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From "Fernando Moraes (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-2100) Nullable fields based on own annotations
Date Thu, 26 Oct 2017 11:17:00 GMT

    [ https://issues.apache.org/jira/browse/AVRO-2100?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16220331#comment-16220331
] 

Fernando Moraes commented on AVRO-2100:
---------------------------------------

Hello,  one way that I was able to solve the situation was by doing the following:


{code:java}

public class Entity {

    @NotNull
    private String name;

    @NotNull
    @Digits(integer = 6, fraction = 2)
    private BigDecimal salary;

}

public final class ReflectDataFactory {

    private final static Schema.Parser PARSER = new Schema.Parser();

    private final static String BIG_DECIMAL_SCHEMA_TEMPLATE
            = "{\n"
            + "  \"type\": \"bytes\",\n"
            + "  \"logicalType\": \"decimal\",\n"
            + "  \"precision\": %d,\n"
            + "  \"scale\": %d\n"
            + "}";

    private static final ReflectData INSTANCE = new ReflectData() {
        @Override
        protected Schema createFieldSchema(Field field, Map<String, Schema> names) {
            final Class<?> c = field.getType();
            final Schema schema
                    = c.isAssignableFrom(BigDecimal.class)
                    ? getSchemaBigDecimal(field)
                    : super.createFieldSchema(field, names);

            return (field.isAnnotationPresent(NotNull.class) && !field.isAnnotationPresent(Nullable.class))
                    ? makeNullable(schema) : schema;
        }

        @Override
        protected Schema createSchema(Type type, Map<String, Schema> names) {
            return super.createSchema(type, names);
        }

    };

    private static Schema getSchemaBigDecimal(final Field field) {
        int precision = 2;
        int scale = 2;
        if (field.isAnnotationPresent(Digits.class)) {
            final Digits digits = field.getAnnotation(Digits.class);
            precision = digits.integer();
            scale = digits.fraction();
        }
        return PARSER.parse(String.format(BIG_DECIMAL_SCHEMA_TEMPLATE, precision, scale));
    }

    public static ReflectData getInstance() {
        return INSTANCE;
    }

    public static void main(String[] args) {

        Schema schema = ReflectDataFactory.getInstance().getSchema(Entity.class);
        System.out.println(schema.toString(true));
    }

}

{code}

The last line, will result in: 


{noformat}
{
  "type" : "record",
  "name" : "Entity",
  "namespace" : "reflect",
  "fields" : [ {
    "name" : "name",
    "type" : [ "null", "string" ],
    "default" : null
  }, {
    "name" : "salary",
    "type" : [ "null", {
      "type" : "bytes",
      "logicalType" : "decimal",
      "precision" : 6,
      "scale" : 2
    } ],
    "default" : null
  } ]
}
{noformat}



> Nullable fields based on own annotations
> ----------------------------------------
>
>                 Key: AVRO-2100
>                 URL: https://issues.apache.org/jira/browse/AVRO-2100
>             Project: Avro
>          Issue Type: Wish
>          Components: java
>    Affects Versions: 1.8.2
>            Reporter: Fernando Moraes
>            Priority: Trivial
>
> Hello! first of all, congratulations on the project.
> I am generating avro schemas from java class, and my class already have annotations referring
to not null. I would like to know if it is possible to somehow override the default behavior
to define the nullable in the schema.
> My code looks like this:
> {code:java}
> public class MyJavaClass {
> 	
> 	@javax.validation.constraints.NotNull // This is necessary for my project.
> 	@org.apache.avro.reflect.Nullable // I wanted to avoid having to use this annotation
> 	private String field;
> }
> Schema schema = ReflectData.get().getSchema(MyJavaClass.class);
> {code}
> thank you all



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