Bug Fix Null Pointer on Stop (#3)

- S3 Delivery Stream threw a null pointer if was stopped before written

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>io.timson</groupId>
     <artifactId>firehose-mock</artifactId>
-    <version>0.0.2</version>
+    <version>0.0.3</version>
 
     <name>Firehose Mock</name>
     <url>https://github.com/ptimson/firehose-mock</url>

src/main/java/io/timson/firehose/stream/S3DeliveryStream.java

@@ -34,11 +34,15 @@ public class S3DeliveryStream implements DeliveryStream {
     private final Long bufferIntervalMs;
     private final Long bufferFlushSizeBytes;
     private final CompressionFormat compressionFormat;
-
+    private final TimerTask flushTimerTask = new TimerTask() {
+        @Override
+        public void run() {
+            flush();
+        }
+    };
     private StringBuilder buffer = new StringBuilder();
     private long bufferSize = 0;
     private Timer flushTimer;
-    private TimerTask flushTimerTask;
 
     private S3DeliveryStream(String name,
                              S3Client s3Client,
@@ -64,17 +68,14 @@ private String extractBucketName(String s3BucketArn) {
     }
 
     private void startFlushTimer() {
-        flushTimerTask = new TimerTask() {
-            @Override
-            public void run() {
-                flush();
-            }
-        };
         flushTimer = new Timer();
         flushTimer.schedule(flushTimerTask, bufferIntervalMs);
     }
 
     private void stopFlushTimer() {
+        if (flushTimer == null) {
+            return;
+        }
         flushTimer.cancel();
     }
 

src/test/java/io/timson/firehose/stream/S3DeliveryStreamTest.java

@@ -144,4 +144,9 @@ public void shouldCreateSnappyS3Object_WhenEncryptionTypeIsSnappy() throws Excep
         verify(s3Client, only()).createSnappyObject(eq(S3_BUCKET), anyString(), eq(MESSAGE_1));
     }
 
+    @Test
+    public void shouldThrowNullPointer_WhenStoppedBeforeMessageWritten() throws Exception {
+        stream.stop();
+    }
+
 }