Hi,
I've never experienced this before but I would suggestb setting a default
value for the UNION {"name": "other", "type": ["null", "Teacher",
"Student"]}
Lewis
On Mon, Dec 2, 2013 at 8:00 PM, andy36 <[email protected]> wrote:
> I am using [Apache Avro][1] for object serialization.
>
> I have one Avro schema for `School` object:
>
> {"namespace": "com.my.model",
> "type": "record",
> "name": "School",
> "fields": [
> {"name": "sid", "type": "int"},
> {"name": "size", "type": "long"},
> {"name": "other", "type": ["null", "Teacher", "Student"]}
> ]
> }
>
> As you see above, the `"other"` field holds an **union data type**, it
> could
> be either `null` or a `Teacher` instance or a `Student` instance.
>
> The **Teacher** object schema:
>
> {"namespace": "com.my.model",
> "type": "record",
> "name": "Teacher",
> "fields": [
> {"name": "isMale", "type": "boolean"}
> ]
> }
>
> The **Student** object schema:
>
> {"namespace": "com.my.model",
> "type": "record",
> "name": "Student",
> "fields": [
> {"name": "age", "type": "int"}
> ]
> }
>
> I compiled above schemas with Avro tool & Avro generated all the Java
> classes for me automatically.
>
> Then, in my java program I am creating `School` instance in the following
> way:
>
> School school = new School();
> school.setSid(3);
> school.setSize(2000);
>
> //create a student object
> Student student = new Student();
> student.setAge(18);
>
> //set student into school instance
> school.setOther(student);
>
> As you see above, the school instance's `other` field holds a student
> object. When I compile my code, however I got the
> **UnresolvedUnionException** . It complains about the **union data type**
> for the `other` field of `School` schema. Seems it can not resolve the
> `student` I set to `school` in my Java code. Why is this exception ?
> Stacktrace is:
>
> org.apache.avro.UnresolvedUnionException: Not in union
>
> ["null",{"type":"record","name":"Student","namespace":"com.my.model","fields":[{"name":"age","type":"long"}]},{"type":"record","name":"Teacher","namespace":"com.model","fields":[{"name":"isMale","type":"boolean"}]}]:
> false
> at
> org.apache.avro.generic.GenericData.resolveUnion(GenericData.java:561)
> at
>
> org.apache.avro.generic.GenericDatumWriter.resolveUnion(GenericDatumWriter.java:144)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:71)
> at
>
> org.apache.avro.generic.GenericDatumWriter.writeRecord(GenericDatumWriter.java:106)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:66)
> at
>
> org.apache.avro.generic.GenericDatumWriter.writeArray(GenericDatumWriter.java:131)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:68)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:73)
> at
>
> org.apache.avro.generic.GenericDatumWriter.writeRecord(GenericDatumWriter.java:106)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:66)
> at
>
> org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:58)
>
>
> [1]: http://avro.apache.org/docs/1.7.4/gettingstartedjava.html
>
>
>
> --
> View this message in context:
> http://apache-avro.679487.n3.nabble.com/Apache-Avro-UnresolvedUnionException-when-using-union-data-type-tp4028641.html
> Sent from the Avro - Users mailing list archive at Nabble.com.
>
--
*Lewis*
