diff --git a/bin/logstash b/bin/logstash
index 2091fd7a001..d9596d8b57e 100755
--- a/bin/logstash
+++ b/bin/logstash
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # Run logstash from source
 #
 # This is most useful when done from a git checkout.
@@ -58,5 +58,14 @@ if [ "$1" = "-V" ] || [ "$1" = "--version" ]; then
   fi
   echo "logstash $LOGSTASH_VERSION"
 else
-  ruby_exec "${LOGSTASH_HOME}/lib/bootstrap/environment.rb" "logstash/runner.rb" "$@"
+  function classpath() {
+    echo -n "$1"
+    shift
+    while [ $# -gt 0 ] ; do
+      echo -n ":${1}"
+      shift
+    done
+  }
+  CLASSPATH="$(classpath ${LOGSTASH_HOME}/logstash-core/lib/jars/*.jar)"
+  exec "${JAVACMD}" ${JAVA_OPTS} -cp "${CLASSPATH}" org.logstash.Logstash "$@"
 fi
diff --git a/bin/logstash.bat b/bin/logstash.bat
index 055d085cdf3..a61bc3db2a8 100644
--- a/bin/logstash.bat
+++ b/bin/logstash.bat
@@ -45,7 +45,18 @@ if exist %LS_JVM_OPTIONS_CONFIG% (
 )
 set JAVA_OPTS=%LS_JAVA_OPTS%
 
-rem jruby launcher will pickup JAVA_OPTS set above to set the JVM options before launching jruby
-%JRUBY_BIN% "%LS_HOME%\lib\bootstrap\environment.rb" "logstash\runner.rb" %*
+for %%i in ("%LS_HOME%\logstash-core\lib\jars\*.jar") do (
+	call :concat "%%i"
+)
+
+%JAVA% %JAVA_OPTS% -cp %CLASSPATH% org.logstash.Logstash %*
 
 endlocal
+
+goto :eof
+:concat
+IF not defined CLASSPATH (
+  set CLASSPATH="%~1"
+) ELSE (
+  set CLASSPATH=%CLASSPATH%;"%~1"
+)
diff --git a/bin/logstash.lib.sh b/bin/logstash.lib.sh
index c352fb9c47e..d8b88d394e4 100755
--- a/bin/logstash.lib.sh
+++ b/bin/logstash.lib.sh
@@ -25,6 +25,7 @@ fi
 
 LOGSTASH_HOME="$(cd `dirname $SOURCEPATH`/..; pwd)"
 export LOGSTASH_HOME
+export LS_HOME="${LOGSTASH_HOME}"
 SINCEDB_DIR="${LOGSTASH_HOME}"
 export SINCEDB_DIR
 
diff --git a/logstash-core/build.gradle b/logstash-core/build.gradle
index abad3e33295..446747f9039 100644
--- a/logstash-core/build.gradle
+++ b/logstash-core/build.gradle
@@ -33,10 +33,15 @@ task javadocJar(type: Jar, dependsOn: javadoc) {
     extension 'jar'
 }
 
+task copyRuntimeLibs(type: Copy) {
+    into project.file('lib/jars/')
+    from configurations.compile, configurations.runtime
+}
+
 // copy jar file into the gem lib dir but without the version number in filename
-task copyGemjar(type: Copy, dependsOn: sourcesJar) {
+task copyGemjar(type: Copy, dependsOn: [sourcesJar, copyRuntimeLibs]) {
     from project.jar
-    into project.file('lib/logstash-core/')
+    into project.file('lib/jars/')
     rename(/(.+)-${project.version}.jar/, '$1.jar')
 }
 
