task: configure log4j2 with json logging

Author: chriswk

examples/cli-example/build.gradle.kts

@@ -40,5 +40,9 @@ jib {
 dependencies {
     implementation("io.getunleash:unleash-client-java:11.2.0-SNAPSHOT")
     implementation("org.slf4j:slf4j-api:2.0.17")
-    implementation("ch.qos.logback:logback-classic:1.5.20")
+    runtimeOnly("org.apache.logging.log4j:log4j-core:2.25.2")
+    runtimeOnly("org.apache.logging.log4j:log4j-api:2.25.2")
+    runtimeOnly("org.apache.logging.log4j:log4j-slf4j2-impl:2.25.2")
+    runtimeOnly("org.apache.logging.log4j:log4j-layout-template-json:2.25.2")
+    runtimeOnly("com.fasterxml.jackson.core:jackson-databind:2.20.1")
 }

examples/cli-example/src/main/resources/log4j2.xml

@@ -0,0 +1,19 @@
+<Configuration xmlns="https://logging.apache.org/xml/ns"
+               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+               xsi:schemaLocation="
+                   https://logging.apache.org/xml/ns
+                   https://logging.apache.org/xml/ns/log4j-config-2.xsd">
+
+    <Appenders>
+        <Console name="CONSOLE">
+            <JsonTemplateLayout />
+        </Console>
+    </Appenders>
+
+    <Loggers>
+        <Root level="INFO">
+            <AppenderRef ref="CONSOLE"/>
+        </Root>
+    </Loggers>
+
+</Configuration>