大数据Spark “蘑菇云”行动前传第20课：Scala提取器、注解深度实战详解及Spark源码鉴赏大数据Spark “蘑菇云”行动前传第20课：Scala提取器、注解深度实战详解及Spark源码鉴

 大数据Spark “蘑菇云”行动前传第20课：Scala提取器、注解深度实战详解及Spark源码鉴赏大数据Spark “蘑菇云”行动前传第20课：Scala提取器、注解深度实战详解及Spark源码鉴赏

1 Spark源码提取器、注解

2 Scala提取器、注解深度

@transient 无需序列化
@volatile   线程刷新变量，简单理解为F5刷新，线程本地变量值刷新到全局变量

@varargs 报警

@throws(classOf[IOException]) 扔出异常

这里是个面试题，模式匹配时候一定会用的到是什么方法呢？答 unapply

 



 

 



 

 



 

 



 

 

 



 

 

 



 

 

 

package com.dt.spark.scala.bascis

@DTCoder(name="scala",salary=1000)

case class Person1(name:String,age:Int){

  val content =name

}

class DTCoder(val name:String,val salary:Int) extends annotation.Annotation

object DTCoder{

  def apply(name:String,salary:Int) ={

    println("DTCoder apply methode invoked !!!")

    new DTCoder(name,salary)

  }

 

  def unapply(information:DTCoder)= {

    Some(( information.name,information.salary  ))

  

 /*    def unapply(information:String)= {

    Some((information.substring(0,information.indexOf(" ")),information.substring(0,information.indexOf(" ")+1)))

    }*/

   

  }

 

 

}

object HelloExtractor {

  def main(args: Array[String]): Unit = {

    val person =Person1.apply("spark",6)

    val Person1(name,age)=person

    println(name+ " : " +age)

   

    person match {

      case Person1(name,age)=>println("wow   "+name+ " : " +age)

    }

   

    val dtcoder = DTCoder("hadoop",200)

    val DTCoder(dtname1,dtsalary1) =dtcoder

    println("dtname1   "+dtname1+ " : " +dtsalary1)

   

    //val DTCoder(dtname,dtsalary) = "spark 100"

     //  println("dtname   "+dtname+ " : " +dtsalary)

 

 

  }

 

}

运行结果

spark : 6

wow   spark : 6

DTCoder apply methode invoked !!!

dtname1   hadoop : 200