There is a web service returning array of something
{"apps": [{"name": "one"}, {"name": "two"}]}
In my code I want to iterate every name
val request = WS.url(s"http://localhost:9000/getData")
val json = request.get.map { response =>
(response.json \ "apps" \\ "name")
}
json.foreach(println)
However all my attempts return single record
// Expect
one
two
// Actual
ListBuffer("one", "two")
First of all, the neat solution here would be:
val request = WS.url(s"http://localhost:9000/getData")
request.get.map { response =>
val names = (response.json \ "apps" \\ "name")
names.foreach(println)
}
Secondly, if you don't want to get confused about the types, you should change your naming standards. For a Future object, you may start with the prefix future, for an Option, it could start with maybe, etc. If you do so, the problem in your example will be more obvious:
val request = WS.url(s"http://localhost:9000/getData")
val futureJson = request.get.map { response =>
(response.json \ "apps" \\ "name")
}
futureJson.foreach(println) // you call foreach for a Future, not for a List
Thirdly, why would Future trait have a method called foreach? I think that's confusing for beginners and even mid-level developers. We know from other languages that, foreach means iterate over a list of objects. In Scala, it is considered part of "Monadic operations" which is still a gray area for me :), but the comment for Future.foreach in Scala source is this:
/** Asynchronously processes the value in the future once the value becomes available.
*
* Will not be called if the future fails.
*/
def foreach[U]
Your value of json is actually a Future[Seq[JsValue]], so when you foreach over the future you get the entire list back. You would need an additional foreach to iterate over the list of values.
Related
I am refactoring a scala http4s application to remove some pesky side effects causing my app to block. I'm replacing .unsafeRunSync with cats.effect.IO. The problem is as follows:
I have 2 lists: alreadyAccessible: IO[List[Page]] and pages: List[Page]
I need to filter out the pages that are not contained in alreadyAccessible.
Then map over the resulting list to "grant Access" in the database to these pages. (e.g. call another method that hits the database and returns an IO[Page].
val addable: List[Page] = pages.filter(p => !alreadyAccessible.contains(p))
val added: List[Page] = addable.map((p: Page) => {
pageModel.grantAccess(roleLst.head.id, p.id) match {
case Right(p) => p
}
})
This is close to what I want; However, it does not work because filter requires a function that returns a Boolean but alreadyAccessible is of type IO[List[Page]] which precludes you from removing anything from the IO monad. I understand you can't remove data from the IO so maybe transform it:
val added: List[IO[Page]] = for(page <- pages) {
val granted = alreadyAccessible.flatMap((aa: List[Page]) => {
if (!aa.contains(page))
pageModel.grantAccess(roleLst.head.id, page.id) match { case Right(p) => p }
else null
})
} yield granted
this unfortunately does not work with the following error:
Error:(62, 7) ';' expected but 'yield' found.
} yield granted
I think because I am somehow mistreating the for comprehension syntax, I just don't understand why I cannot do what I'm doing.
I know there must be a straight forward solution to such a problem, so any input or advice is greatly appreciates. Thank you for your time in reading this!
granted is going to be an IO[List[Page]]. There's no particular point in having IO inside anything else unless you truly are going to treat the actions like values and reorder them/filter them etc.
val granted: IO[List[Page]] = for {
How do you compute it? Well, the first step is to execute alreadyAccessible to get the actual list. In fact, alreadyAccessible is misnamed. It is not the list of accessible pages; it is an action that gets the list of accessible pages. I would recommend you rename it getAlreadyAccessible.
alreadyAccessible <- getAlreadyAccessible
Then you filter pages with it
val required = pages.filterNot(alreadyAccessible.contains)
Now, I cannot decipher what you're doing to these pages. I'm just going to assume you have some kind of function grantAccess: Page => IO[Page]. If you map this function over required, you will get a List[IO[Page]], which is not desirable. Instead, we should traverse with grantAccess, which will produce a IO[List[Page]] that executes each IO[Page] and then assembles all the results into a List[Page].
granted <- required.traverse(grantAccess)
And we're done
} yield granted
If I want to read a single parameter in a get request in scalatra I can do it as follows:
get("mypath/:id") {
val id = params("id")
...
}
According to the scalatra documentation I can also use multiParams to get a sequence of parameters:
val ids = multiParams("ids")
But it does not say how the URL should be formed should I wish to pass more than one parameter. So if I wanted to pass multiple ids what is the format for the URL?
I have tried it with ampersands, commas and semi-colons but to no avail: e.g.
../mypath/id1&id2
Check the docs: http://scalatra.org/guides/2.4/http/routes.html
As an example, let’s hit a URL with a GET like this:
/articles/52?foo=uno&bar=dos&baz=three&foo=anotherfoo
Look closely: there are two “foo” keys in there.
Assuming there’s a matching route at /articles/:id, we get the
following results inside the action:
get("/articles/:id") {
params("id") // => "52"
params("foo") // => "uno" (discarding the second "foo" parameter value)
params("unknown") // => generates a NoSuchElementException
params.get("unknown") // => None - this is what Scala does with unknown keys in a Map
multiParams("id") // => Seq("52")
multiParams("foo") // => Seq("uno", "anotherfoo")
multiParams("unknown") // => an empty Seq
}
So you would need to name each param. e.g. /mypath/?ids=id1&ids=id2&ids=id3
You can embed multiple same name parameters in the path and get them through multiParams:
// http://localhost:8080/articles/id1/id2
get("/articles/:id/:id"){
println(multiParams("id")) // => Seq("id1", "id2")
}
Scala is pretty new for me and I have problems as soon as a leave the gatling dsl.
