How to iterate through table rows in Java?

Question

I want to iterate through an sql table using JPA, example of use:
I have the table Person which contains 100 columns

id | gender | firstname | lastname |  address1 | address2 | number | ....+100
------------------------------------------------------------------------------
-  |  ...   |   .....   |   ...    |   ....    |   ....   |   ..   |  ....
------------------------------------------------------------------------------
-  |  ...   |   .....   |   ...    |   ....    |   ....   |   ..   |  ....

and in my Java program, I want to do the following (as an example):

• for each row
• get the firstname
• get the number
• do operation with firstname
• do operation with number

the problem is that I don't want to create an Entity class of Person because it contains 100 columns and it's quite cumbersome and I'm not interested with all of them.

Also, I don't want to retrieve the row in an Object[] type, because suppose that I want to extract 40 columns out of 100, it will be confusing to manipulate such a type.

I'm using spring data JPA and not JDBC.

Answer 1

You can create an entity class with only the columns you're interrested in.

And then, with Spring data, you will get a collection of Person class which you can iterate through the way you like.