restapi(6)- do it the functional way, 重溫函數語言程式設計
再次看了看上篇部落格的原始碼,發現連自己都看不懂了。想是為了趕時間交貨不知不覺又回到OOP行令模式了,看看下面這段程式碼:
(post & parameters('pid,'desc.?,'width.as[Int].?,'heigth.as[Int].?)) { (pid, optDesc, optWid, optHgh) => val futCount: Future[Int] = repository.count(pid).value.value.runToFuture.map { eoi => eoi match { case Right(oi) => oi match { case Some(i) => i case None => -1 } case Left(err) => -1 } } val count: Int = Await.result(futCount, 2 seconds) var doc = Document( "pid" -> pid, "seqno" -> count ) if (optDesc != None) doc = doc + ("desc" -> optDesc.get) if (optWid != None) doc = doc + ("desc" -> optWid.get) if (optHgh != None) doc = doc + ("desc" -> optHgh.get) withoutSizeLimit { decodeRequest { extractDataBytes { bytes => val fut = bytes.runFold(ByteString()) { case (hd, bs) => hd ++ bs } onComplete(fut) { case Success(b) => doc = doc + ("pic" -> b.toArray) val futmsg: Future[String] = repository.insert(doc).value.value.runToFuture.map { eoc => eoc match { case Right(oc) => oc match { case Some(c) => count.toString // c.toString() case None => "insert may not complete!" } case Left(err) => err.getMessage } } complete(futmsg) case Failure(err) => complete(err) } } } }
有人能從這段程式碼裡理解它的功能嗎?本來作者的目的很簡單:前端通過httprequest提交了一張圖片及產品編號pid、系統讀取MongoDB查詢相同pid的數量count,然後將圖片和描述包括count寫入資料庫並在reponse裡返回count。把一個簡單功能的實現搞的這麼複雜都是我的錯,可能受OOP荼毒太深。這次希望靜下心來用函數語言程式設計模式把這段程式碼從新實現一次,示範一下函數語言程式設計的程式碼精煉和高雅特點。首先介紹一下DBResult[A]這個型別:這是一個Monad,為了應付Future[Either[Option[R]]]這樣的型別而設計的,是一個表現資料庫操作比較全面的型別,但同時它又是造成上面這段程式碼混亂的元凶。現在我們可以用隱式轉換implicit conversion方式進行程式碼簡化重用:
import monix.execution.Scheduler.Implicits.global implicit class DBResultToFuture(dbr: DBOResult[_]){ def toFuture[R] = { dbr.value.value.runToFuture.map { eor => eor match { case Right(or) => or match { case Some(r) => r.asInstanceOf[R] case None => throw new RuntimeException("Operation produced None result!") } case Left(err) => throw new RuntimeException(err) } } } }
用這個隱式轉換型別為任何DBOResult[R]增加一個函式toFuture[R]。現在整個futCount算式可以簡化成下面這樣:
val futCount: Future[Int] = repository.count(pid).value.value.runToFuture.map { eoi => eoi match { case Right(oi) => oi match { case Some(i) => i case None => -1 } case Left(err) => -1 } } futCount:Future[Int]=repository.count(pid).toFuture
真正的簡單易明。
不知怎麼搞的,我盡然在這段程式碼中間使用了Await.result。從OOP角度分析這很容易理解,下一段程式需要上一段程式的結果來繼續執行。在上面的例子裡我們需要先獲取count然後把count塞進Document再把Document存入資料庫。邏輯思路上沒問題,不過這樣的做法是典型的行令式程式設計模式。在函數語言程式設計模式裡,階段性的運算結果是在包嵌在Monad中的。Monad本身只是一個運算計劃,只有真正運算時才能獲取結果。Monad本身是函式元件,可以實現多個Monad的函式組合。在這裡可以形象的把Monad函式組合描述為資料庫操作步驟:先count、再insert,這兩個步驟產生的結果還是留在Monad裡的,直到所謂的世界末日,即實際運算完成後才取出,所以Monad是一種典型的程式運算流程管道。假如我們再把insert這段程式寫成addPicture(...): DBOResult[_], 如下:
def addPicuture(pid: String,seqno: Int, optDesc: Option[String] ,optWid:Option[Int],optHgh:Option[Int], bytes: Array[Byte]):DBOResult[Completed] ={ var doc = Document( "pid" -> pid, "seqno" -> seqno, "pic" -> bytes ) if (optDesc != None) doc = doc + ("desc" -> optDesc.get) if (optWid != None) doc = doc + ("desc" -> optWid.get) if (optHgh != None) doc = doc + ("desc" -> optHgh.get) repository.insert(doc) }
好了,現在整篇程式碼變成了下面這樣:
