Implement Connection#isValid

[enqueue]

Summary

The API doc for Connection says:

Returns true if the connection has not been closed and is still valid. The driver shall submit a query on the connection or use some other mechanism that positively verifies the connection is still valid when this method is called.

1. Do not throw Exception when connection is closed.
2. Check that connection may be used to perform queries.

Client already provides ping method with timeout which is used here.

Closes #2472

Checklist

• [ ✅ ] Closes Result of connection.isValid() returned true even incorrect credentials provided #2472
• [ ✅ ] Unit and integration tests covering the common scenarios were added

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[Copilot]

Pull Request Overview

This PR implements the Connection#isValid(int) method to correctly return false for closed connections and to use the client’s ping mechanism, and it adds integration tests for both closed and invalid-credential scenarios.

• Replace placeholder implementation of isValid with real logic (check closed, call client.ping)
• Add two integration tests covering closed connections and wrong credentials
• Change createValidDatabaseNames DataProvider to private static

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
jdbc-v2/src/main/java/com/clickhouse/jdbc/ConnectionImpl.java	Implement isValid(int): handle closed state and delegate to ping
jdbc-v2/src/test/java/com/clickhouse/jdbc/ConnectionTest.java	Add tests for closed/invalid connections and adjust DataProvider visibility

Comments suppressed due to low confidence (3)

jdbc-v2/src/main/java/com/clickhouse/jdbc/ConnectionImpl.java:491

• The negative timeout branch (timeout < 0) isn't covered by existing tests. Add a unit test that verifies isValid(-1) throws the expected SQLException.

        if (timeout < 0) {

jdbc-v2/src/main/java/com/clickhouse/jdbc/ConnectionImpl.java:490

• [nitpick] Update the Javadoc for isValid(int) to explain the behavior when the connection is closed and that it delegates to client.ping under the hood, in line with the JDBC API contract.

    public boolean isValid(int timeout) throws SQLException {

jdbc-v2/src/test/java/com/clickhouse/jdbc/ConnectionTest.java:597

• TestNG DataProvider methods are typically required to be public; making this method private may prevent the framework from discovering it. Consider reverting to public static visibility.

    private static Object[][] createValidDatabaseNames() {