;
Statement statement = connection.createStatement();
String sql = "delete from users where id=5";
int row = statement.executeUpdate(sql);
System.out.println(row);
if (row > 0) {
System.out.println("删除成功");
}
statement.close();
connection.close();
}
@Test
public void testSelect() throws Exception {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/myjdbc?user=root&password=123456";
Connection connection = DriverManager.getConnection(url);
Statement statement = connection.createStatement();
// 查询
String sql = "select id, name, email from users";
ResultSet resultSet = statement.executeQuery(sql);
// 处理结果集
while (resultSet.next()) {
// 可以直接填字段名称
System.out.print(resultSet.getObject("id") + " ");
System.out.print(resultSet.getObject("name") + " ");
System.out.println(resultSet.getObject("email") + " ");
}
resultSet.close();
statement.close();
connection.close();
}
连接数据库时的异常处理
public static void main(String[] args) {
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/myjdbc";
connection = DriverManager.getConnection(url, "root", "123456");
statement = connection.createStatement();
String sql = "select * from users";
resultSet = statement.executeQuery(sql);
// 处理结果集(把数据的记录封装到对象中)
ArrayList
arrayList = new ArrayList<>();
while(resultSet.next()) {
// 创建 User 对象
User user = new User();
user.setId(resultSet.getInt("id"));
user.setName(resultSet.getString("name"));
user.setPassword(resultSet.getString("password"));
user.setEmail(resultSet.getString("email"));
user.setBirthday(resultSet.getDate("birthday"));
// 放入集合中
arrayList.add(user);
}
// 遍历查看
for (User user : arrayList) {
System.out.println(user);
}
} catch (ClassNotFoundException e) {
// 停止程序
throw new RuntimeException("驱动加载失败");
} catch (SQLException e) {
throw new RuntimeException("获取连接失败");
} finally {
// 关闭资源前,要做非空判断,防止空指针异常
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
throw new RuntimeException("资源关闭失败");
}
// 加快
系统回收的速度
resultSet = null;
}
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
throw new RuntimeException("资源关闭失败");
}
// 加快系统回收的速度
statement = null;
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
throw new RuntimeException("资源关闭失败");
}
// 加快系统回收的速度
connection = null;
}
}
}
创建 dbinfo.properties 文件,作为配置文件
driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/myjdbc
user=root
password=123456
将 JDBC 封装为一个工具类方法使用
public class JDBCUtil {
private static String driverClass;
private static String url;
private static String user;
private static String password;
// 使用静态代码块加载驱动,读取配置文件
static {
// 第一种读取配置文件的方法:利用集合读取文件
Properties properti