Automatic-Module-Name entry provides a stable JDK9 module name, when Netty is used in a modular JDK9 applications. More info: http://blog.joda.org/2017/05/java-se-9-jpms-automatic-modules.html
When Netty migrates to JDK9 in the future, the entry can be replaced by actual module-info descriptor.
Modification:
The POM-s are configured to put the correct module names to the manifest.
Result:
Fixes#7218.
Motivation:
- A `hashCode` of the SmtpCommand is recalculated on each call of `hashCode()`. Cached hash code value can be just replaced with call of `name.hashCode()`.
- The commands cache don't work for strings: `SmtpCommand.valueOf("HELO")` returns a new instance.
- Field `contentExpected` is redundant and can be replaced with `equals(DATA)`.
Modifications:
- Use the `name.hashCode()` as hash code result.
- Fix a command cache: use strings as map keys.
- Replace field `contentExpected` to using `this.equals(DATA)`.
- Add unit tests.
Result:
More correct and clean code.
Motivation:
The `AsciiString#toString` method calculate string value and cache it into field. If an `AsciiString` created from the `String` value, we can avoid rebuilding strings if we cache them immediately when creating `AsciiString`. It would be useful for constants strings, which already stored in the JVMs string table, or in cases where an unavoidable `#toString `method call is assumed.
Modifications:
- Add new static method `AsciiString#cache(String)` which save string value into cache field.
- Apply a "benign" data race in the `#hashCode` and `#toString` methods.
Result:
Less memory usage in some `AsciiString` use cases.
Motivation:
1. Some encoders used a `ByteBuf#writeBytes` to write short constant byte array (2-3 bytes). This can be replaced with more faster `ByteBuf#writeShort` or `ByteBuf#writeMedium` which do not access the memory.
2. Two chained calls of the `ByteBuf#setByte` with constants can be replaced with one `ByteBuf#setShort` to reduce index checks.
3. The signature of method `HttpHeadersEncoder#encoderHeader` has an unnecessary `throws`.
Modifications:
1. Use `ByteBuf#writeShort` or `ByteBuf#writeMedium` instead of `ByteBuf#writeBytes` for the constants.
2. Use `ByteBuf#setShort` instead of chained call of the `ByteBuf#setByte` with constants.
3. Remove an unnecessary `throws` from `HttpHeadersEncoder#encoderHeader`.
Result:
A bit faster writes constants into buffers.
Motivation:
If the remote server returns an invalid response in the form "000 \r\n"
(i.e. a three digit code, then space, but no details), null is added
as a singletonList to the response being constructed.
This seems unexpected and it would be easier to handle an empty
details list in client code.
Modifications:
If detail is null (because frame.isReadable() returned false after
reading the separator), initialise DefaultSmtpResponse with an empty
list instead of a list containing a single null value.
Result:
When encountering this malformed server response, a DefaultSmtpResponse
with a code but no details will be created.
Motivation:
If the remote server returns a 4xx/5xx error in response to
a DATA command (or earlier command if using pipelining),
SmtpRequestEncoder can become stuck in an invalid state,
not allowing any requests to be sent.
This makes the channel unusable and the connection has to be closed,
or the encoder handler has to be replaced.
Modifications:
If a RSET command is written to the channel, the contentExpected
flag is set to false, and the RSET is written to the channel.
Result:
Sending a RSET command after a server 4xx/5xx error will make it
possible to use the current connection for new mail transactions.