(post & parameters('pid,'desc.?,'width.as[Int].?,'heigth.as[Int].?)) { (pid, optDesc, optWid, optHgh) => withoutSizeLimit { decodeRequest { extractDataBytes { bytes => val futBytes = bytes.runFold(ByteString()) { case (hd, bs) => hd ++ bs } val futSeqno = for { cnt <- repository.count(pid).toFuture barr <- futBytes _ <- addPicuture(pid, cnt, optDesc, optWid, optHgh, barr.toArray).toFuture } yield cnt complete(futSeqno.map(_.toString)) } }
現在是不是變得簡單易明瞭?如果你覺著這樣看起來更加容易理解,那麼我建議你現在開始多點接觸瞭解函數語言程式設計。
接著用同樣方式把整個專案重新實現一次。修改後的原始碼如下:
MongoRepo.scala
package com.datatech.rest.mongo import org.mongodb.scala._ import org.bson.conversions.Bson import org.mongodb.scala.result._ import com.datatech.sdp.mongo.engine._ import MGOClasses._ import MGOEngine._ import MGOCommands._ import com.datatech.sdp.result.DBOResult.DBOResult object MongoRepo { class MongoRepo[R](db:String, coll: String, converter: Option[Document => R])(implicit client: MongoClient) { def getAll[R](next:Option[String],sort:Option[String],fields:Option[String],top:Option[Int]): DBOResult[Seq[R]] = { var res = Seq[ResultOptions]() next.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_FILTER,Some(Document(b)))} sort.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_SORT,Some(Document(b)))} fields.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_PROJECTION,Some(Document(b)))} top.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_LIMIT,None,b)} val ctxFind = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_QUERY) .setCommand(Find(andThen = res)) mgoQuery[Seq[R]](ctxFind,converter) } def query[R](filtr: Bson, next:Option[String]=None,sort:Option[String]=None,fields:Option[String]=None,top:Option[Int]=None): DBOResult[Seq[R]] = { var res = Seq[ResultOptions]() next.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_FILTER,Some(Document(b)))} sort.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_SORT,Some(Document(b)))} fields.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_PROJECTION,Some(Document(b)))} top.foreach {b => res = res :+ ResultOptions(FOD_TYPE.FOD_LIMIT,None,b)} val ctxFind = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_QUERY) .setCommand(Find(filter = Some(filtr),andThen = res)) mgoQuery[Seq[R]](ctxFind,converter) } import org.mongodb.scala.model.Filters._ def count(pid: String):DBOResult[Int] = { val ctxCount = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_QUERY) .setCommand(Count(filter=Some(equal("pid",pid)))) mgoQuery[Int](ctxCount,None) } def getOneDocument(filtr: Bson): DBOResult[Document] = { val ctxFind = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_QUERY) .setCommand(Find(filter = Some(filtr),firstOnly = true)) mgoQuery[Document](ctxFind,None) } def getOnePicture[R](pid: String, seqno: Int): DBOResult[R] = { val ctxFind = MGOContext(dbName = db, collName = coll) .setActionType(MGO_ACTION_TYPE.MGO_QUERY) .setCommand(Find(filter = Some(and(equal("pid",pid),equal("seqno",seqno))), firstOnly = true)) mgoQuery[R](ctxFind, converter) } def insert(doc: Document): DBOResult[Completed] = { val ctxInsert = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_UPDATE) .setCommand(Insert(Seq(doc))) mgoUpdate[Completed](ctxInsert) } def