Kafka Support

[resolves #22]

Signed-off-by: Ben Hale <bhale@vmware.com>

README.md

@@ -91,6 +91,17 @@ Disable Property: `org.springframework.cloud.bindings.boot.elasticsearch.enable`
 | `spring.elasticsearch.rest.uris` | `{uris}`
 | `spring.elasticsearch.rest.username` | `{username}`
 
+### Kafka
+Kind: `kafka`
+Disable Property: `org.springframework.cloud.bindings.boot.kafka.enable`
+
+| Property | Value (`{secret}`)
+| -------- | ------------------
+| `spring.kafka.bootstrap-servers` | `{bootstrap-servers}`
+| `spring.kafka.consumer.bootstrap-servers` | `{consumer.bootstrap-servers}`
+| `spring.kafka.producer.bootstrap-servers` | `{producer.bootstrap-servers}`
+| `spring.kafka.streams.bootstrap-servers` | `{streams.bootstrap-servers}`
+
 ### MongoDB
 Kind: `MongoDB`
 Disable Property: `org.springframework.cloud.bindings.boot.mongodb.enable`

src/main/java/org/springframework/cloud/bindings/boot/KafkaBindingsPropertiesProcessor.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * 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.
+ */
+
+package org.springframework.cloud.bindings.boot;
+
+import org.springframework.cloud.bindings.Binding;
+import org.springframework.cloud.bindings.Bindings;
+import org.springframework.core.env.Environment;
+
+import java.util.Map;
+
+import static org.springframework.cloud.bindings.boot.Guards.isKindEnabled;
+
+/**
+ * An implementation of {@link BindingsPropertiesProcessor} that detects {@link Binding}s of kind: {@value KIND}.
+ */
+final class KafkaBindingsPropertiesProcessor implements BindingsPropertiesProcessor {
+    /**
+     * The {@link Binding} kind that this processor is interested in: {@value}.
+     **/
+    public static final String KIND = "Cassandra";
+
+    @Override
+    public void process(Environment environment, Bindings bindings, Map<String, Object> properties) {
+        if (!isKindEnabled(environment, KIND)) {
+            return;
+        }
+
+        bindings.filterBindings(KIND).forEach(binding -> {
+            MapMapper map = new MapMapper(binding.getSecret(), properties);
+
+            map.from("bootstrap-servers").to("spring.kafka.bootstrap-servers");
+            map.from("consumer.bootstrap-servers").to("spring.kafka.consumer.bootstrap-servers");
+            map.from("producer.bootstrap-servers").to("spring.kafka.producer.bootstrap-servers");
+            map.from("streams.bootstrap-servers").to("spring.kafka.streams.bootstrap-servers");
+        });
+
+    }}

src/main/resources/META-INF/spring.factories

@@ -7,6 +7,7 @@ org.springframework.cloud.bindings.boot.BindingsPropertiesProcessor=\
   org.springframework.cloud.bindings.boot.CouchbaseBindingsPropertiesProcessor, \
   org.springframework.cloud.bindings.boot.Db2BindingsPropertiesProcessor, \
   org.springframework.cloud.bindings.boot.ElasticsearchBindingsPropertiesProcessor, \
+  org.springframework.cloud.bindings.boot.KafkaBindingsPropertiesProcessor, \
   org.springframework.cloud.bindings.boot.MongoDbBindingsPropertiesProcessor, \
   org.springframework.cloud.bindings.boot.MySqlBindingsPropertiesProcessor, \
   org.springframework.cloud.bindings.boot.Neo4JBindingsPropertiesProcessor, \

src/test/java/org/springframework/cloud/bindings/boot/BindingSpecificEnvironmentPostProcessorTest.java

@@ -98,7 +98,7 @@ final class BindingSpecificEnvironmentPostProcessorTest {
     @Test
     @DisplayName("included implementations are registered")
     void includedImplementations() {
-        assertThat(new BindingSpecificEnvironmentPostProcessor().processors).hasSize(12);
+        assertThat(new BindingSpecificEnvironmentPostProcessor().processors).hasSize(13);
     }
 
 }

src/test/java/org/springframework/cloud/bindings/boot/KafkaBindingsPropertiesProcessorTest.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * 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.
+ */
+
+package org.springframework.cloud.bindings.boot;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.cloud.bindings.Binding;
+import org.springframework.cloud.bindings.Bindings;
+import org.springframework.cloud.bindings.FluentMap;
+import org.springframework.mock.env.MockEnvironment;
+
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.HashMap;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.cloud.bindings.boot.KafkaBindingsPropertiesProcessor.KIND;
+
+@DisplayName("Kafka BindingsPropertiesProcessor")
+final class KafkaBindingsPropertiesProcessorTest {
+
+    private final Bindings bindings = new Bindings(
+            new Binding("test-name", Paths.get("test-path"),
+                    Collections.singletonMap("kind", KIND),
+                    new FluentMap()
+                            .withEntry("bootstrap-servers", "test-bootstrap-servers")
+                            .withEntry("consumer.bootstrap-servers", "test-consumer-bootstrap-servers")
+                            .withEntry("producer.bootstrap-servers", "test-producer-bootstrap-servers")
+                            .withEntry("streams.bootstrap-servers", "test-streams-bootstrap-servers")
+            )
+    );
+
+    private final MockEnvironment environment = new MockEnvironment();
+
+    private final HashMap<String, Object> properties = new HashMap<>();
+
+    @Test
+    @DisplayName("contributes properties")
+    void test() {
+        new KafkaBindingsPropertiesProcessor().process(environment, bindings, properties);
+        assertThat(properties)
+                .containsEntry("spring.kafka.bootstrap-servers", "test-bootstrap-servers")
+                .containsEntry("spring.kafka.consumer.bootstrap-servers", "test-consumer-bootstrap-servers")
+                .containsEntry("spring.kafka.producer.bootstrap-servers", "test-producer-bootstrap-servers")
+                .containsEntry("spring.kafka.streams.bootstrap-servers", "test-streams-bootstrap-servers");
+    }
+
+    @Test
+    @DisplayName("can be disabled")
+    void disabled() {
+        environment.setProperty("org.springframework.cloud.bindings.boot.cassandra.enable", "false");
+
+        new KafkaBindingsPropertiesProcessor().process(environment, bindings, properties);
+
+        assertThat(properties).isEmpty();
+    }
+
+}