高效的Scala_Oracle大会资料.ppt

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text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,高效的,Scala,HENRIK ENGSTRM,TYPESAFE,软件工程师,h3nk3,Typesafe,控制台技术负责人,Akka,团队荣誉会员,从,2010,年开始进行,Scala,编程,自我介绍,从,1998,年开始做咨询,主要针对,Java,从,2011,年开始为,Typesafe,公司工作,阿森纳球迷,+,武术家,关于,Typesafe,Typesafe,平台,Play,、,Akka,、,Scala,、,Scala IDE,、,Slick,、,SBT,等,订阅,培训和咨询,议题,基础知识,Scala,中的对象定位,隐式,类型,集合,模式匹配,函数式编程,基础知识,/REPL=Read Eval Print Loop,$,scala_home,/,bin,/,scala,Welcome,to,Scala,version,2.10,.,0,scala,println,(,Hello,world!,),Hello,world,!,scala,使用,REPL,/Put JAR files in scala_home/lib to get access,$,scala_home,/,bin,/,scala,Welcome,to,Scala,version,2.10,.,0,scala,import,com.x.y.z.MyClass,scala,val,instance,=,new,MyClass,scala,instance,.,myMethod,REPL,和,JAR,REPL 2013,IDE,工作表,Scala IDE,：棒极了,IntelliJ,：很好,/JAVA,String,result,=,null,;,if,(,z,9,),result,=,=9,;,System,.,out,.,println,(,Result:,+,result,);,/SCALA,println,(,Result:,+,(,if,(,z,9,),=9,),表达式与语句,/What type is variable quiz?,var,x,=,1,val,quiz,=,while,(,x,MHS,def,findPeopleInCity,(,c,:,String,ppl,:,Seq,People,),:,Set,People,=,val,found,=,new,MHS,People,(),for,(,p,-,ppl,),for,(,a,-,p,.,address,),if,(,a,.,city,=,c,),found,.,put,(,p,),found,请注意无钓鱼说明！,def,findPeopleInCity,(,c,:,String,ppl,:,Seq,People,),:,Set,People,=,for,p,-,ppl,.,toSet,People,a,Mutable code leads to worse performance,class,Footballer,private,var,cars,=,Array,Car,(),def,setCars,(,c,:,Array,Car,),:,Unit,=,cars,=,c,.,clone,def,getCars,:,Array,Car,=,cars,.,clone,保持不可变,/Safer code-use immutable collection,class,Footballer,private,var,cars,=,Vector,.,empty,Car,def,setCars,(,c,:,Vector,Car,),=,cars,=,c,def,getCars,:,Vector,Car,=,cars,保持不可变,/Case classes make the class immutable,scala,case,class,Car,(,brand,:,String,),scala,case,class,Footballer,(,name,:,String,team,:,String,cars,:,Vector,Car,=,Vector,.,empty,),scala,var,jw,=,new,Footballer,(,Jack Wilshire,Arsenal,),Footballer,(,Jack,Wilshire,Arsenal,Vector,(),scala,jw,=,jw,.,copy,(,cars,=,Vector,(,Car,(,Porsche,),Footballer,(,Jack,Wilshire,Arsenal,Vector,(,Car,(,Porsche,),Case,类,ftw,不可变的优势,简单均等,简单散列代码,无需锁定,无防御性复制,Scala Case,类,自动均等,+,散列代码,(Murmur),还有很多其他好处（例如复制）,/Sometimes local mutability makes sense,import,scala.collection.mutable.ArrayBuffer,class,MyClass,def,theData,:,Seq,Int,=,val,buffer,=,new,ArrayBuffer,Int,(),populateData,(,buffer,),buffer,.,toSeq,局部可变性,/A classic game of