[GitHub] incubator-metron pull request #370: METRON-586 add FILL_LEFT and FILL_RIGHT ...

[nickwallen <gi...@git.apache.org>]

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

    https://github.com/apache/incubator-metron/pull/370#discussion_r90759526
  
    --- Diff: metron-platform/metron-common/src/main/java/org/apache/metron/common/dsl/functions/StringFunctions.java ---
    @@ -222,4 +222,71 @@ public Object apply(List<Object> args) {
           return null;
         }
       }
    +
    +  private enum FillDirection{
    +    LEFT,
    +    RIGHT
    +  }
    +
    +  @Stellar(name="FILL_LEFT"
    +          , description="Fills or pads a given string with a given character, to a given length on the left"
    +          , params = { "input - string", "fill - the fill character", "len - the required length"}
    +          , returns = "Filled String"
    +  )
    +  public static class FillLeft extends BaseStellarFunction {
    +    @Override
    +    public Object apply(List<Object> args) {
    +      if(args.size() < 3) {
    +        throw new IllegalStateException("FILL_LEFT expects three args: [string,char,length] where char is the fill character string and length is the required length of the result");
    +      }
    +      return fill(FillDirection.LEFT,args.get(0),args.get(1),args.get(2));
    +    }
    +  }
    +
    +  @Stellar(name="FILL_RIGHT"
    +          , description="Fills or pads a given string with a given character, to a given length on the right"
    +          , params = { "input - string", "fill - the fill character", "len - the required length"}
    +          , returns = "Filled String"
    +  )
    +  public static class FillRight extends BaseStellarFunction {
    +    @Override
    +    public Object apply(List<Object> args) {
    +      if(args.size() < 3) {
    +        throw new IllegalStateException("FILL_RIGHT expects three args: [string,char,length] where char is the fill character string and length is the required length of the result");
    +      }
    +      return fill(FillDirection.RIGHT,args.get(0),args.get(1),args.get(2));
    +    }
    +  }
    +
    +  private static Object fill(FillDirection direction, Object inputObject, Object fillObject, Object requiredLengthObject){
    +    if(inputObject == null) {
    +      return null;
    +    }
    +    String input = inputObject.toString();
    +
    +    if(requiredLengthObject == null || fillObject == null) {
    +      return input;
    --- End diff --
    
    Should this blow-up and throw an exception if we don't have a length or fill?
    
    Consider the case where I write an expression for the length or fill.  In many cases, if something unexpected happens in that expression, like a missing field, it returns null.  So the null would propagate here and the original string would be returned.   I would wonder why I am just getting the original string back when I expected it to be filled.  That seems hard to debug.  


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