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Flux into Mono List Object - project reactor

I'm using project reactor and I've the next issue:
I've one method that return Mono<CustomerResponse> that contains a CustomerDto list, each client has attributes, one of theirs attributes is a payment list. But this payment list is null.
I've another method that receive client id and returns a Flux payment Flux<PaymentDto> for that client.
This are the model
public class CustomerResponse {
private List<CustomerDto> customers;
}
public class CustomerDto {
private int id;
private String fullname;
private String documentNumber;
private List<PaymentDto> payments;
}
These are the interfaces
public interface CustomerService {
public Mono<CustomerResponse> customerSearch(CustomerRequest request);
}
public interface PaymentService {
public Flux<PaymentDto> getPayments(int clientId);
}
This is my method
public Mono<CustomerResponse> getCustomer(CustomerRequest request) {
return customerService.customerSearch(request).map(resp -> resp.getCustomers())
.flatMap(customerList -> {
List<CustomerDto> newCustomerList = customerList.parallelStream().map(customer -> {
Flux<PaymentDto> paymentFlux =
paymentService.getPayments(customer.getId());
// Here: java.lang.IllegalStateException: block()/blockFirst()/blockLast()
customer.setPayments(paymentFlux.collectList().block());
return customer;
}).collect(Collectors.toList());
return Mono.just(new CustomerResponse(newCustomerList));
});
}
I've the next exception:
java.lang.IllegalStateException: block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-4
at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:83) ~[reactor-core-3.3.6.RELEASE.jar:3.3.6.RELEASE]
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
I would like to know if there is a non-blocking or optimal way to do it

You can refactor your code like this to avoid blocking call:
public Mono<CustomerResponse> getCustomer(CustomerRequest request) {
Flux<CustomerDto> customerDtoFluxEnriched = customerService.customerSearch(request)
.map(CustomerResponse::getCustomers).flatMapMany(Flux::fromIterable).flatMap(customerDto -> {
Flux<PaymentDto> paymentFlux = paymentService.getPayments(customerDto.getId());
Mono<List<PaymentDto>> paymentListMono = paymentFlux.collectList();
return paymentListMono.map(paymentList -> {
customerDto.setPayments(paymentList);
return customerDto;
});
});
return customerDtoFluxEnriched.collectList().map(customerList -> {
CustomerResponse customerResponse = new CustomerResponse();
customerResponse.setCustomers(customerList);
return customerResponse;
});
}

