Register Bean Validation ValueExtractor with Spring/Spring Boot

Question

Setup

I have a custom container class:

public class PatchField<T> {

    private boolean isSet;
    private T value;

    public PatchField(T value) {
        this.isSet = true;
        this.value = value;
    }

    public PatchField(boolean isSet, T value) {
        this.isSet = isSet;
        this.value = value;
    }

    //Getters and Setters
}

I have a request which I would like to use as a @RequestBody in Spring REST endpoint. Do note that I annotated String with @NotEmpty. That means I need a custom ValueExtractor.

Request:

@ApiModel
@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)
public class Request {

    private PatchField<@NotEmpty String> name = PatchField.empty();

    //Getters and Setters

}

I have created PatchFieldValueExtractor as per documentation:

public class PatchFieldValueExtractor implements ValueExtractor<PatchField<@ExtractedValue ?>> {

    @Override
    public void extractValues(PatchField<?> originalValue, ValueReceiver receiver) {
        receiver.value(null, originalValue.getValue());
    }
}

Problem

However, I cannot find a way to register PatchFieldValueExtractor with Spring or customize automatically created Validator like I can, for example RestTemplate via RestTemplateBuilder. If I annotate PatchFieldValueExtractor with @Component in Spring Boot, it does not get picked up automatically. I get the following error:

javax.validation.ConstraintDeclarationException: HV000197: No value extractor found for type parameter 'T' of type com.example.PatchField.
    at org.hibernate.validator.internal.metadata.core.MetaConstraints.addValueExtractorDescriptorForTypeArgumentLocation(MetaConstraints.java:145) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.core.MetaConstraints.create(MetaConstraints.java:61) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.createTypeArgumentMetaConstraint(AnnotationMetaDataProvider.java:795) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.lambda$findTypeUseConstraints$2(AnnotationMetaDataProvider.java:783) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195) ~[na:na]
    at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1654) ~[na:na]
    at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658) ~[na:na]
    at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:274) ~[na:na]
    at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[na:na]
    at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
    at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578) ~[na:na]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.findTypeUseConstraints(AnnotationMetaDataProvider.java:784) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.findTypeArgumentsConstraints(AnnotationMetaDataProvider.java:762) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.findTypeAnnotationConstraints(AnnotationMetaDataProvider.java:581) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.findPropertyMetaData(AnnotationMetaDataProvider.java:237) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.getFieldMetaData(AnnotationMetaDataProvider.java:225) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.retrieveBeanConfiguration(AnnotationMetaDataProvider.java:133) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider.getBeanConfiguration(AnnotationMetaDataProvider.java:124) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.BeanMetaDataManager.getBeanConfigurationForHierarchy(BeanMetaDataManager.java:232) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.BeanMetaDataManager.createBeanMetaData(BeanMetaDataManager.java:199) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.metadata.BeanMetaDataManager.getBeanMetaData(BeanMetaDataManager.java:166) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validate(ValidatorImpl.java:157) ~[hibernate-validator-6.0.17.Final.jar:6.0.17.Final]
    at org.springframework.validation.beanvalidation.SpringValidatorAdapter.validate(SpringValidatorAdapter.java:117) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.validation.DataBinder.validate(DataBinder.java:889) ~[spring-context-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.validateIfApplicable(AbstractMessageConverterMethodArgumentResolver.java:266) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:137) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:167) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:880) ~[spring-webmvc-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:108) ~[spring-boot-actuator-2.2.0.RELEASE.jar:2.2.0.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.0.RELEASE.jar:5.2.0.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1579) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.27.jar:9.0.27]
    at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

Ofcourse, I could, just create my own Validator Bean. I have tested it and it works:

@Configuration
public class CustomValidator {

    @Bean
    public Validator validator() {
        ValidatorFactory validatorFactory = Validation.byDefaultProvider()
                .configure()
                .addValueExtractor(new PatchFieldValueExtractor())
                .buildValidatorFactory();
        return validatorFactory.getValidator();
    }
}

However, I fear that by doing so, I opt-out of current or future AutoConfiguration "goodies" that I am not aware. For example, there are nuances with RestTemplate and RestTemplateBuilder, which can lead to unexpected runtime behaviours as outlined in this article. Thus I am reluctant to go this route. Is there a better version on how to customize Validator?

Sources I have looked

Spring Framework Documentation. Bean Validation. Per documentation:

You can use the LocalValidatorFactoryBean to configure a default Validator as a Spring bean.

The basic configuration in the preceding example triggers bean validation to initialize by using its default bootstrap mechanism. A JSR-303 or JSR-349 provider, such as the Hibernate Validator, is expected to be present in the classpath and is automatically detected.

Additional Configuration Options

The default LocalValidatorFactoryBean configuration suffices for most cases. There are a number of configuration options for various Bean Validation constructs, from message interpolation to traversal resolution. See the LocalValidatorFactoryBean javadoc for more information on these options.

LocalValidatorFactoryBean

This API does not contain clear information how could I register custom ValueExtractor.

Spring Boot Documentation. No mentioning of LocalValidatorFactoryBean or how to customize it.

Answer 1

To register custom ValueExtractor, one has extend LocalValidatorFactoryBean :

@Component
public class CustomLocalValidatorFactoryBean extends LocalValidatorFactoryBean {

    @Override
    protected void postProcessConfiguration(Configuration<?> configuration) {
        super.postProcessConfiguration(configuration);

        configuration.addValueExtractor(new PatchFieldValueExtractor());
    }
}

Answer 2

Maybe you can register in Resources/META-INF/services/javax.validation.valueextraction.ValueExtractor

com.yourpackagename.PatchFieldValueExtractor