Enable CheckStyle Plugin in structured-event-log module (apache#14483)

structured-event-log/pom.xml

@@ -58,4 +58,23 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-checkstyle-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>checkstyle</id>
+            <phase>verify</phase>
+            <goals>
+              <goal>check</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+
 </project>

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/EventGroup.java

@@ -21,7 +21,7 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
-@Retention(value=RetentionPolicy.RUNTIME)
+@Retention(value = RetentionPolicy.RUNTIME)
 public @interface EventGroup {
     String component();
 }

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/EventResourcesImpl.java

@@ -40,7 +40,7 @@ public EventResources resource(String key, Object value) {
 
     @Override
     public EventResources resource(String key, Supplier<String> value) {
-        resource(key, (Object)value);
+        resource(key, (Object) value);
         return this;
     }
 
@@ -77,7 +77,7 @@ public static void forEach(List<Object> list, BiConsumer<String, String> process
             String key = String.valueOf(list.get(i));
             Object value = list.get(i + 1);
             if (value instanceof Supplier) {
-                value = ((Supplier<?>)value).get();
+                value = ((Supplier<?>) value).get();
             }
             process.accept(key, String.valueOf(value));
         }

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/StructuredEventLog.java

@@ -85,7 +85,7 @@ public interface StructuredEventLog {
     /**
      * Create a new logger object, from which root events can be created.
      */
-    public static StructuredEventLog newLogger() {
+    static StructuredEventLog newLogger() {
         return Slf4jStructuredEventLog.INSTANCE;
     }
 }

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/package-info.java

@@ -0,0 +1,19 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.pulsar.structuredeventlog;

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/slf4j/Slf4jEvent.java

@@ -28,15 +28,13 @@
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
-
 import org.apache.pulsar.structuredeventlog.Event;
 import org.apache.pulsar.structuredeventlog.EventGroup;
 import org.apache.pulsar.structuredeventlog.EventResources;
 import org.apache.pulsar.structuredeventlog.EventResourcesImpl;
-
-import org.slf4j.MDC;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
 
 class Slf4jEvent implements Event {
     private static final ThreadLocal<Map<Object, Logger>> loggersTLS = ThreadLocal.withInitial(() -> new HashMap<>());
@@ -89,7 +87,7 @@ public Event sampled(Object samplingKey, int duration, TimeUnit unit) {
     @Override
     public Event resources(EventResources other) {
         if (other instanceof EventResourcesImpl) {
-            this.resources.copyFrom((EventResourcesImpl)other);
+            this.resources.copyFrom((EventResourcesImpl) other);
         }
         return this;
     }
@@ -115,7 +113,7 @@ public Event attr(String key, Object value) {
 
     @Override
     public Event attr(String key, Supplier<String> value) {
-        this.attr(key, (Object)value);
+        this.attr(key, (Object) value);
         return this;
     }
 

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/slf4j/Slf4jStructuredEventLog.java

@@ -19,14 +19,13 @@
 package org.apache.pulsar.structuredeventlog.slf4j;
 
 import java.time.Clock;
-
 import org.apache.pulsar.structuredeventlog.Event;
 import org.apache.pulsar.structuredeventlog.EventResources;
 import org.apache.pulsar.structuredeventlog.EventResourcesImpl;
 import org.apache.pulsar.structuredeventlog.StructuredEventLog;
 
 public class Slf4jStructuredEventLog implements StructuredEventLog {
-    public static Slf4jStructuredEventLog INSTANCE = new Slf4jStructuredEventLog();
+    public static final Slf4jStructuredEventLog INSTANCE = new Slf4jStructuredEventLog();
     // Visible for testing
     Clock clock = Clock.systemUTC();
 

structured-event-log/src/main/java/org/apache/pulsar/structuredeventlog/slf4j/package-info.java

@@ -0,0 +1,19 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.pulsar.structuredeventlog.slf4j;