Reactor Mono - execute parallel tasks

I am new to Reactor framework and trying to utilize it in one of our existing implementations. LocationProfileService and InventoryService both return a Mono and are to executed in parallel and have no dependency on each other (from the MainService). Within LocationProfileService - there are 4 queries issued and the last 2 queries have a dependency on the first query.
What is a better way to write this? I see the calls getting executed sequentially, while some of them should be executed in parallel. What is the right way to do it?
public class LocationProfileService {
static final Cache<String, String> customerIdCache //define Cache
#Override
public Mono<LocationProfileInfo> getProfileInfoByLocationAndCustomer(String customerId, String location) {
//These 2 are not interdependent and can be executed immediately
Mono<String> customerAccountMono = getCustomerArNumber(customerId,location) LocationNumber).subscribeOn(Schedulers.parallel()).switchIfEmpty(Mono.error(new CustomerNotFoundException(location, customerId))).log();
Mono<LocationProfile> locationProfileMono = Mono.fromFuture(//location query).subscribeOn(Schedulers.parallel()).log();
//Should block be called, or is there a better way to do ?
String custAccount = customerAccountMono.block(); // This is needed to execute and the value from this is needed for the next 2 calls
Mono<Customer> customerMono = Mono.fromFuture(//query uses custAccount from earlier step).subscribeOn(Schedulers.parallel()).log();
Mono<Result<LocationPricing>> locationPricingMono = Mono.fromFuture(//query uses custAccount from earlier step).subscribeOn(Schedulers.parallel()).log();
return Mono.zip(locationProfileMono,customerMono,locationPricingMono).flatMap(tuple -> {
LocationProfileInfo locationProfileInfo = new LocationProfileInfo();
//populate values from tuple
return Mono.just(locationProfileInfo);
});
}
private Mono<String> getCustomerAccount(String conversationId, String customerId, String location) {
return CacheMono.lookup((Map)customerIdCache.asMap(),customerId).onCacheMissResume(Mono.fromFuture(//query).subscribeOn(Schedulers.parallel()).map(x -> x.getAccountNumber()));
}
}
public class InventoryService {
#Override
public Mono<InventoryInfo> getInventoryInfo(String inventoryId) {
Mono<Inventory> inventoryMono = Mono.fromFuture(//inventory query).subscribeOn(Schedulers.parallel()).log();
Mono<List<InventorySale>> isMono = Mono.fromFuture(//inventory sale query).subscribeOn(Schedulers.parallel()).log();
return Mono.zip(inventoryMono,isMono).flatMap(tuple -> {
InventoryInfo inventoryInfo = new InventoryInfo();
//populate value from tuple
return Mono.just(inventoryInfo);
});
}
}
public class MainService {
#Autowired
LocationProfileService locationProfileService;
#Autowired
InventoryService inventoryService
public void mainService(String customerId, String location, String inventoryId) {
Mono<LocationProfileInfo> locationProfileMono = locationProfileService.getProfileInfoByLocationAndCustomer(....);
Mono<InventoryInfo> inventoryMono = inventoryService.getInventoryInfo(....);
//is using block fine or is there a better way to do?
Mono.zip(locationProfileMono,inventoryMono).subscribeOn(Schedulers.parallel()).block();
}
}

You don't need to block in order to get the pass that parameter your code is very close to the solution. I wrote the code using the class names that you provided. Just replace all the Mono.just(....) with the call to the correct service.
public Mono<LocationProfileInfo> getProfileInfoByLocationAndCustomer(String customerId, String location) {
Mono<String> customerAccountMono = Mono.just("customerAccount");
Mono<LocationProfile> locationProfileMono = Mono.just(new LocationProfile());
return Mono.zip(customerAccountMono, locationProfileMono)
.flatMap(tuple -> {
Mono<Customer> customerMono = Mono.just(new Customer(tuple.getT1()));
Mono<Result<LocationPricing>> result = Mono.just(new Result<LocationPricing>());
Mono<LocationProfile> locationProfile = Mono.just(tuple.getT2());
return Mono.zip(customerMono, result, locationProfile);
})
.map(LocationProfileInfo::new)
;
}
public static class LocationProfileInfo {
public LocationProfileInfo(Tuple3<Customer, Result<LocationPricing>, LocationProfile> tuple){
//do wathever
}
}
public static class LocationProfile {}
private static class Customer {
public Customer(String cutomerAccount) {
}
}
private static class Result<T> {}
private static class LocationPricing {}
Pleas remember that the first zip is not necessary. I re write it to mach your solution. But I would solve the problem a little bit differently. It would be clearer.
public Mono<LocationProfileInfo> getProfileInfoByLocationAndCustomer(String customerId, String location) {
return Mono.just("customerAccount") //call the service
.flatMap(customerAccount -> {
//declare the call to get the customer
Mono<Customer> customerMono = Mono.just(new Customer(customerAccount));
//declare the call to get the location pricing
Mono<Result<LocationPricing>> result = Mono.just(new Result<LocationPricing>());
//declare the call to get the location profile
Mono<LocationProfile> locationProfileMono = Mono.just(new LocationProfile());
//in the zip call all the services actually are executed
return Mono.zip(customerMono, result, locationProfileMono);
})
.map(LocationProfileInfo::new)
;
}

