Thanks again Scott,
Yes, I am using AVRO to serialize existing Java classes, so tools to
generate code will not help me.
Are there tools that go the other way, such as JAXB for XML? I really
want to point to a root Java object, and say "serialize this, and
everything it points to, as AVRO".
BTW AVRO Rocks! My objects contain are amounts of data, and I am *very*
impressed with the speed of serialization/deserialization.
Cheers
P
On 7/14/11 10:10 PM, Scott Carey wrote:
AvroIDL can handle imports, but it generates classes. The Avro API's
for this can be used to generate Schemas without making objects if you
wish.
The Avro schema compiler (*.avsc, *.avpr) does not support imports, it
is a feature requested by many but not contributed by anyone.
You may be interested in the code-gen capabilities of Avro, which has
a Velocity templating engine to create Java classes based on schemas.
This can be customized to generate classes in custom ways.
However, if you are using Avro to serialize objects that have
pre-existing classes, the Reflect API or an enhancement of it may be
more suitable.
More information on your use case may help to point you in the right
direction.
-Scott
On 7/14/11 6:43 PM, "Peter Wolf" <opus...@gmail.com
<mailto:opus...@gmail.com>> wrote:
Many thanks Scott,
I am looking for the equivalent of #include or import. I want to
make a complicated schema with many record types, but manage it in
separate strings.
In my application, I am using AVRO to serialize a tree of
connected Java objects. The record types mirror Java classes.
The schema descriptions live in the different Java classes, and
reference each other.
My current code looks like this...
public class Foo {
static String schemaDescription =
"{" +
" \"namespace\": \"foo\", " +
" \"name\": \"Foo\", " +
" \"type\": \"record\", " +
" \"fields\": [ " +
" {\"name\": \"notes\", \"type\":
\"string\" }, " +
" {\"name\": \"timestamp\", \"type\":
\"string\" }, " +
" {\"name\": \"bah\", \"type\": " +
Bah.schemaDescription + " }," +
" {\"name\": \"zot\", \"type\": " +
Zot.schemaDescription + " }" +
" ]" +
"}";
static Schema schema = Schema.parse(schemaDescription);
So, I am referencing by copying the schemaDescriptions. The top
level schemaDescription strings therefore get really big.
Is there already a clean coding Pattern for doing this-- I can't
be the first. Is there a document describing best practices?
Thanks
P
On 7/14/11 7:02 PM, Scott Carey wrote:
The name and namespace is part of any named schema (Type.RECORD,
Type.FIXED, Type.ENUM).
We don't currently have an API to search a schema for subschemas
that match names. It would be useful, you might want to create a
JIRA ticket explaining your use case.
So it would be a little more complex.
Schema schema = Schema.parse(schemaDescription);
Schema.Type type = schema.getType();
switch (type) {
case RECORD:
String name = schema.getName();
String namespace = schema.getNamespace();
List<Field> fields = schema.getFields();
}
etc.
In general, I have created SpecificRecord objects from schemas
using the specific compiler (and the ant task or maven plugin)
and then within those generated classes there is a static SCHEMA
variable to reference.
Avro IDL is alo an easier way to define related schemas.
Currently there are only build tools that generate code from
these, though there are APIs to extract schemas.
-Scott
On 7/13/11 10:43 AM, "Peter Wolf" <opus...@gmail.com
<mailto:opus...@gmail.com>> wrote:
Hello, this a dumb question, but I can not find the answer in
the docs
I want to have a complicated schema with lots of Records
referencing other Records.
Like this...
{
"namespace": "com.foobah",
"name": "Bah",
"type": "record",
"fields": [
{"name": "value", "type": "int"}
]
}
{
"namespace": "com.foobah",
"name": "Foo",
"type": "record",
"fields": [
{"name": "bah", "type": "Bah"}
]
}
Using the Java API, how do I reference types within a
schema? Let's say I want to make a Foo object, I want to do
something like this...
Schema schema = Schema.parse(schemaDescription);
>>> Schema foo = schema.getSchema("com.foobah.Foo"); <<<
GenericData o = new GenericData( foo );
Many thanks in advance
Peter
