Spring 引导 rest API - Querydsl，谓词不能是 null

Question

Is the Predicate supposed to be nullable using MongoRepository ?

The standard JPA PagingAndSortingRepository always seems to return a valid Predicate , no matter which query parameters are provided.

Stacktrace

java.lang.IllegalArgumentException: Predicate must not be null!
        at org.springframework.util.Assert.notNull(Assert.java:198) ~[spring-core-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor.findAll(QuerydslMongoPredicateExecutor.java:165) ~[spring-data-mongodb-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
        at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
        at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:359) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:644) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:608) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$invoke$3(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.1.3.RELEASE.jar:2.1.3.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.3.RELEASE.jar:5.1.3.RELEASE]

Curl

http://localhost:8080/api/notifications?page=1 # stacktrace
http://localhost:8080/api/notifications?id=1&page=1" # does work

Controller

@RestController
@RequestMapping(produces = "application/json; charset=UTF-8")
@Api(description = "Operations concerning notifications")
public class NotificationController {

    @Autowired
    private NotificationFacade notificationFacade;

    @Autowired
    private NotificationRepository notificationRepository;

    @ApiOperation(value = "Retrieve a list of available notifications")
    @GetMapping("/api/notifications")
    public Page<Notification> findAll(@QuerydslPredicate() Predicate predicate,
                                      @PageableDefault(sort = "id") Pageable pageable) {
        return notificationRepository.findAll(predicate, pageable);
    }

}

Repository

public interface NotificationRepository extends MongoRepository<Notification, String>, QuerydslPredicateExecutor<Notification> {}

Entity

@Data
@Document(collection = "notifications")
public class Notification {

    @Id
    private String id;

    @NonNull
    private String message;



}

Answer 1

Add an extra check

        if (predicate == null) {
            predicate = QNotification.notification.id.ne("");
        }
        return notificationRepository.findAll(predicate, pageable);

Answer 2

my problem was sorted out by a new compiler plugin block in pom.xml with lombok-mapstruct-binding, not to generate mapstruct before lombok getters setters have been done - special thx for my teacher @ BME for the solution: ]