Following DTO Projection doc

Hello,

I was following the DTO Projection documentation but can’t make it work.

My set up : spring-boot 2.7.3 (data couchbase 4.4.2)

First, this documentation has example using spring data JPA (@Entity and @OneToOne annotations). Is it normal ?

Second, here is my simple test and the exception I get :

Person document :

@Document
@Scope("dev")
@Collection("person")
data class Person(
    @field:Id
    val id: String,

    @field:Field
    val name: String
)

Projection interface :

interface Name {
    fun getName(): String
}

Person repository :

interface PersonRepository : ReactiveCouchbaseRepository<Person, String> {
    fun findByName(name: String): Flux<Name>
}

Exception :

java.lang.IllegalArgumentException: returnType must not be null!
	at org.springframework.util.Assert.notNull(Assert.java:201) ~[spring-core-5.3.22.jar:5.3.22]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	*__checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
	*__checkpoint ⇢ HTTP POST "/person" [ExceptionHandlingWebHandler]
Original Stack Trace:
		at org.springframework.util.Assert.notNull(Assert.java:201) ~[spring-core-5.3.22.jar:5.3.22]
		at org.springframework.data.couchbase.core.ReactiveFindByQueryOperationSupport$ReactiveFindByQuerySupport.as(ReactiveFindByQueryOperationSupport.java:134) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.couchbase.repository.query.AbstractReactiveCouchbaseQuery.lambda$getExecutionToWrap$1(AbstractReactiveCouchbaseQuery.java:122) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.couchbase.repository.query.ReactiveCouchbaseQueryExecution$ResultProcessingExecution.execute(ReactiveCouchbaseQueryExecution.java:77) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.couchbase.repository.query.AbstractReactiveCouchbaseQuery.doExecute(AbstractReactiveCouchbaseQuery.java:91) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.couchbase.repository.query.AbstractCouchbaseQueryBase.execute(AbstractCouchbaseQueryBase.java:133) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.couchbase.repository.query.AbstractCouchbaseQueryBase.execute(AbstractCouchbaseQueryBase.java:113) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137) ~[spring-data-commons-2.7.2.jar:2.7.2]
		at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121) ~[spring-data-commons-2.7.2.jar:2.7.2]
		at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:160) ~[spring-data-commons-2.7.2.jar:2.7.2]
		at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:139) ~[spring-data-commons-2.7.2.jar:2.7.2]
		at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.22.jar:5.3.22]
		at org.springframework.data.couchbase.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:141) ~[spring-data-couchbase-4.4.2.jar:4.4.2]
		at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.22.jar:5.3.22]
		at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-5.3.22.jar:5.3.22]
		at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.22.jar:5.3.22]
		at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:99) ~[spring-data-commons-2.7.2.jar:2.7.2]
		at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.22.jar:5.3.22]
		at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.22.jar:5.3.22]
		at jdk.proxy2/jdk.proxy2.$Proxy101.findByName(Unknown Source) ~[na:na]
		at com.rbleuse.spring.reactive.couchbase.service.PersonService.getProjectionByName(PersonService.kt:13) ~[main/:na]

Is the documentation is up to date, and can we use projection with spring data couchbase ?

[mikereiche]

My mistake - the id is always required when anything other than one simple field is projected. So just project “” as __id.

[mikereiche]

Yes. An id is(was) always expected for an entity. Also cas. It doesn’t matter what it is though. You can have “” as __id, 0 as __cas.

There is a change to only require __id and __cas if they are needed : https://github.com/spring-projects/spring-data-couchbase/issues/1402

That shows commits in main (May 3), 4.4.x (May 9) and 4.3.x (May 11). So it will be in the releases of those which occurred after (June 20 and July 15) https://calendar.spring.io/. July 15 shows 2021.1.6 -> 4.3.6, 2021.2.2 -> 4.4.2 and 2022.0.0 -> 5.0.0-M5.