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From "Niels Basjes (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1614) Always getting a value...
Date Mon, 01 Dec 2014 15:53:12 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14229920#comment-14229920

Niels Basjes commented on AVRO-1614:

Basic idea of this approach:
In a Builder in addition to the actual value of a field there is now also a "Builder" field
for that field possible.
If that is used then you can have the incomplete form of the sub-schema in a Builder.
So for any Builder instance there is a getFooBuilder() that either returns the existing or
creates a new Builder instance for the Foo field if such a builder is supported.

As a consequence: 
- schema validation is postponed until the actual build() is called.
- for the fields where this Builder is used the actual build() call becomes recursive.

So in my testing code I can now do this:
    Measurement.Builder measurementBuilder = Measurement.newBuilder();


    Measurement measurement = measurementBuilder.build();

Open question: I have not seen unit tests that validate the generated Java code. How to approach

> Always getting a value...
> -------------------------
>                 Key: AVRO-1614
>                 URL: https://issues.apache.org/jira/browse/AVRO-1614
>             Project: Avro
>          Issue Type: New Feature
>          Components: java
>            Reporter: Niels Basjes
>         Attachments: AVRO-1614-2014-12-01-v2.patch, AVRO-1614-20141027-v1.patch
> Sometimes the Avro structure becomes deeply nested.
> If in such a scenario you want to be able to set a specific value deep in this tree you
want to do this:
> {code}
> public void setSomething(String value) {
>     myStruct
>             .getFoo()
>             .getBar()
>             .getOne()
>             .getOther()
>             .setSomething(value);
> }
> {code}
> The 'problem' I ran into is that any of the 4 get methods can return a null value so
the code I have to write is really huge.
> For every step in this method I have to build null checks and create the underlying instance
if it is null.
> I already started writing helper methods to do this for parts of my tree.
> To solve this in a way that makes this code readable I came up with the following which
I want to propose to you guys (before I start working on a patch).
> My idea is to generate a new 'get' method in addition to the existing normal get method
for the regular instance of the class.
> So in addition to the 
> {code}
> public Foo getFoo() {
>     return foo;
> }
> {code}
> I propose to generate something like this as well in the cases where this is a type of
structure that you may want to traverse as shown in the example.
> {code}
> public Foo getAlwaysFoo() {
>     if (foo == null) {
>         setFoo(Foo.newBuilder().build());
>     }
>     return foo;
> }
> {code}
> This way the automatically created instance immediately has all the defaults I have defined.
> Assuming this naming my code will be readable because it will look like this:
> {code}
> public void setSomething(String value) {
>     myStruct
>             .getAlwaysFoo()
>             .getAlwaysBar()
>             .getAlwaysOne()
>             .getAlwaysOther()
>             .setSomething(value);
> }
> {code}

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