2019-02-20

```

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.sql.*;

//导入必需的 java 库

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

// 扩展 HttpServlet 类

public class a extends HttpServlet {

  private String message;

  private String name;

  public void init() throws ServletException

  {

  System.out.println("连接数据库...");

  // 执行必需的初始化

      message = "Hello World";

      String JDBC_DRIVER = "com.mysql.jdbc.Driver"; 

      String DB_URL = "jdbc:mysql://cdb-4gsyv8oy.bj.tencentcdb.com:10071/rdk";

      // 数据库的用户名与密码，需要根据自己的设置

      String USER = "root";

      String PASS = "1qazxsw2";

      Connection conn = null;

      Statement stmt = null;

      System.out.println("123...");

      try {

Class.forName("com.mysql.jdbc.Driver");

// 打开链接

System.out.println("连接数据库...");

conn = DriverManager.getConnection(DB_URL, USER, PASS);

// 执行查询

System.out.println(" 实例化Statement对象...");

stmt = conn.createStatement();

String sql;

sql = "SELECT id, name, url FROM websites";

ResultSet rs = stmt.executeQuery(sql);

name = "没有脸上数据库";

while(rs.next()){

            // 通过字段检索

            int id  = rs.getInt("id");

            name = rs.getString("name");

            String url = rs.getString("url");

            // 输出数据

            System.out.print("ID: " + id);

            System.out.print(", 站点名称: " + name);

            System.out.print(", 站点 URL: " + url);

            System.out.print("\n");

        }

        // 完成后关闭

        rs.close();

        stmt.close();

        conn.close();

} catch (Exception e) {

System.out.println(" 实例化Statement对象...");

e.printStackTrace();

}

  }

  public void doGet(HttpServletRequest request,

                    HttpServletResponse response)

            throws ServletException, IOException

  {

      // 设置响应内容类型

      response.setContentType("text/html");

      // 实际的逻辑是在这里

      PrintWriter out = response.getWriter();

      out.println("<h1>" + message + "</h1>");

      out.println("<h1>" + name + "</h1>");

  }

  public void destroy()

  {

      // 什么也不做

  }

}

```