null,def,auth,(,usr,:,String,pwd,:,String,),:,Privileges,=,if,(,usr,=,null,|,usr,.,isEmpty,|,pwd,=,null,|,pwd,.,isEmpty,|,!,validCredentials,(,usr,pwd,),withPrivileges,(,Anonymous,),else,privilegesFor,(,usr,),使用选项,def,auth,(,usr,:,Option,String,pwd,:,Option,String,),:,Privileges,=,val,privileges,:,Option,Privileges,=,u,-,usr,p,val,r1,=,new,Rectangle,(,1,314,),scala,r1,.,height,res0,:,Int,=,314,scala,r1,.,area,res1,:,Int,=,0,抽象成员的,val,Scala,初始化顺序,摘自,Scala,规范（第,5.1,节）,www.scala-lang.org/docu/files/ScalaReference.pdf,首先评估超类构建函数,然后是模板线性化中的所有基类,最后评估语句序列状态,trait,SquareShape,def,width,:,Int,def,height,:,Int,def,area,:,Int,=,width,*,height,class,Rect,(,w,:,Int,h,:,Int,),extends,SquaredShape,override,val,width,=,w,override,val,height,=,h,/or even better,case,class,Rect,(,width,:,Int,height,:,Int,),extends,SquaredShape,def,is much better,/Non-trivial return types should always be,/annotated!,def,convert,(,x,:,Int,),=,x,match,case,1,=,1.,toChar,case,2,=,true,case,z,=,z,.,toByte,def,convert,(,x,:,Int,),:,AnyVal,=,x,match,为您的,API,加批注,组合与继承,与继承相比，更偏好组合,易于修改（例如,DI,）,组合可在,Scala,中使用继承,引向著名的“蛋糕”模式,trait,UserRepoComponent,def,userLocator,:,UserLocator,def,userUpdater,:,UserUpdater,trait,UserLocator,def,findAll,:,Vector,User,trait,UserUpdater,def,save,(,user,:,User,),让我们来烘培一块“蛋糕”,trait,JPAUserRepoComponent,extends,UserRepoComponent,def,em,:,EntityManager,def,userLocator,=,new,JPAUserLocator,(,em,),def,userUpdater,=,new,JPAUserUpdater,(,em,),class,JPAUserLocator,(,em,:,EntityManager,),extends,UserLocator,def,findAll,:,Vector,User,=,em,.,createQuery,(,from User,classOf,User,).,getResultList,.,toVector,class,JPAUserUpdater,(,em,:,EntityManager,),extends,UserUpdater,def,save,(,user,:,User,),=,em,.,persist,(,user,),正在烘培,trait,UserServiceComponent,def,userService,:,UserService,trait,UserService,def,findAll,:,Vector,User,def,save,(,user,:,User,),:,Unit,def,checkStatusOf,(,user,:,User,),:,String,服务层,trait,DefaultUserServiceComponent,extends,UserServiceComponent,this:,UserRepositoryComponent,=,def,userService,=,new,DefaultUserService,class,DefaultUserService,extends,UserService,def,findAll,=,userLocator,.,findAll,def,save,(,user,:,User,),=,userUpdater,.,save,(,user,),def,checkStatus,(,user,:,User,),=,s,User$user seems okay to me,服务层实现,object,MyApplication,extends,Application,val,compService,=,new,DefaultUserServiceComponent,with,JPAUserRepositoryComponent,def,em,=,Persistence,.,createEntityManagerFactory,(,cakepattern,).,createEntityManager,(),val,service,=,compService,.,userService,/use the service,投入使用,class,MyTest,extends,WordSpec,with,MustMatchers,with,Mockito,trait,MockedEntityManager,def,em,=,mock,EntityManager,service,must,return all users,in,val,compService,=,new,DefaultUserServiceComponent,with,JPAUserRepositoryComponent,with,MockedEntityManager,/perform tests,进行测试,隐式,有何作用？