Criteria4s

Criteria4s is a simple domain-specific language (DSL) to define criteria and predicate expressions for any data stores by using Scala type class mechanisms in a type-safe way. It pretends to be agnostic to any data store, and it is extensible to support any kind of data stores.

Formal Definition of the Expressions

The formal definition of the Criteria4s' type-classes (expressions) is as follows:

Criteria    :=  ConjOp Criteria Criteria | PredOp Ref Ref | Value<Boolean>
Ref         :=  Value<T> | Col
ConjOp      :=  AND | OR
PredOp      :=  EQ | NEQ | GT | LT | GEQ | LEQ | IN | LIKE | IS_NULL | IS_NOT_NULL ...

Where:

• Criteria is the main expression of the DSL
• ConjOp is the conjunction operator expression
• PredOp is the predicate operator expression
• Ref is a reference to a value or a column
• Value<T> is a value expression of a certain type T
• Col is a column expression

Getting Started

To use dsl of Criteria4s, you need to add the following dependency to your project:

SonaType Repository

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

SBT

libraryDependencies += "io.github.rafafrdz" %% "criteria4s-core" % "<version>" // Core library
libraryDependencies += "io.github.rafafrdz" %% "criteria4s-sql" % "<version>" // SQL implementation

Maven

<!-- Core library -->
<dependency>
    <groupId>io.github.rafafrdz</groupId>
    <artifactId>criteria4s-core_2.13</artifactId>
    <version>0.7.0</version>
</dependency>

<!-- SQL implementation -->
<dependency>
    <groupId>io.github.rafafrdz</groupId>
    <artifactId>criteria4s-core_2.13</artifactId>
    <version>0.7.0</version>
</dependency>

Important

Criteria4s is a work in progress and it is not ready for production use. Also, it is just available for Scala 2.13.

Examples

Here, we will show some examples of how to use the Criteria DSL.

import io.github.rafafrdz.criteria4s.core._
import io.github.rafafrdz.criteria4s.examples.datastores._
import io.github.rafafrdz.criteria4s.extensions._
import io.github.rafafrdz.criteria4s.functions._

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

def expr[T <: CriteriaTag : LEQ : EQ : AND : OR : Sym]: Criteria[T] =
  (col[T]("a") leq lit(3)) and (col[T]("b") leq lit(4)) or (col[T]("c") === lit("c"))

def expr2[T <: CriteriaTag : EQ : Sym](fieldName: String, id: UUID): Criteria[T] =
  col[T](fieldName) === lit(id.toString)

And then we can use the ageCriteria, expr and expr2 functions to generate criteria expressions for different datastores:

ageCriteria[WeirdDatastore]
// res: {left: {left: age, opt: >, right: 18 }, opt: AND, right: {left: age, opt: <, right: 65 } }

expr[MySQL]
// res: ((a <<< '3') AND (b <<< '4')) OR (c = 'c')

expr2[Postgres]("USER_ID", UUID.randomUUID())
// res: `USER_ID` = '07715cee-5d87-427d-99a7-cc03f2b5ef4a'

Or maybe we can use the Criteria DSL inline:

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

You can find more examples in the criteria4s-examples module.