JSON Patch uses org.springframework.core.convert.support.DefaultConversionService#getSharedInstance

[buckett]

When a JSON patch request is made the paths are parsed and converted into org.springframework.data.rest.webmvc.json.patch.SpelPath when values are then replaced the SpEL paths are then evaluated using a org.springframework.expression.spel.ExpressionState and this uses a org.springframework.expression.spel.support.SimpleEvaluationContext which then ended up using a org.springframework.expression.spel.support.StandardTypeConverter, this in turn uses org.springframework.core.convert.support.DefaultConversionService#getSharedInstance for it's conversion service.

This works for simple cases (Strings and Ints), but the DefaultConversionService doesn't have complete support for Java 8 date and time classes and the JavaDoc on the method recommends that the service should only be used as a fallback.

There doesn't seem to be a way to override the ConversionService that is used when evaluating SpEL paths in JSON Patch files and it doesn't seem to be possible to add additional converters to the DefaultConversionService.

One solution might be to have org.springframework.data.rest.webmvc.json.patch.SpelPath.TypedSpelPath#CONTEXT setable at runtime and therefore allow a EvaluationContext with a different conversion service to be used.

[buckett]

I've got a tiny test that shows this problem in: https://github.com/buckett/spring-data-rest/tree/test-2233

[odrotbohm]

Would you mind zooming out a bit and describe a user level problem this results in?

[odrotbohm]

Nevermind, your test case has all I need to think about this.

[buckett]

Just to check I wasn't missing anything I did also create a test project showing the issue: https://github.com/buckett/json-patch-test

[odrotbohm]

I've just pushed a fix that included the test case you provided with the earlier project now succeeding. Would you mind trying the 4.0.3 snapshots (spring-data-bom.version to 4.0.3-SNAPSHOT)?

[buckett]

Failing with the BOM

I tried added <spring-data-bom.version>4.0.3-SNAPSHOT</spring-data-bom.version> to the Spring Boot app and then it tries to download org.springframework.data:spring-data-bom:pom:4.0.3-SNAPSHOT but fails.
I tried adding the Spring specific snapshot repository:

	<repositories>
		<repository>
			<id>spring-snapshot</id>
			<name>Spring Snapshot Repository</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
	</repositories>

but this doesn't appear to help and I can't see any similar versions in the UI: https://repo.spring.io/ui/packages/gav:%2F%2Forg.springframework.data:spring-data-bom?name=spring-data-bom&type=packages

Pulling in 4.0.x branch

Instead I've tried pulling <spring-data-bom.version>2022.0.3-SNAPSHOT</spring-data-bom.version> and this seems to depend on 4.0.3-SNAPSHOT after a bit of messing about (mvn dependency:purge) I have it downloading the latest artifacts and the fix looks good, in my test project after creating a person:

## Create a person
POST http://localhost:8080/persons
Content-Type: application/json

{
  "id": 1,
  "name": "Test",
  "birthday": "2000-01-01"
}

I then attempted to patch the birthday field:

PATCH http://localhost:8080/persons/1
Content-Type: application/json-patch+json

[
  {"op": "replace", "path": "/birthday", "value": "1980-02-20"}
]

it worked (HTTP 204) 👍 and double checking the person now has the new birthday.

[odrotbohm]

Yeez, I messed the version numbers up: it's got to be 2022.0.3-SNAPSHOT for the spring-data-bom.version property. That should give you 4.0.3-SNAPSHOT of SD REST. Looks like you got it working nonetheless. So looking forward to the release! 🥳