1、怎么做？

• 在Servlet中直接编写Java代码即可（JDBC）
• 需要将驱动jar包拷贝到webapps\crm\WEB-INF\lib目录下

  2、实现连接数据库

  ```java package Servlet;

/**

• @Author: 小雷学长
• @Date: 2022/3/16 - 10:06
• @Version: 1.8 */

import jakarta.servlet.Servlet; import jakarta.servlet.ServletException; import jakarta.servlet.*;

import java.io.IOException;

import java.io.IOException; import java.io.PrintWriter; import java.sql.*;

public class StudentServlet implements Servlet {

public void init(ServletConfig config)
        throws ServletException {
}
public void service(ServletRequest request, ServletResponse response)
        throws ServletException, IOException {
    /*
    打印到浏览器上
     */
    response.setContentType("text/html");
    //返回out
    PrintWriter out = response.getWriter();
    /*
    编写JDBC代码，连接数据，查询所有信息
     */
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try {
        //注册驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //获取连接
        String url = "jdbc:mysql://localhost:3306/practice";
        String user = "root";
        String password = "123456";
        conn = DriverManager.getConnection(url, user, password);
        //获取预编译的数据库操作对象
        String sql = "select id,informant_name from t_student";
        ps = conn.prepareStatement(sql);
        //执行SQL
        rs = ps.executeQuery();
        //处理查询结果集
        while (rs.next()) {
            String id = rs.getString("id");
            String informant_name = rs.getString("informant_name");
            //打印out
            out.print(id + "," + informant_name + "<br>");
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        //释放资源
        if (rs != null) {
            try {
                rs.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        if (ps != null) {
            try {
                ps.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}
public void destroy() {
}
public String getServletInfo() {
    return "";
}
public ServletConfig getServletConfig() {
    return null;
}

}

```