AVRO-3968

Add support for custom AvroTypeName annotation to allow overriding namespace when generating schema with reflection

lang/java/avro/src/main/java/org/apache/avro/reflect/AvroTypeName.java

@@ -0,0 +1,33 @@
+/*
+ * 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
+ *
+ *     https://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.avro.reflect;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Sets the avrotypename for this java type. When reading into this class, a
+ * reflectdatumreader looks for a schema field with the avrotypename.
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.TYPE })
+public @interface AvroTypeName {
+  String value() default "";
+}

lang/java/avro/src/main/java/org/apache/avro/reflect/ReflectData.java

@@ -706,9 +706,7 @@ protected Schema createSchema(Type type, Map<String, Schema> names) {
         AvroDoc annotatedDoc = c.getAnnotation(AvroDoc.class); // Docstring
         String doc = (annotatedDoc != null) ? annotatedDoc.value() : null;
         String name = c.getSimpleName();
-        String space = c.getPackage() == null ? "" : c.getPackage().getName();
-        if (c.getEnclosingClass() != null) // nested class
-          space = c.getEnclosingClass().getName().replace('$', '.');
+        String space = getNamespace(c);
         Union union = c.getAnnotation(Union.class);
         if (union != null) { // union annotated
           return getAnnotatedUnion(union, names);
@@ -802,6 +800,21 @@ private String simpleName(Class<?> c) {
     return simpleName;
   }
 
+  /*
+   * Function checks if there is @AvroTypeName annotation on the class. If present
+   * then returns the value of the annotation else returns the package of the
+   * class
+   */
+  private String getNamespace(Class<?> c) {
+    AvroTypeName avroTypeName = c.getAnnotation(AvroTypeName.class);
+    if (avroTypeName != null) {
+      return avroTypeName.value();
+    }
+    if (c.getEnclosingClass() != null) // nested class
+      return c.getEnclosingClass().getName().replace('$', '.');
+    return c.getPackage() == null ? "" : c.getPackage().getName();
+  }
+
   private static final Schema THROWABLE_MESSAGE = makeNullable(Schema.create(Schema.Type.STRING));
 
   // if array element type is a class with a union annotation, note it

lang/java/avro/src/main/java/org/apache/avro/reflect/package.html

@@ -83,7 +83,10 @@
 <p> The {@link org.apache.avro.reflect.AvroName AvroName} annotation renames 
 the field in the schema to the given name. The reflect datum reader will look 
 for a schema field with the given name, when trying to read into such an 
-annotated java field. 
+annotated java field.
+
+<p> The {@link org.apache.avro.reflect.AvroTypeName AvroTypeName} annotation renames
+the namespace in the schema to the given namespace.
 
 <p>The {@link org.apache.avro.reflect.AvroMeta AvroMeta} annotation adds an 
 arbitrary key:value pair in the schema at the node of the java field.

lang/java/avro/src/test/java/org/apache/avro/reflect/TestReflect.java

@@ -1415,4 +1415,24 @@ void avroDoc() {
             + "{\"name\":\"foo\",\"type\":\"int\",\"doc\":\"Some Documentation\"}" + "]}");
   }
 
+  @AvroTypeName("org.apache.avro.reflect.OverrideNamespace")
+  private static class NamespaceTest {
+
+    @AvroTypeName("org.apache.avro.reflect.InnerOverrideNamespace")
+    private static class InnerNamespaceTest {
+    }
+  }
+
+  @Test
+  void avroOverrideNamespaceTest() {
+    check(NamespaceTest.class,
+        "{\"type\":\"record\",\"name\":\"NamespaceTest\",\"namespace\":\"org.apache.avro.reflect.OverrideNamespace\",\"fields\":[]}");
+  }
+
+  @Test
+  void avroOverrideInnerNamespaceTest() {
+    check(NamespaceTest.InnerNamespaceTest.class,
+        "{\"type\":\"record\",\"name\":\"InnerNamespaceTest\",\"namespace\":\"org.apache.avro.reflect.InnerOverrideNamespace\",\"fields\":[]}");
+  }
+
 }