开发笔记:JavaWeb技术：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 }