Configuration

As you develop, test, and get ready for final deployment, you’ll need to configure things about your app: its environment, its settings, initial configurations when it starts up, and the software it depends on.


Configuring your app using the ScalatraBootstrap file

As of 2.1.x, the ScalatraBootstrap file is the recommended way of configuring your application. It allows you to easily mount different servlets, set application parameters, and run initialization code for your app, without touching much in the way of XML.

If you’ve just started a new project in Scalatra 2.2.x, using the giter8 template, all of this will already be set up for you. However, if you’re upgrading from 2.0.x, or you just want to understand what’s going on, read on.

First, the bad news: there is some XML involved, because this is one of the points where Scalatra needs to interface with Java servlets, the underlying technology it’s sitting on top of.

All Scalatra projects have a web.xml file, in src/main/webapp/WEB-INF/. Find yours and open it.

In a regular Java servlet application, most application configuration is done inside web.xml. However, Scalatra applications can drop in some standard config code, and use regular Scala code for configuration afterwards.

The XML which allows you to do this is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
      version="3.0">
    <listener>
      <listener-class>org.scalatra.servlet.ScalatraListener</listener-class>
    </listener>
</web-app>

If you started your project in an older version of Scalatra, and want to start using the new ScalatraBootstrap configuration style, drop that XML into your web.xml and you’re all set.

Note that there are no servlet-names, servlet classes, etc. That’s all handled dynamically by the ScalatraListener class, which will supply our actual configuration to the underlying servlet container.

This closes the XML portion of our broadcast.

Note that there is also a file called ScalatraBootstrap.scala in your src/main/scala directory. This is the Scalatra bootstrap config file, and it’s where you should do most of your app configuration work.

The simplest version of this file, which gets generated when you make a new project using the giter8 template, looks something like this:

import org.scalatra.LifeCycle
import javax.servlet.ServletContext
import org.yourdomain.projectname._

class ScalatraBootstrap extends LifeCycle {

  override def init(context: ServletContext) {

    // mount servlets like this:
    context mount (new ArticlesServlet, "/articles/*")
  }
}

Custom location of Scalatra bootstrap class

If you would like to move the ScalatraBootstrap.scala out of the default package and into one of your own, you can specify the location of the bootstrap file in your web.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
      version="3.0">
    <context-param>
        <param-name>org.scalatra.LifeCycle</param-name>
        <param-value>org.yourdomain.project.MyScalatraBootstrap</param-value>
    </context-param>
    <listener>
      <listener-class>org.scalatra.servlet.ScalatraListener</listener-class>
    </listener>
</web-app>

Now your bootstrap class file can be located in the com.example.app package and be named MyScalatraBootstrap.scala.

Mounting multiple servlets (or filters)

If you’ve got more than one servlet or filter in your application, you’ll need to mount them.

If you're coming from a dynamic language, such as PHP, Ruby, Python, or Perl, you may be shocked to find that servlet-based applications, including Scalatra, are unable to dynamically require and use controller classes. You'll need to explicitly tell your application about a new `ScalatraServlet` or `ScalatraFilter` whenever you add one.

The ScalatraBootstrap config class allows you to mount servlets or filters (or both) into your application, and define URL path patterns that they’ll respond to.

override def init(context: ServletContext) {

  // mount a first servlet like this:
  context mount (new ArticlesServlet, "/articles/*")

  // mount a second servlet like this:
  context mount (new CommentsServlet, "/comments/*")

}

Init params

You can set init params in the Scalatra bootstrap file. For instance, you can set the org.scalatra.environment init parameter to set the application environment:

override def init(context: ServletContext) {

  // mount a first servlet like this:
  context mount (new ArticlesServlet, "/articles/*")

  // Let's set the environment
  context.initParameters("org.scalatra.environment") = "production"

}

Each init param can be set in one of two ways.

The first form looks like this:

context.setInitParameter(org.scalatra.EnvironmentKey, "production")

The second form has a bit of syntactic sugar on it, so it looks a little less Java:

context.initParameters("org.scalatra.environment") = "production"

The two forms are equivalent.

Environment init param

context.setInitParameter(org.scalatra.EnvironmentKey, "production") or context.initParameters("org.scalatra.environment") = "production"

This init param sets the application environment.

The default is development.

If the environment starts with “dev”, then isDevelopmentMode returns true.

In development mode, a few things happen.

