Support for JSON logging, like in decentralized-identity/universal-registrar#97

Author: peacekeeper

uni-resolver-web/pom.xml

@@ -83,6 +83,11 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-log4j2</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-layout-template-json</artifactId>
+            <scope>runtime</scope>
+        </dependency>
         <dependency>
             <groupId>io.micrometer</groupId>
             <artifactId>micrometer-registry-prometheus</artifactId>

uni-resolver-web/src/main/resources/log4j2.xml

@@ -1,20 +1,38 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Configuration status="WARN">
     <Appenders>
-        <Console name="Console" target="SYSTEM_OUT">
+        <!-- JSON structured logging to Console (defaults to Elastic Common Schema, ECS).
+             Override the event template via LOGGING_JSON_EVENT_TEMPLATE_URI.
+             ECS docs: https://www.elastic.co/docs/reference/ecs/logging/intro
+             Predefined Log4j event templates:
+        https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-templates -->
+        <Console name="json" target="SYSTEM_OUT">
+            <JsonTemplateLayout
+                eventTemplateUri="${env:LOGGING_JSON_EVENT_TEMPLATE_URI:-classpath:EcsLayout.json}" />
+        </Console>
 
+        <!-- Colored plaintext logging to Console -->
+        <Console name="plain" target="SYSTEM_OUT">
             <PatternLayout
-                    pattern="%style{%d{ISO8601}}{red} %highlight{%-5level }[%style{%t}{bright,blue}] %style{%C{1.}}{bright,yellow}: %msg%n%throwable"/>
+                pattern="%style{%d{ISO8601}}{red} %highlight{%-5level }[%style{%t}{bright,blue}] %style{%C{1.}}{bright,yellow}: %msg%n%throwable" />
         </Console>
     </Appenders>
 
     <Loggers>
-        <Root level="info">
-            <AppenderRef ref="Console"/>
+        <!-- Set Root Logging level with 'LOGGING_LEVEL_ROOT' environment variable -->
+        <!-- Valid log levels are: trace, debug, info, warn, error, fatal, off -->
+        <Root level="${env:LOGGING_LEVEL_ROOT:-info}">
+            <!-- Default to plain layout, switch to json if LOGGING_FORMAT=json -->
+            <AppenderRef ref="${env:LOGGING_FORMAT:-plain}" />
         </Root>
-        <Logger name="uniresolver" level="debug" additivity="false">
-            <AppenderRef ref="Console"/>
+
+        <!-- Set Uniresolver Logging level with 'LOGGING_LEVEL_uniresolver' environment variable -->
+        <!-- Valid log levels are: trace, debug, info, warn, error, fatal, off -->
+        <Logger name="uniresolver" level="${env:LOGGING_LEVEL_uniresolver:-debug}"
+            additivity="false">
+            <!-- Default to plain layout, switch to json if LOGGING_FORMAT=json -->
+            <AppenderRef ref="${env:LOGGING_FORMAT:-plain}" />
         </Logger>
     </Loggers>
 
-</Configuration>
+</Configuration>