Criteria4s

Criteria4s is a straightforward domain-specific language (DSL) designed to define criteria and predicate expressions for any data store using Scala's type class mechanisms in a type-safe manner. Its core is designed to be agnostic to any specific data store, making it extensible and capable of supporting a variety of data storage systems.

Getting Started

To utilize the Criteria4s DSL in your project, add the following dependencies to your build configuration:

Sonatype Repository

• Core library: criteria4s-core
• SQL implementation: criteria4s-sql
• MongoDB implementation: criteria4s-mongodb

SBT

Add these to your build.sbt:

libraryDependencies += "com.eff3ct" %% "criteria4s-core" % "<version>" // Core library
libraryDependencies += "com.eff3ct" %% "criteria4s-sql" % "<version>" // SQL implementation
libraryDependencies += "com.eff3ct" %% "criteria4s-mongodb" % "<version>" // MongoDB implementation

Important

Criteria4s is currently a work in progress and not ready for production use. It is available exclusively for Scala 2.13.

Dialects Supported

Criteria4s is extensible, supporting various types of data stores. Presently, it supports the following dialects:

Dialect	Package
SQL	sql
MongoDB	mongodb
PostgresSQL	postgresql

Examples

Here are examples demonstrating how to use the Criteria DSL. More samples are available in the criteria4s-examples module.

Imports

Start by importing the Criteria4s DSL and the SQL dialect:

import com.eff3ct.criteria4s.core._
import com.eff3ct.criteria4s.examples.datastores._
import com.eff3ct.criteria4s.extensions._
import com.eff3ct.criteria4s.functions._

Defining Criteria Expressions

Define criteria expressions in a polymorphic way using the Criteria DSL. Additional examples are provided in the Defining Criteria Expressions document.

def expr[T <: CriteriaTag : LEQ : EQ : AND : OR : Show[Column, *]]: Criteria[T] =
  (col[T]("field1") leq lit(3)) and (col[T]("field2") leq lit(4)) or (col[T]("field3") === lit("c"))

Use Cases

The following code snippets demonstrate how to use the defined criteria expressions:

def ageCriteria[T <: CriteriaTag : GT : LT : AND : Show[Column, *]]: Criteria[T] =
  (col[T]("age") gt lit(18)) and (col[T]("age") lt lit(65))

def refCriteria[T <: CriteriaTag : EQ : Show[Column, *]](fieldName: String, id: UUID): Criteria[T] =
  col[T](fieldName) === lit(id.toString)

Evaluating Criteria Expressions

Utilize these expressions to generate criteria for different data stores by importing the corresponding dialects. Evaluation examples for various dialects are available in the following documents:

• PostgreSQL Dialect: Evaluate criteria expressions for PostgreSQL data stores.
• MongoDB Dialect: Evaluate criteria expressions for MongoDB data stores.
• MySQL Dialect: Evaluate criteria expressions for MySQL data stores.
• Custom Dialect: Evaluate criteria expressions for custom data stores.

Inline Criteria DSL

Leverage the Criteria DSL in an inline manner:

(col[PostgreSQL]("field1") leq lit(3)) and (col[PostgreSQL]("field2") leq lit(4)) or (col[PostgreSQL]("field3") === lit("c"))
// res: (('field1' <= 3) AND ('field2' <= 4)) OR ('field3' = c)

(col[MongoDB]("field1") leq lit(3)) and (col[MongoDB]("field2") leq lit(4)) or (col[MongoDB]("field3") === lit("c"))
// res: {$or: [{$and: [{"field1": {$lte: 3}}, {"field2": {$lte: 4}}]}, {"field3": {$eq: c}}]}

(col[WeirdDatastore]("field1") leq lit(3)) and (col[WeirdDatastore]("field2") leq lit(4)) or (col[WeirdDatastore]("field3") === lit("c"))
// res: {left: {left: {left: field1, opt: <=, right: 3 }, opt: AND, right: {left: field2, opt: <=, right: 4 } }, opt: OR, right: {left: field3, opt: =, right: c } }