Merge Strategy in sbt assembly and missing application loader

I have a Play web app that I am working on and I would like to be able to deploy it as a fat jar using sbt assembly. While running the application in debug i have no problems with guice library being recognized as it is added in my build.sbt file: libraryDependencies += guice. I have created my sbt assembly MergeStrategy configuration and ran sbt assembly and successfully compiled the jar file for the project, However when i attempt to run the jar i get the following Exception in console:

Oops, cannot start the server.
java.lang.RuntimeException: No application loader is configured. Please 
configure an application loader either using the play.application.loader 
configuration property, or by depending on a module that configures one. You 
can add the Guice support module by adding "libraryDependencies += guice" to 
your build.sbt.
    at scala.sys.package$.error(package.scala:27)
    at play.api.ApplicationLoader$.play$api$ApplicationLoader$$loaderNotFound(ApplicationLoader.scala:44)
    at play.api.ApplicationLoader$.apply(ApplicationLoader.scala:70)
    at play.core.server.ProdServerStart$.start(ProdServerStart.scala:50)
    at play.core.server.ProdServerStart$.main(ProdServerStart.scala:25)
    at play.core.server.ProdServerStart.main(ProdServerStart.scala)

and here is my build.sbt file:

name := """Product-Inventory"""
organization := "com.example"

version := "1.0-SNAPSHOT"

lazy val root = (project in file(".")).enablePlugins(PlayScala)

scalaVersion := "2.12.3"

//libraryDependencies += Defaults.sbtPluginExtra("com.eed3si9n" % "sbt-assembly" % "0.7.4", "0.12.0-M2", "2.9.1")

// https://mvnrepository.com/artifact/net.ruippeixotog/scala-scraper
libraryDependencies += "net.ruippeixotog" %% "scala-scraper" % "2.0.0"


libraryDependencies += guice //GUICE IS ADDED HERE
libraryDependencies += "org.scalatestplus.play" %% "scalatestplus-play" % "3.1.2" % Test

libraryDependencies += "org.scala-lang.modules" %% "scala-async" % "0.9.7"

libraryDependencies += jdbc
libraryDependencies += "postgresql" % "postgresql" % "9.1-901.jdbc4"

// Adds additional packages into Twirl
//TwirlKeys.templateImports += "com.example.controllers._"

// Adds additional packages into conf/routes
// play.sbt.routes.RoutesKeys.routesImport += "com.example.binders._"

mainClass in assembly := Some("play.core.server.ProdServerStart")
fullClasspath in assembly += 
Attributed.blank(PlayKeys.playPackageAssets.value)

assemblyMergeStrategy in assembly := {

  case PathList("META-INF", xs @ _*) => MergeStrategy.discard
  case referenceOverrides if referenceOverrides.contains("reference-
overrides.conf") => MergeStrategy.concat
case PathList("reference-overrides.conf") => MergeStrategy.concat
case x => {
MergeStrategy.first
}
}

Since i have already added guice I am not sure what has happened or how to fix this. could this possibly be due to an incorrect MergeStrategy? Or is it something else? Below I am also including the list of files merged and merge strategies applied in case this is of any help.

