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