  • In a ScalatraServlet, the notFound handler is enhanced so that it dumps the effective request path and the list of routes it tried to match. This does not happen in a ScalatraFilter, which just delegates to the filterChain when no route matches.
  • Meaningful error pages are enabled (e.g. on 404s, 500s).
  • The Scalate console is enabled.
Container init params

context.setInitParameter(ScalatraBase.HostNameKey, "myapp.local") or context.initParameters("org.scalatra.HostName") = "myapp.local"

context.setInitParameter(ScalatraBase.PortKey, 443) or context.initParameters("org.scalatra.Port") = 443

context.setInitParameter(ScalatraBase.ForceHttpsKey, "true") or context.initParameters("org.scalatra.ForceHttps") = "true"

By default, the values for hostname, port, and SSL settings are inherited from the servlet container’s settings. You can set these init params if you want to override the domain or port your website is hosted on, or force the use of https.

So if Jetty is running at http://localhost:8080 on your machine you may want to expose it as: https://myapp.local:443 (with an appropriate entry in /etc/hosts).

Cross Origin Resource Sharing init params

These keys and their purposes are documented in the CORS guide, but for completeness, here they are.

The CORS guide uses the alternate forms of these keys, so check in that guide if you’d like to see the alternate form.

context.setInitParameter(CorsSupport.AllowedOriginsKey, "www.other.com,www.foo.com") context.setInitParameter(CorsSupport.AllowedMethodsKey, "GET,PUT") context.setInitParameter(CorsSupport.AllowedHeadersKey, "Content-Type") context.setInitParameter(CorsSupport.AllowCredentialsKey, "true") context.setInitParameter(CorsSupport.PreflightMaxAgeKey, 1800)

Async init params

context.setAttribute(AsyncSupport.ExecutionContextKey, executionContext) or context.initParameters("org.scalatra.ExecutionContext") = executionContext

This key sets the ExecutionContext which Scalatra should use when creating an Akka Future.

Running code at application start

The ScalatraBootstrap file is also a good place to put things like database initialization code, which need to be set up once in your application. You can mix in whatever traits you want, and run any Scala code you want from inside the init method:

import org.scalatra.LifeCycle
import javax.servlet.ServletContext

// Import the trait:
import com.yourdomain.yourapp.DatabaseInit

// Mixing in the trait:
class ScalatraBootstrap extends LifeCycle with DatabaseInit {

  override def init(context: ServletContext) {

    // call a method that comes from inside our DatabaseInit trait:
    configureDb()

    // Mount our servlets as normal:
    context mount (new Articles, "/articles/*")
    context mount (new Users, "/users/*")
  }
}

Configuring your app using web.xml

If you're an old Java hand, you'll be quite comfortable mounting servlets through the web.xml file in traditional servlet style, so you may not want to use the Scalatra bootstrap file. If you want, you can use web.xml for some things and the Scalatra bootstrap file for others.

Mounting multiple servlets (or filters) using web.xml

You can see an example of mounting multiple servlets in the Scalatra 2.0.x examples web.xml file.

An extract from that file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
  <servlet>
    <servlet-name>BasicAuthExample</servlet-name>
    <servlet-class>org.scalatra.BasicAuthExample</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>TemplateExample</servlet-name>
    <servlet-class>org.scalatra.TemplateExample</servlet-class>
  </servlet>
</web-app>

Setting init params using web.xml

You can set init params for your servlets in the normal manner:

<servlet>
  <servlet-name>BasicAuthExample</servlet-name>
  <servlet-class>org.scalatra.BasicAuthExample</servlet-class>
  <init-param>
    <param-name>org.scalatra.environment</param-name>
    <param-value>development</param-value>
  </init-param>
</servlet>

Application environments

The application environment is defined by:

  1. The org.scalatra.environment system property.
  2. The org.scalatra.environment init parameter.

You can set the application’s environment in the following ways:

  1. The preferred method: as an init-param in the Scalatra Bootstrap file.
  2. As an init-param in web.xml.
  3. As a system property: this is most commonly set with a -D option on the command line: java -Dorg.scalatra.environment=development

When you deploy your application to a production environment, you’ll typically want to change its environment to “production”.

There are a few ways you can accomplish this.

Environment variables

If you’re using Scalatra 2.1 or better, you can set it in your ScalatraBootstrap file based on an environment variable that’s present on production machines.

Massaging your WAR file

If you’re using Scalatra 2.0.x or just happen to like XML configuration, you can use a post-hook in the xsbt-web-plugin to massage the contents of your WAR file during packaging.

Load the Web.xml file and replace the value for org.scalatra.environment using Scala’s standard XML tools.

Changing the port in development

Add containerPort in Jetty := 8081 to project/build.scala if you would like your Scalatra app to run on something other than the default port (8080).

You may need to add the following imports if you get errors upon adding the configuration above:

import com.earldouglas.xwp.JettyPlugin
import com.earldouglas.xwp.JettyPlugin.autoImport._
import com.earldouglas.xwp.ContainerPlugin.autoImport._