[info] Merging files...
[warn] Merging 'META-INF\CHANGES' with strategy 'discard'
[warn] Merging 'META-INF\COPYRIGHT.html' with strategy 'discard'
[warn] Merging 'META-INF\DEPENDENCIES' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_commons-codec-1.10.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_commons-io-2.5.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_commons-lang3-3.6.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_commons-logging-1.2.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_guice-4.1.0' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_guice-assistedinject-4.1.0' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_httpclient-4.5.3' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_httpcore-4.4.6' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_httpmime-4.5.3' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jackson-annotations-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jackson-core-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jackson-databind-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jackson-datatype-jsr310-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_joda-convert-1.2.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_joda-time-2.9.9.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jsoup-1.10.2' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_jta-1.1.txt' with strategy 'discard'
[warn] Merging 'META-INF\LICENSE_xercesImpl-2.11.0' with strategy 'discard'
[warn] Merging 'META-INF\MANIFEST.MF' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_commons-codec-1.10.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_commons-io-2.5.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_commons-lang3-3.6.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_commons-logging-1.2.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_guice-4.1.0' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_guice-assistedinject-4.1.0' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_httpclient-4.5.3' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_httpcore-4.4.6' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_httpmime-4.5.3' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_jackson-core-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_jackson-databind-2.8.11' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_joda-convert-1.2.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_joda-time-2.9.9.txt' with strategy 'discard'
[warn] Merging 'META-INF\NOTICE_xercesImpl-2.11.0' with strategy 'discard'
[warn] Merging 'META-INF\README_jsoup-1.10.2' with strategy 'discard'
[warn] Merging 'META-INF\maven\cglib\cglib\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\cglib\cglib\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\ch.qos.logback\logback-classic\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\ch.qos.logback\logback-classic\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\ch.qos.logback\logback-core\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\ch.qos.logback\logback-core\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-annotations\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-annotations\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-core\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-core\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-databind\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.core\jackson-databind\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.datatype\jackson-datatype-jdk8\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.datatype\jackson-datatype-jdk8\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.datatype\jackson-datatype-jsr310\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.fasterxml.jackson.datatype\jackson-datatype-jsr310\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.errorprone\error_prone_annotations\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.errorprone\error_prone_annotations\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.guava\guava\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.guava\guava\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.j2objc\j2objc-annotations\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.google.j2objc\j2objc-annotations\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.googlecode.usc\jdbcdslog\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.googlecode.usc\jdbcdslog\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.jolbox\bonecp\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.jolbox\bonecp\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.zaxxer\HikariCP\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\com.zaxxer\HikariCP\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-codec\commons-codec\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-codec\commons-codec\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-io\commons-io\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-io\commons-io\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-logging\commons-logging\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\commons-logging\commons-logging\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\io.jsonwebtoken\jjwt\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\io.jsonwebtoken\jjwt\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\joda-time\joda-time\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\joda-time\joda-time\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.cssparser\cssparser\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.cssparser\cssparser\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.htmlunit\htmlunit\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.htmlunit\htmlunit\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.htmlunit\neko-htmlunit\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\net.sourceforge.htmlunit\neko-htmlunit\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.commons\commons-lang3\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.commons\commons-lang3\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpclient\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpclient\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpcore\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpcore\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpmime\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.apache.httpcomponents\httpmime\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.codehaus.mojo\animal-sniffer-annotations\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.codehaus.mojo\animal-sniffer-annotations\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-api\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-api\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-client\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-client\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-common\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty.websocket\websocket-common\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-client\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-client\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-http\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-http\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-io\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-io\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-util\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.eclipse.jetty\jetty-util\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.joda\joda-convert\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.joda\joda-convert\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.jsoup\jsoup\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.jsoup\jsoup\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\jcl-over-slf4j\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\jcl-over-slf4j\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\jul-to-slf4j\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\jul-to-slf4j\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\slf4j-api\pom.properties' with strategy 'discard'
[warn] Merging 'META-INF\maven\org.slf4j\slf4j-api\pom.xml' with strategy 'discard'
[warn] Merging 'META-INF\resources\webjars\product-inventory\1.0-SNAPSHOT\javascripts\main.js' with strategy 'discard'
[warn] Merging 'META-INF\resources\webjars\product-inventory\1.0-SNAPSHOT\stylesheets\bootstrap.min.css' with strategy 'discard'
[warn] Merging 'META-INF\resources\webjars\product-inventory\1.0-SNAPSHOT\stylesheets\main.css' with strategy 'discard'
[warn] Merging 'META-INF\services\com.fasterxml.jackson.core.JsonFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\com.fasterxml.jackson.core.ObjectCodec' with strategy 'discard'
[warn] Merging 'META-INF\services\com.fasterxml.jackson.databind.Module' with strategy 'discard'
[warn] Merging 'META-INF\services\java.sql.Driver' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.servlet.ServletContainerInitializer' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.datatype.DatatypeFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.parsers.DocumentBuilderFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.parsers.SAXParserFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.stream.XMLEventFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.transform.TransformerFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.validation.SchemaFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\javax.xml.xpath.XPathFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\org.apache.commons.logging.LogFactory' with strategy 'discard'
[warn] Merging 'META-INF\services\org.apache.xalan.extensions.bsf.BSFManager' with strategy 'discard'
[warn] Merging 'META-INF\services\org.apache.xml.dtm.DTMManager' with strategy 'discard'
[warn] Merging 'META-INF\services\org.eclipse.jetty.http.HttpFieldPreEncoder' with strategy 'discard'
[warn] Merging 'META-INF\services\org.eclipse.jetty.websocket.api.extensions.Extension' with strategy 'discard'
[warn] Merging 'META-INF\services\org.w3c.dom.DOMImplementationSourceList' with strategy 'discard'
[warn] Merging 'META-INF\services\org.xml.sax.driver' with strategy 'discard'
[warn] Merging 'org\apache\commons\logging\Log.class' with strategy 'first'
[warn] Merging 'org\apache\commons\logging\LogConfigurationException.class' with strategy 'first'
[warn] Merging 'org\apache\commons\logging\LogFactory.class' with strategy 'first'
[warn] Merging 'org\apache\commons\logging\impl\NoOpLog.class' with strategy 'first'
[warn] Merging 'org\apache\commons\logging\impl\SimpleLog$1.class' with strategy 'first'
[warn] Merging 'org\apache\commons\logging\impl\SimpleLog.class' with strategy 'first'
[warn] Merging 'play\reference-overrides.conf' with strategy 'concat'
[warn] Merging 'reference.conf' with strategy 'first'
[warn] Strategy 'concat' was applied to a file
[warn] Strategy 'discard' was applied to 137 files
[warn] Strategy 'first' was applied to 7 files
[info] Assembly up to date: C:\Users\zemcd\Extras\Play_Apps\product-inventory\target\scala-2.12\Product-Inventory-assembly-1.0-SNAPSHOT.jar
[success] Total time: 15 s, completed Mar 21, 2018 11:19:27 AM

this line was also included: [info] Including from cache: play-guice_2.12-2.6.12.jar and this one as well [info] Including from cache: guice-4.1.0.jar. If these two jars are causing conflict how should this be resolved? remove jar? or modify merge strategy? Any other clues to what the problem could be?

Play documents the following merge strategy to be used with sbt-assembly:

assemblyMergeStrategy in assembly := {
  case manifest if manifest.contains("MANIFEST.MF") =>
    // We don't need manifest files since sbt-assembly will create
    // one with the given settings
    MergeStrategy.discard
  case referenceOverrides if referenceOverrides.contains("reference-overrides.conf") =>
    // Keep the content for all reference-overrides.conf files
    MergeStrategy.concat
  case x =>
    // For all the other files, use the default sbt-assembly merge strategy
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}

play-scala-sbt-assembly-example is a working example demonstrating the necessary configuration.

It looks like Play has their own dist function that uses the sbt native packager plugin under the hood. I was able to get my program working by following the instructions here: https://www.playframework.com/documentation/2.7.x/Deploying#Using-the-dist-task

来源：https://stackoverflow.com/questions/49414413/merge-strategy-in-sbt-assembly-and-missing-application-loader

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