I've created a very basic Spring boot (v. 2.5.4 and also v. 2.6.0) project and I want to perform a simple query to MongoDB (v 4.4.4):

@SpringBootTest
class DemoApplicationTests {

    @Autowired
    MongoOperations operations;

    @Test
    void sliceSimple() {
        final Criteria criteria = Criteria.where("_id").is(new ObjectId("5a3931f6d60180000f16db8c"));
        Query query = Query.query(criteria);
        query.fields().slice("subcategories", 0, 1);
        operations.find(query, Category.class);
    }

}
public class Category {

    public List<String> subcategories;
}

But it results with an exception:

Can't find a codec for class [Ljava.lang.Integer;.
org.bson.codecs.configuration.CodecConfigurationException: Can't find a codec for class [Ljava.lang.Integer;.
    at org.bson.internal.CodecCache.lambda$getOrThrow$1(CodecCache.java:52)
    at java.base/java.util.Optional.orElseThrow(Optional.java:408)
    at org.bson.internal.CodecCache.getOrThrow(CodecCache.java:51)
    at org.bson.internal.OverridableUuidRepresentationCodecRegistry.get(OverridableUuidRepresentationCodecRegistry.java:72)
    at org.bson.internal.ChildCodecRegistry.get(ChildCodecRegistry.java:52)
    at org.bson.codecs.DocumentCodec.writeValue(DocumentCodec.java:202)
    at org.bson.codecs.DocumentCodec.writeMap(DocumentCodec.java:217)
    at org.bson.codecs.DocumentCodec.writeValue(DocumentCodec.java:200)
    at org.bson.codecs.DocumentCodec.writeMap(DocumentCodec.java:217)
    at org.bson.codecs.DocumentCodec.encode(DocumentCodec.java:159)
    at org.bson.codecs.DocumentCodec.encode(DocumentCodec.java:46)
    at org.bson.BsonDocumentWrapper.getUnwrapped(BsonDocumentWrapper.java:195)
    at org.bson.BsonDocumentWrapper.isEmpty(BsonDocumentWrapper.java:115)
    at com.mongodb.internal.operation.DocumentHelper.putIfNotNullOrEmpty(DocumentHelper.java:43)
    at com.mongodb.internal.operation.FindOperation.getCommand(FindOperation.java:826)
    at com.mongodb.internal.operation.FindOperation.access$1700(FindOperation.java:80)
    at com.mongodb.internal.operation.FindOperation$4.create(FindOperation.java:893)
    at com.mongodb.internal.operation.CommandOperationHelper.executeCommandWithConnection(CommandOperationHelper.java:221)
    at com.mongodb.internal.operation.FindOperation$1.call(FindOperation.java:658)
    at com.mongodb.internal.operation.FindOperation$1.call(FindOperation.java:652)
    at com.mongodb.internal.operation.OperationHelper.withReadConnectionSource(OperationHelper.java:583)
    at com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:652)
    at com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:80)
    at com.mongodb.client.internal.MongoClientDelegate$DelegateOperationExecutor.execute(MongoClientDelegate.java:170)
    at com.mongodb.client.internal.MongoIterableImpl.execute(MongoIterableImpl.java:135)
    at com.mongodb.client.internal.MongoIterableImpl.iterator(MongoIterableImpl.java:92)
    at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:2807)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2543)
    at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2525)
    at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:847)
    at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:833)
    at com.example.demo.DemoApplicationTests.sliceSimple(DemoApplicationTests.java:22)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:99)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:79)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:75)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:61)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
    at com.sun.proxy.$Proxy2.stop(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.stop(TestWorker.java:133)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164)
    at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
    at java.base/java.lang.Thread.run(Thread.java:834)


Looking at the slice(String, int, int) definition, there is a usage of Integer[]:

/**
     * Project a {@code $slice} of the array {@code field} using the first {@code size} elements starting at
     * {@code offset}.
     *
     * @param field the document field name to project, must be an array field.
     * @param offset the offset to start at.
     * @param size the number of elements to include.
     * @return {@code this} field projection instance.
     */
    public Field slice(String field, int offset, int size) {

        slices.put(field, new Integer[] { offset, size });
        return this;
    }

Do somebody know if what is happening? Am I missing something in my configuration? My build.gradle:

plugins {
    id 'org.springframework.boot' version '2.5.4'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-data-mongodb'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

test {
    useJUnitPlatform()
}

Ps. I was also trying to use custom converter for Integer array:

public class JavaIntegerArrayToListConverter implements Converter<Integer[], List<Integer>> {

    @Override
    public List<Integer> convert(final Integer[] source) {
        return source == null ? null : Arrays.asList(source);
    }
}

and register with:

@Primary
    @Bean
    public MongoTemplate mongoTemplate(MongoDatabaseFactory mongoDbFactory,
                                       MappingMongoConverter mappingMongoConverter) {

        mappingMongoConverter.setCustomConversions(new MongoCustomConversions(
                Collections.singletonList(new JavaIntegerArrayToListConverter())));

        mappingMongoConverter.afterPropertiesSet();

        return new MongoTemplate(mongoDbFactory, mappingMongoConverter);
    }

But without any effect.

Thanks in advance for any help.

Comment From: bclozel

I don't see any code specific to Spring Framework here. Maybe you meant to open this issue against the Spring Data MongoDB project?

I'm closing this for now - feel free to reopen it the issue happens because of a Spring Framework behavior. Thanks!