https://github.com/michaelbull/kotlin-inline-logger
A logger facilitating lazily-evaluated log calls via Kotlin's inline classes & functions.
https://github.com/michaelbull/kotlin-inline-logger
inline jvm kotlin logger multiplatform slf4j
Last synced: 8 months ago
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A logger facilitating lazily-evaluated log calls via Kotlin's inline classes & functions.
- Host: GitHub
- URL: https://github.com/michaelbull/kotlin-inline-logger
- Owner: michaelbull
- License: isc
- Created: 2019-06-08T16:40:30.000Z (almost 7 years ago)
- Default Branch: master
- Last Pushed: 2024-01-23T13:09:01.000Z (over 2 years ago)
- Last Synced: 2025-07-10T23:04:50.660Z (11 months ago)
- Topics: inline, jvm, kotlin, logger, multiplatform, slf4j
- Language: Kotlin
- Homepage:
- Size: 531 KB
- Stars: 90
- Watchers: 1
- Forks: 6
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# kotlin-inline-logger
[](https://search.maven.org/search?q=g:com.michael-bull.kotlin-inline-logger) [](https://github.com/michaelbull/kotlin-inline-logger/actions?query=workflow%3Aci) [](https://github.com/michaelbull/kotlin-inline-logger/blob/master/LICENSE)
A logger facilitating lazily-evaluated log calls via Kotlin's inline [classes][inline-classes] & [functions][inline-functions].
## Installation
```groovy
repositories {
mavenCentral()
}
dependencies {
implementation("com.michael-bull.kotlin-inline-logger:kotlin-inline-logger:1.0.6")
}
```
## Introduction
`kotlin-inline-logger` has been structured as a [`multiplatform project`][mpp].
Currently the only implementation supports the JVM, utilising [SLF4J][slf4j],
however in future other platforms can also be supported by implementing the
necessary platform-specific APIs found in [`src/commonMain`](src/commonMain).
If you would like to implement support for a platform, please don't hesitate
to open a pull request on [GitHub][github].
### JVM
On the JVM, `kotlin-inline-logger` provides inline functions that delegate
to [SLF4J][slf4j]. Users migrating from an existing SLF4J solution will find
existing calls to logging functions like `logger.info("Example")` now marked as
`@Deprecated`, prompting them to replace their existing code with the
lazily-evaluated alternatives.
#### Creating loggers
By default, passing no argument when creating an `InlineLogger()` will utilise
`MethodHandles.lookup()`, introduced in JDK7, to derive the name of the logger
from the class that created it. This is described in SLF4J's documentation as
an [idiomatic method of declaring a logger][slf4j-idiom] that is resistant to
cut-and-paste errors:
```kotlin
class TransactionExecutor {
val transactionLogger = InlineLogger() // named com.package.TransactionExecutor
}
```
Named loggers can be created by passing a `String`:
```kotlin
val transactionLogger = InlineLogger("DatabaseTransactions")
```
Class loggers can be created by passing a `::class` reference:
```kotlin
class TransactionExecutor
val transactionLogger = InlineLogger(TransactionExecutor::class)
```
#### Effectiveness
The code examples below illustrate how the Kotlin you write is compiled to
interoperable Java, demonstrating how the `expensiveCalculation()` function is
only invoked and interpolated with the log message if warn-level logging is
enabled.
This allows you to replace usages of SLF4J's [MessageFormatter][slf4j-formatter],
with the more idiomatic [string templates][string-templates] Kotlin provides.
##### Kotlin:
```kotlin
import com.github.michaelbull.logging.InlineLogger
val logger = InlineLogger("CalculationLogger")
fun expensiveCalculation(): Int {
return 1234 * 5678
}
fun main() {
logger.warn { "The result is: ${expensiveCalculation()}" }
}
```
##### Decompiled Java:
```java
import com.github.michaelbull.logging.InlineLogger;
import org.jetbrains.annotations.NotNull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public final class ExampleKt {
@NotNull
private static final Logger logger;
@NotNull
public static Logger getLogger() {
return logger;
}
public static int expensiveCalculation() {
return 1234 * 5678;
}
public static void main() {
Logger $this$iv = logger;
if (InlineLogger.isWarnEnabled-impl((Logger) $this$iv)) {
String string = "The result is: " + ExampleKt.expensiveCalculation();
$this$iv.warn(String.valueOf(string));
}
}
public static /* synthetic */ void main(String[] arrstring) {
ExampleKt.main();
}
static {
Logger delegate$iv = LoggerFactory.getLogger("CalculationLogger");
logger = InlineLogger.constructor-impl((Logger) delegate$iv);
}
}
```
## Contributing
Bug reports and pull requests are welcome on [GitHub][github].
## License
This project is available under the terms of the ISC license. See the
[`LICENSE`](LICENSE) file for the copyright information and licensing terms.
[inline-classes]: https://kotlinlang.org/docs/reference/inline-classes.html
[inline-functions]: https://kotlinlang.org/docs/reference/inline-functions.html
[mpp]: https://kotlinlang.org/docs/reference/multiplatform.html
[string-templates]: https://kotlinlang.org/docs/reference/basic-types.html#string-templates
[github]: https://github.com/michaelbull/kotlin-inline-logger
[slf4j]: https://www.slf4j.org/
[slf4j-idiom]: https://www.slf4j.org/faq.html#declaration_pattern
[slf4j-formatter]: https://www.slf4j.org/api/org/slf4j/helpers/MessageFormatter.html