No, it should not initialize the field to the default.
Default values are for readers, not writers. The intended use case is schema
evolution. A reader on version N+1 has field foo with default 'quux', but
reads data that was written without that field. The reader will see foo =
'quux'.
A writer must always correctly provide data for all of the fields in the schema
it declared it is writing.
The specific API does make this a bit more difficult than it needs to be, it is
something I would like to address at a later time. In the meantime I use
wrapper classes around the SpecificRecord objects that provide restricted
getters and restrictive constructors or factory methods to prevent other users
from forgetting to set a field.
-Scott
On Jun 7, 2010, at 1:53 PM, Bill de hOra wrote:
> Hi,
>
> I.m wondering if I'm missing an incantation for 'compile
> schema/protocol' in Avro tools to handle defaults. Given this schema,
>
> [[[
> {
> "name": "avro.Message",
> "type": "record",
> "fields": [
> {
> "name": "foo",
> "type": "string",
> "default":"quux"
> },
> {
> "name": "bar",
> "type": "string"
> }
> ]
>
> }
> ]]]
>
> and running it through 'avro-tools-1.3.2.jar compile schema', I get this
> object
>
> [[[
> package avro;
>
> @SuppressWarnings("all")
> public class Message extends org.apache.avro.specific.SpecificRecordBase
> implements org.apache.avro.specific.SpecificRecord {
> public static final org.apache.avro.Schema SCHEMA$ =
> org.apache.avro.Schema.parse("{\"type\":\"record\",\"name\":\"Message\",\"namespace\":\"avro\",\"fields\":[{\"name\":\"foo\",\"type\":\"string\",\"default\":\"quux\"},{\"name\":\"bar\",\"type\":\"string\"}]}");
> public org.apache.avro.util.Utf8 foo = new Utf8("quux");
> public org.apache.avro.util.Utf8 bar;
> public org.apache.avro.Schema getSchema() { return SCHEMA$; }
> public java.lang.Object get(int field$) {
> switch (field$) {
> case 0: return foo;
> case 1: return bar;
> default: throw new org.apache.avro.AvroRuntimeException("Bad index");
> }
> }
> @SuppressWarnings(value="unchecked")
> public void put(int field$, java.lang.Object value$) {
> switch (field$) {
> case 0: foo = (org.apache.avro.util.Utf8)value$; break;
> case 1: bar = (org.apache.avro.util.Utf8)value$; break;
> default: throw new org.apache.avro.AvroRuntimeException("Bad index");
> }
> }
> }
> ]]]
>
> Should this line,
>
> [[[
> public org.apache.avro.util.Utf8 foo;
> ]]]
>
> be,
>
> [[[
> public org.apache.avro.util.Utf8 foo
> = new org.apache.avro.util.Utf8("quux");
> ]]]
>
> ?
>
> Fwiw, changing the object's 'foo' field above to have the default stops
> the IPC server from barfing with an NPE (@
> org.apache.avro.io.BinaryEncoder.writeString(BinaryEncoder.java:133))
> when a client creates a message object only sets 'bar', and then sends
> the Message to the server via .
>
> Bill
>
>
>
