[jira] [Created] (AVRO-3186) Avro can't decode union field of a record

["Yubao Liu (Jira)" <ji...@apache.org>]

Yubao Liu created AVRO-3186:
-------------------------------

             Summary: Avro can't decode union<null, logicalType> field of a record 
                 Key: AVRO-3186
                 URL: https://issues.apache.org/jira/browse/AVRO-3186
             Project: Apache Avro
          Issue Type: Bug
          Components: java
    Affects Versions: 1.10.2
         Environment: JDK 11, macOS.
            Reporter: Yubao Liu


[https://github.com/apache/avro/blob/release-1.10.2/lang/java/avro/src/main/java/org/apache/avro/generic/GenericDatumReader.java#L163]

{code:java}
  protected Object read(Object old, Schema expected, ResolvingDecoder in) throws IOException {
    Object datum = readWithoutConversion(old, expected, in);
    LogicalType logicalType = expected.getLogicalType();
    if (logicalType != null) {
      Conversion<?> conversion = getData().getConversionFor(logicalType);  // <---- bad
      if (conversion != null) {
        return convert(datum, expected, logicalType, conversion);
      }
    }
    return datum;
  }
 {code}
 
For a logic type field in a union,  getData().getConversionFor(logicalType) returns null, the cause is SpecificData.getForSchema() isn't compatible with JDK >= 9,  it can't depend on Class.forName() to load user class.

[https://github.com/apache/avro/blob/release-1.10.2/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java#L147]

{code:diff}
diff --git a/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java b/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java
index 58bc660b..33fc3418 100644
--- a/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java
+++ b/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java
@@ -140,15 +140,9 @@ public class SpecificData extends GenericData {
    */
   public static SpecificData getForSchema(Schema reader) {
     if (reader != null && reader.getType() == Type.RECORD) {
-      final String className = getClassName(reader);
-      if (className != null) {
-        final Class<?> clazz;
-        try {
-          clazz = Class.forName(className);
-          return getForClass(clazz);
-        } catch (ClassNotFoundException e) {
-          return SpecificData.get();
-        }
+      final Class<?> clazz = SpecificData.get().getClass(reader);
+      if (clazz != null) {
+        return getForClass(clazz);
       }
     }
     return SpecificData.get();
{code}



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