@@ -48,22 +53,6 @@ task cleanGemjar {
 
 clean.dependsOn(cleanGemjar)
 jar.finalizedBy(copyGemjar)
-task gemspec_jars {
-    def gemspecJars = file("${projectDir}/gemspec_jars.rb")
-    outputs.files gemspecJars
-    doLast {
-        gemspecJars.newWriter().withWriter { w ->
-            w << "# This file is generated by Gradle as part of the build process. It extracts the build.gradle\n"
-                w << "# runtime dependencies to generate this gemspec dependencies file to be eval'ed by the gemspec\n"
-                w << "# for the jar-dependencies requirements.\n\n"
-                configurations.runtime.allDependencies.each { dependency ->
-                    w << "gem.requirements << \"jar ${dependency.group}:${dependency.name}, ${dependency.version}\"\n"
-                }
-        }
-    }
-}
-
-compileJava.dependsOn gemspec_jars
 
 configurations.create('sources')
 configurations.create('javadoc')
@@ -128,13 +117,11 @@ dependencies {
     compile "com.fasterxml.jackson.core:jackson-annotations:${jacksonVersion}"
     compile 'org.codehaus.janino:janino:3.0.7'
     compile "com.fasterxml.jackson.dataformat:jackson-dataformat-cbor:${jacksonVersion}"
+    compile "org.jruby:jruby-complete:${jrubyVersion}"
     testCompile 'org.apache.logging.log4j:log4j-core:2.6.2:tests'
     testCompile 'org.apache.logging.log4j:log4j-api:2.6.2:tests'
     testCompile 'junit:junit:4.12'
     testCompile 'net.javacrumbs.json-unit:json-unit:1.9.0'
     testCompile 'org.elasticsearch:securemock:1.2'
     testCompile 'org.assertj:assertj-core:3.8.0'
-    testCompile "org.jruby:jruby-complete:${jrubyVersion}"
-    provided "org.jruby:jruby-core:${jrubyVersion}"
 }
-
diff --git a/logstash-core/gemspec_jars.rb b/logstash-core/gemspec_jars.rb
deleted file mode 100644
index 857e8f648f2..00000000000
--- a/logstash-core/gemspec_jars.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-# This file is generated by Gradle as part of the build process. It extracts the build.gradle
-# runtime dependencies to generate this gemspec dependencies file to be eval'ed by the gemspec
-# for the jar-dependencies requirements.
-
-gem.requirements << "jar org.apache.logging.log4j:log4j-slf4j-impl, 2.9.1"
-gem.requirements << "jar org.apache.logging.log4j:log4j-api, 2.9.1"
-gem.requirements << "jar org.apache.logging.log4j:log4j-core, 2.9.1"
-gem.requirements << "jar com.fasterxml.jackson.core:jackson-core, 2.9.1"
-gem.requirements << "jar com.fasterxml.jackson.core:jackson-databind, 2.9.1"
-gem.requirements << "jar com.fasterxml.jackson.core:jackson-annotations, 2.9.1"
-gem.requirements << "jar org.codehaus.janino:janino, 3.0.7"
-gem.requirements << "jar com.fasterxml.jackson.dataformat:jackson-dataformat-cbor, 2.9.1"
diff --git a/logstash-core/lib/logstash-core/logstash-core.rb b/logstash-core/lib/logstash-core/logstash-core.rb
index fc62ca933e9..36b8e906c02 100644
--- a/logstash-core/lib/logstash-core/logstash-core.rb
+++ b/logstash-core/lib/logstash-core/logstash-core.rb
@@ -2,36 +2,15 @@
 
 require "java"
 
