[AVRO-3077] Ability of select string deserializing mode by configuration

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.10.1
• Component/s: java
• Assignee: Unassigned
• Reporter: Emilio Jose Mena Cebrian
• Created: 11/Mar/21 10:15
• Updated: 02/Apr/23 14:38

Description

Current Java generator modifies the source schema to add a property to describe the way a reader decodes a string. (see AVRO-2918)

I think this is a design problem. The way a reader deserializes a string shouldn't modify the schema (the schema describes the structure of avro message, not the way a reader converts to a usable form).

On the other hand, a reader might require the strings as a CharSequence because it knows how to handle them and other as a String.

The only way to do this now is modifying the schema itself in each reader. If you use Avro with other technologies like Kafka (or confluent) It migth be non-viable.

 

I think that the way a reader decodes messages should be specified by the reader and It'll be desirable to specify this using a configuration.

 

Maybe if a System property (like useCustomCoders feature) or something similar could be added to modify the default value for String decoding.

Form GenericDatumReader

 

    protected Class findStringClass(Schema schema) {
            String name = schema.getProp(GenericData.STRING_PROP);
            if (name == null)
              return CharSequence.class;

            switch (GenericData.StringType.valueOf(name)) {
            case String:
              return String.class;
            default:
              return CharSequence.class;
            }
          }

Maybe adding a "forced" configuration may help: if reader configures string representation, use it, if not do it the current way.

 

And do something similar in SpecificDatumReader

 

 

 

 

 

 

Issue Links

• is related to: AVRO-2838 Schema in generated Java class is different than the original one