JsonGenerationException: Can not write a field name

My problem lies in the fields of JsonSerialization as implemented in Jackson FasterXML Library. I have a series of endpoints through which I exchange content between my back-end and a MVVM front-end framework. This is working, but now I am a little stuck as I got to the point where I want to handle user creation/registration.
This is the model (entity) that represents a group in my application (I omit irrelevant import declarations and JPA annotations):
#JsonRootName(value="userGroup")
#JsonInclude(JsonInclude.Include.NON_NULL)
public class Groups extends MetaInfo implements Serializable {
private String groupName;
private Set<Credential> credentials = new HashSet<>();
public Groups() {
super();
}
public Groups(String groupName) {
this();
this.groupName = groupName;
}
public Groups(String createdBy, String groupName) {
this();
setCreatedBy(createdBy);
this.groupName = groupName;
}
#JsonGetter("group_Name")
// #JsonValue
public String getGroupName() {
return groupName;
}
public void setGroupName(String groupName) {
this.groupName = groupName;
updateModified();
}
#JsonIgnore
public Set<Credential> getCredentials() {
return credentials;
}
public void setCredentials(Set<Credential> credentials) {
this.credentials = credentials;
}
public void addCredential(Credential c) {
credentials.add(c);
if (c.getGroup() != this) {
c.setGroup(this);
}
}
#Override
public String toString() {
return "Groups{" + "groupName=" + groupName + '}';
}
}
And this is the method in the endpoint that retrieves (if exists) and returns a serialized version of a Groups to a JavaScript client:
#Path("/groups")
#Produces("application/json")
public class GroupsResourceService extends RimmaRestService{
#Inject
#Production
private GroupsRepository groupsRepository;
...
#GET
#Path("{group}")
public Response getGroup(#PathParam("group") String group){
if(InputValidators.stringNotNullNorEmpty.apply(group)){
//proceed with making call to the repo
Optional<Groups> optGroup = ofNullable(groupsRepository.getByGroupName(group));
if(optGroup.isPresent()){//ultimately success scenario
try {
String output = getMapper().writeValueAsString(optGroup.get());
return Response.ok(output).build();
} catch (JsonProcessingException e) {
logger.error("Serialization error: "+e.getMessage()+
"\n"+e.getClass().getCanonicalName());
throw new InternalServerErrorException("Server error "
+ " serializing the requested group \""+group+"\"");
}
} else{
throw new NotFoundException("Group " + group + " could not be found");
}
}else{//empty space after the slash
throw new BadRequestException("You haven't provided a group parameter",
Response.status(Response.Status.BAD_REQUEST).build());
}
}
}
Trying to test this code like this:
#Test
public void successfullResponse(){
Response success = groupsResourceService.getGroup("admin");
assertTrue(success.getStatus()==200);
}
...cruelly fails:
<< ERROR!
javax.ws.rs.InternalServerErrorException: Server error serializing the requested group "admin"
at com.vgorcinschi.rimmanew.rest.services.GroupsResourceService.getGroup(GroupsResourceService.java:54)
at com.vgorcinschi.rimmanew.services.GroupsResourceServiceTest.successfullResponse(GroupsResourceServiceTest.java:48)
In this case stack trace is of 0 help, though - that's why I am pasting the output of the log that catches the underlying Json exception:
15:05:05.857 [main] ERROR com.vgorcinschi.rimmanew.rest.services.GroupsResourceService - Serialization error: Can not write a field name, expecting a value
com.fasterxml.jackson.core.JsonGenerationException
Having visited and analyzed 13 similar complaints links (of which 3 are from stackoverflow) I came up with a solution which is more a workaround - if you look back at the entity, I have commented #JsonValue. If I uncomment that and comment #JsonGetter("group_Name") then the test passes with the following output:
{"userGroup":"admin"}
This being only a workaround, I decided to recur to asking for help which I hope someone will be able and kind enough to provide.

