implementing ThreadLocal and JDBC Connections in Java 8 under Spring Boot
I just started working with I'm working with an scenario with using `ThreadLocal` for managing JDBC connections in a Spring Boot application. My application is structured to utilize a `ThreadLocal` variable to hold a connection for the duration of a request, but I'm running into `SQLException` stating that the connection is closed after the first usage. My setup looks something like this: ```java public class ConnectionManager { private static final ThreadLocal<Connection> threadLocalConnection = new ThreadLocal<>(); public Connection getConnection() throws SQLException { if (threadLocalConnection.get() == null) { Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password"); threadLocalConnection.set(connection); } return threadLocalConnection.get(); } public void closeConnection() throws SQLException { Connection connection = threadLocalConnection.get(); if (connection != null && !connection.isClosed()) { connection.close(); threadLocalConnection.remove(); } } } ``` In my service class, I call `getConnection()` in a `@Transactional` method, but after the first database operation, subsequent attempts lead to the aforementioned behavior as if the connection was prematurely closed. I've tried logging the connection state and confirmed that the connection is indeed being closed after the first use. Here's how I use the `ConnectionManager`: ```java @Service public class MyService { private final ConnectionManager connectionManager; @Autowired public MyService(ConnectionManager connectionManager) { this.connectionManager = connectionManager; } @Transactional public void performDatabaseOperation() throws SQLException { Connection connection = connectionManager.getConnection(); // some database operations connection.createStatement().executeQuery("SELECT * FROM users"); // Attempt another operation which fails after the first one connection.createStatement().executeUpdate("UPDATE users SET name = 'John' WHERE id = 1"); } } ``` I suspect it could be related to how Spring manages transactions or connection lifecycles, but I'm unsure how to resolve this and maintain the benefits of using `ThreadLocal`. Any insights into this behavior would be greatly appreciated! Thanks for taking the time to read this!