How to write fields dynamically to a csv file using a tJava - talend

Question

I'm using Talend to extract database field names from the table and write to a csv them after replacing the "_" in field names with " ". I want to have these values against the actual headers.
eg:
|First_Name|Last_Name|
|----------|---------|
|First Name|Last Name|
My job looks similar to following.
Code in tJavaRow is as follows:
for (java.lang.reflect.Field field:
input_row.getClass().getDeclaredFields()) {
String fieldName = field.getName();
String newFieldName = null;
newFieldName = fieldName.replaceAll("_", " ");
context.columnName = newFieldName;
System.out.println("Field name is " + context.columnName );
}
How can I get the value of this context variable for each field in csv file? If I directly use it in the tmap it will only have name of the last field as value.
tmap I had between tJava and the tFileOutputDelimited.

Answer 1

you cannot change schema as they are treated as declared variables in java code which is generated in backend.
your schema "|First_Name|Last_Name|" is converted into as below:
String First_Name =null;
String Last_Name = null;
So you cannot change those schema column names on fly.
But you can create a record from the column names which you are retrieving from database by using the delimiter you want(lets take comma)
for (java.lang.reflect.Field field : input_row.getClass().getDeclaredFields()) {
String fieldName = field.getName();
context.columnName = context.columnName + "," + fieldName.replaceAll("_", " ");
}
And now, before writing your data into a csv file, write this header record in context.columnName into that csv file.
After writing the header record, append your data to that file by checking "Append" check box in tFileOutputDelimitted.