Adjusted code formatting of StopStreaming and added null checks for…

… constructor arguments. Added unit tests for `StopStreaming`.

Signed-off-by: Juergen Fickel <juergen.fickel@bosch-si.com>

services/gateway/streaming/src/main/java/org/eclipse/ditto/services/gateway/streaming/StopStreaming.java

@@ -12,27 +12,34 @@
  */
 package org.eclipse.ditto.services.gateway.streaming;
 
+import static org.eclipse.ditto.model.base.common.ConditionChecker.checkNotNull;
+
 import java.util.Objects;
 
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
 import org.eclipse.ditto.services.models.concierge.streaming.StreamingType;
 
 /**
  * Message indicating a demand to receive entities of a specified {@link StreamingType} via a "streaming" connection.
  */
+@Immutable
 public final class StopStreaming {
 
     private final StreamingType streamingType;
     private final String connectionCorrelationId;
 
     /**
-     * Constructs a new {@link StopStreaming} instance.
+     * Constructs a new {@code StopStreaming} object.
      *
      * @param streamingType the type of entity to start the streaming for.
-     * @param connectionCorrelationId the correlationId of the connection/session.
+     * @param connectionCorrelationId the correlation ID of the connection/session.
+     * @throws NullPointerException if any argument is {@code null}.
      */
     public StopStreaming(final StreamingType streamingType, final String connectionCorrelationId) {
-        this.streamingType = streamingType;
-        this.connectionCorrelationId = connectionCorrelationId;
+        this.streamingType = checkNotNull(streamingType, "streamingType");
+        this.connectionCorrelationId = checkNotNull(connectionCorrelationId, "connectionCorrelationId");
     }
 
     /**
@@ -47,9 +54,13 @@ public String getConnectionCorrelationId() {
     }
 
     @Override
-    public boolean equals(final Object o) {
-        if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
+    public boolean equals(@Nullable final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
         final StopStreaming that = (StopStreaming) o;
         return streamingType == that.streamingType &&
                 Objects.equals(connectionCorrelationId, that.connectionCorrelationId);
@@ -67,4 +78,5 @@ public String toString() {
                 ", connectionCorrelationId=" + connectionCorrelationId +
                 "]";
     }
+
 }

services/gateway/streaming/src/test/java/org/eclipse/ditto/services/gateway/streaming/StopStreamingTest.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2019 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.eclipse.ditto.services.gateway.streaming;
+
+import static org.assertj.core.api.Assertions.assertThatNullPointerException;
+import static org.mutabilitydetector.unittesting.MutabilityAssert.assertInstancesOf;
+import static org.mutabilitydetector.unittesting.MutabilityMatchers.areImmutable;
+
+import org.assertj.core.api.SoftAssertions;
+import org.eclipse.ditto.services.models.concierge.streaming.StreamingType;
+import org.junit.Test;
+
+import nl.jqno.equalsverifier.EqualsVerifier;
+
+/**
+ * Unit test for {@link StopStreaming}.
+ */
+public final class StopStreamingTest {
+
+    @Test
+    public void assertImmutability() {
+        assertInstancesOf(StopStreaming.class, areImmutable());
+    }
+
+    @Test
+    public void testHashCodeAndEquals() {
+        EqualsVerifier.forClass(StopStreaming.class)
+                .usingGetClass()
+                .verify();
+    }
+
+    @Test
+    public void tryToCreateInstanceWithNullStreamingType() {
+        assertThatNullPointerException()
+                .isThrownBy(() -> new StopStreaming(null, "my-correlation-id"))
+                .withMessage("The streamingType must not be null!")
+                .withNoCause();
+    }
+
+    @Test
+    public void tryToCreateInstanceWithNullCorrelationId() {
+        assertThatNullPointerException()
+                .isThrownBy(() -> new StopStreaming(StreamingType.LIVE_COMMANDS, null))
+                .withMessage("The connectionCorrelationId must not be null!")
+                .withNoCause();
+    }
+
+    @Test
+    public void gettersReturnExpected() {
+        final StreamingType streamingType = StreamingType.EVENTS;
+        final String connectionCorrelationId = "my-correlation-id";
+
+        final StopStreaming underTest = new StopStreaming(streamingType, connectionCorrelationId);
+
+        final SoftAssertions softly = new SoftAssertions();
+        softly.assertThat(underTest.getStreamingType()).isEqualTo(streamingType);
+        softly.assertThat(underTest.getConnectionCorrelationId()).isEqualTo(connectionCorrelationId);
+        softly.assertAll();
+    }
+
+}