlet("/insert")
+public class Insert extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        super.doGet(req, resp);
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        String sql= "insert into student values(?,?,?)";
+        String id = req.getParameter("id");
+        String name = req.getParameter("name");
+        String age = req.getParameter("age");
+        int i = 0;
+        try {
+            i = DBUtil.update(sql,id,name,age);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        if (i>0){
+            System.out.println("添加成功");
+        }else{
+            System.out.println("添加失败了");
+        }
+    }
+}
+
+```
+
+```java
+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 java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+@WebServlet("/select")
+public class Select extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        super.doGet(req, resp);
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        String sql= "select * from student";
+        try {
+            ResultSet rs = DBUtil.query(sql);
+            while (rs.next()){
+                int id = rs.getInt(1);
+                String name = rs.getString(2);
+                String age = rs.getString(3);
+                resp.getWriter().write("编号："+id+","+name+","+age);
+            }
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}
+
+```
+
+```java
+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 java.io.IOException;
+import java.sql.SQLException;
+@WebServlet("/delete")
+public class Delete extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        super.doGet(req, resp);
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        String sql= "delete from student set name=? where id=?";
+        String id = req.getParameter("id");
+        String name = req.getParameter("name");
+        String age = req.getParameter("age");
+        int i = 0;
+        try {
+            i = DBUtil.update(sql,id,name,age);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        if (i>0){
+            resp.getWriter().write("删除成功");
+        }else{
+            resp.getWriter().write("删除失败了");
+        }
+    }
+}
+
+```
+
+```java
+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 java.io.IOException;
+import java.sql.SQLException;
+@WebServlet("/update")
+public class Update extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        super.doGet(req, resp);
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        String sql= "update student set name=? where id=?";
+        String id = req.getParameter("id");
+        String name = req.getParameter("name");
+        String age = req.getParameter("age");
+        int i = 0;
+        try {
+            i = DBUtil.update(sql,id,name,age);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        if (i>0){
+            resp.getWriter().write("更新成功");
+        }else{
+            resp.getWriter().write("更新失败了");
+        }
+    }
+}
+
+```
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>测试</title>
+</head>
+<body>
+    <h1>查询学生</h1>
+<form action="./select" method="post">
+    <input type="submit" value="查询">
+</form>
+<h1>添加学生</h1>
+<form action="./insert" method="post">
+    学号 <input type="text" name="id"><br>
+    姓名 <input type="text" name="name"><br>
+    年龄 <input type="text" name="age"><br>
+    <input type="submit" value="添加">
+</form>
+
+<h1>修改学生信息</h1>
+<form action="./update" method="post">
+    学号 <input type="text" name="id1"><br>
+    姓名 <input type="text" name="name1"><br>
+    <input type="submit" value="修改">
+</form>
+
+<h1>删除学生</h1>
+<form action="./delect" method="post">
+    学号 <input type="text" name="id2"> <br>
+    <input type="submit" value="删除">
+</form>
+</body>
+</html>
+```
+
-- 
Gitee