Question
Answer and Explanation
An SQLException: Login failed error, even with correct credentials, is a common issue when connecting to a database. Several factors can cause this, despite providing what seems to be the right username and password. Let's explore some of the most common causes and solutions:
1. Incorrect Database Hostname or Port:
- Double-check that the hostname or IP address of the database server is correct. A typo or an outdated address can lead to connection failures. Also, ensure the port number is correct. The default port for SQL Server is 1433, but it may be different in your configuration. Example connection string:
jdbc:sqlserver://your_server_address:1433;databaseName=your_database_name;user=your_user_name;password=your_password
2. SQL Server Authentication Mode:
- SQL Server supports Windows Authentication and SQL Server Authentication (username/password). Ensure that SQL Server Authentication is enabled if you are using a username and password. To verify this, connect to SQL Server using SQL Server Management Studio (SSMS), right-click on the server instance, select "Properties," go to the "Security" page, and check the "Server authentication" mode.
3. User Account Disabled or Locked:
- The user account may be disabled or locked due to multiple failed login attempts. Check the status of the user account in SQL Server. In SSMS, navigate to Security -> Logins, find the user, right-click, and select "Properties." Under the "Status" page, ensure that "Login" is enabled.
4. Password Expiration or Policy:
- The user's password might have expired, or there might be a password policy enforced that requires a password reset. If password expiration is enabled, the user needs to reset the password. This can be done via SSMS or programmatically.
5. Network Connectivity Issues:
- Verify that there are no firewall rules blocking access to the SQL Server port. Also, check if the SQL Server Browser service is running, as it helps clients locate the correct instance of SQL Server on the network. Use tools like ping or telnet to test connectivity to the SQL Server.
6. Incorrect Database Name:
- Ensure that the database name specified in the connection string is correct and that the user has permissions to access that database. The user needs to be mapped to the database in the "User Mapping" section of the Login properties.
7. Case Sensitivity:
- Usernames and passwords in SQL Server are not case-sensitive by default, but some configurations might enforce case sensitivity. Double-check that the username and password are entered correctly, paying attention to case.
8. Insufficient Permissions:
- The user might not have the necessary permissions to connect to the database. Grant the user the CONNECT SQL permission on the server and db_datareader and db_datawriter permissions on the database.
9. SQL Server Not Running:
- Confirm that the SQL Server service is running. Check the SQL Server Configuration Manager or Services panel to ensure that the SQL Server instance is started.
10. Firewall Blocking Connections:
- The Windows Firewall or other firewall software may be blocking connections to the SQL Server. You need to create inbound rules to allow traffic on port 1433 (or whichever port your SQL Server is listening on).
By systematically checking these potential issues, you should be able to diagnose and resolve the "SQLException: Login failed" error, even when the credentials appear to be correct. Always remember to check the SQL Server error logs for more detailed information about the failure.