delete(filter: Bson): DBOResult[DeleteResult] = { val ctxDelete = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_UPDATE) .setCommand(Delete(filter)) mgoUpdate[DeleteResult](ctxDelete) } def update(filter: Bson, update: Bson, many: Boolean): DBOResult[UpdateResult] = { val ctxUpdate = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_UPDATE) .setCommand(Update(filter,update,None,!many)) mgoUpdate[UpdateResult](ctxUpdate) } def replace(filter: Bson, row: Document): DBOResult[UpdateResult] = { val ctxUpdate = MGOContext(dbName = db,collName=coll) .setActionType(MGO_ACTION_TYPE.MGO_UPDATE) .setCommand(Replace(filter,row)) mgoUpdate[UpdateResult](ctxUpdate) } } import monix.execution.Scheduler.Implicits.global implicit class DBResultToFuture(dbr: DBOResult[_]){ def toFuture[R] = { dbr.value.value.runToFuture.map { eor => eor match { case Right(or) => or match { case Some(r) => r.asInstanceOf[R] case None => throw new RuntimeException("Operation produced None result!") } case Left(err) => throw new RuntimeException(err) } } } } }
MongoRoute.scala
package com.datatech.rest.mongo
import akka.http.scaladsl.server.Directives
import com.datatech.sdp.file._
import scala.util._
import org.mongodb.scala._
import com.datatech.sdp.file.Streaming._
import org.mongodb.scala.result._
import MongoRepo._
import akka.stream.ActorMaterializer
import com.datatech.sdp.result.DBOResult._
import org.mongodb.scala.model.Filters._
import com.datatech.sdp.mongo.engine.MGOClasses._
import monix.execution.CancelableFuture
import akka.util._
import akka.http.scaladsl.model._
import akka.http.scaladsl.coding.Gzip
import akka.stream.scaladsl._
import MongoModels.WebPic
import scala.concurrent._
import scala.concurrent.duration._
object MongoRoute {
class MongoRoute[M <: ModelBase[Document]](val pathName: String)(repository: MongoRepo[M])(
implicit c: MongoClient, m: Manifest[M], mat: ActorMaterializer) extends Directives with JsonConverter {
import monix.execution.Scheduler.Implicits.global
var dbor: DBOResult[Seq[M]] = _
var dbou: DBOResult[UpdateResult] = _
val route = pathPrefix(pathName) {
pathPrefix("pictures") {
(post & parameters('pid,'desc.?,'width.as[Int].?,'heigth.as[Int].?)) { (pid, optDesc, optWid, optHgh) =>
withoutSizeLimit {
decodeRequest {
extractDataBytes { bytes =>
val futBytes = bytes.runFold(ByteString()) { case (hd, bs) =>
hd ++ bs
}
val futSeqno = for {
cnt <- repository.count(pid).toFuture[Int]
barr <- futBytes
_ <- addPicuture(pid, cnt, optDesc, optWid, optHgh, barr.toArray).toFuture[Completed]
} yield cnt
complete(futSeqno.map(_.toString))
}
}
} ~
(get & parameters('pid, 'seqno.as[Int].?, 'width.as[Int].?, 'height.as[Int].?)) {
(pid, optSeq, optWid, optHght) =>
if (optSeq == None) {
val futRows = repository.query(equal("pid", pid)).toFuture
complete(futureToJson(futRows))
} else {
val futPicRow = repository.getOnePicture(pid, optSeq.get).toFuture[WebPic]
onComplete(futPicRow) {
case Success(row) =>
val width = if (optWid == None) row.width.getOrElse(128) else optWid.getOrElse(128)
val height = if (optHght == None) row.heigth.getOrElse(128) else optHght.getOrElse(128)