-module LogStash
-end
-
-require "logstash-core_jars"
-
-# local dev setup
-alt_classdir = File.expand_path("../../../out/production/classes", __FILE__) #IntelliJ's gradle output as of 2017.02 https://youtrack.jetbrains.com/issue/IDEA-175172
-if File.directory?(alt_classdir)
-  classes_dir = alt_classdir
-  resources_dir = File.expand_path("../../../out/production/resources", __FILE__)
-else
-  classes_dir = File.expand_path("../../../build/classes/java/main", __FILE__)
-  resources_dir = File.expand_path("../../../build/resources/main", __FILE__)
-end
-
-
-
-if File.directory?(classes_dir) && File.directory?(resources_dir)
-  # if in local dev setup, add target to classpath
-  $CLASSPATH << classes_dir unless $CLASSPATH.include?(classes_dir)
-  $CLASSPATH << resources_dir unless $CLASSPATH.include?(resources_dir)
-else
-  # otherwise use included jar
-  begin
-    require "logstash-core/logstash-core.jar"
-  rescue Exception => e
-    raise("Error loading logstash-core/logstash-core.jar file, cause: #{e.message}")
+# This block is used to load Logstash's Java libraries when using a Ruby entrypoint and
+# LS_JARS_LOADED is not globally set.
+# Currently this happens when using the `bin/rspec` executable to invoke specs instead of the JUnit
+# wrapper.
+unless $LS_JARS_LOADED
+  jar_path = File.join(File.dirname(File.dirname(__FILE__)), "jars")
+  $:.unshift jar_path
+  Dir.glob(jar_path + '/*.jar') do |jar|
+    require File.basename(jar)
   end
+  java_import org.logstash.RubyUtil
 end
-
-# Load Logstash's Java-defined RubyClasses by classloading RubyUtil which sets them up in its
-# static constructor
-java_import org.logstash.RubyUtil
diff --git a/logstash-core/lib/logstash-core_jars.rb b/logstash-core/lib/logstash-core_jars.rb
deleted file mode 100644
index 8802ba2b874..00000000000
--- a/logstash-core/lib/logstash-core_jars.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-# this is a generated file, to avoid over-writing it just delete this comment
-begin
-  require 'jar_dependencies'
-rescue LoadError
-  require 'org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar'
-  require 'com/fasterxml/jackson/core/jackson-databind/2.9.1/jackson-databind-2.9.1.jar'
-  require 'com/fasterxml/jackson/core/jackson-annotations/2.9.1/jackson-annotations-2.9.1.jar'
-  require 'org/apache/logging/log4j/log4j-api/2.9.1/log4j-api-2.9.1.jar'
-  require 'org/apache/logging/log4j/log4j-core/2.9.1/log4j-core-2.9.1.jar'
-  require 'com/fasterxml/jackson/dataformat/jackson-dataformat-cbor/2.9.1/jackson-dataformat-cbor-2.9.1.jar'
-  require 'org/codehaus/janino/commons-compiler/3.0.7/commons-compiler-3.0.7.jar'
-  require 'org/apache/logging/log4j/log4j-slf4j-impl/2.9.1/log4j-slf4j-impl-2.9.1.jar'
-  require 'com/fasterxml/jackson/core/jackson-core/2.9.1/jackson-core-2.9.1.jar'
-  require 'org/codehaus/janino/janino/3.0.7/janino-3.0.7.jar'
-end
-
-if defined? Jars
-  require_jar( 'org.slf4j', 'slf4j-api', '1.7.25' )
-  require_jar( 'com.fasterxml.jackson.core', 'jackson-databind', '2.9.1' )
-  require_jar( 'com.fasterxml.jackson.core', 'jackson-annotations', '2.9.1' )
-  require_jar( 'org.apache.logging.log4j', 'log4j-api', '2.9.1' )
-  require_jar( 'org.apache.logging.log4j', 'log4j-core', '2.9.1' )
-  require_jar( 'com.fasterxml.jackson.dataformat', 'jackson-dataformat-cbor', '2.9.1' )
-  require_jar( 'org.codehaus.janino', 'commons-compiler', '3.0.7' )
-  require_jar( 'org.apache.logging.log4j', 'log4j-slf4j-impl', '2.9.1' )
-  require_jar( 'com.fasterxml.jackson.core', 'jackson-core', '2.9.1' )
-  require_jar( 'org.codehaus.janino', 'janino', '3.0.7' )
-end
diff --git a/logstash-core/lib/logstash/environment.rb b/logstash-core/lib/logstash/environment.rb
index fe9f4f7cdf6..1b40ff0916e 100644
--- a/logstash-core/lib/logstash/environment.rb
+++ b/logstash-core/lib/logstash/environment.rb
@@ -1,4 +1,5 @@
 # encoding: utf-8
+require "logstash-core/logstash-core"
 require "logstash/errors"
 require "logstash/java_integration"
 require "logstash/config/cpu_core_strategy"
diff --git a/logstash-core/logstash-core.gemspec b/logstash-core/logstash-core.gemspec
index 48eef59a8fa..aef15267f0b 100644
--- a/logstash-core/logstash-core.gemspec
+++ b/logstash-core/logstash-core.gemspec
@@ -70,13 +70,6 @@ Gem::Specification.new do |gem|
 
