This appears to be a bug. A field seems to have been created with a null name
or schema. Aliases are new in 1.4.
Can you file a JIRA ticket on this?
Thanks!
-Scott
On Nov 23, 2010, at 7:15 PM, Ryan Holmes wrote:
> I'm getting an NPE when writing an Avro file with one schema and reading back
> with a slightly modified schema. The only difference between the writer and
> the reader schemas is that the reader renames a single field and adds an
> alias. I'm just testing Avro's schema evolution features, so the code is
> indeed as trivial as it appears. Here's the stack trace I get when reading:
>
> Exception in thread "main" java.lang.NullPointerException
> at org.apache.avro.Schema$Field.hashCode(Schema.java:421)
> at java.util.AbstractList.hashCode(AbstractList.java:527)
> at org.apache.avro.Schema$RecordSchema.hashCode(Schema.java:602)
> at
> org.apache.avro.io.parsing.ValidatingGrammarGenerator$LitS.hashCode(ValidatingGrammarGenerator.java:133)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator$LitS2.hashCode(ResolvingGrammarGenerator.java:461)
> at java.util.HashMap.get(HashMap.java:300)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.resolveRecords(ResolvingGrammarGenerator.java:197)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.generate(ResolvingGrammarGenerator.java:118)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.generate(ResolvingGrammarGenerator.java:50)
> at org.apache.avro.io.ResolvingDecoder.resolve(ResolvingDecoder.java:76)
> at org.apache.avro.io.ResolvingDecoder.<init>(ResolvingDecoder.java:46)
> at
> org.apache.avro.generic.GenericDatumReader.getResolver(GenericDatumReader.java:93)
> at
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:103)
> at org.apache.avro.file.DataFileStream.next(DataFileStream.java:198)
> at org.apache.avro.file.DataFileStream.next(DataFileStream.java:185)
> ...
>
>
> The writer schema:
>
> { "type": "record",
> "name": "Message",
> "namespace": "com.edmunds.avro.data",
> "fields" : [
> {"name": "id", "type": "long"},
> {"name": "time", "type": "long"},
> {"name": "body", "type": ["string", "null"]}
> ]
> }
>
>
> The reader schema:
>
> { "type": "record",
> "name": "Message",
> "namespace": "com.edmunds.avro.data",
> "fields" : [
> {"name": "messageId", "type": "long", "aliases": ["id"]},
> {"name": "time", "type": "long"},
> {"name": "body", "type": ["string", "null"]}
> ]
> }
>
>
> Here's the writing code:
>
> private void writeMessages() {
>
> File file = getAvroFile();
>
> if(file.exists()) {
> file.delete();
> }
>
> DatumWriter<Message> writer = new
> SpecificDatumWriter<Message>(Message.class);
> DataFileWriter<Message> dataFileWriter = new
> DataFileWriter<Message>(writer);
> try {
> dataFileWriter.create(Message.SCHEMA$, file);
> for(Message m : createMessages()) {
> dataFileWriter.append(m);
> System.out.println("Wrote message: " + objToString(m));
> }
> dataFileWriter.close();
> } catch (IOException e) {
> e.printStackTrace();
> }
> }
>
>
> And the reading code:
>
> private void readMessages() {
>
> File file = getAvroFile();
> DatumReader<Message> reader = new
> SpecificDatumReader<Message>(Message.class);
>
> DataFileReader<Message> dataFileReader;
> try {
> dataFileReader = new DataFileReader<Message>(file, reader);
> } catch (IOException e) {
> e.printStackTrace();
> return;
> }
>
> while(dataFileReader.hasNext()) {
> Message m = dataFileReader.next();
> System.out.println("Read message: " + objToString(m));
> }
> }
>
>
>
> I'm using Avro 1.4.1 and the avro-maven-plugin (updated to Avro 1.4.1) to
> generate the Message class(es). My code works fine when I use the exact same
> schema for the reader and writer. What am I doing wrong?
>
