[apache#24292] Create Avro extension for Java SDK

sdks/java/core/src/main/java/org/apache/beam/sdk/io/BlockBasedSource.java

@@ -140,7 +140,7 @@ protected abstract static class Block<T> {
    * byte of the block is within the range {@code [start, end)}.
    */
   @Experimental(Kind.SOURCE_SINK)
-  protected abstract static class BlockBasedReader<T> extends FileBasedReader<T> {
+  public abstract static class BlockBasedReader<T> extends FileBasedReader<T> {
     private boolean atSplitPoint;
 
     protected BlockBasedReader(BlockBasedSource<T> source) {
@@ -195,7 +195,7 @@ public final T getCurrent() throws NoSuchElementException {
      * block boundaries.
      */
     @Override
-    protected boolean isAtSplitPoint() {
+    public boolean isAtSplitPoint() {
       return atSplitPoint;
     }
 

sdks/java/core/src/main/java/org/apache/beam/sdk/io/DefaultFilenamePolicy.java

@@ -269,7 +269,7 @@ public static DefaultFilenamePolicy fromParams(Params params) {
    * ".txt", with shardNum = 1 and numShards = 100, the following is produced:
    * "path/to/output-001-of-100.txt".
    */
-  static ResourceId constructName(
+  public static ResourceId constructName(
       ResourceId baseFilename,
       String shardTemplate,
       String suffix,

sdks/java/core/src/main/java/org/apache/beam/sdk/io/ReadAllViaFileBasedSource.java

@@ -47,7 +47,7 @@
 public class ReadAllViaFileBasedSource<T>
     extends PTransform<PCollection<ReadableFile>, PCollection<T>> {
 
-  protected static final boolean DEFAULT_USES_RESHUFFLE = true;
+  public static final boolean DEFAULT_USES_RESHUFFLE = true;
   private final long desiredBundleSizeBytes;
   private final SerializableFunction<String, ? extends FileBasedSource<T>> createSource;
   private final Coder<T> coder;

sdks/java/extensions/avro/build.gradle

@@ -0,0 +1,56 @@
+/*
+ * 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.
+ */
+
+plugins { id 'org.apache.beam.module' }
+applyJavaNature(
+    automaticModuleName: 'org.apache.beam.sdk.extensions.avro',
+    disableLintWarnings: ['rawtypes'], // Avro-generated test code has raw-type errors
+    publish: false,
+    exportJavadoc: false,
+)
+applyAvroNature()
+
+description = "Apache Beam :: SDKs :: Java :: Extensions :: Avro"
+
+// Exclude tests that need a runner
+test {
+  systemProperty "beamUseDummyRunner", "true"
+  useJUnit {
+    excludeCategories "org.apache.beam.sdk.testing.NeedsRunner"
+  }
+}
+
+dependencies {
+  implementation library.java.byte_buddy
+  implementation library.java.vendored_guava_26_0_jre
+  implementation (project(path: ":sdks:java:core", configuration: "shadow")) {
+    // Exclude Avro dependencies from "core" since Avro support moved to this extension
+    exclude group: "org.apache.avro", module: "avro"
+  }
+  implementation library.java.error_prone_annotations
+  implementation library.java.avro
+  implementation library.java.joda_time
+  testImplementation (project(path: ":sdks:java:core", configuration: "shadowTest")) {
+    // Exclude Avro dependencies from "core" since Avro support moved to this extension
+    exclude group: "org.apache.avro", module: "avro"
+  }
+  testImplementation library.java.avro_tests
+  testImplementation library.java.junit
+  testRuntimeOnly project(path: ":runners:direct-java", configuration: "shadow")
+  testRuntimeOnly library.java.slf4j_jdk14
+}