JavaWeb技术（三）：JDBC中核心接口

 1 import java.sql.Connection;
 2 import java.sql.DriverManager;
 3 import java.sql.SQLException;
 4 
 5 public class DriverManagerDemo {
 6     
 7     public static void main(String[] args) {
 8         // 数据库连接引用变量
 9         Connection conn = null;
10         
11         // 加载数据库驱动程序
12         try {
13             Class.forName("com.mysql.jdbc.Driver");
14         } catch (ClassNotFoundException e) {
15             e.printStackTrace();
16         }
17         
18         try {
19             // 获取数据库连接对象
20             conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctest", "root", "1234");
21         } catch (SQLException e) {
22             e.printStackTrace();
23         }
24     }
25 }

 1 import java.io.FileReader;
 2 import java.io.Reader;
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.SQLException;
 6 import java.util.Properties;
 7 
 8 /** 动态获取数据库连接参数 */
 9 public class DBUtil {
10     private static String driver;
11     private static String url;
12     private static String username;
13     private static String password;
14 
15     // 静态代码块，初始化成员变量
16     static {
17         Properties prop = new Properties();
18         Reader in;
19         try {
20             in = new FileReader("src\\dbconfig.properties");
21             // 从输入流中加载配置文件
22             prop.load(in);
23             
24         } catch (Exception e) {
25             e.printStackTrace();
26         }
27 
28         driver = prop.getProperty("driver");
29         url = prop.getProperty("url");
30         username = prop.getProperty("username");
31         password = prop.getProperty("password");
32     }
33 
34     // 获得一个数据库连接
35     public static Connection open() {
36         try {
37             Class.forName(driver);
38             return DriverManager.getConnection(url, username, password);
39         } catch (Exception e) {
40             e.printStackTrace();
41         }
42 
43         // 抛出异常，方法返回null
44         return null;
45     }
46 
47     // 关闭数据库连接
48     public static void close(Connection conn) {
49         if (conn != null) {
50             try {
51                 conn.close();
52             } catch (SQLException e) {
53                 e.printStackTrace();
54             }
55         }
56     }
57 }

 1 import java.sql.Connection;
 2 import java.sql.ResultSet;
 3 import java.sql.SQLException;
 4 import java.sql.Statement;
 5 
 6 public class StatementDemo {
 7 
 8     public static void main(String[] args) {
 9         String sql = "update from CustomerTb1 set name=? where id=?";
10         Connection conn = DBUtil.open(); // 获取数据库连接
11 
12         // 生成Statement对象用于执行sql语句
13         try {
14             Statement stmt = conn.createStatement();
15             ResultSet rs = stmt.executeQuery(sql); // 执行查询，返回结果集
16 
17             while (rs.next()) {
18                 int id = rs.getInt(1);
19                 String name = rs.getString(2);
20                 String email = rs.getString("email");
21 
22                 System.out.println(id + ", " + name + ", " + email);
23             }
24         } catch (SQLException e) {
25             e.printStackTrace();
26         } finally {
27             DBUtil.close(conn);
28         }
29     }
30 }

 1 import java.sql.Connection;
 2 import java.sql.PreparedStatement;
 3 import java.sql.SQLException;
 4 
 5 public class StatementDemo {
 6 
 7     public static void main(String[] args) {
 8         String sql = "update CustomerTb1 set name=? where id=?";
 9         Connection conn = DBUtil.open(); // 获取数据库连接
10 
11         /** 预定义sql语句，?为占位符，在运行中动态生成sql语句 */
12         try {
13             PreparedStatement pstmt = conn.prepareStatement(sql);
14             // 对占位符替换赋值
15             pstmt.setString(1, "gepeng");
16             pstmt.setInt(2, 3);
17 
18             pstmt.executeUpdate(); // 执行更新
19 
20         } catch (SQLException e) {
21             e.printStackTrace();
22         } finally {
23             DBUtil.close(conn);
24         }
25     }
26 }