diff --git a/.github/workflows/build.yml b/.github/workflows/check.yml
similarity index 68%
rename from .github/workflows/build.yml
rename to .github/workflows/check.yml
index 6c38f09..1af6e5a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/check.yml
@@ -1,19 +1,21 @@
-name: Build and test
-
-on: push
-
+name: Check
+on: [ pull_request, push ]
 jobs:
-  build:
-
+  check:
     runs-on: ubuntu-latest
-
+    # push: always run.
+    # pull_request: run only when the PR is submitted from a forked repository, not within this repository.
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
+    strategy:
+      fail-fast: false
     steps:
       - uses: actions/checkout@v2
-
-      - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
+      - name: Set up OpenJDK 8
+        uses: actions/setup-java@v2
         with:
-          java-version: 1.8
+          java-version: 8
+          distribution: "temurin"
+          cache: "gradle"
 
       - name: Run elastisearch container
         run: docker-compose up -d
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
new file mode 100644
index 0000000..b5c7bda
--- /dev/null
+++ b/.github/workflows/publish.yml
@@ -0,0 +1,33 @@
+name: Publish
+on:
+  push:
+    tags:
+      - "v0.*"
+jobs:
+  publish:
+    environment:
+      name: maven-central-and-ruby-gems
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up OpenJDK 8
+      uses: actions/setup-java@v2
+      with:
+        java-version: 8
+        distribution: "temurin"
+        cache: "gradle"
+    - name: Publish
+      run: |
+        mkdir -p $HOME/.gem
+        touch $HOME/.gem/credentials
+        chmod 0600 $HOME/.gem/credentials
+        printf -- "---\n:rubygems_api_key: ${RUBYGEMS_API_KEY}\n" > $HOME/.gem/credentials
+        ./gradlew --stacktrace publishMavenPublicationToMavenCentralRepository gemPush
+      env:
+        ORG_GRADLE_PROJECT_ossrhUsername: embulk
+        ORG_GRADLE_PROJECT_ossrhPassword: ${{ secrets.OSSRH_PASSWORD }}
+        ORG_GRADLE_PROJECT_signingKey: ${{ secrets.GPG_PRIVATE_KEY_ARMOR }}
+        ORG_GRADLE_PROJECT_signingPassword: ${{ secrets.GPG_PRIVATE_KEY_PASSWORD }}
+        RUBYGEMS_API_KEY: ${{ secrets.RUBYGEMS_API_KEY }}
diff --git a/NOTICE b/NOTICE
new file mode 100644
index 0000000..de6cdcc
--- /dev/null
+++ b/NOTICE
@@ -0,0 +1,5 @@
+embulk-output-elasticsearch
+Copyright 2015 The Embulk project
+
+This product includes software developed at
+The Embulk project (https://www.embulk.org/).
diff --git a/README.md b/README.md
index 12936d7..b175704 100644
--- a/README.md
+++ b/README.md
@@ -45,7 +45,7 @@ This mode writes data to existing index.
 
 #### replace:
 
-1. Create new temporary index 
+1. Create new temporary index
 2. Insert data into the new index
 3. replace the alias with the new index. If alias doesn't exists, plugin will create new alias.
 4. Delete existing (old) index if exists
@@ -58,7 +58,7 @@ out:
   mode: replace
   nodes:
   - {host: localhost, port: 9200}
-  index: <alias name> # plugin generates index name like <index>_%Y%m%d-%H%M%S 
+  index: <alias name> # plugin generates index name like <index>_%Y%m%d-%H%M%S
   index_type: <index type>
 ```
 
@@ -86,13 +86,6 @@ out:
   index_type: <index type>
 ```
 
-## Build
-
-```
-$ ./gradlew gem  # -t to watch change of files and rebuild continuously
-$ ./gradlew bintrayUpload # release embulk-output-elasticsearch to Bintray maven repo
-```
-
 ## Test
 
 Firstly install Docker and Docker compose then `docker-compose up -d`,
@@ -110,3 +103,37 @@ embulk-output-elasticsearch_server   /docker-entrypoint.sh elas ...   Up      0.
 
