java-web与jdbc 的使用

1：本地连接数据库的步骤

 1 public class LoginDao {
 2
 3     // jdbc操作的五部曲
 4
 5     // 1: 导入jar包
 6     // 2: 加载驱动
 7     // 3: 获取连接
 8     // 4: 预处理
 9     // 5: 执行SQL
10     // 6: 处理结果集
11     // 7: 关闭连接
12
13     static String url = "jdbc:mysql://127.0.0.1:3306/week11";
14     static String name = "root";
15     static String pass = "root";
16
17     public static void main(String[] args) {
18
19         try {
20             // 加载驱动
21             Class.forName("com.mysql.jdbc.Driver");
22             // 获取连接
23             Connection connection = (Connection) DriverManager.getConnection(url, name, pass);
24
25             String sql = "select * from t_admin where aname=? and apass=?";
26             // 预处理SQL语句
27             PreparedStatement ps = (PreparedStatement) connection.prepareStatement(sql);
28
29             // 设置预处理SQL的参数
30             ps.setObject(1, "dabu");
31             ps.setObject(2, "123");
32
33             // 执行查询
34             ResultSet rs = ps.executeQuery();
35
36             // 如果查询到了数据
37             if (rs.next()) {
38                 System.out.println("查询成功");
39             } else {
40                 System.err.println("查询失败");
41             }
42
43         } catch (Exception e) {
44
45             e.printStackTrace();
46         }
47
48     }

 2：与web相结合

 1 @WebServlet("/LoginServlet")
 2 public class LoginServlet extends HttpServlet {
 3     private static final long serialVersionUID = 1L;
 4
 5     public LoginServlet() {
 6         // TODO Auto-generated constructor stub
 7     }
 8
 9     protected void doGet(HttpServletRequest request, HttpServletResponse response)
10             throws ServletException, IOException {
11         // TODO Auto-generated method stub
12         response.getWriter().append("Served at: ").append(request.getContextPath());
13     }
14
15     protected void doPost(HttpServletRequest request, HttpServletResponse response)
16             throws ServletException, IOException {
17         // TODO Auto-generated method stub
18         doGet(request, response);
19     }
20
21     static String url = "jdbc:mysql://127.0.0.1:3306/week11?useUnicode=true&characterEncoding=utf-8&useSSL=false";
22     static String name = "root";
23     static String pass = "root";
24
25     @Override
26     protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
27
28         // 获取浏览器发过来的值
29         HttpServletRequest req = (HttpServletRequest) arg0;
30
31         //这个方法负责具体的实践
32         HttpServletResponse sr=(HttpServletResponse)arg1;
33         PrintWriter out=sr.getWriter();
34
35         // 获取前台传过来的值
36         String userName = req.getParameter("username");
37         String userPass = req.getParameter("userpass");
38
39         // 去数据库里面查询有没有
40         // 2: 加载驱动
41         // 3: 获取连接
42         // 4: 预处理
43         // 5: 执行SQL
44         // 6: 处理结果集
45         // 7: 关闭连接
46
47         String sql = "select * from t_admin where aname=? and apass=?";
48
49         Connection connection=null;
50         PreparedStatement ps=null;
51         ResultSet rs=null;
52         try {
53
54             //加载驱动
55             Class.forName("com.mysql.jdbc.Driver");
56             //获取连接
57             connection = (Connection) DriverManager.getConnection(url, name, pass);
58             //预处理SQL
59             ps = (PreparedStatement) connection.prepareStatement(sql);
60
61
62             //设置从前台取出来的参数
63             ps.setString(1,"username");
64             ps.setString(2,"userpass");
65             //执行查询得到结果集
66             rs=ps.executeQuery();
67             //判断结果
68             if(rs.next()){
69                 out.print("login success");
70             }else {
71                 out.print("login fail");
72             }
73
74         } catch (Exception e) {
75
76             e.printStackTrace();
77         }finally {
78
79             try {
80                 rs.close();
81                 ps.close();
82                 connection.close();
83             } catch (SQLException e) {
84                 // TODO Auto-generated catch block
85                 e.printStackTrace();
86             }
87
88         }
89     }

login.jsp页面：

 1 <body>
 2     <!--
 3         action:当前表单提交的那个路径
 4         method:当前表单提交的方式
 5         name:对应我们的servlet去获取前台的值
 6
 7           -->
 8     <form action="LoginServlet" method="get">
 9
10         用户名：<input name="username" type="text"/>
11         密码：<input name="userpass" type="password"/>
12
13         <!-- 默认是submit -->
14         <button>提交</button>
15     </form>
16 </body>

结果：