Logging interface in Kotlin.
This library provides access to the log-front
Java library in a Kotlin
idiomatic manner.
To instantiate a Logger
for the current class, regardless of whether the call is made from within the class or its
companion object:
val log = getLogger() // requires: import net.pwall.log.getLogger
To output a log "INFO"-level message:
log.info { "message content" }
Because the lambda is evaluated only if logging is enabled for this logger and this level, complex substitutions may be used in the message with no loss of efficiency.
There are similar functions trace
, debug
, warn
and error
, and an additional version of error
that takes a
Throwable
as the first parameter:
log.error(exception) { "Something went wrong!" }
The functionality of this library is largely documented with the Java library. There are a small number of additional functions, along with some different patterns of usage.
There are several top-level functions to acquire a Logger
instance.
These should be used in place of the functions of the Log
class – they achieve the same result, but the return
type of these functions is non-nullable, as opposed to the Java functions which are of indeterminate nullability.
getLogger()
getLogger(name: String)
getLogger(javaClass: Class<*>)
getLogger(kClass: KClass<*>)
getLogger(level: Level)
getLogger(name: String, level: Level)
getLogger(javaClass: Class<*>, level: Level)
getLogger(kClass: KClass<*>, level: Level)
getLogger(clock: Clock)
getLogger(name: String, clock: Clock)
getLogger(javaClass: Class<*>, clock: Clock)
getLogger(kClass: KClass<*>, clock: Clock)
getLogger(level: Level, clock: Clock)
getLogger(name: String, level: Level, clock: Clock)
getLogger(javaClass: Class<*>, level: Level, clock: Clock)
getLogger(kClass: KClass<*>, level: Level, clock: Clock)
When no logger name is provided, the name will be determined automatically from the calling class.
Otherwise, the name may be specified as a String
, or as a Java Class
or a Kotlin KClass
, in which case the
fully-qualified class name will be used.
The Level
and Clock
, if specified, will be provided to the LoggerFactory
to be used in the instantiation of the
Logger
, although as noted in the description of the log-front
library, not all implementations will make use of
these parameters.
There is also an additional getLogger
function on LoggerFactory
which takes a Kotlin KClass
:
val log = loggerFactory.getLogger(ThisClass::class)
The function also allows the Level
and a Clock
to be specified as optional parameters:
val log = loggerFactory.getLogger(ThisClass::class, level = Level.INFO,
clock = Clock.fixed(Instant.now(), ZoneOffset.UTC))
This library also includes some additional functions to help with the use of the
LogListener
functionality of the Java library.
To test whether a LogItem
is an INFO
-level item with the text "Hello":
if (logItem isInfo "Hello") {
// whatever...
}
Or to test whether a LogItem
is an ERROR
-level item with a message starting with "File not found ":
if (logItem isError Regex("^File not found ")) {
// whatever...
}
There are, of course, isTrace
, isDebug
and isWarning
functions in both the exact match (string) and regex forms.
The LoggerDelegate
class from previous versions of the library is retained, but its use has been superseded by the
getLogger()
functions.
It may be deprecated in future releases.
The latest version of the library is 5.3.1, and it may be obtained from the Maven Central repository.
<dependency>
<groupId>net.pwall.log</groupId>
<artifactId>log-front-kotlin</artifactId>
<version>5.3.1</version>
</dependency>
implementation 'net.pwall.log:log-front-kotlin:5.3.1'
implementation("net.pwall.log:log-front-kotlin:5.3.1")
Peter Wall
2024-07-25