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+# README - slf4j-reference
+
+This project gives an example of ONAP-compliant logging using SLF4J logging.
+
+## Adapter
+
+In ```org.onap.logging.ref.slf4j```, there are TWO classes:
+1. ```org.onap.logging.ref.slf4j.ONAPLogConstants```, providing declarations of standard ONAP Markers, MDCs and HTTP headers.
+2. ```org.onap.logging.ref.slf4j.ONAPLogAdapter```, providing a lightweight, compliant implementation of the ONAP logging spec.
+
+The adapter provides:
+1. A loosely-coupled SLF4j logging wrapper:
+ * To be used for logging ONAP ```entry```, ```exit``` and ```invoke``` behavior.
+ * Devolving all *application* logging to the component, via the regular SLF4J ```Logger``` facade.
+2. Customization options:
+ * *Cheap*, by way of bean properties. This is suited to most Use Cases.
+ * *Sophisticated*:
+    * By OPTIONALLY implementing one of a number of adapters:
+      * ```RequestAdapter``` to read incoming headers.
+      * ```ServiceDescriptor``` for reporting attributes of the current service.
+      * ```ResponseDescriptor``` for reporting outcomes.
+      * ```RequestBuilder``` for setting southbound request headers.
+    * By OPTIONALLY overriding methods like ```ONAPLogAdapter#setMDCs(RequestAdapter)```.
+
+Note that:
+* The adapter implementation uses static inner classes in order to fit in a single source file. This was an objective. 
+
+## WAR
+
+Building produces a simple (spring-boot](https://projects.spring.io/spring-boot/) example WAR, which can be launched from this directory with:
+
+```bash
+$ java -war target/*war
+```
+
+The example WAR in ```logging-slf4j-demo``` publishes four web services:
+1. ```services/alpha```
+2. ```services/beta```
+3. ```services/gamma```
+4. ```services/delta```
+
+... each of which can invoke the others.
+
+The purpose of the WAR is to demonstrate minimalist ONAP-compliant logging for web components, but a secondary purpose is to demonstrate that the call graph can be generated for a (mostly) representative set of interacting REST services.
+
+## Tests
+
+Tests for:
+1. Code in the (potentially) reusable ``common`` package.
+2. Validating that emitted logs can be used to generate an unambiguous call graph.