[
https://issues.apache.org/jira/browse/AVRO-1811?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Ryon Day updated AVRO-1811:
---------------------------
Description:
{panel:title=Description|titleBGColor=#3FA|bgColor=#DDD}
When the Avro compiler creates Java objects, you have the option to have them
generate fields of type {{string}} with the Java standard {{String}} type, for
wide interoperability with existing Java applications and APIs.
By default, however, the compiler outputs these fields in the Avro-specific
{{Utf8}} type, requiring frequent usage of the {{toString()}} method in order
for default domain objects to be used with the majority of Java libraries.
There are two ways to get around this. The first is to annotate every
{{string}} field in a schema like so:
{code}
{
"name": "some_string",
"doc": "a field that is guaranteed to compile to java.lang.String",
"type": [
"null",
{
"type": "string",
"avro.java.string": "String"
}
]
},
{code}
Unfortunately, long schemas containing many string fields can be dominated by
this annotation by volume; for teams using heterogenous clients, they may to
want to avoid Java-specific annotation in their schema files, or may not think
to use it unless there exist Java exploiters of the schema at the time the
schema is proposed and written.
The other solution to the problem is to compile the schema into Java objects
using the {{SpecificCompiler}}'s string type selection. This option actually
alters the schema carried by the object's {{SCHEMA$}} field to have the above
annotation in it, ensuring that when used by the Java API, the String type will
be used.
Unfortunately, this method is not interoperable with GenericRecords created by
libraries that use the _original_ schema.
{panel}
{panel:title=Steps To Reproduce|titleBGColor=#8DB|bgColor=#DDD}
# Create a schema with several {{string}} fields.
# Parse the schema using the standard Avro schema parser
# Create Java domain objects for that schema ensuring usage of the
{{java.lang.String}} string type.
# Create a message of some sort that ends up as a {{GenericRecord}} of the
original schema
# Attempt to use {{SpecificData.deepCopy()}} to make a {{SpecificRecord}} out
of the {{GenericRecord}}
There is a unit test that demonstrate this
[here|https://github.com/ryonday/avroDecodingHelp/blob/master/1.8.0/src/test/java/com/ryonday/avro/test/v180/AvroDeepCopyTest.java]
{panel}
{panel:title=Expected Results|titleBGColor=#AD3|bgColor=#DDD}
As the schemas are literally identical aside from string type, the conversion
should work (and does work for schema that are exactly identical).
{panel}
{panel:title=Actual Results|titleBGColor=#D55|bgColor=#DDD}
{{ClassCastException}} with the message {{org.apache.avro.util.Utf8 cannot be
cast to java.lang.String}}
{panel}
was:
{panel:title=Description|titleBGColor=#3FA|bgColor=#DDD}
When the Avro compiler creates Java objects, you have the option to have them
generate fields of type {{string}} with the Java standard {{String}} type, for
wide interoperability with existing Java applications and APIs.
By default, however, the compiler outputs these fields in the Avro-specific
{{UTF8}} type, requiring frequent usage of the {{toString()}} method in order
for default domain objects to be used with the majority of Java libraries.
There are two ways to get around this. The first is to annotate every
{{string}} field in a schema like so:
{code}
{
"name": "some_string",
"doc": "a field that is guaranteed to compile to java.lang.String",
"type": [
"null",
{
"type": "string",
"avro.java.string": "String"
}
]
},
{code}
Unfortunately, long schemas containing many string fields can be dominated by
this annotation by volume; for teams using heterogenous clients, they may to
want to avoid Java-specific annotation in their schema files, or may not think
to use it unless there exist Java exploiters of the schema at the time the
schema is proposed and written.
The other solution to the problem is to compile the schema into Java objects
using the {{SpecificCompiler}}'s string type selection. This option actually
alters the schema carried by the object's {{SCHEMA$}} field to have the above
annotation in it, ensuring that when used by the Java API, the String type will
be used.
Unfortunately, this method is not interoperable with GenericRecords created by
libraries that use the _original_ schema.
