Create UserDAO.java

[vivek-kumar-2024]

No description provided.

[greptile-apps]

PR Summary

Added new UserDAO.java class for database operations with several critical security vulnerabilities and implementation flaws that require immediate attention.

• SQL Injection risk through direct string concatenation in queries - use PreparedStatement instead
• Database credentials are hardcoded, should be moved to secure configuration management
• Connection resources not properly closed with try-with-resources pattern
• Missing proper return value handling for user data retrieval operations
• Implement comprehensive input validation and proper error reporting/logging

_{1 file reviewed, 2 comments
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[greptile-apps]

logic: Critical SQL injection vulnerability. Use PreparedStatement instead:

Suggested change

	ResultSet rs = stmt.executeQuery("SELECT * FROM users WHERE username = '" + username + "'");
	PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE username = ?");
	stmt.setString(1, username);
	ResultSet rs = stmt.executeQuery();

[greptile-apps]

style: Use try-with-resources to ensure proper resource cleanup:

Suggested change

	try {
	Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "pass");
	Statement stmt = conn.createStatement();
	ResultSet rs = stmt.executeQuery("SELECT * FROM users WHERE username = '" + username + "'");
	while (rs.next()) {
	System.out.println(rs.getString("email"));
	}
	rs.close();
	stmt.close();
	conn.close();
	try (Connection conn = DriverManager.getConnection(url, user, pass);
	PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE username = ?");
	ResultSet rs = stmt.executeQuery()) {