[GitHub] flink pull request #3176: [FLINK-5571] [table] add open and close methods fo...

[wuchong]

Github user wuchong commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3176#discussion_r99568239
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/UserDefinedFunction.scala
 ---
    @@ -24,4 +24,19 @@ package org.apache.flink.table.functions
       * User-defined functions must have a default constructor and must be 
instantiable during runtime.
       */
     trait UserDefinedFunction {
    --- End diff --
    
    Did you create a Java class which extends `ScalarFunction` or 
`TableFunction` ? I tried this in my environment but the compiling is failed.
    
    ```java
    public class MyScalarFunction extends ScalarFunction {
        public int eval(int a) {
                return a + 1;
        }
    }
    ```
    
    ```
    Error:(25, 8) java: 
org.apache.flink.table.examples.java.MyScalarFunction不是抽象的,
     
并且未覆盖org.apache.flink.table.functions.UserDefinedFunction中的抽象方法close()
    ```


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