I use Spring JPA with hibernate,WebFlux and have problems with it. I've tried to fetch some entities from database, but lazy load exception occurred when i try to convert my entity to DTO. I understand why it happen and i can avoid it by creating DTO's per entity graph (to fetch only eager properties), but it's seem's to be overkill. Also i tried to skip lazy properties using setPropertyCondition() and Hibernate.isInitialized(), but exception was throwed before property condition was checked by model mapper. I tried to return entity object in my mapping but i couldn't find correct configuration for jackson Hibernate5Module usage. So, i ask you how i should use @EntityGraph with my repositories to have no errors in controller, ideally lazy-loaded properties should be null.
I solved the problem with lazy initialization exception by skipping lazy properties during DTO mapping process. I created own value reader for it and applied it to java model mapper instance.
public class CustomValueReader implements ValueReader<Object> {
@Override
public Object get(Object source, String memberName) {
try {
Field field = source.getClass().getDeclaredField(memberName);
field.setAccessible(true);
return field.get(source);
}
catch(Exception e) {
return null;
}
}
@Override
public Member<Object> getMember(Object source, String memberName) {
final Object value = get(source, memberName);
Class<?> memberType = value != null ? value.getClass() : Object.class;
return new Member<Object>(memberType) {
@Override
public Object getOrigin() {
return null;
}
@Override
public Object get(Object source, String memberName) {
return CustomValueReader.this.get(source, memberName);
}
};
}
@Override
@SuppressWarnings({ "unchecked", "rawtypes" })
public Collection<String> memberNames(Object source) {
List<String> properties = new ArrayList<>();
for (Field field : source.getClass().getDeclaredFields()) {
field.setAccessible(true);//needed for accessing field using reflection
boolean valid = true;
Object fieldValue = null;
try{
fieldValue = field.get(source);
}
catch(Exception e) {
valid = false;
}
boolean isInited = valid && Hibernate.isInitialized(fieldValue);
if (isInited){
properties.add(field.getName());
}
}
return properties;
}
@Override
public String toString() {
return "Costum";
}
}
Apply it to mapper
mapper.getConfiguration().addValueReader(new CustomValueReader());
Also i noticed that usage of entity graph make all properties eager or lazy (depending on EntityGraph.EntityGraphType) ignoring attributeNodes. My class definition looks like
@NamedEntityGraphs({
@NamedEntityGraph(name = ClinicVisit.CLINIC_VISIT_ENTITY_GRAPH_WITH_PATIENT_AND_DEVICES,
attributeNodes = @NamedAttributeNode(value = "patient",subgraph = "CVEG_DEVICES"),
subgraphs = @NamedSubgraph(name = "CVEG_DEVICES", attributeNodes = @NamedAttributeNode("notificationDevices"))
),
@NamedEntityGraph(name = ClinicVisit.CLINIC_VISIT_ENTITY_GRAPH_WITH_PATIENT,
attributeNodes = @NamedAttributeNode(value = "patient")
)
})
@Entity
@Table(name="clinic_visit_request")
@Getter
@Setter
public class ClinicVisit {
public final static String CLINIC_VISIT_ENTITY_GRAPH_WITH_PATIENT_AND_DEVICES = "clinic_visit_request_patient_devices";
public final static String CLINIC_VISIT_ENTITY_GRAPH_WITH_PATIENT = "clinic_visit_request_patient";
@Id
@GeneratedValue
protected Long id;
@Column(name = "visit_date")
protected Date visitDate;
@Column(name = "update_date")
protected Date updateDate;
protected Boolean informed;
@Column( columnDefinition = "boolean default false", nullable = false)
protected Boolean handled = false;
@ManyToOne()
protected ClinicUser doctor;
@ManyToOne()
protected ClinicUser patient;
@ManyToOne()
protected ClinicUser confirmer;
}
My repository method definition:
@EntityGraph(value=ClinicVisit.CLINIC_VISIT_ENTITY_GRAPH_WITH_PATIENT,type= EntityGraph.EntityGraphType.FETCH)
List<ClinicVisit> findAll();
All works fine, it was my misunderstanding. I had three fields (doctor, patient, confirmer) and save same user in them, so when I added NamedAttributeNode for patient i expected that only patient will be loaded, but other fields were loaded because hibernate is clever.
I understand why Hibernate5Module wasn't working. I use WebFlux, so configuration for JacksonMapper should look like
@Configuration
public class AppConfig {
@Bean
Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer(){
return jacksonObjectMapperBuilder -> jacksonObjectMapperBuilder
.featuresToEnable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
.propertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE)
.modules(new Hibernate5Module());
}
@Bean
Jackson2JsonEncoder jackson2JsonEncoder(ObjectMapper mapper){
return new Jackson2JsonEncoder(mapper);
}
@Bean
Jackson2JsonDecoder jackson2JsonDecoder(ObjectMapper mapper){
return new Jackson2JsonDecoder(mapper);
}
@Bean
WebFluxConfigurer webFluxConfigurer(Jackson2JsonEncoder encoder, Jackson2JsonDecoder decoder) {
return new WebFluxConfigurer() {
@Override
public void configureHttpMessageCodecs(ServerCodecConfigurer configurer) {
configurer.defaultCodecs().jackson2JsonEncoder(encoder);
configurer.defaultCodecs().jackson2JsonDecoder(decoder);
}
};
}
}
