cli: Replace log4j2 with logback

cli/build.gradle.kts

@@ -155,10 +155,12 @@ dependencies {
     implementation(libs.jacksonDatabind)
     implementation(libs.jacksonModuleKotlin)
     implementation(libs.kotlinxCoroutines)
-    implementation(libs.log4jCore)
-    implementation(libs.log4jImplSlf4j)
+    implementation(libs.logbackClassic)
     implementation(libs.postgres)
     implementation(libs.reflections)
+    implementation(libs.slf4jApi)
+    implementation(libs.slf4jJcl)
+    implementation(libs.slf4jJul)
     implementation(libs.sw360Client)
 
     testImplementation(project(":utils:test-utils"))

cli/src/main/kotlin/OrtMain.kt

@@ -20,6 +20,13 @@
 
 package org.ossreviewtoolkit.cli
 
+import ch.qos.logback.classic.Level
+import ch.qos.logback.classic.Logger
+import ch.qos.logback.classic.LoggerContext
+import ch.qos.logback.classic.encoder.PatternLayoutEncoder
+import ch.qos.logback.classic.spi.ILoggingEvent
+import ch.qos.logback.core.ConsoleAppender
+
 import com.github.ajalt.clikt.completion.completionOption
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.core.context
@@ -39,9 +46,6 @@ import java.io.File
 
 import kotlin.system.exitProcess
 
-import org.apache.logging.log4j.Level
-import org.apache.logging.log4j.core.config.Configurator
-
 import org.ossreviewtoolkit.cli.commands.*
 import org.ossreviewtoolkit.model.config.LicenseFilenamePatterns
 import org.ossreviewtoolkit.model.config.OrtConfiguration
@@ -57,6 +61,8 @@ import org.ossreviewtoolkit.utils.ort.ortConfigDirectory
 import org.ossreviewtoolkit.utils.ort.ortDataDirectory
 import org.ossreviewtoolkit.utils.ort.printStackTrace
 
+import org.slf4j.LoggerFactory
+
 /**
  * Helper class for mutually exclusive command line options of different types.
  */
@@ -171,7 +177,7 @@ class OrtMain : CliktCommand(name = ORT_NAME, invokeWithoutSubcommand = true) {
     }
 
     override fun run() {
-        Configurator.setRootLevel(logLevel)
+        initLogging()
 
         log.debug { "Used command line arguments: ${currentContext.originalArgv}" }
 
@@ -222,4 +228,26 @@ class OrtMain : CliktCommand(name = ORT_NAME, invokeWithoutSubcommand = true) {
 
         return header.joinToString("\n", postfix = "\n")
     }
+
+    private fun initLogging() {
+        val logCtx: LoggerContext = LoggerFactory.getILoggerFactory() as LoggerContext
+
+        val logEncoder = PatternLayoutEncoder()
+
+        logEncoder.setContext(logCtx)
+        logEncoder.setPattern("%-12date{YYYY-MM-dd HH:mm:ss.SSS} %-5level – %msg%n")
+        logEncoder.start()
+
+        val logConsoleAppender = ConsoleAppender<ILoggingEvent>()
+
+        logConsoleAppender.setContext(logCtx)
+        logConsoleAppender.setName("console")
+        logConsoleAppender.setEncoder(logEncoder)
+        logConsoleAppender.start()
+
+        val rootLogger: Logger = logCtx.getLogger(Logger.ROOT_LOGGER_NAME)
+
+        rootLogger.level = logLevel as Level
+        rootLogger.addAppender(logConsoleAppender)
+    }
 }

gradle/libs.versions.toml

@@ -47,6 +47,7 @@ kotlinxSerialization = "1.3.3"
 ktor = "1.6.8"
 log4j = "2.17.2"
 log4jApiKotlin = "1.1.0"
+logbackClassic = "1.2.11"
 maven = "3.8.6"
 # @pin this version as it needs to be aligned with "maven".
 mavenResolver = "1.7.3"
@@ -61,6 +62,7 @@ retrofitConverterKotlinxSerialization = "0.8.0"
 saxonHe = "11.3"
 scanoss = "1.1.6"
 semver4j = "3.1.0"
+slf4j = "1.7.36"
 springCore = "5.3.21"
 svnkit = "1.10.6"
 # @pin this version as there are only newer weekly releases.
@@ -135,8 +137,7 @@ ktorClientOkHttp = { module = "io.ktor:ktor-client-okhttp", version.ref = "ktor"
 # @keep this library which is only being used via force().
 log4jApi = { module = "org.apache.logging.log4j:log4j-api", version.ref = "log4j" }
 log4jApiKotlin = { module = "org.apache.logging.log4j:log4j-api-kotlin", version.ref = "log4jApiKotlin" }
-log4jCore = { module = "org.apache.logging.log4j:log4j-core", version.ref = "log4j" }
-log4jImplSlf4j = { module = "org.apache.logging.log4j:log4j-slf4j-impl", version.ref = "log4j" }
+logbackClassic = { module = "ch.qos.logback:logback-classic", version.ref = "logbackClassic" }
 mavenCompat = { module = "org.apache.maven:maven-compat", version.ref = "maven" }
 mavenCore = { module = "org.apache.maven:maven-core", version.ref = "maven" }
 mavenResolverConnectorBasic = { module = "org.apache.maven.resolver:maven-resolver-connector-basic", version.ref = "mavenResolver" }
@@ -156,6 +157,9 @@ retrofitConverterScalars = { module = "com.squareup.retrofit2:converter-scalars"
 saxonHe = { module = "net.sf.saxon:Saxon-HE", version.ref = "saxonHe" }
 scanoss = { module = "com.scanoss:scanner", version.ref = "scanoss" }
 semver4j = { module = "com.vdurmont:semver4j", version.ref = "semver4j" }
+slf4jApi = { module = "org.slf4j:slf4j-api", version.ref = "slf4j" }
+slf4jJcl = { module = "org.slf4j:jcl-over-slf4j", version.ref = "slf4j" }
+slf4jJul = { module = "org.slf4j:jul-to-slf4j", version.ref = "slf4j" }
 springCore = { module = "org.springframework:spring-core", version.ref = "springCore" }
 svnkit = { module = "org.tmatesoft.svnkit:svnkit", version.ref = "svnkit" }
 sw360Client = { module = "org.eclipse.sw360:client", version.ref = "sw360Client" }

