Getting started

Suppose you have a relational database for saving books, and there exists the Books table with the following schema:

Column	Type
title	String
author	String
genre	String
release_date	DateTime

To filter books by the author Svetlana Isakova we need to create a Criteria instance adding a filter by the author field.

val criteria = criteria {
    filter("author", "Svetlana Isakova", FilterOperator.EQUALS)
}

If we want to sort the result to get the most recent released books we can add an orderBy clause.

val criteria = criteria {
    // ...
    orderBy("release_date", Order.DESC)
}

Also we can define a FieldMap for hide the real field names by other one. For example, we can filter by author field referencing it as author_name. (See more about FieldMap on next steps)

val fieldMap = mapOf(
    // this will indicate the field author_name points to author field
    "author_name" to "author"
)

val criteria = criteria {
   filter("author_name", "Svetlana Isakova", FilterOperator.EQUALS)
}

To run a query using our Criteria we need to adapt it to our favorite database driver or ORM.

Next steps

• Adaptar criteria a MongoDB

• Adaptar criteria a Spring Data JPA