I have a basic SpringBoot app. using Spring Initializer, JPA, embedded Tomcat, Thymeleaf template engine, and package as an executable JAR file
I have this piece of code to compare POJOs, but the compartor seems not to work because lastDeviceEvent and firstDeviceEvent are the same object with the same ID
DeviceEvent lastDeviceEvent = null;
DeviceEvent firstDeviceEvent = null;
try {
lastDeviceEvent = deviceEvents
.stream()
.filter (o -> o.getId().equals(deviceId))
.sorted(comparing((DeviceEvent de) -> de.getId()).reversed())
.findFirst().get();
firstDeviceEvent = deviceEvents
.stream()
.filter (o -> o.getId().equals(deviceId))
.sorted(comparing((DeviceEvent de) -> de.getId()))
.findFirst().get();
LOG.info("lastDeviceEvent --> " + lastDeviceEvent.getId());
LOG.info("firstDeviceEvent -> " + firstDeviceEvent.getId());
} catch (NoSuchElementException nse) {
throw new AccessDeniedException("403 Forbidden");
}
The comparator seems correct. The problem seems to be in your filter clause, where you compare the event id to the device id
lastDeviceEvent = deviceEvents
.stream()
.filter (o -> o.getDeviceId().equals(deviceId)) // Original code used getId()
.sorted(comparing((DeviceEvent de) -> de.getId()).reversed())
.findFirst()
.get();
Related
So I'm basically trying to figure out if there is a way to avoid having the same code twice and also get key in the place where I'm getting the syntax error.
List<String> listOfKeys = new ArrayList<>(
Arrays.asList("key1", "key2", "key3", "key4", "key5"));
String path = "something.something.";
listOfKeys.stream()
.map(key -> path + key)
.map(getConfig()::getString)
.forEach(value -> {
if (value == null || value.isEmpty())
getLogger().info(key + " is empty");
});
List<String> listOfValue = listOfKeys.stream()
.map(key -> path + key)
.map(getConfig()::getString)
.collect(Collectors.toList());
I know that key in the log method is syntax error but I'm wondering how would I be able to access the key in that point and send the message with the key that had the null value?
Also is it possible to do all of it while creating the listOfValues in the second stream?
You can use peek. It evaluates a block of code and continues streaming:
List<String> listOfValue = listOfKeys.stream()
.map(key -> path + key)
.map(getConfig()::getString)
.peek(value -> {
if (value == null || value.isEmpty())
getLogger().info(key + " is empty");
})
.collect(Collectors.toList());
If you want to use the key in logging, you can use Map.Entry:
List<String> listOfValue = listOfKeys.stream()
.map(key -> new AbstractMap.SimpleEntry(key, getConfig().getString(path + key))
.peek(entry -> {
if (entry.getValue() == null || entry.getValue().isEmpty())
getLogger().info(entry.getKey() + " is empty");
})
.map(AbstractMap.SimpleEntry::getValue)
.collect(Collectors.toList());
I'm trying to rewrite code with nested conditions using Optional and Stream. That's how he looked:
if (transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION") != null) {
editObj = (EmployeeWorkstation) transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION");
} else {
if (editObj != null) {
editObj = editObj.getEditInstance(transaction);
} else {
editObj = HOME.newEmployeeWorkstation(compId);
}
}
I tried to rewrite so:
editObj =
ofNullable(
(EmployeeWorkstation) transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION"))
.orElse(
editObj != null
? editObj.getEditInstance(transaction)
: HOME.newEmployeeWorkstation(compId));
And it works fine but my mentor said that it can be simplified
then I tried so:
editObj =
Optional.ofNullable(
(EmployeeWorkstation) transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION"))
.map(obj -> obj.getEditInstance(transaction))
.orElse(HOME.newEmployeeWorkstation(compId));
I understand that my .map() does not work as described above in the first versions. How can I rewrite .map so that it works as described above?
You can use a nested Optional:
EmployeeWorkstation edit = Optional.ofNullable((EmployeeWorkstation) transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION"))
.orElseGet(() -> Optional.ofNullable(editObj)
.map(e -> e.getEditInstance(transaction))
.orElseGet(() -> HOME.newEmployeeWorkstation(compId)));
If you are using Java 9 or higher you can use Optional.or():
EmployeeWorkstation edit = Optional.ofNullable((EmployeeWorkstation) transaction.getObjectByName("EDIT_EMPLOYEE_WORKSTATION"))
.or(() -> Optional.ofNullable(editObj).map(edit -> edit.getEditInstance(transaction)))
.orElseGet(() -> HOME.newEmployeeWorkstation(compId));
I am newbie in RxJava and need help to improve my code. Here is what I've done:
public Single<List<MenuItemsBlocks>> loadMenuItemsBlocks() {
Completable.fromAction(() -> DataStoreRepository.deleteMenuItemsBlock())
.subscribeOn(Schedulers.io()).blockingAwait();
List<MenuItemsBlocks> blocks = new ArrayList<>();
Set<String> aliasList = getAliasFromMenuItems();
for (String alias : aliasList) {
List<MenuItemsBlocks> itemsBlocks = ApiRepository.getMenuItemBlocks(alias)
.subscribeOn(Schedulers.io())
.flatMapIterable(list -> list)
.map(item -> new MenuItemsBlocks(
item.getId(),
item.getType(),
item.getImagePosition(),
item.getTextField(),
item.getSortOrder(),
item.getFileTimeStamp(),
alias
))
.doOnNext(block -> DataStoreRepository.saveMenuItemsBlock(block))
.subscribeOn(Schedulers.io())
.toList()
.blockingGet();
blocks.addAll(itemsBlocks);
}
return Single.just(blocks);
}
There is no problem at runtime with this code, but I want to improve it in rx style, I've tried to rewrite it something like this (but it's not working):
public Single<List<MenuItemsBlocks>> loadMenuItemsBlocks() {
Completable.fromAction(() -> DataStoreRepository.deleteMenuItemsBlock())
.subscribeOn(Schedulers.io()).blockingAwait();
Set<String> aliasList = getAliasFromMenuItems();
return Observable.fromIterable(aliasList)
.switchMap(alias -> ApiRepository.getMenuItemBlocks(alias)
.subscribeOn(Schedulers.io())
.flatMapIterable(list -> list)
.map(item -> new MenuItemsBlocks(
item.getId(),
item.getType(),
item.getImagePosition(),
item.getTextField(),
item.getSortOrder(),
item.getFileTimeStamp(),
alias
))
.doOnNext(block -> DataStoreRepository.saveMenuItemsBlock(block))
.subscribeOn(Schedulers.io())
.toList()
);
}
And I am stuck with it and need your help!