   gem.add_runtime_dependency "jrjackson", "~> #{ALL_VERSIONS.fetch('jrjackson')}" #(Apache 2.0 license)
 
-  gem.add_runtime_dependency "jar-dependencies"
-  # as of Feb 3rd 2016, the ruby-maven gem is resolved to version 3.3.3 and that version
-  # has an rdoc problem that causes a bundler exception. 3.3.9 is the current latest version
-  # which does not have this problem.
-  gem.add_runtime_dependency "ruby-maven", "~> 3.3.9"
   gem.add_runtime_dependency "elasticsearch", "~> 5.0", ">= 5.0.4" # Ruby client for ES (Apache 2.0 license)
   gem.add_runtime_dependency "manticore", '>= 0.5.4', '< 1.0.0'
-
-  eval(File.read(File.expand_path("../gemspec_jars.rb", __FILE__)))
 end
diff --git a/logstash-core/src/main/java/org/logstash/Logstash.java b/logstash-core/src/main/java/org/logstash/Logstash.java
new file mode 100644
index 00000000000..459ca33b7e0
--- /dev/null
+++ b/logstash-core/src/main/java/org/logstash/Logstash.java
@@ -0,0 +1,146 @@
+package org.logstash;
+
+import java.io.InputStream;
+import java.io.PrintStream;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.jruby.Ruby;
+import org.jruby.RubyException;
+import org.jruby.RubyInstanceConfig;
+import org.jruby.RubyNumeric;
+import org.jruby.exceptions.RaiseException;
+import org.jruby.runtime.builtin.IRubyObject;
+
+/**
+ * Logstash Main Entrypoint.
+ */
+public final class Logstash implements Runnable, AutoCloseable {
+
+    private static final Logger LOGGER = LogManager.getLogger(Logstash.class);
+
+    /**
+     * Configuration for {@link #ruby}.
+     */
+    private final RubyInstanceConfig config;
+
+    /**
+     * JRuby Runtime Environment.
+     */
+    private final Ruby ruby;
+
+    /**
+     * Ruby Entrypoint Script.
+     */
+    private final InputStream script;
+
+    /**
+     * Main Entrypoint.
+     * Requires environment {@code "LS_HOME"} to be set to the Logstash root directory.
+     * @param args Logstash CLI Arguments
+     */
+    public static void main(final String... args) {
+        final String lsHome = System.getenv("LS_HOME");
+        if (lsHome == null) {
+            throw new IllegalStateException(
+                "LS_HOME environment variable must be set. This is likely a bug that should be reported."
+            );
+        }
+        final Path home = Paths.get(lsHome).toAbsolutePath();
+        try (
+            final Logstash logstash = new Logstash(home, args, System.out, System.err, System.in)
+        ) {
+            logstash.run();
+        } catch (final Throwable t) {
+            LOGGER.error(t);
+            System.exit(1);
+        }
+        System.exit(0);
+    }
+
+    /**
+     * Ctor.
+     * @param home Logstash Root Directory
+     * @param args Commandline Arguments
+     * @param output Output Stream Capturing StdOut
+     * @param error Output Stream Capturing StdErr
+     * @param input Input Stream Capturing StdIn
+     */
+    Logstash(final Path home, final String[] args, final PrintStream output,
+        final PrintStream error, final InputStream input) {
+        config = buildConfig(home, args);
+        config.setOutput(output);
+        config.setError(error);
+        config.setInput(input);
+        script = config.getScriptSource();
+        ruby = Ruby.newInstance(config);
+    }
+
+    @Override
+    public void run() {
+        // @todo: Refactor codebase to not rely on global constant for Ruby Runtime
+        if (RubyUtil.RUBY != ruby) {
+            throw new IllegalStateException(
+                "More than one JRuby Runtime detected in the current JVM!"