In my case I call an API (Mailhog) which responds with a lot of mails in json-format. I can’t grab all the values.
I need it with “jsonPath” and I need to “regex” as well.
That leads into a map and a list which I need to iterate through and save each value.
.check(jsonPath("$[*]").ofType[Map[String,Any]].findAll.saveAs("id_map"))
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.saveAs("url_list"))
At first I wanted to loop the “checks” but I did’nt find any to repeat them without repeating the “get”-request too. So it’s a map and a list.
1) I need every value of the map and was able to solve the problem with the following foreach loop.
.foreach("${id_map}", "idx") {
exec(session => {
val idMap = session("idx").as[Map[String,Any]]
val ID = idMap("ID")
session.set("ID", ID)
})
.exec(http("Test")
.get("/{ID}"))
})}
2) I need every 3rd value of the list and make a get-request on them. Before I can do this, I need to replace a part of the string. I tried to replace parts of the string while checking for them. But it won’t work with findAll.
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.transform(raw => raw.replace("""=\r\n""","")).saveAs("url"))
How can I replace a part of every string in my list?
also how can I make a get-request on every 3rd element in the list.
I can't get it to work with the same foreach structure above.
I was abole to solve the problem by myself. At first I made a little change to my check(regex ...) part.
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.transform(_.map(raw => raw.replace("""=\r\n""",""))).saveAs("url_list"))
Then I wanted to make a Get-Request only on every third element of my list (because the URLs I extracted appeared three times per Mail).
.exec(session => {
val url_list =
session("url_list").as[List[Any]].grouped(3).map(_.head).toList
session.set("url_list", url_list)
})
At the end I iterate through my final list with a foreach-loop.
foreach("${url_list}", "urls") {
exec(http("Activate User")
.get("${urls}")
)
}
I'm current creating some Gatling simulation to test a REST API. I don't really understand Scala.
I've created a scenario with several exec and pause;
object MyScenario {
val ccData = ssv("cardcode_fr.csv").random
val nameData = ssv("name.csv").random
val mobileData = ssv("mobile.csv").random
val emailData = ssv("email.csv").random
val itemData = ssv("item_fr.csv").random
val scn = scenario("My use case")
.feed(ccData)
.feed(nameData)
.feed(mobileData)
.feed(emailData)
.feed(itemData)
.exec(
http("GetCustomer")
.get("/rest/customers/${CardCode}")
.headers(Headers.headers)
.check(
status.is(200)
)
)
.pause(3, 5)
.exec(
http("GetOffers")
.get("/rest/offers")
.queryParam("customercode", "${CardCode}")
.headers(Headers.headers)
.check(
status.is(200)
)
)
}
And I've a simple Simulation :
class MySimulation extends Simulation {
setUp(MyScenario.scn
.inject(
constantUsersPerSec (1 ) during (1)))
.protocols(EsbHttpProtocol.httpProtocol)
.assertions(
global.successfulRequests.percent.is(100))
}
The application I'm trying to simulate is a multilocation mobile App, so I've prepared a set of samples data for each Locale (US, FR, IT...)
My REST API handles all the locales, therefore I want to make the simulation concurrently execute several instances of MyScenario, each with a different locale sample, to simulate the global load.
Is it possible to execute my simulation without having to create/duplicate the scenario and change the val ccData = ssv("cardcode_fr.csv").random for each one?
Also, each locale has its own load, how can I create a simulation that takes a single scenario and executes it several times concurrently with a different load and feeders?
Thanks in advance.
From what you've said, I think this may be a good approach:
Start by grouping your data in such a way that you can look up each item you want to send based on the current locale. For this, I would recommend using a Map that matches a locale string (such as "FR") to the item that matches that locale for the field you're looking to fill in. Then, at the start of each iteration of the scenario, you just pick which locale you want to use for the current iteration from a list. It would look something like this:
val locales = List("US", "FR", "IT")
val names = Map( "US" -> "John", "FR" -> "Pierre", "IT" -> "Guillame")
object MyScenario {
//These two lines pick a random locale from your list
val random_index = rand.nextInt(locales.length);
val currentLocale = locales(random_index);
//This line gets the name
val name = names(currentLocale)
//Do the rest of your logic here
}
This is a very simplified example - you'll have to figure out how you actually want to retrieve the data from files and put it into a Map structure, as I assume you don't want to hard code every item for every field into your code.
I have standard list of objects which is used for the some analysis. The analysis generates a list of Strings and i need to look through the standard list of objects and retrieve objects with same name.
case class TestObj(name:String,positions:List[Int],present:Boolean)
val stdLis:List[TestObj]
//analysis generates a list of strings
var generatedLis:List[String]
//list to save objects found in standard list
val lisBuf = new ListBuffer[TestObj]()
//my current way
generatedLis.foreach{i=>
val temp = stdLis.filter(p=>p.name.equalsIgnoreCase(i))
if(temp.size==1){
lisBuf.append(temp(0))
}
}
Is there any other way to achieve this. Like having an custom indexof method that over rides and looks for the name instead of the whole object or something. I have not tried that approach as i am not sure about it.
stdLis.filter(testObj => generatedLis.exists(_.equalsIgnoreCase(testObj.name)))
use filter to filter elements from 'stdLis' per predicate
use exists to check if 'generatedLis' has a value of ....
Don't use mutable containers to filter sequences.
Naive solution:
val lisBuf =
for {
str <- generatedLis
temp = stdLis.filter(_.name.equalsIgnoreCase(str))
if temp.size == 1
} yield temp(0)
if we discard condition temp.size == 1 (i'm not sure it is legal or not):
val lisBuf = stdLis.filter(s => generatedLis.exists(_.equalsIgnoreCase(s.name)))