From 65c2cd6c01dc2fb92f01854a1ce15bad73eae348 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BC=A0=E8=B5=B7=E7=91=9E?= <3148024859@qq.com>
Date: Thu, 25 May 2023 12:58:18 +0800
Subject: [PATCH] =?UTF-8?q?=E7=AC=AC=E4=B8=89=E6=AC=A1=E4=BD=9C=E4=B8=9A?=
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diff --git "a/50 \345\274\240\350\265\267\347\221\236/20230523   tomcat.md" "b/50 \345\274\240\350\265\267\347\221\236/20230523   tomcat.md"
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+## Web连接数据库
+
+## 查询
+
+```java
+import com.mysql.jdbc.util.ResultSetUtil;
+
+import java.sql.*;
+import java.util.concurrent.locks.Condition;
+
+public class Day01 {
+    private static String url="jdbc:mysql:///student_db?useSSL=false&characterEncoding=utf8";
+    private static String user="root";
+    private static String password="root";
+    static {
+        try {
+            Class.forName("com.mysql.jdbc.Driver");
+        } catch (ClassNotFoundException e) {
+            e.printStackTrace();
+            System.out.println("驱动包异常");
+        }
+    }
+    public static Connection getconn(){
+        Connection conn = null;
+        try {
+            conn = DriverManager.getConnection(url, user, password);
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return conn;
+    }
+    public static ResultSet query(String sql, String ...key){
+        ResultSet rs = null;
+        try {
+            Connection ge = getconn();
+            PreparedStatement prt = ge.prepareStatement(sql);
+            for (int i = 0; i < key.length; i++) {
+                prt.setString((i+1),key[i]);
+            }
+            rs = prt.executeQuery();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return rs;
+    }
+}
+
+```
+
+### 查询测试类
+
+```java
+@WebServlet("/stu")
+public class SelectTest extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        PrintWriter wr = resp.getWriter();
+        String sql="select * from studen";
+        ResultSet que =Select.query(sql);
+        wr.write("<table border=1>");
+        wr.write("<tr><th>编号</th><th>姓名</th><th>性别</th></tr>");
+        try {
+            while (que.next()){
+                String id=que.getString(1);
+                String name=que.getString(2);
+                String sex= que.getString(3);
+                wr.write("<tr><td>"+id+"</td><td>"+name+"</td><td>"+sex+"</td></tr>");
+            }
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        wr.write("</table>");
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        super.doPost(req, resp);
+    }
+}
+
+```
+
+## 增删改
+
+```java
+public class ZenSanGai {
+    private static String url="jdbc:mysql:///student_db?useSSL=false&characterEncoding=utf8";
+    private static String user="root";
+    private static String password="root";
+    static {
+        try {
+            Class.forName("com.mysql.jdbc.Driver");
+        } catch (ClassNotFoundException e) {
+            e.printStackTrace();
+            System.out.println("驱动包加载异常");
+        }
+    }
+    public static Connection getconn(){
+        Connection conn = null;
+        try {
+            conn = DriverManager.getConnection(url, user, password);
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return conn;
+    }
+    public static int query(String sql, String ...key) {
+        int ii = 0;
+        try {
+            Connection ge = getconn();
+            PreparedStatement prt = ge.prepareStatement(sql);
+            for (int i = 0; i < key.length; i++) {
+                prt.setString((i + 1), key[i]);
+            }
+            ii = prt.executeUpdate();
+        } catch (SQLException e) {
+            e.printStackTrace();
+        }
+        return ii;
+    }
+}
+
+```
+
+### 增删改测试类
+
+```java
+@WebServlet("/up")
+public class ZenSanGaiTest extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=utf-8");
+        resp.setCharacterEncoding("utf-8");
+        PrintWriter wr = resp.getWriter();
+        String sql="update studen set name='新名字' where id=1";//修改
+//        String sql="delete from studen where id=1";//删除
+//        String sql="insert into studen values(1,'二星代瑞代')";//添加
+        try {
+            int que = ZenSanGai.query(sql);
+            wr.write("修改成功！");
+        } catch (Exception e) {
+            wr.write("修改失败！");
+        }
+    }
+```
+
-- 
Gitee