Flink Socket WordCount common exceptions and solutions

A. Code implementation　

Package cn.socket 

Import org.apache.flink.streaming.api.scala._ // Data type of exception, the dynamic data into
 // Import org.apache.flink.api.scala._ // Data type of exception, the introduction of static data 

/ ** 
  * the Created by Administrator ON 2020/3/22. 
  * / 

Object SocketWindowWordCount { 
  DEF main (args: the Array [String]): Unit = { 

    // the specified IP interfaces and 
    val hostname: String = "192.168.136.7" 
    Port Val: Int = 9001 // acquisition stream processing environment 
    Val the env: = StreamExecutionEnvironment StreamExecutionEnvironment.getExecutionEnvironment // Get data calculation socket

    

    
    text Val: DataStream [String] = env.socketTextStream (hostname, Port, '\ n-' ) 

    text.print () 
    // WordCount 
    Val windowCounts = text 
      .flatMap {W => w.split ( "\\ S" )} 
      .map (W => (W,. 1 )) 
      .keyBy (_._. 1) 
      .sum ( . 1 ) 

    // set the degree of parallelism, printing 
    windowCounts.print (). setParallelism (. 1 ) 

    // execution 
    env.execute ( "Socket the WordCount the Window " ) 
  } 
}

II. Common exceptions

Error:(15, 16) could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[String]
      .flatMap { w => w.split("\\s") }
               ^

Error:(15, 16) not enough arguments for method flatMap: (implicit evidence$11: org.apache.flink.api.common.typeinfo.TypeInformation[String])
org.apache.flink.streaming.api.scala.DataStream[String].
Unspecified value parameter evidence$11.
      .flatMap { w => w.split("\\s") }
               ^

　　Figure:

　　

　　Cause Analysis:

　　　　In most flink the operator, the definition does not default implicit type parameter, we do not explicitly specify the type in use, and therefore will be reported type of exception.

III. Solution

Import org.apache.flink.streaming.api.scala._ // Data type of exception, the dynamic data into 
Import org.apache.flink.api.scala._ // Data type of exception, the introduction of static data