dcrankshaw / dropwizard-scala

Scala language integration for Dropwizard

Dropwizard Scala

Scala support for Dropwizard.

Usage

Just add a dependency to dropwizard-scala-core and dropwizard-scala-jdbi (optional) to your project:

SBT

libraryDependencies += "net.nicktelford.dropwizard.scala" %% "dropwizard-scala-core" % "0.7.1-1"

Maven

Include the dropwizard-scala-core artifact in your POM:

<dependency>
    <groupId>net.nicktelford.dropwizard.scala</groupId>
    <artifactId>dropwizard-scala-core_2.10.2</artifactId>
    <version>0.7.1-1</version>
</dependency>

It's good practice to keep your Scala version as a global property that you can use elsewhere to ensure coherence in your POM:

<properties>
    <scala.version>2.10.2</scala.version>
    <dropwizard.version>0.7.1-1</dropwizard.version>
    <dropwizard.scala.version>${dropwizard.version}-1</dropwizard.scala.version>
</properties>

<dependencies>
    <dependency>
        <groupId>net.nicktelford.dropwizard.scala</groupId>
        <artifactId>dropwizard-scala-core_${scala.version}</artifactId>
        <version>${dropwizard.scala.version}</version>
    </dependency>
</dependencies>

Core

• A base ScalaApplication trait for applications to be defined as a singleton object:

import io.dropwizard.Configuration
import net.nicktelford.dropwizard.scala.ScalaApplication

case class MyConfiguration(
  @NotEmpty greeting: String, 
  @NotNull greeters: List[String]
) extends Configuration

object MyApplication extends ScalaApplication[MyConfiguration] {
  def init(bootstrap: Bootstrap[MyConfiguration]) {
    
  }

  def run(conf: MyConfiguration, env: Environment) {

  }
}

When you build an application like this, the ScalaBundle is automatically added, providing everything else described here.

• Jackson support for Scala collections, Option and case classes, enabling (de)serialization of Scala collections/case classes in configurations and within Jersey request/response entities.

• A Logging trait and macro-derived conditional logging, courtesey of Scala Logging.

Jersey

• Jersey support for Scala collections and Option in resource method parameters and for request/response entities.

• Jersey support for Scala's native Boolean, Int and Long types in resource method parameters via the BooleanParam, IntParam and LongParam wrapper types.

JDBI

• JDBI marshalling of Scala collections, Option and case classes, in both method parameters and result types.

• A more idiomatic JDBI API:

import net.nicktelford.dropwizard.scala.jdbi._

val db = JDBI(dataSource)
val dao = db.onDemand[MyDAO]
val result: Int = db.inTransaction {
  handle: Handle => handle.attach[MyDAO].myQuery(123)
}

To enable Scala integration for JDBI, you will need to add an extra dependency:

SBT

libraryDependencies += "net.nicktelford.dropwizard.scala" %% "dropwizard-scala-jdbi" % "0.7.1-1"

Maven

<dependency>
    <groupId>net.nicktelford.dropwizard.scala</groupId>
    <artifactId>dropwizard-scala-jdbi_${scala.version}</artifactId>
    <version>${dropwizard.scala.version}</version>
</dependency>

Validation

• Support for all JSR-303 and Hibernate Validator constraints on Scala types. In particular, support is added for @NotEmpty and @Size on Scala collections. All other constraint annotations work on Scala types out of the box.

• Validation of Scala case class properties using JSR-303 and Hibernate Validator constraints. To validate a case class, you will need to use the wrapper constraints defined in net.nicktelford.dropwizard.scala.validation.constraints:

import net.nicktelford.dropwizard.scala.validation.constraints._

case class MyConfiguration(
  @NotEmpty names: List[String], 
  @Min(0) age: Int
) extends Configuration

Limitations

In order to cascade validation using @Valid on collection types, Hibernate requires that the collection provide a Java Iterator. Since Scala collections don't provide this, they cannot cascade validation.

In the following example, only MyConfiguration is validated. Person values held in the people collection are not validated, though the size of people is.

case class MyConfiguration(@Valid @NotEmpty people: List[Person]) 
  extends Configuration

case class Person(@NotEmpty name: String, @Min(0) age: Int)