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https://issues.apache.org/jira/browse/AVRO-1186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15101978#comment-15101978
]
Christopher Ng commented on AVRO-1186:
--------------------------------------
FYI to make it work in IDL you have to be careful about where you place the
annotation. Naively you would probably lay it out like this:
{code}
@namespace("org.apache.avro.ipc.specific")
protocol JavaAnnotation {
@javaAnnotation("org.apache.avro.TestAnnotation")
record AnnotatedRecord {
@javaAnnotation(["org.apache.avro.TestAnnotation"])
string name;
}
}
{code}
but this won't work, it will end up with the annotation applied to the type,
which will then be ignored:
{code}
{
"protocol" : "JavaAnnotation",
"namespace" : "org.apache.avro.ipc.specific",
"types" : [ {
"type" : "record",
"name" : "AnnotatedRecord",
"fields" : [ {
"name" : "name",
"type" : {
"type" : "string",
"javaAnnotation" : [ "org.apache.avro.TestAnnotation" ]
}
} ],
"javaAnnotation" : "org.apache.avro.TestAnnotation"
} ],
"messages" : { }
{code}
Instead you have to make sure the annotation is applied to the field name:
{code}
@namespace("org.apache.avro.ipc.specific")
protocol JavaAnnotation {
@javaAnnotation("org.apache.avro.TestAnnotation")
record AnnotatedRecord {
string @javaAnnotation(["org.apache.avro.TestAnnotation"]) name;
}
}
{code}
which results in:
{code}
{
"protocol" : "JavaAnnotation",
"namespace" : "org.apache.avro.ipc.specific",
"types" : [ {
"type" : "record",
"name" : "AnnotatedRecord",
"fields" : [ {
"name" : "name",
"type" : "string",
"javaAnnotation" : [ "org.apache.avro.TestAnnotation" ]
} ],
"javaAnnotation" : "org.apache.avro.TestAnnotation"
} ],
"messages" : { }
}
{code}
and the annotation applied correctly to the field.
It would be nice if you could apply annotations to the getter/setters, though,
they only apply to the fields.
> Java Annotations via IDL
> ------------------------
>
> Key: AVRO-1186
> URL: https://issues.apache.org/jira/browse/AVRO-1186
> Project: Avro
> Issue Type: New Feature
> Components: java
> Reporter: Sharmarke Aden
> Assignee: Doug Cutting
> Fix For: 1.7.3
>
> Attachments: AVRO-1186.patch, AVRO-1186.patch
>
>
> We would like to have the ability to add Java annotations to fields in the
> Avro IDL (i.e. JSR 303 Bean Validation annotations). From a protocol stand
> point these annotations may not mean much (or could they?) but from the
> application stand point having this feature would allow developers to use
> Avro generated beans application wide. From view layer all the way to the
> data layer. To support this feature an IDL file could look something like
> this:
> {code}
> @namespace("test.annotations")
> protocol TestProto {
> record User {
> //declare the annotations that are imported in the generated record class
> @header{
> import org.hibernate.validator.constraints.NotBlank;
> import org.hibernate.validator.constraints.Email;
> }
>
> //for each field one can specify an annotation they would like to use.
> @{@NotBlank} string username;
> string password;
> @{@Email} string email;
> }
> }
> {code}
> The above IDL would generate a Java class that looks something like this:
> {code}
> /**
> * Autogenerated by Avro
> *
> * DO NOT EDIT DIRECTLY
> */
> package com.simvia.mode.avro;
> import org.hibernate.validator.constraints.NotBlank;
> import org.hibernate.validator.constraints.Email;
> @SuppressWarnings("all")
> public class User extends org.apache.avro.specific.SpecificRecordBase
> implements org.apache.avro.specific.SpecificRecord {
> ...
> @Deprecated @NotBlank public java.lang.CharSequence username;
> @Deprecated public java.lang.CharSequence password;
> @Deprecated @Email public java.lang.CharSequence email;
> ...
> }
> {code}
> Perhaps this is too language specific but IMO the benefits of this feature in
> the Java world is worth the effort and the exception.
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