How to access column names in a schema

[aaronrums]

Hello! Is it possible to somehow figure out what column names are in a schema that's getting passed through?

Lets say the schema is PersonID, FirstName, LastName. I would want to generate a string that said "PersonID, FirstName, LastName". Then I could split this string on the "," and get one-record-per-column-name.

Is this possible? One solution I have is to write one record to a CSV, which will have the column names as the first line. Then read the first line of that CSV as a raw text file. But this is not an ideal solution at all.

Thank you!

[anselmopeixoto]

Hello @Aaron Rumley​ 

You could use the row that connects the component from which you want to extract the column names and convert it fully to String.

Lets say you have tDBInput -> row1 -> tJava

Then on tJava component you can use the expression row1.toString() to convert the whole Struct to text.

This expression above will return something like this:

project.job_0_1.job$row1Struct@3f57bcad[PersonId=value,FirstName=value,LastName=value]

Next you could use some regular expression or even some substring/split methods to extract the column names from the resulting String.

I hope it helps.

[aaronrums]

This is a good start, thank you! It'd be nice if Talend had some built in functionality for this.

[aaronrums]

if anyone in the future is interested, here's my code for this. It probably won't work if one of your columns has a record that has a "," in it's value, or if the value is JSON, since that contains lots of commas and also square brackets.

/***

   * if your component is connected with a "row1" connection, for example

   * then call row1.toString(), and pass in that string to this method. It will produce an array of the column names in row1.

   * 

   * At the moment, this doesn't work if the schema contains columns that contain json.  

   * 

   */

  public static ArrayList<String> PrintColumnNames(String schemaString)

  {

   String parsedString = StringHandling.RIGHT(schemaString, schemaString.length() - schemaString.indexOf("[")).replaceAll("\\[|\\]", "");

   String[] arrayOfStr = parsedString.split(",");

   ArrayList<String> nameList = new ArrayList<String>(); 

  for (int i = 0; i < arrayOfStr.length; i++)

   {

   String extract = StringHandling.LEFT(arrayOfStr[i], (arrayOfStr[i].length() - (arrayOfStr[i].length() - arrayOfStr[i].indexOf("=")) ));

   nameList.add(extract);

   //System.out.println(extract);

   }

  return nameList;

  }