,在特定上下文中移除样板代码,编译时安全,但是必须明确,trait,AutoRepository,def,find,(,regId,:,String,)(,implicit,dbId,:,DBId,),:,Option,Car,def,findAll,(,country,:,String,)(,implicit,dbId,:,DBId,),:,Seq,Car,class,DefaultAutoRepository,extends,AutoRepository,def,find,(,regId,:,String,)(,implicit,dbId,:,DBId,),:,Option,Car,=,/.,def,findAll,(,country,:,String,)(,implicit,dbId,:,DBId,),:,Seq,Car,=,/.,示例,/Anti pattern,class,CarFinder,val,dbId,=,DbId,(,Dealer1,),val,repo,=,new,DefaultAutoRepository,def,getCar,(,regId,:,String,),:,Option,Car,=,repo,.,find,(,regId,)(,dbId,),def,listCars,(,country,:,String,),:,Seq,Car,=,repo,.,findAll,(,country,)(,dbId,),示例（续）,/Use implicits=much cleaner code,class,CarFinder,implicit,val,dbId,=,DbId,(,Dealer1,),val,repo,=,new,DefaultAutoRepository,def,getCar,(,regId,:,String,),:,Option,Car,=,repo,.,find,(,regId,),def,listCars,(,country,:,String,),:,Seq,Car,=,repo,.,findAll,(,country,),示例（续）,编译器练习,隐式作用域,词法：当前作用域、显式导入、通配符导入,部分类型的伴生对象：类型的伴生对象、参数类型的伴生对象、嵌套类型的外部对象,编译时可能会消耗大量资源，应谨慎使用,trait,Logger,def,log,(,msg,:,String,),object,Logger,implicit,object,DefaultLogger,extends,Logger,def,log,(,msg,:,String,),=,println,(,DL,+,msg,),def,log,(,msg,:,String,)(,implicit,logger,:,Logger,),=,logger,.,log,(,msg,),隐式值,scala,Logger,.,log,(,a small test,),DL a small test,scala,class,MyLogger,extends,Logger,def,log,(,msg,:,String,),=,println,(,ML:,+,msg,),scala,implicit,def,myLogger,=,new,MyLogger,scala,Logger,.,log,(,another test,),ML:another test,隐式值,隐式智慧？,deech deech,调试,#scala,隐式内容如同,在一个拥挤的房间中寻找,farter,类型特性,/describes generic interfaces using type,/parameters such that the implementations can,/be created for any type,trait,Encodable,T,def,from,(,t,:,T,),:,String,def,to,(,s,:,String,),:,T,object,Encodable,implicit,object,IntEncoder,extends,Encodable,Int,def,from,(,i,:,Int,),:,String,=,int,+,i,def,to,(,s,:,String,),:,Int,=,s,.,substring,(,s,.,indexOf,(,int,)+,3,s,.,length,).,toInt,即，类型类,class,MyHandler,def,convert,T,(,t,:,T,)(,implicit,enc,:,Encodable,T,),:,String,=,enc,.,from,(,t,),def,convert,T,(,s,:,String,)(,implicit,enc,:,Encodable,T,),:,T,=,enc,.,to,(,s,),scala,val,myHandler,=,new,MyHandler,scala,myHandler,.,convert,(,12345,),res0,:,String,=,int12345,scala,myHandler,.,convert,(,res0,),res1,:,Int,=,12345,使用示例,scala,myHandler,.,convert,(,12345L,),:15:error:could not find implicit value,for parameter encoder:EncodableLong,scala,implicit,object,LongEnc,extends,Encodable,Long,def,from,(,l,:,Long,),:,String,=,long,+,l,def,to,(,s,:,String,),:,Long,=,s,.,substring,(,s,.,indexOf,(,long,)+,4,s,.,length,).,toLong,scala,myHandler,.,convert,(,12345L,),示例（续）,集合,集合概述,不可变集合,可变集合,/It is absolutely*awesome*,scala,val,seq,=,Seq,(),scala,seq,.,+:+:/:/:+:addString aggregate andThen apply applyOrElse asInstanceOf canEqual collect collectFirst combinations companion compose contains containsSlice copyToArray copyToBuffer corresponds count diff distinct drop dropRight dropWhile endsWith