JIRA: https://jira.spring.io/browse/INT-3501
There were several problems:
When a `Folder` is open, an activity on the `Store` opens a new
connection.
The `PingTask` called `isConnected()` on the store, creating a new
connection. The pings (NOOPs) were performed on this connection and
therefore did NOT cancel the `IDLE`.
In any case, the `IDLE` was issued on the folder not the store and
the only way to cancel that IDLE is to cause its `waitIfIdle()` to
be invoked. Conveniently, simply calling `isOpen()` invokes that
method and cancels the IDLE.
Finally, the `SimpleMessageCountListener` unnecessarily invoked
`message.getLineCount()` when a simple `folder.isOpen()` is
sufficient.
Fixes:
1. Do not invoke `openSession` if `this.folder` is not null.
2. Change the `PingTask` to simply invoke `isOpen()`.
3. Move the `PingTask to the receiver for a more efficient algorithm
instead of running on fixed interval. Rename it `IdleCanceler`.
4. Increase the PING timer from 10 to 120 seconds; add setters for it
and the `reconnectionDelay`.
TODO: Namespace support for 4.1. (Not to be back ported).
Add a test IMAP server (ported from Java DSL and enhanced to simulate IDLE
with a new message arriving for the first idle period.
INT-3501 Polishing - PR Comments
Polishing for `PoorMansMailServer` to get rid of `smtp` and `pop3` servers to avoid unnecessary Base64 dependency
Conflicts:
spring-integration-mail/src/main/java/org/springframework/integration/mail/ImapIdleChannelAdapter.java
spring-integration-mail/src/test/java/org/springframework/integration/mail/ImapMailReceiverTests.java
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