added some comments and copyrights

Author: Mike Skells

.github/workflows/codeql-analysis.yml

@@ -47,6 +47,11 @@ jobs:
         uses: github/codeql-action/init@v3
         with:
           languages: ${{ matrix.language }}
+    # Initializes the CodeQL tools for scanning.
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v2
+        with:
+          languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
         # By default, queries listed here will override any specified in a config file.
         # Prefix the list here with "+" to use these queries and those in the config file.

commons/src/main/java/io/aiven/kafka/connect/common/config/extractors/DataExtractor.java

@@ -1,8 +1,33 @@
+/*
+ * Copyright 2020 Aiven Oy
+ *
+ * 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 io.aiven.kafka.connect.common.config.extractors;
 
 import org.apache.kafka.connect.sink.SinkRecord;
 
+/**
+ * Extracts data from a {@link SinkRecord}. The actual data extracted is implementation specific
+ */
 public interface DataExtractor {
 
+    /**
+     * Extracts data from a {@link SinkRecord}.
+     *
+     * @param record the record to extract data from
+     * @return the extracted data
+     */
     Object extractDataFrom(final SinkRecord record);
 }

commons/src/main/java/io/aiven/kafka/connect/common/config/extractors/HeaderValueExtractor.java

@@ -1,11 +1,37 @@
+/*
+ * Copyright 2020 Aiven Oy
+ *
+ * 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 io.aiven.kafka.connect.common.config.extractors;
 
 import org.apache.kafka.connect.header.Header;
 import org.apache.kafka.connect.sink.SinkRecord;
 
+/**
+ * A DataExtractor that extracts the value of a header from a SinkRecord
+ * If there are multiple headers with the same ane, then the last occurrence will be used
+ * If the header does not exist, then the extraction will yield null
+ */
 public class HeaderValueExtractor implements DataExtractor {
     private final String headerKey;
 
+    /**
+     * Create a new HeaderValueExtractor
+     *
+     * @param headerKey the key of the header to extract.
+     */
     public HeaderValueExtractor(final String headerKey) {
         this.headerKey = headerKey;
     }

commons/src/main/java/io/aiven/kafka/connect/common/config/extractors/SimpleValuePath.java

@@ -26,6 +26,22 @@
 import java.util.Map;
 import java.util.regex.Pattern;
 
+/*
+ * Copyright 2020 Aiven Oy
+ *
+ * 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.
+ */
+
 public final class SimpleValuePath implements DataExtractor {
     private final String[] terms;