Added a readme to annotations

Author: lksfrnz

annotations/README.md

@@ -0,0 +1,75 @@
+# Annotations
+
+## Setup
+
+Getting this package to work requires the following additions to a gradle build file:
+```gradle
+plugins {
+    ...
+    id "io.freefair.aspectj.post-compile-weaving" version "6.4.3"
+}
+
+dependencies {
+    ...
+    implementation project(':annotations')
+    implementation "org.aspectj:aspectjweaver:1.9.8.RC3"
+}
+
+```
+
+## Usage
+
+This pacakge adds `@CountMetric` and `@ExecutionTimeMetric` method annotations.
+
+### @CountMetric
+@CountMetric will log a value of 1 whenever it is triggered.
+
+### @ExecutionTimeMetric
+@ExecutionTimeMetric will log the execution time of a method whenever it is triggered.
+
+### Annotation Parameters
+
+- `String Name` (Default: `""`)
+    - The name the metric is published under
+    - If the name is left null it will be replaced with `"<ClassName>.<MethodName>.<AnnotationType>"` when being sent to CWL
+- `Boolean logSuccess` (Default `True` )
+    - Determines if this annotation will log a metric when the method exits successfully
+- `Class<? extends Throwable>[] LogErrors`  (Default: `[Throwable.class]` )
+    - Determines if this annotation will log a metric when the method exits with an error (will log if the method exits by a throwing an in the given list)
+- `String Logger` (Default: `""`)
+    - Determines which logger this annotation’s metric will be put into.
+    - If `null` or there is no logger associated with that key then the default logger will be used
+- `bool flush` (Default: `false` )
+    - Determines whether the metric logger attached to this annotation should flush after this function
+
+
+### Loggers
+This package also implements a singleton `MetricAnnotationMediator` which handles the logging of all metrics created by annotations. This singleton contains a default `MetricsLogger` instance that all annotations will default to; however, other loggers can be added to it using its `addLogger(name, logger)` method. Annotations can then be sent to the added logger by specifying the name of the logger as an annotation parameter.
+
+There are two ways to flush these metrics to CloudWatch:
+1. Call `MetricAnnotationMediator.flushAll()` which flushes all the loggers that the singleton has a reference to
+2. Flush the logger that the metrics have been added to. Loggers can be retrieved from the `MetricAnnotationMediator` using the methods `MetricAnnotationMediator.getDefaultLogger()` and `MetricAnnotationMediator.getLogger(name)`
+
+```java
+import software.amazon.cloudwatchlogs.emf.annotations.CountMetric;
+import software.amazon.cloudwatchlogs.emf.annotations.ExecutionTimeMetric;
+import software.amazon.cloudwatchlogs.emf.annotations.MetricAnnotationMediator;
+
+class Example {
+
+    @CountMetric
+    @ExecutionTimeMetric
+    public static void doSomething() {
+        // Do something
+        ...
+    }
+
+    public static void main(String[] args) {
+		MetricsLogger metrics = new MetricsLogger();
+
+        doSomething();
+
+        MetricAnnotationMediator.flushAll();
+	}
+}
+```