Adding client class for sending message to topic

1) Adding TopicSinkClient class for sending messages to topic. The same
class will be used for PAP->PDP & PDP->PAP communication.

2) Once this review is through, will raise another one to remove
PdpClient from policy/pap.

Change-Id: I7253683d9e88885cfbe2ac9041d01da239b9321b
Issue-ID: POLICY-1443
Signed-off-by: ramverma <ram.krishna.verma@est.tech>

4 files changed, 340 insertions, 0 deletions

diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClient.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClient.java
new file mode 100644
index 00000000..3188b8d4
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClient.java
@@ -0,0 +1,104 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * Modifications Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.event.comm.client;
+
+
+import java.util.List;
+
+import lombok.Getter;
+
+import org.onap.policy.common.endpoints.event.comm.TopicEndpoint;
+import org.onap.policy.common.endpoints.event.comm.TopicSink;
+import org.onap.policy.common.utils.coder.Coder;
+import org.onap.policy.common.utils.coder.CoderException;
+import org.onap.policy.common.utils.coder.StandardCoder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Client for sending messages to a Topic using TopicSink.
+ */
+public class TopicSinkClient {
+    private static final Logger logger = LoggerFactory.getLogger(TopicSinkClient.class);
+
+    /**
+     * Coder used to encode messages being sent to the topic.
+     */
+    private static final Coder CODER = new StandardCoder();
+
+    /**
+     * Topic to which messages are published.
+     */
+    @Getter
+    private final String topic;
+
+    /**
+     * Where messages are published.
+     */
+    private final TopicSink sink;
+
+    /**
+     * Constructs the object.
+     *
+     * @param topic topic to which messages should be published
+     * @throws TopicSinkClientException if the topic does not exist
+     */
+    public TopicSinkClient(final String topic) throws TopicSinkClientException {
+        this.topic = topic;
+
+        final List<TopicSink> lst = getTopicSinks(topic);
+        if (lst.isEmpty()) {
+            throw new TopicSinkClientException("no sinks for topic: " + topic);
+        }
+
+        this.sink = lst.get(0);
+    }
+
+    /**
+     * Sends a message to the topic, after encoding the message as json.
+     *
+     * @param message message to be encoded and sent
+     * @return {@code true} if the message was successfully sent/enqueued, {@code false} otherwise
+     */
+    public boolean send(final Object message) {
+        try {
+            final String json = CODER.encode(message);
+            return sink.send(json);
+
+        } catch (RuntimeException | CoderException e) {
+            logger.warn("send to {} failed because of {}", topic, e.getMessage(), e);
+            return false;
+        }
+    }
+
+    // the remaining methods are wrappers that can be overridden by junit tests
+
+    /**
+     * Gets the sinks for a given topic.
+     *
+     * @param topic the topic of interest
+     * @return the sinks for the topic
+     */
+    protected List<TopicSink> getTopicSinks(final String topic) {
+        return TopicEndpoint.manager.getTopicSinks(topic);
+    }
+}
diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientException.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientException.java
new file mode 100644
index 00000000..608393b3
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientException.java
@@ -0,0 +1,51 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * Modifications Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.event.comm.client;
+
+/**
+ * Exception thrown by TopicSink client classes.
+ */
+public class TopicSinkClientException extends Exception {
+    private static final long serialVersionUID = 1L;
+
+    public TopicSinkClientException() {
+        super();
+    }
+
+    public TopicSinkClientException(final String message) {
+        super(message);
+    }
+
+    public TopicSinkClientException(final Throwable cause) {
+        super(cause);
+    }
+
+    public TopicSinkClientException(final String message, final Throwable cause) {
+        super(message, cause);
+    }
+
+    public TopicSinkClientException(final String message, final Throwable cause, final boolean enableSuppression,
+            final boolean writableStackTrace) {
+        super(message, cause, enableSuppression, writableStackTrace);
+    }
+
+}
diff --git a/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientExceptionTest.java b/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientExceptionTest.java