spring data mongodb Cannot perform cascade save on child object without id set

I am using #CascadeSave to save child object in separate collection.
My Document classes are :
public class FbUserProfile{
#Id
private long id;
#DBRef(lazy=true)
#CascadeSave()
private Set<FacebookFriend> friends;
#DBRef(lazy=true)
#CascadeSave()
private Set<FacebookFriendList> customFriendList;
}
public class FacebookFriend{
#Id
private long id;
private String name;
}
public class FacebookFriendList{
#Id
private long id;
private String name;
private String list_type;
}
I add some object in both friends,customFriendList.
and try to update fbUserProfile object using:
mongoTemplate.save(fbUserProfile);
note: fbUserProfile already exists in db. Now I am updating this
Error Message: Cannot perform cascade save on child object without id set
If I remove #CascadeSave. It works fine for me. How I can Cascade set objects.
I am also using #CascadeSave with other objects. Its working fine but they are not set object.

I found the same tutorials somewhere else: Baeldung's and JavaCodeGeeks (this is the one i've followed)
I've had that same problem, and I could solve it.
It happens when you try to persist a collection. It doesn't matter that the collection's items have the #Id, because the collection itself won't have it. I edited the code in the EventListener's onBeforeConvert to check if the field you're trying to CascadeSave is a collection (in my case a List). If it's a list, you just cycle through it checking each individual item for #Id and saving them.
If it's not a collection you still have to persist them the same way you did before
#Override
public void onBeforeConvert(Object source) {
ReflectionUtils.doWithFields(source.getClass(), new ReflectionUtils.FieldCallback() {
#Override
public void doWith(Field field)
throws IllegalArgumentException, IllegalAccessException {
ReflectionUtils.makeAccessible(field);
if (field.isAnnotationPresent(DBRef.class) && field.isAnnotationPresent(CascadeSave.class)){
final Object fieldValue = field.get(source);
if(fieldValue instanceof List<?>){
for (Object item : (List<?>)fieldValue){
checkNSave(item);
}
}else{
checkNSave(fieldValue);
}
}
}
});
}
private void checkNSave(Object fieldValue){
DbRefFieldCallback callback = new DbRefFieldCallback();
ReflectionUtils.doWithFields(fieldValue.getClass(), callback);
if (!callback.isIdFound()){
throw new MappingException("Oops, something went wrong. Child doesn't have #Id?");
}
mongoOperations.save(fieldValue);
}

The best way to set an ID on the dependent child object is to write a listener class by extending AbstractMongoEventListener class and override the onConvert() method.
public class CustomMongoEventListener extends
AbstractMongoEventListener<Object> {
#Autowired
private MongoOperations mongoOperations;
#Override
public void onBeforeConvert(final Object entity) {
if (entity.id == null || entity.id.isEmpty()) {
entity.id = generateGuid(); //generate random sequence ID
}
public static String generateGuid() {
SecureRandom randomGen = new SecureRandom();
byte[] byteArray = new byte[16];
randomGen.nextBytes(byteArray);
return new Base32().encodeToString(byteArray).substring(0,26);
}
}
Finally register your custom listener in `your configuration file. For annotation approach use the following code to register :
#Bean
public CustomMongoEventListener cascadingMongoEventListener() {
return new CustomMongoEventListener();
}

The above solution works fine incase if you have a list. But we can avoid firing a save query for each element from the list, as it reduces the performance. Here is the solution I have found out of the above code.
#Override
public void onBeforeConvert(BeforeConvertEvent<Object> event) {
Object source = event.getSource();
ReflectionUtils.doWithFields(source.getClass(), new ReflectionUtils.FieldCallback() {
#Override
public void doWith(Field field)
throws IllegalArgumentException, IllegalAccessException {
ReflectionUtils.makeAccessible(field);
if (field.isAnnotationPresent(DBRef.class) && field.isAnnotationPresent(CascadeSave.class)){
final Object fieldValue = field.get(source);
if(fieldValue instanceof List<?>){
for (Object item : (List<?>)fieldValue){
checkNAdd(item);
}
}else{
checkNAdd(fieldValue);
}
mongoOperations.insertAll(documents);
}
}
});
}
private void checkNAdd(Object fieldValue){
DbRefFieldCallback callback = new DbRefFieldCallback();
ReflectionUtils.doWithFields(fieldValue.getClass(), callback);
if (!callback.isIdFound()){
throw new MappingException("Oops, something went wrong. Child doesn't have #Id?");
}
documents.add(fieldValue);
}

