MappingRedisConverter.writeCollection breaks on NULL values and missing next elements [DATAREDIS-1076]

binakot opened DATAREDIS-1076 and commented

Good day!

I'm using spring-data-redis to store some collections with nullable elements. There are cases when some elements may be null. I was surpriced when I found a losing of ending elements in my collections.

I did a search the reason, and I found it: https://github.com/spring-projects/spring-data-redis/commit/2492fbe332b7565e0724b8f7ec6c62f5d3178b25#diff-b71f4f4366952781ed005f6224ff7d5dR511

This break is still in the project https://github.com/spring-projects/spring-data-redis/blob/master/src/main/java/org/springframework/data/redis/core/convert/MappingRedisConverter.java#L705

Why is it required to break the writing elements on the first null in MappingRedisConverter.writeCollection? And why it didn't required before this commit https://github.com/spring-projects/spring-data-redis/commit/2492fbe332b7565e0724b8f7ec6c62f5d3178b25#diff-b71f4f4366952781ed005f6224ff7d5dR511?

I made a project with sample of the problem with different cases: leading/ending nulls and null in a middle of collections. https://github.com/binakot/spring-data-redis-null-elements/blob/master/src/test/java/com/baeldung/spring/data/redis/repo/NullableCollectionRepositoryIntegrationTest.java#L51

I'm using spring-boot version 1.5.22.RELEASE in my application, but this behaviour is repeatable with version 2.1.9.RELEASE. 

 

Redis stores the elements in separate values this way:

java:

Integer[] collection = {1,2,3,4,5};

redis:

collection.[0]: 1

collection.[1]: 2

collection.[2]: 3

collection.[3]: 4

collection.[4]: 5

 

When some element is null, Redis just skips the elements:

java:

Integer[] collection = {1,2,3,null,null};

redis:

collection.[0]: 1

collection.[1]: 2

collection.[2]: 3

 

But when nulls are not in the end:

java:

Integer[] collection = {1,2,null,4,5};

redis:

collection.[0]: 1

collection.[1]: 2

... lost 4 and 5

 

I'm using array, that's why I get null elements, if Redis cannot find value with certain index. And it's a behaviour which I excpect. At this moment I'm losing any values after the first null in an array. Behaviour of List and Array are similar, here is same tests for array of Integers https://github.com/binakot/spring-data-redis-null-elements/blob/master/src/test/java/com/baeldung/spring/data/redis/repo/NullableArrayRepositoryIntegrationTest.java#L50

 

What can I do? I cannot use some pseudo-null like Integer.MIN_VALUE or smth else.

 

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Affects: 2.2.3 (Moore SR3)

Reference URL: https://github.com/binakot/spring-data-redis-null-elements/blob/master/src/test/java/com/baeldung/spring/data/redis/repo/NullableCollectionRepositoryIntegrationTest.java#L50