Fix: client breaks when evaluation contains segments or unknown response fields by liamhughes · Pull Request #5 · OctopusDeploy/openfeature-provider-java

liamhughes · 2026-03-25T22:40:57Z

Background

The provider was failing to deserialise evaluation API responses in two scenarios:

If segments were present
New (or otherwise unknown) response fields

https://linear.app/octopus/issue/DEVEX-80/java-client-breaks-on-segments-and-new-response-fields

Changes

Added Segment class
- Replaces Map.Entry<String, String> as the type for segment data, with required key and value fields.
- Uses @JsonCreator/@JsonProperty for deserialisation.
Added OctopusObjectMapper
- Wraps a shared, static ObjectMapper instance configured with case-insensitive property matching and FAIL_ON_UNKNOWN_PROPERTIES disabled, so API responses with differing capitalisation or new fields deserialise correctly.
- ObjectMapper is static to avoid the cost of repeated instantiation.
getSegments() returns an immutable list.
Added FeatureToggleEvaluationDeserializationTests
- Unit tests covering: enabled/disabled toggles, null or missing segments field, toggles with one or more segments, a list of toggles, responses containing extraneous/unknown properties, and responses with differing field capitalisation.
- Note: some these tests can perhaps be removed when we add the new specification tests.

Notes for review

I have opted to not implement equals/hashCode on Segment because it's verbose and not needed at this time. I think we can rely on tests to make sure we don't get caught out, but happy for a difference of opinion here.

Copilot

Pull request overview

Fixes Jackson deserialization failures in the provider client when the evaluation response includes segments or introduces previously-unknown fields, by adding targeted Jackson configuration and tests.

Changes:

Added a custom Jackson SegmentDeserializer to map { "key": "...", "value": "..." } into Map.Entry<String,String>.
Updated FeatureToggleEvaluation to (a) ignore unknown response properties and (b) wire the custom deserializer for segments.
Added unit tests + JSON fixtures covering segments, missing/null segments, list responses, and extraneous properties.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

File	Description
`src/main/java/com/octopus/openfeature/provider/SegmentDeserializer.java`	Adds custom element deserialization for `segments` entries.
`src/main/java/com/octopus/openfeature/provider/FeatureToggleEvaluation.java`	Ignores unknown fields and applies the segment entry deserializer.
`src/test/java/com/octopus/openfeature/provider/FeatureToggleEvaluationDeserializationTests.java`	Adds coverage for the previously failing deserialization scenarios.
`src/test/resources/com/octopus/openfeature/provider/*.json`	Adds fixture payloads for the deserialization tests.

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src/main/java/com/octopus/openfeature/provider/SegmentDeserializer.java

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

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dylanlerch

Looks good. One question about case-insensitivity.

dylanlerch · 2026-03-26T01:32:16Z

src/main/java/com/octopus/openfeature/provider/SegmentDeserializer.java

+            return null;
+        }
+
+        JsonNode keyNode = node.get("key");


Is this case-insensitive?

And can we add a test for it to make sure that it is (I couldn't find one but I also might just be a silly boy that missed it).

To answer your question: none of this JSON deserialisation was case insensitive.

Implementing case insensitivity led me to two major changes:

a shared ObjectMapper which also replaced the previous solution to extraneous fields

introducing a Segment type rather than further complicate the SegmentDeserializer

Significant changes since.

Copilot

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 5 comments.

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src/main/java/com/octopus/openfeature/provider/OctopusContext.java

src/main/java/com/octopus/openfeature/provider/Segment.java

Copilot · 2026-03-26T05:06:44Z

src/main/java/com/octopus/openfeature/provider/OctopusObjectMapper.java

+class OctopusObjectMapper {
+    static final ObjectMapper INSTANCE = JsonMapper.builder()
+            .enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)
+            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+            .build();


OctopusObjectMapper.INSTANCE is a mutable ObjectMapper that can be reconfigured by any code in the package, which can lead to surprising cross-test or runtime behavior. Consider making the class final with a private constructor and exposing the mapper via a method that returns the shared instance (or a copy) while preventing external reconfiguration.

Suggested change

class OctopusObjectMapper {

static final ObjectMapper INSTANCE = JsonMapper.builder()

.enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)

.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)

.build();

final class OctopusObjectMapper {

private static final ObjectMapper INSTANCE = JsonMapper.builder()

.enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)

.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)

.build();

private OctopusObjectMapper() {

// Utility class; prevent instantiation.

}

static ObjectMapper getInstance() {

// Return a defensive copy to avoid shared mutable configuration.

return INSTANCE.copy();

}

Hmm...the whole point was to reuse the same instance. Making the wrapper final wouldn't hurt, but seems unnecessary?

Copilot · 2026-03-26T05:06:45Z

src/test/java/com/octopus/openfeature/provider/FeatureToggleEvaluationDeserializationTests.java

+
+import java.io.InputStream;
+import java.util.List;
+import java.util.Map;


Unused import java.util.Map can be removed to keep the test focused and avoid IDE/linter noise.

Suggested change

import java.util.Map;

liamhughes added 2 commits March 26, 2026 09:39

JSON deserialisation tests

1b0dffa

Apply fixes

f6a013c

liamhughes requested a review from Copilot March 25, 2026 22:51

Copilot started reviewing on behalf of liamhughes March 25, 2026 22:51 View session

Copilot AI reviewed Mar 25, 2026

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src/main/java/com/octopus/openfeature/provider/SegmentDeserializer.java Outdated Show resolved Hide resolved

liamhughes and others added 4 commits March 26, 2026 09:57

Add more checks during segment deserialisation

c6a8855

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Add SegmentDeserializerTests

2310f22

Idiomatic handling of null warnings

d4b0cfb

SimpleImmutableEntry

633c026

liamhughes marked this pull request as ready for review March 25, 2026 23:32

liamhughes requested review from a team and Copilot March 25, 2026 23:34

Copilot started reviewing on behalf of liamhughes March 25, 2026 23:35 View session

Copilot AI reviewed Mar 25, 2026

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dylanlerch previously approved these changes Mar 26, 2026

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liamhughes mentioned this pull request Mar 26, 2026

test: JSON deserialisation tests #4

Closed

liamhughes added 3 commits March 26, 2026 15:27

Make deserialisation case insensitive

1046508

Replace Map.Entry<String, String> with Segment

a839dfe

Make getSegments return immutable

6626ea6

liamhughes added 3 commits March 26, 2026 15:43

Clean up

5cca0e0

Make ObjectMapper static for performance

12f7edb

Make Segment key and value required

6d04e1f

liamhughes requested review from Copilot and dylanlerch March 26, 2026 05:02

Copilot started reviewing on behalf of liamhughes March 26, 2026 05:02 View session

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dylanlerch approved these changes Mar 27, 2026

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liamhughes merged commit ce8282e into main Mar 27, 2026
9 checks passed

liamhughes deleted the liamhughes/devex-80-java-client-breaks-on-segments-and-new-response-fields branch March 27, 2026 04:37

liamhughes mentioned this pull request Mar 30, 2026

Use new evaluations endpoint #7

Merged

liamhughes mentioned this pull request Apr 7, 2026

feat: Use new evaluations endpoint OctopusDeploy/openfeature-provider-ts-web#48

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Fix: client breaks when evaluation contains segments or unknown response fields#5

Fix: client breaks when evaluation contains segments or unknown response fields#5
liamhughes merged 12 commits intomainfrom
liamhughes/devex-80-java-client-breaks-on-segments-and-new-response-fields

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