Okey I extend the class and it will check if the document is exist if it exist it will update the document else it insert the document:
#Component
class GenericCascadeMongo(
private val mongoTemplate: MongoTemplate
) : AbstractMongoEventListener<Any>() {
override fun onBeforeConvert(event: BeforeConvertEvent<Any?>) {
val source = event.source
?: return
ReflectionUtils.doWithFields(source.javaClass) { field ->
ReflectionUtils.makeAccessible(field)
if (field.isAnnotationPresent(DBRef::class.java) && field.isAnnotationPresent(CascadeSave::class.java)) {
val fieldValue = field[source]
?: return#doWithFields
if (fieldValue is List<*>) {
fieldValue.filterNotNull().forEach {
checkAndSave(it)
}
} else {
checkAndSave(fieldValue)
}
}
}
}
private fun checkAndSave(fieldValue: Any) {
try {
val callback = DbRefFieldCallback(fieldValue)
ReflectionUtils.doWithFields(fieldValue.javaClass, callback)
if (!callback.isIdFound && callback.id == null) {
mongoTemplate.insert(fieldValue)
}
if (callback.id != null) {
val findById = mongoTemplate.exists(Query(Criteria.where(MConst.MONGO_ID).`is`(callback.id)), fieldValue.javaClass)
if (findById) {
mongoTemplate.save(fieldValue)
} else {
mongoTemplate.insert(fieldValue)
}
}
} catch (e: Exception) {
e.printStackTrace()
}
}
private class DbRefFieldCallback(val fieldValue: Any?) : FieldCallback {
var isIdFound = false
private set
var id: String? = null
private set
#Throws(IllegalArgumentException::class, IllegalAccessException::class)
override fun doWith(field: Field) {
ReflectionUtils.makeAccessible(field)
if (field.isAnnotationPresent(Id::class.java)) {
isIdFound = true
id = ReflectionUtils.getField(field, fieldValue)?.toString()
}
}
}
}