helper-cli/build.gradle.kts

@@ -96,6 +96,8 @@ dependencies {
     implementation(libs.exposedCore)
     implementation(libs.hikari)
     implementation(libs.jslt)
-    implementation(libs.log4jCore)
-    implementation(libs.log4jImplSlf4j)
+    implementation(libs.logbackClassic)
+    implementation(libs.slf4jApi)
+    implementation(libs.slf4jJcl)
+    implementation(libs.slf4jJul)
 }

helper-cli/src/main/kotlin/HelperMain.kt

@@ -19,6 +19,13 @@
 
 package org.ossreviewtoolkit.helper
 
+import ch.qos.logback.classic.Level
+import ch.qos.logback.classic.Logger
+import ch.qos.logback.classic.LoggerContext
+import ch.qos.logback.classic.encoder.PatternLayoutEncoder
+import ch.qos.logback.classic.spi.ILoggingEvent
+import ch.qos.logback.core.ConsoleAppender
+
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.core.context
 import com.github.ajalt.clikt.core.subcommands
@@ -28,9 +35,6 @@ import com.github.ajalt.clikt.parameters.options.flag
 import com.github.ajalt.clikt.parameters.options.option
 import com.github.ajalt.clikt.parameters.options.switch
 
-import org.apache.logging.log4j.Level
-import org.apache.logging.log4j.core.config.Configurator
-
 import org.ossreviewtoolkit.helper.commands.CreateAnalyzerResultCommand
 import org.ossreviewtoolkit.helper.commands.DownloadResultsFromPostgresCommand
 import org.ossreviewtoolkit.helper.commands.ExtractRepositoryConfigurationCommand
@@ -57,6 +61,8 @@ import org.ossreviewtoolkit.helper.commands.scanstorage.ScanStorageCommand
 import org.ossreviewtoolkit.helper.common.ORTH_NAME
 import org.ossreviewtoolkit.utils.ort.printStackTrace
 
+import org.slf4j.LoggerFactory
+
 /**
  * The entry point for the application with [args] being the list of arguments.
  */
@@ -106,9 +112,31 @@ internal class HelperMain : CliktCommand(name = ORTH_NAME, epilog = "* denotes r
     }
 
     override fun run() {
-        Configurator.setRootLevel(logLevel)
+        initLogging()
 
         // Make the parameter globally available.
         printStackTrace = stacktrace
     }
+
+    private fun initLogging() {
+        val logCtx: LoggerContext = LoggerFactory.getILoggerFactory() as LoggerContext
+
+        val logEncoder = PatternLayoutEncoder()
+
+        logEncoder.setContext(logCtx)
+        logEncoder.setPattern("%-12date{YYYY-MM-dd HH:mm:ss.SSS} %-5level – %msg%n")
+        logEncoder.start()
+
+        val logConsoleAppender = ConsoleAppender<ILoggingEvent>()
+
+        logConsoleAppender.setContext(logCtx)
+        logConsoleAppender.setName("console")
+        logConsoleAppender.setEncoder(logEncoder)
+        logConsoleAppender.start()
+
+        val rootLogger: Logger = logCtx.getLogger(Logger.ROOT_LOGGER_NAME)
+
+        rootLogger.level = logLevel as Level
+        rootLogger.addAppender(logConsoleAppender)
+    }
 }

utils/test/build.gradle.kts

@@ -33,6 +33,9 @@ dependencies {
     implementation(libs.jacksonModuleKotlin)
     implementation(libs.kotestExtensionsJunitXml)
     implementation(libs.kotestFrameworkEngine)
-    implementation(libs.log4jImplSlf4j)
+    implementation(libs.logbackClassic)
+    implementation(libs.slf4jApi)
+    implementation(libs.slf4jJcl)
+    implementation(libs.slf4jJul)
     implementation(libs.postgresEmbedded)
 }