exists filter filterNot find flatMap flatten fold foldLeft foldRight forall foreach genericBuilder groupBy grouped hasDefiniteSize head headOption indexOf indexOfSlice indexWhere indices init inits intersect isDefinedAt isEmpty isInstanceOf isTraversableAgain iterator last lastIndexOf lastIndexOfSlice lastIndexWhere lastOption length lengthCompare lift map max maxBy min minBy mkString nonEmpty orElse padTo par partition patch permutations prefixLength product reduce reduceLeft reduceLeftOption reduceOption reduceRight reduceRightOption repr reverse reverseIterator reverseMap runWith sameElements scan scanLeft scanRight segmentLength seq size slice sliding sortBy sortWith sorted span splitAt startsWith stringPrefix sum tail tails take takeRight takeWhile to toArray toBuffer toIndexedSeq toIterable toIterator toList toMap toSeq toSet toStream toString toTraversable toVector transpose union unzip unzip3 updated view withFilter zip zipAll zipWithIndex,了解和学习,API,给,Java,开发人员的信息,使用,Vector,而不是,List,它更快,它对内存的使用更高效,模式匹配,scala,.,annotation,.,tailrec,def,len,A,(,v,:,Vector,A,l,:,Int,),:,Int,=,v,match,case,h,:,t,=,len,(,t,l,+,1,),case,Nil,=,l,scala,len,(,Vector,(,a,b,c,d,),res0,:,Int,=,4,FP,模式匹配,def,convertedAge,(,a,:,Animal,),:,Int,=,a,match,case,Dog,(,name,age,),=,age,*,7,case,Human,(,_,age,_,),=,age,case,Walrus,(,Donny,age,),=,age,/,10,case,Walrus,(,name,age,),if,name,=,Walter,=,age,case,_,=,0,提取并进行“,instanceof”,判断,相关成本,请注意，模式匹配实际上是,if-else if,。,尝试在开始时放入最常见的发现，以减少跳跃次数,函数式编程,忠告,了解函数式编程的模式,阅读有关,Functor,、,Applicative,和,Monad,的精彩文章,adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html,查看,scalaz,了解,Scala,中,FP,的更多信息,值和上下文,23,值,(+8),函数,31,23,值和上下文,23,SomeInt,无,选项,上下文,值,Functor,23,(+8),不适用！,23,23,(+8),31,31,SomeInt,SomeInt,X,(+8),X,无,无,trait,Functor,F,_,def,fmap,A,B,(,fa,:,F,A,f,:,A,=,B,),:,F,B,Functor,定义,def,dblFunc,(,values,:,Vector,Int,),:,Vector,Int,=,values,map,_,*,2,scala,dblFunc,(,Vector,(,1,2,3,4,),res0,:,Vector,(,2,4,6,8,),Scala,中的,Functor,Applicative,23,SomeInt,(+8),Somef(x),23,(+8),31,SomeInt,scala,Vector,(,1,2,3,),res0,:,Vector,Int,=,Vector,(,1,2,3,),scala,List,(,A,B,C,),res1,:,List,String,=,List,(,A,B,C,),scala,res0,zip,res1,res2,:,List,(,Int,String,),=,List,(,1,A,),(,2,B,),(,3,C,),Scala Applicative,示例,Monad,23,SomeInt,23,isEven,24,24,48,24,24,SomeInt,isEven,*2,无,import,scala.language.higherKinds,trait,Monad,M,_,def,pure,A,(,a,:,A,),:,M,A,def,bind,A,B,(,ma,:,M,A,)(,f,:,A,=,M,B,),:,M,B,Monad,定义,def,even,(,number,:,Option,Int,),:,Option,Int,=,for,n,even,(,Some,(,22,),res1,:,Option,Int,=,Some,(,22,),scala,even,(,Some,(,21,),res2,:,Option,Int,=,None,Scala Monad,示例,总结,FUNCTOR,将函数应用到包装值,APPLICATIVE,将包装函数应用到包装值,MONAD,将返回包装值的函数应用到包装值,推荐的,Scala,书籍,EOFh3nk3,