Spring Data Rest: Target bean is not of type of the persistent entity - spring-data-rest

Question

I have a data model called Project which is lifecycled from an Angular app via Spring Data Rest. The Project has Scenes, Scenes have UpstreamKeys held in a Map<Integer, UpstreamKey> and UpstreamKey is an abstract class with two implementations ChromaKey and LumaKey. (see code below)
When I edit (PUT) and existing Project with a ChromaKey in the map, and change that to a LumaKey, I get an error message in the backend:
Caused by: java.lang.IllegalArgumentException: Target bean of type io.mewald.notime.designer.model.scene.usk.LumaKey is not of type of the persistent entity (io.mewald.notime.designer.model.scene.usk.chroma.ChromaKey)!: io.mewald.notime.designer.model.scene.usk.LumaKey
at org.springframework.util.Assert.instanceCheckFailed(Assert.java:702) ~[spring-core-5.3.10.jar:5.3.10]
at org.springframework.util.Assert.isInstanceOf(Assert.java:621) ~[spring-core-5.3.10.jar:5.3.10]
at org.springframework.data.mapping.model.BasicPersistentEntity.verifyBeanType(BasicPersistentEntity.java:584) ~[spring-data-commons-2.5.5.jar:2.5.5]
at org.springframework.data.mapping.model.BasicPersistentEntity.getPropertyAccessor(BasicPersistentEntity.java:458) ~[spring-data-commons-2.5.5.jar:2.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader$MergingPropertyHandler.<init>(DomainObjectReader.java:639) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.lambda$mergeForPut$1(DomainObjectReader.java:141) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at java.base/java.util.Optional.map(Optional.java:265) ~[na:na]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.mergeForPut(DomainObjectReader.java:139) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.lambda$mergeMaps$6(DomainObjectReader.java:429) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at java.base/java.util.Optional.map(Optional.java:265) ~[na:na]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.mergeMaps(DomainObjectReader.java:418) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.access$000(DomainObjectReader.java:65) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader$MergingPropertyHandler.doWithPersistentProperty(DomainObjectReader.java:673) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:374) ~[spring-data-commons-2.5.5.jar:2.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.lambda$mergeForPut$1(DomainObjectReader.java:143) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at java.base/java.util.Optional.map(Optional.java:265) ~[na:na]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.mergeForPut(DomainObjectReader.java:139) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.lambda$mergeCollections$7(DomainObjectReader.java:469) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at java.base/java.util.Optional.map(Optional.java:265) ~[na:na]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.mergeCollections(DomainObjectReader.java:452) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.access$100(DomainObjectReader.java:65) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader$MergingPropertyHandler.doWithPersistentProperty(DomainObjectReader.java:675) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.mapping.model.BasicPersistentEntity.doWithProperties(BasicPersistentEntity.java:374) ~[spring-data-commons-2.5.5.jar:2.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.lambda$mergeForPut$1(DomainObjectReader.java:143) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at java.base/java.util.Optional.map(Optional.java:265) ~[na:na]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.mergeForPut(DomainObjectReader.java:139) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.json.DomainObjectReader.readPut(DomainObjectReader.java:116) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.config.JsonPatchHandler.applyPut(JsonPatchHandler.java:100) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.readPutForUpdate(PersistentEntityResourceHandlerMethodArgumentResolver.java:234) ~[spring-data-rest-webmvc-3.5.5.jar:3.5.5]
... 90 common frames omitted
My interpretation is that it is somehow trying to merge the LumaKey into the ChromaKey and - of course - that doesn't work. Why is it not simply replacing the bean? What would be a fix to get this working?
Here's the structure of the data model relevant to this questions:
#NoArgsConstructor #Data #SuperBuilder #AllArgsConstructor
#Document
public class Project {
#Id
private String id;
...
private List<Scene> scenes;
}
#NoArgsConstructor #Data #SuperBuilder #AllArgsConstructor #EqualsAndHashCode(callSuper = false)
public class Scene {
...
private Map<Integer, UpstreamKey> upstreamKeys;
}
#Data #NoArgsConstructor #AllArgsConstructor #SuperBuilder(toBuilder = true)
#JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
#JsonSubTypes({
#JsonSubTypes.Type(value = ChromaKey.class, name = "ChromaKey"),
#JsonSubTypes.Type(value = LumaKey.class, name = "LumaKey")
})
public abstract class UpstreamKey {
...
public abstract String getType();
}
#Data #EqualsAndHashCode(callSuper = true) #NoArgsConstructor #AllArgsConstructor #SuperBuilder(toBuilder = true)
public class ChromaKey extends UpstreamKey {
...
#Override
public String getType() {
return "ChromaKey";
}
}
#Data #EqualsAndHashCode(callSuper = true) #NoArgsConstructor #AllArgsConstructor #SuperBuilder(toBuilder = true)
public class LumaKey extends UpstreamKey {
...
#Override
public String getType() {
return "LumaKey";
}
}
EDIT: Taken from the documentation at https://docs.spring.io/spring-data/rest/docs/current/reference/html/#repository-resources.item-resource
The PUT method replaces the state of the target resource with the supplied request body.
The documentation explicitly talks about replace so I am wondering why a method called mergeForPut is involved at all.
EDIT: Just realised my spring-boot-starter-parent was a bit old. I updated to 2.6.4 but the error remains.
EDIT: I just refactored everything so that scene.upstreamKeys can be a List instead of a Map just in case this might cause it. But it does not. Still the same error.
EDIT: As requested, I created a minimum project that replicates the error I am describing above: https://github.com/mathias-ewald/demo-sdr-target-bean-is-not-of-type

Answer 1

Though I can achieve the update in spring data mongodb, it's not possible in spring data rest now. In current spring data rest implementation, a PUT request try to merge the nested collection member by calling DomainObjectReader.mergeForPut(...) which fails on type mismatch, rather than replace it. See this github issue and pull request.
So the workaround is implement a controller yourself.
Edit 2022-04-05
Annotate UpstreamKey with #Immutable make spring data rest perform replacement rather than merge. This solution only works if the nested collection member is just value (no id, no audit data, no #JsonIgnore to hide server side data) instead of entity (with id).
Find the updated project and the diff
Below is result mongo data after the put opertaion.
{
_id: ObjectId('624b9fe3f32185579ff56849'),
name: 'Project 1',
scenes: [
{
name: 'Scene 1',
usks: [
{
c: 3,
a: 1,
_class: 'com.example.demo.LumaKey'
}
]
}
],
_class: 'com.example.demo.Project'
}

Answer 2

Shortly you want to do type casting between LumaKey and ChromaKey. So it's not ok with Java.
You can check this answer. I debug your code and this is what you want.
https://stackoverflow.com/a/17004028/8909313
Edit 1
You try to delete ChromaKey and add LumaKey.
Edit 2
Please debug this
PersistentEntityResourceHandlerMethodArgumentResolver.java (line 158 [readPutForUpdate method])
In this method request json and mongo json deserialize. And Object Mapper map them.
When mongodb object's usks field's type is ChromaKey but your request's type LumaKey.
And then spring call mapper method for mapping.
mapper.readerFor(target.getClass()).readValue(source);
for this line target's type is ChromaKey but source's type is LumaKey.
So mapper cannot cast your ChromaKey to LumaKey.
I try to write custom JsonDeserializer but it didn't solve your problem. Maybe you can try this way.
I think it's a logical problem.