[NIFI-6500] Add padLeft() and padRight() functions to expression language

• Type: New Feature
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.9.2
• Fix Version/s: 1.10.0
• Component/s: Core Framework
• Assignee: Alessandro D'Armiento
• Reporter: Alessandro D'Armiento
• Created: 29/Jul/19 13:47
• Updated: 24/Aug/19 09:30
• Resolved: 24/Aug/19 02:38

Description

Current Situation

• Expression Language string manipulation doesn't have anything to perform string padding

• Existing solutions to achieve left or right padding are unintuitive
  • Es: ${prop:prepend('0000'):substring(${prop:length()},${prop:length():plus(4)})}

Improvement Proposal

• Support two new expression language methods
  • padLeft:
    • padLeft(int n) will prepend a default character to of the input string until it reaches the length n
    • padLeft(int n, char c) will prepend the c characters to the input string until it reaches the length n
  • padRight:
    • padRight(int n) will append a default character to the input string until it reaches the length n
    • padRight(int n, char c) will append the c character to the input string until it reaches the length n
  • Default character should be a renderable character such as underscore
  • If the input string is already longer than the padding length, no operation should be performed

Examples

---

input = "myString"

---

• ${input:padLeft(10, '#')} => "##myString"
• ${input:padRight(10, '#')} => "myString##"
• ${input:padLeft(10)} => "__myString"
• ${input:padRight(10)} => "myString__"

Issue Links

• links to: GitHub Pull Request #3615