First of all, if you have blockingAwait in non-test code, you are doing it wrong. Second, you probably need concatMap instead of switchMap as it will just keep switching to later list elements, cancelling the outstanding API calls.
public Single<List<MenuItemsBlocks>> loadMenuItemsBlocks() {
return Completable.fromAction(() -> DataStoreRepository.deleteMenuItemsBlock())
.subscribeOn(Schedulers.io())
.andThen(Single.defer(() -> {
Set<String> aliasList = getAliasFromMenuItems();
return Observable.fromIterable(aliasList)
.concatMap(alias -> ApiRepository.getMenuItemBlocks(alias)
.subscribeOn(Schedulers.io())
.flatMapIterable(list -> list)
.map(item -> new MenuItemsBlocks(
item.getId(),
item.getType(),
item.getImagePosition(),
item.getTextField(),
item.getSortOrder(),
item.getFileTimeStamp(),
alias
))
.doOnNext(block -> DataStoreRepository.saveMenuItemsBlock(block))
.subscribeOn(Schedulers.io())
)
.toList();
}));
}
I have 2 URLs to fetch the data, for example: \location_1\{userid} and \location_2\{userid}. for the first i get the list of the users and then need to fetch user details by above requests. the issue is that i need to call the \location_1\{userid} and in case there is an error(exception) fetch the data from \location_2\{userid}. is it possible to make it with single rx-chain? i've tried try/catch as described here but looks catch newer calls, only onErrorResumeNext calls.
Observable<List<TestModel2>> observable = apiTest
.performTest()
.flatMapIterable(items -> items)
.flatMap(testModel -> {
try
{
return apiTest.performTest2(testModel.userId);
} catch (Exception e)
{
return apiTest.performTest3(testModel.userId);
}
}).doOnNext(testModel2 -> {Log.d("TestItemData", "doOnNext --- " + testModel2.title);})
.onErrorResumeNext(throwable ->{
Log.d("TestItemData", "onErrorResumeNext -------- ");
return Observable.empty();
})
.toList()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
Use onErrorResumeNext (as you already did a bit later in the flow):
Observable<List<TestModel2>> observable = apiTest
.performTest()
.flatMapIterable(items -> items)
.flatMap(testModel ->
apiTest.performTest2(testModel.userId)
.onErrorResumeNext(e -> apiTest.performTest3(testModel.userId)); // <----------------
)
.doOnNext(testModel2 -> {
Log.d("TestItemData", "doOnNext --- " + testModel2.title);
})
.onErrorResumeNext(throwable ->{
Log.d("TestItemData", "onErrorResumeNext -------- ");
return Observable.empty();
})
.toList()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
I am fairly new to functional programming and reactive RxJava. I want to get id and name of a device from database and store it in a Map, I am doing it in RxJava style. I am calling a function that doesn't need to return anything
.doOnNext(t -> updateAssetNameMap())
then the function looks like;
private void updateDeviceNameMap() {
LOGGER.debug("Reading device name and id from database");
Observable<SQLConnection> jdbcConnection = createJdbcConnection();
Scheduler defaultScheduler = RxHelper.scheduler(vertx);
Observable<JsonArray> res = jdbcConnection //need to return JsonArray
.flatMap(connection -> just(connection)
.flatMap(j -> runQuery(connection, "SELECT name,id FROM device")
.observeOn(defaultScheduler)
.doOnNext(m -> LOGGER.info("size: " + m.size()))
.flatMap(job -> { LOGGER.info(">>" + job.getJsonArray(0));
//or if I can extract JsonArray items here,
//I can update my Map here too.
return just(job.getJsonArray(0));
}
)
.doOnError(e -> { LOGGER.error("failed to connect to db", e);
connection.close(); })
.doOnCompleted(connection::close)
.onErrorReturn(e -> null));
//System.out.println("" + res.map(d -> LOGGER.info(d.toString())));
//get the JsonArray and update the deviceNameMap
The connection to DB is made successfully and query is also done correctly.
I can convert any Object to Observable by Observable.from(ObjectName), but can't to the opposite. An appropriate mapping needs to be done after .flatMap(job -> just(job.getJsonArray(0)) but I have no clue how. After running the Verticle, I even cannot see anything logged from line .flatMap(job -> { LOGGER.info(">>" + job.getJsonArray(0));.
Am I missing something ?
You must subscribe to your Observable<JsonArray> otherwise nothing happens.