{panel}
{panel:title=Steps To Reproduce|titleBGColor=#8DB|bgColor=#DDD}
# Create a schema with several {{string}} fields.
# Parse the schema using the standard Avro schema parser
# Create Java domain objects for that schema ensuring usage of the
{{java.lang.String}} string type.
# Create a message of some sort that ends up as a {{GenericRecord}} of the
original schema
# Attempt to use {{SpecificData.deepCopy()}} to make a {{SpecificRecord}} out
of the {{GenericRecord}}
There is a unit test that demonstrate this
[here|https://github.com/ryonday/avroDecodingHelp/blob/master/1.8.0/src/test/java/com/ryonday/avro/test/v180/AvroDeepCopyTest.java]
{panel}
{panel:title=Expected Results|titleBGColor=#AD3|bgColor=#DDD}
As the schemas are literally identical aside from string type, the conversion
should work (and does work for schema that are exactly identical).
{panel}
{panel:title=Actual Results|titleBGColor=#D55|bgColor=#DDD}
{{ClassCastException}} with the message {{org.apache.avro.util.Utf8 cannot be
cast to java.lang.String}}
{panel}
> SpecificData.deepCopy() cannot be used if schema compiler generated Java
> objects with Strings instead of UTF8
> -------------------------------------------------------------------------------------------------------------
>
> Key: AVRO-1811
> URL: https://issues.apache.org/jira/browse/AVRO-1811
> Project: Avro
> Issue Type: Bug
> Affects Versions: 1.8.0
> Reporter: Ryon Day
>
> {panel:title=Description|titleBGColor=#3FA|bgColor=#DDD}
> When the Avro compiler creates Java objects, you have the option to have them
> generate fields of type {{string}} with the Java standard {{String}} type,
> for wide interoperability with existing Java applications and APIs.
> By default, however, the compiler outputs these fields in the Avro-specific
> {{Utf8}} type, requiring frequent usage of the {{toString()}} method in order
> for default domain objects to be used with the majority of Java libraries.
> There are two ways to get around this. The first is to annotate every
> {{string}} field in a schema like so:
> {code}
> {
> "name": "some_string",
> "doc": "a field that is guaranteed to compile to java.lang.String",
> "type": [
> "null",
> {
> "type": "string",
> "avro.java.string": "String"
> }
> ]
> },
> {code}
> Unfortunately, long schemas containing many string fields can be dominated by
> this annotation by volume; for teams using heterogenous clients, they may to
> want to avoid Java-specific annotation in their schema files, or may not
> think to use it unless there exist Java exploiters of the schema at the time
> the schema is proposed and written.
> The other solution to the problem is to compile the schema into Java objects
> using the {{SpecificCompiler}}'s string type selection. This option actually
> alters the schema carried by the object's {{SCHEMA$}} field to have the above
> annotation in it, ensuring that when used by the Java API, the String type
> will be used.
> Unfortunately, this method is not interoperable with GenericRecords created
> by libraries that use the _original_ schema.
> {panel}
> {panel:title=Steps To Reproduce|titleBGColor=#8DB|bgColor=#DDD}
> # Create a schema with several {{string}} fields.
> # Parse the schema using the standard Avro schema parser
> # Create Java domain objects for that schema ensuring usage of the
> {{java.lang.String}} string type.
> # Create a message of some sort that ends up as a {{GenericRecord}} of the
> original schema
> # Attempt to use {{SpecificData.deepCopy()}} to make a {{SpecificRecord}} out
> of the {{GenericRecord}}
> There is a unit test that demonstrate this
> [here|https://github.com/ryonday/avroDecodingHelp/blob/master/1.8.0/src/test/java/com/ryonday/avro/test/v180/AvroDeepCopyTest.java]
> {panel}
> {panel:title=Expected Results|titleBGColor=#AD3|bgColor=#DDD}
> As the schemas are literally identical aside from string type, the conversion
> should work (and does work for schema that are exactly identical).
> {panel}
> {panel:title=Actual Results|titleBGColor=#D55|bgColor=#DDD}
> {{ClassCastException}} with the message {{org.apache.avro.util.Utf8 cannot be
> cast to java.lang.String}}
> {panel}
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