new file mode 100644
index 00000000..c0814703
--- /dev/null
+++ b/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientExceptionTest.java
@@ -0,0 +1,35 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * Modifications Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.event.comm.client;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.onap.policy.common.utils.test.ExceptionsTester;
+
+public class TopicSinkClientExceptionTest {
+
+    @Test
+    public void test() {
+        assertEquals(5, new ExceptionsTester().test(TopicSinkClientException.class));
+    }
+}
diff --git a/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientTest.java b/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientTest.java
new file mode 100644
index 00000000..725c0418
--- /dev/null
+++ b/policy-endpoints/src/test/java/org/onap/policy/common/endpoints/event/comm/client/TopicSinkClientTest.java
@@ -0,0 +1,150 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * Modifications Copyright (C) 2019 Nordix Foundation.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.event.comm.client;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Properties;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.internal.util.reflection.Whitebox;
+import org.onap.policy.common.endpoints.event.comm.Topic.CommInfrastructure;
+import org.onap.policy.common.endpoints.event.comm.TopicEndpoint;
+import org.onap.policy.common.endpoints.event.comm.TopicListener;
+import org.onap.policy.common.endpoints.event.comm.TopicSink;
+
+public class TopicSinkClientTest {
+    private static final String SINK_FIELD_NAME = "sink";
+    private static final String TOPIC = "my-topic";
+
+    private TopicSinkClient client;
+    private TopicSink sink;
+    private List<TopicSink> sinks;
+
+    /**
+     * Creates mocks and an initial client object.
+     *
+     * @throws Exception if an error occurs
+     */
+    @Before
+    public void setUp() throws Exception {
+        sink = mock(TopicSink.class);
+        when(sink.send(anyString())).thenReturn(true);
+
+        sinks = Arrays.asList(sink, null);
+
+        client = new TopicSinkClient2(TOPIC);
+    }
+
+    @AfterClass
+    public static void tearDown() throws Exception {
+        // clear all topics after the tests
+        TopicEndpoint.manager.shutdown();
+    }
+
+    /**
+     * Uses a real NO-OP topic sink.
+     */
+    @Test
+    public void testGetTopicSinks() throws Exception {
+        // clear all topics and then configure one topic
+        TopicEndpoint.manager.shutdown();
+
+        final Properties props = new Properties();
+        props.setProperty("noop.sink.topics", TOPIC);
+        TopicEndpoint.manager.addTopicSinks(props);
+
+        sink = TopicEndpoint.manager.getNoopTopicSink(TOPIC);
+        assertNotNull(sink);
+
+        final AtomicReference<String> evref = new AtomicReference<>(null);
+
+        sink.register(new TopicListener() {
+            @Override
+            public void onTopicEvent(final CommInfrastructure infra, final String topic, final String event) {
+                evref.set(event);
+            }
+        });
+
+        sink.start();
+
+        client = new TopicSinkClient(TOPIC);
+        client.send(100);
+
+        assertEquals("100", evref.get());
+    }
+
+    @Test
+    public void testTopicSinkClient_testGetTopic() {
+        assertEquals(TOPIC, client.getTopic());
+        assertSame(sink, Whitebox.getInternalState(client, SINK_FIELD_NAME));
+
+        // unknown topic -> should throw exception
+        sinks = new LinkedList<>();
+        assertThatThrownBy(() -> new TopicSinkClient2(TOPIC)).isInstanceOf(TopicSinkClientException.class)
+                .hasMessage("no sinks for topic: my-topic");
+    }
+
+    @Test
+    public void testSend() throws Exception {
+        client.send(Arrays.asList("abc", "def"));
+        verify(sink).send("['abc','def']".replace('\'', '"'));
+
+        // sink send fails
+        when(sink.send(anyString())).thenReturn(false);
+        assertFalse(client.send("ghi"));
+
+        // sink send throws an exception
+        final RuntimeException ex = new RuntimeException("expected exception");
+        when(sink.send(anyString())).thenThrow(ex);
+        assertFalse(client.send("jkl"));
+    }
+
+    /**
+     * TopicSinkClient with some overrides.
+     */
+    private class TopicSinkClient2 extends TopicSinkClient {
+
+        public TopicSinkClient2(final String topic) throws TopicSinkClientException {
+            super(topic);
+        }
+
+        @Override
+        protected List<TopicSink> getTopicSinks(final String topic) {
+            return sinks;
+        }
+    }
+}