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Tech notes for scala

Scala: Simplest Jersey service with Jetty returning JSON via Jackson

If you want a quick web service with Jersey in Jetty returning JSON, you must:

Define the basic Jersey class with annotations.
Use JettyHttpContainerFactory to start the Jetty service.

Let's put it all together, in a file called rest.scala.

import java.util.ArrayList
import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
import javax.ws.rs.{ApplicationPath, GET, Path, Produces}
import javax.ws.rs.core.{MediaType, UriBuilder}
import javax.ws.rs.{ApplicationPath, GET, Path, Produces}
import javax.ws.rs.core.{MediaType}
import org.eclipse.jetty.server.handler.AbstractHandler
import org.eclipse.jetty.server.{Server, Request}
import org.glassfish.jersey.server.ResourceConfig
import org.glassfish.jersey.jetty.JettyHttpContainerFactory

object rest {

  @Path("/") class Hello {
    @Path("hello") @GET @Produces(Array(MediaType.APPLICATION_JSON))
    // Returns ArrayList, not a scala List, since Jackson can't convert that
    def example() : ArrayList[String] = {
      var al = new ArrayList[String]()
      al.add("hmm")
      return al
    }
  }

  // Not run from a scala script, since that strangely can't find Hello
  def main(args: Array[String]) : Unit = {
    JettyHttpContainerFactory.createServer(
      UriBuilder.fromUri("http://localhost/").port(9998).build(),
      new ResourceConfig(classOf[Hello])
    )
  }
}

You need these dependencies, which you can use with this via gradle -b deps.gradle copyDependencies:

    compile 'org.glassfish.jersey.bundles:jaxrs-ri:2.23.1'
    compile 'org.glassfish.jersey.containers:jersey-container-jetty-http:2.23.1'
    compile 'org.glassfish.jersey.media:jersey-media-json-jackson:2.16'

Or just download them all via this bash script (urls obtained via the stderr output of the above script):

wget -P dependencies/ https://repo1.maven.org/maven2/javax/inject/javax.inject/1/javax.inject-1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/javax/annotation/javax.annotation-api/1.2/javax.annotation-api-1.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/javax/ws/rs/javax.ws.rs-api/2.0.1/javax.ws.rs-api-2.0.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/javax/validation/validation-api/1.1.0.Final/validation-api-1.1.0.Final.jar
wget -P dependencies/ https://repo1.maven.org/maven2/javax/servlet/javax.servlet-api/3.1.0/javax.servlet-api-3.1.0.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/eclipse/jetty/jetty-http/9.2.14.v20151106/jetty-http-9.2.14.v20151106.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/eclipse/jetty/jetty-io/9.2.14.v20151106/jetty-io-9.2.14.v20151106.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/eclipse/jetty/jetty-server/9.2.14.v20151106/jetty-server-9.2.14.v20151106.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/eclipse/jetty/jetty-util/9.2.14.v20151106/jetty-util-9.2.14.v20151106.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/eclipse/jetty/jetty-continuation/9.2.14.v20151106/jetty-continuation-9.2.14.v20151106.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-core/2.3.2/jackson-core-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-databind/2.3.2/jackson-databind-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-annotations/2.3.2/jackson-annotations-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/jaxrs/jackson-jaxrs-base/2.3.2/jackson-jaxrs-base-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/jaxrs/jackson-jaxrs-json-provider/2.3.2/jackson-jaxrs-json-provider-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/com/fasterxml/jackson/module/jackson-module-jaxb-annotations/2.3.2/jackson-module-jaxb-annotations-2.3.2.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/core/jersey-server/2.23.1/jersey-server-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/core/jersey-client/2.23.1/jersey-client-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/core/jersey-common/2.23.1/jersey-common-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/containers/jersey-container-servlet-core/2.23.1/jersey-container-servlet-core-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/containers/jersey-container-servlet/2.23.1/jersey-container-servlet-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/containers/jersey-container-jetty-http/2.23.1/jersey-container-jetty-http-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/bundles/jaxrs-ri/2.23.1/jaxrs-ri-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/bundles/repackaged/jersey-guava/2.23.1/jersey-guava-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/media/jersey-media-json-jackson/2.16/jersey-media-json-jackson-2.16.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/media/jersey-media-jaxb/2.23.1/jersey-media-jaxb-2.23.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/jersey/ext/jersey-entity-filtering/2.16/jersey-entity-filtering-2.16.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/hk2-api/2.4.0-b34/hk2-api-2.4.0-b34.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/hk2-locator/2.4.0-b34/hk2-locator-2.4.0-b34.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/osgi-resource-locator/1.0.1/osgi-resource-locator-1.0.1.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/hk2-utils/2.4.0-b34/hk2-utils-2.4.0-b34.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/external/aopalliance-repackaged/2.4.0-b34/aopalliance-repackaged-2.4.0-b34.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/glassfish/hk2/external/javax.inject/2.4.0-b34/javax.inject-2.4.0-b34.jar
wget -P dependencies/ https://repo1.maven.org/maven2/org/javassist/javassist/3.18.1-GA/javassist-3.18.1-GA.jar

Finally run the program with scala -cp "dependencies/*" rest.scala. You should see:

2016-08-14 16:34:13.759:INFO::main: Logging initialized @791ms
2016-08-14 16:34:14.160:INFO:oejs.Server:main: jetty-9.2.14.v20151106
2016-08-14 16:34:14.181:INFO:oejs.ServerConnector:main: Started ServerConnector@5efa40fe{HTTP/1.1}{0.0.0.0:9998}
2016-08-14 16:34:14.182:INFO:oejs.Server:main: Started @1213ms

You can test it via:

curl localhost:9998/hello
["hmm"]

scala java-jersey java-jetty java-jackson

Simplest Jetty server in Scala

Let's first download the jetty runner:

wget http://central.maven.org/maven2/org/eclipse/jetty/jetty-runner/9.4.0.M0/jetty-runner-9.4.0.M0.jar

Then create a Scala file, server.scala, that creates a AbstractHandler class, which handles incoming request, and outputs some text.

import org.eclipse.jetty.server.handler.AbstractHandler
import org.eclipse.jetty.server.{Server, Request}
import javax.servlet.http.{HttpServletRequest, HttpServletResponse}

class Handler extends AbstractHandler {
  var html = <h1>Something, innit</h1>

  override def handle(target: String,
                      req: Request,
                      httpReq: HttpServletRequest,
                      httpRes: HttpServletResponse) = {
    httpRes.setContentType("text/html")
    httpRes.setStatus(HttpServletResponse.SC_OK)
    httpRes.getWriter().println(html.toString)
    req.setHandled(true)
  }
}

val server = new Server(8080)
server.setHandler(new Handler)
server.start

Finally run the Scala program.

scala -cp jetty-runner-9.4.0.M0.jar server.scala

You can now visit http://localhost:8080 to reach it. It'll take about 15 seconds to load.

scala java-jetty

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