+            );
+        }
+        try {
+            Thread.currentThread().setContextClassLoader(ruby.getJRubyClassLoader());
+            ruby.runFromMain(script, config.displayedFileName());
+        } catch (final RaiseException ex) {
+            final RubyException rexep = ex.getException();
+            if (ruby.getSystemExit().isInstance(rexep)) {
+                final IRubyObject status =
+                    rexep.callMethod(ruby.getCurrentContext(), "status");
+                if (status != null && !status.isNil() && RubyNumeric.fix2int(status) != 0) {
+                    throw new IllegalStateException(ex);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void close() throws Exception {
+        ruby.tearDown(false);
+        script.close();
+    }
+
+    /**
+     * Sets up the correct {@link RubyInstanceConfig} for a given Logstash installation and set of
+     * CLI arguments.
+     * @param home Logstash Root Path
+     * @param args Commandline Arguments Passed to Logstash
+     * @return RubyInstanceConfig
+     */
+    private static RubyInstanceConfig buildConfig(final Path home, final String[] args) {
+        final String[] arguments = new String[args.length + 2];
+        System.arraycopy(args, 0, arguments, 2, args.length);
+        arguments[0] = safePath(home, "lib", "bootstrap", "environment.rb");
+        arguments[1] = safePath(home, "logstash-core", "lib", "logstash", "runner.rb");
+        final RubyInstanceConfig config = new RubyInstanceConfig();
+        config.processArguments(arguments);
+        return config;
+    }
+
+    /**
+     * Builds the correct path for a file under the given Logstash root and defined by its sub path
+     * elements relative to the Logstash root.
+     * Ensures that the file exists and throws an exception of it's missing.
+     * This is done to avoid hard to interpret errors thrown by JRuby that could result from missing
+     * Ruby bootstrap scripts.
+     * @param home Logstash Root Path
+     * @param subs Path elements relative to {@code home}
+     * @return Absolute Path a File under the Logstash Root.
+     */
+    private static String safePath(final Path home, final String... subs) {
+        Path resolved = home;
+        for (final String element : subs) {
+            resolved = resolved.resolve(element);
+        }
+        if (!resolved.toFile().exists()) {
+            throw new IllegalArgumentException(String.format("Missing: %s.", resolved));
+        }
+        return resolved.toString();
+    }
+}
diff --git a/logstash-core/src/main/java/org/logstash/RubyUtil.java b/logstash-core/src/main/java/org/logstash/RubyUtil.java
index eec17665604..f22edf9c608 100644
--- a/logstash-core/src/main/java/org/logstash/RubyUtil.java
+++ b/logstash-core/src/main/java/org/logstash/RubyUtil.java
@@ -92,6 +92,7 @@ public final class RubyUtil {
             abstractQueue, AbstractJRubyQueue.RubyAckedMemoryQueue::new,
             AbstractJRubyQueue.RubyAckedMemoryQueue.class
         );
+        RUBY.getGlobalVariables().set("$LS_JARS_LOADED", RUBY.newString("true"));
     }
 
     private RubyUtil() {
diff --git a/rakelib/artifacts.rake b/rakelib/artifacts.rake
index 37289c66fca..116b743728a 100644
--- a/rakelib/artifacts.rake
+++ b/rakelib/artifacts.rake
@@ -22,7 +22,6 @@ namespace "artifact" do
       "logstash-core/vendor/**/*",
       "logstash-core/versions-gem-copy.yml",
       "logstash-core/*.gemspec",
-      "logstash-core/gemspec_jars.rb",
 
       "logstash-core-plugin-api/lib/**/*",
       "logstash-core-plugin-api/*.gemspec",