Java, Storing JSON Array to class and calling it from other class

I am trying to pull data from class in another class and populate a JPanel with the data, but it is not working for some reason.
Here is the full restConnector class where I pull the JSON data.
As far as I know this works fine.
public class restConnector {
private static final Logger LOGGER = LoggerFactory.getLogger(restConnector.class);
private static final restConnector INSTANCE = new restConnector();
public static restConnector getInstance() {
return restConnector.INSTANCE;
}
private restConnector(){
}
private static String user = "ss";
private static String pwd = "ee
public static String encode(String user, String pwd) {
final String credentials = user+":"+pwd;
BASE64Encoder encoder = new sun.misc.BASE64Encoder();
return encoder.encode(credentials.getBytes());
}
//Open REST connection
public static void init() {
restConnector.LOGGER.info("Starting REST connection...");
try {
Client client = Client.create();
client.addFilter(new LoggingFilter(System.out));
WebResource webResource = client.resource("https://somewebpage.com/
String url = "activepersonal";
ClientResponse response = webResource
.path("api/alerts/")
.queryParam("filter", ""+url)
.header("Authorization", "Basic "+encode(user, pwd))
.header("x-api-version", "1")
.accept("Application/json")
.get(ClientResponse.class);
if (response.getStatus() != 200) {
}else{
restConnector.LOGGER.info("REST connection STARTED.");
}
String output = response.getEntity(String.class);
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(new MyNameStrategy());
try {
List<Alert> alert = mapper.readValue(output, new TypeReference<List<Alert>>(){});
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void close() {
}
}
However, when I try to pull the data in another class it gives me just null values from the system.out.print inside refreshData() method. Here is the code that is supposed to print the data
public class Application{
Alert alerts = new Alert();
public Application() {
refreshData();
}
private void initComponents() {
restConnector.init();
refreshData();
}
private void refreshData() {
System.out.println("appalertList: "+alerts.getComponentAt(0));
}
}
Here is my Alert class
#JsonIgnoreProperties(ignoreUnknown = true)
#JsonInclude(Include.NON_EMPTY)
public class Alert {
private int pasID;
private String status;
private boolean shared;
private String header;
private String desc;
public int getPasID() {
return pasID;
}
public void setPasID(int pasID) {
this.pasID = pasID;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public boolean isShared() {
return shared;
}
public void setShared(boolean shared) {
this.shared = shared;
}
public String getHeader() {
return header;
}
public void setHeader(String header) {
this.header = header;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
#Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("\n***** Alert Details *****\n");
sb.append("PasID="+getPasID()+"\n");
sb.append("Status="+getStatus()+"\n");
sb.append("Shared="+isShared()+"\n");
sb.append("Header="+getHeader()+"\n");
sb.append("Description="+getDesc()+"\n");
sb.append("*****************************");
return sb.toString();
}
public String getComponentAt(int i) {
return toString();
}
}
I'm kind a lost with this and been stuck here for a couple of days already so all help would be really appreciated. Thanks for the help in advance.
Edit: Formatted the code a bit and removed the NullPointerException as it was not happening anymore.

As stated in comments:
Me: In your first bit of code you have this try { List<Alert> alert.., but you do absolutely nothing with the newly declared alert List<Alert>. It this where the data is supposed to be coming from?
OP: I'm under the impression that that bit of code is the one that pushes the JSON Array to the Alert.class. Is there something I'm missing there?
Me: And what makes you think it does that? All it does is read the json, and the Alert.class argument is the class type argument, so the mapper know the results should be mapped to the Alert attributes when it creates the Alert objects. That's how doing List<Alert> is possible, because passing Alert.class decribes T in List<T>. The List<Alert> is what's returned from the reading, but you have to determine what to actually do with the list. And currently, you do absolutely nothing with it
You maybe want to change the class just a bit.
Now this is in no way a good design, just an example of how you can get it to work. I would take some time to sit and think about how you want the restConnector to be fully utilized
That being said, you can have a List<Alert> alerts; class member in the restConnector class. And have a getter for it
public class restConnector {
private List<Alert> alerts;
public List<Alert> getAlerts() {
return alerts;
}
...
}
Then when deserializing with the mapper, assign the value to private List<Alert> alerts. What you are doing is declaring a new locally scoped list. So instead of
try {
List<Alert> alert = mapper.readValue...
do this instead
try {
alerts = mapper.readValue
Now the class member is assigned a value. So in the Application class you can do something like
public class Application {
List<Alert> alerts;
restConnector connect;
public Application() {
initComponents();
}
private void initComponents() {
connector = restConnector.getInstance();
connector.init();
alerts = connector.getAlerts();
refreshData();
}
private void refreshData() {
StringBuilder sb = new StringBuilder();
for (Alert alert : alerts) {
sb.append(alert.toString()).append("\n");
}
System.out.println("appalertList: "+ sb.toString());
}
}
Now you have access to the Alerts in the list.
But let me reiterate: THIS IS A HORRIBLE DESIGN. For one you are limiting the init method to one single call, in which it is only able to obtain one and only one resource. What if the rest service needs to access a different resource? You have made the request set in stone, so you cant.
Take some time to think of some good OOP designs where the class can be used for different scenarios.