[AVRO-3186] Java: Avro can't decode union<null, logicalType> field of a record

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.10.2
• Fix Version/s: 1.11.0
• Component/s: java
• Labels: pull-request-available

Environment

JDK 11, macOS.

• Assignee: Yubao Liu
• Reporter: Yubao Liu
• Created: 13/Aug/21 10:37
• Updated: 04/Mar/22 10:23
• Resolved: 05/Oct/21 12:33

Description

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

  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;
  }
 

 
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

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();

Issue Links

• is duplicated by: AVRO-3156 Performance degradation in SpecificRecordBuilder introduced in 1.9.0
• links to: GitHub Pull Request #1304