if (row.pic != None) {
withoutSizeLimit {
encodeResponseWith(Gzip) {
complete(
HttpEntity(
ContentTypes.`application/octet-stream`,
ByteArrayToSource(Imaging.setImageSize(row.pic.get.getData, width, height)
))
)
}
}
} else complete(StatusCodes.NotFound)
case Failure(err) => complete(err)
}
}
}
}
} ~
pathPrefix("blob") {
(get & parameter('filter)) { filter =>
val filtr = Document(filter)
val futOptPic: CancelableFuture[Option[MGOBlob]] = repository.getOneDocument(filtr).toFuture
onComplete(futOptPic) {
case Success(optBlob) => optBlob match {
case Some(blob) =>
withoutSizeLimit {
encodeResponseWith(Gzip) {
complete(
HttpEntity(
ContentTypes.`application/octet-stream`,
ByteArrayToSource(blob.getData)
)
)
}
}
case None => complete(StatusCodes.NotFound)
}
case Failure(err) => complete(err)
}
} ~
(post & parameter('bson)) { bson =>
val bdoc = Document(bson)
withoutSizeLimit {
decodeRequest {
extractDataBytes { bytes =>
val futbytes = bytes.runFold(ByteString()) { case (hd, bs) =>
hd ++ bs
}
val futmsg:Future[Completed] = for {
bytes <- futbytes
doc = Document(bson) + ("photo" -> bytes.toArray)
c <- repository.insert(doc).toFuture[Completed]
} yield c
complete(futmsg.map(_.toString))
}
}
}
}
} ~
(get & parameters('filter.?,'fields.?,'sort.?,'top.as[Int].?,'next.?)) {
(filter,fields,sort,top,next) => {
dbor = {
filter match {
case Some(fltr) => repository.query(Document(fltr),next,sort,fields,top)
case None => repository.getAll(next,sort,fields,top)
}
}
val futRows:Future[Seq[WebPic]] = dbor.toFuture[Seq[WebPic]]
complete(futureToJson(futRows))
}
} ~ post {
entity(as[String]) { json =>
val extractedEntity: M = fromJson[M](json)
val doc: Document = extractedEntity.to
val futmsg = repository.insert(doc).toFuture[Completed]
complete(futmsg.map(_.toString))
}
} ~ (put & parameter('filter,'set.?, 'many.as[Boolean].?)) { (filter, set, many) =>
val bson = Document(filter)
if (set == None) {
entity(as[String]) { json =>
val extractedEntity: M = fromJson[M](json)
val doc: Document = extractedEntity.to
val futmsg = repository.replace(bson, doc).toFuture
complete(futureToJson(futmsg))
}
} else {
set match {
case Some(u) =>
val ubson = Document(u)
dbou = repository.update(bson, ubson, many.getOrElse(true))
case None =>
dbou = Left(new IllegalArgumentException("missing set statement for update!"))
}
val futmsg:Future[UpdateResult] = dbou.toFuture[UpdateResult]
complete(futureToJson(futmsg.map(_.toString)))
}
} ~ (delete & parameters('filter, 'many.as[Boolean].?)) { (filter,many) =>
val bson = Document(filter)
val futmsg:Future[DeleteResult] = repository.delete(bson).toFuture[DeleteResult]
complete(futureToJson(futmsg.map(_.toString)))
}
}
def addPicuture(pid: String,seqno: Int, optDesc: Option[String]
,optWid:Option[Int],optHgh:Option[Int],
bytes: Array[Byte]):DBOResult[Completed] ={
var doc = Document(
"pid" -> pid,
"seqno" -> seqno,
"pic" -> bytes
)
if (optDesc != None)
doc = doc + ("desc" -> optDesc.get)
if (optWid != None)
doc = doc + ("desc" -> optWid.get)
if (optHgh != None)
doc = doc + ("desc" -> optHgh.get)
repository.insert(doc)
}
}
}
&n