 $ ./gradlew test  # -t to watch change of files and rebuild continuously
 ```
+
+For Maintainers
+----------------
+
+### Release
+
+Modify `version` in `build.gradle` at a detached commit, and then tag the commit with an annotation.
+
+```
+git checkout --detach master
+(Edit: Remove "-SNAPSHOT" in "version" in build.gradle.)
+git add build.gradle
+git commit -m "Release vX.Y.Z"
+git tag -a vX.Y.Z
+(Edit: Write a tag annotation in the changelog format.)
+```
+
+See [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) for the changelog format. We adopt a part of it for Git's tag annotation like below.
+
+```
+## [X.Y.Z] - YYYY-MM-DD
+### Added
+- Added a feature.
+### Changed
+- Changed something.
+### Fixed
+- Fixed a bug.
+```
+
+Push the annotated tag, then. It triggers a release operation on GitHub Actions after approval.
+
+```
+git push -u origin vX.Y.Z
+```
diff --git a/build.gradle b/build.gradle
index ccbe0b1..8ba3ab0 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,7 +4,7 @@ plugins {
     id "signing"
     id "jacoco"
     id "checkstyle"
-    id "org.embulk.embulk-plugins" version "0.4.2"
+    id "org.embulk.embulk-plugins" version "0.5.5"
 }
 
 repositories {
@@ -18,8 +18,8 @@ group = "org.embulk"
 version = "0.6.0-SNAPSHOT"
 description = "Elasticsearch output plugin is an Embulk plugin that loads records to Elasticsearch read by any input plugins."
 
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 tasks.withType(JavaCompile) {
     options.compilerArgs << "-Xlint:deprecation" << "-Xlint:unchecked"
@@ -35,7 +35,7 @@ dependencies {
     compileOnly "org.embulk:embulk-api:0.10.28"
     compileOnly "org.embulk:embulk-spi:0.10.28"
 
-    compile("org.embulk:embulk-util-config:0.3.0") {
+    implementation("org.embulk:embulk-util-config:0.3.2") {
         // They conflict with embulk-core. They are once excluded here,
         // and added explicitly with versions exactly the same with embulk-core:0.10.28.
         exclude group: "com.fasterxml.jackson.core", module: "jackson-annotations"
@@ -47,23 +47,23 @@ dependencies {
 
     // They are once excluded from transitive dependencies of other dependencies,
     // and added explicitly with versions exactly the same with embulk-core:0.10.28.
-    compile "com.fasterxml.jackson.core:jackson-annotations:2.6.7"
-    compile "com.fasterxml.jackson.core:jackson-core:2.6.7"
-    compile "com.fasterxml.jackson.core:jackson-databind:2.6.7"
-    compile "com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.6.7"
-    compile "javax.validation:validation-api:1.1.0.Final"
+    implementation "com.fasterxml.jackson.core:jackson-annotations:2.6.7"
+    implementation "com.fasterxml.jackson.core:jackson-core:2.6.7"
+    implementation "com.fasterxml.jackson.core:jackson-databind:2.6.7"
+    implementation "com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.6.7"
+    implementation "javax.validation:validation-api:1.1.0.Final"
 
-    compile "org.embulk:embulk-base-restclient:0.10.1"
-    compile "org.embulk:embulk-util-retryhelper-jetty92:0.8.2"
+    implementation "org.embulk:embulk-base-restclient:0.10.1"
+    implementation "org.embulk:embulk-util-retryhelper-jetty92:0.8.2"
 
-    compile "org.embulk:embulk-util-timestamp:0.2.1"
+    implementation "org.embulk:embulk-util-timestamp:0.2.1"
 
-    testCompile "junit:junit:4.13.2"
-    testCompile "org.embulk:embulk-core:0.10.28"
-    testCompile "org.embulk:embulk-core:0.10.28:tests"
-    testCompile "org.embulk:embulk-standards:0.10.28"
-    testCompile "org.embulk:embulk-junit4:0.10.28"
-    testCompile "org.embulk:embulk-deps:0.10.28"
+    testImplementation "junit:junit:4.13.2"
+    testImplementation "org.embulk:embulk-core:0.10.28"
+    testImplementation "org.embulk:embulk-core:0.10.28:tests"
+    testImplementation "org.embulk:embulk-standards:0.10.28"
+    testImplementation "org.embulk:embulk-junit4:0.10.28"
+    testImplementation "org.embulk:embulk-deps:0.10.28"
 }
 
 embulkPlugin {
@@ -74,21 +74,30 @@ embulkPlugin {
 
 javadoc {
     options {
-        locale = 'en_US'
-        encoding = 'UTF-8'
+        locale = "en_US"
+        encoding = "UTF-8"
     }
 }
 
 jar {
-    from rootProject.file("LICENSE")
+    metaInf {
+        from rootProject.file("LICENSE")
+        from rootProject.file("NOTICE")
+    }
 }
 
 sourcesJar {
-    from rootProject.file("LICENSE")
+    metaInf {
+        from rootProject.file("LICENSE")
+        from rootProject.file("NOTICE")
+    }
 }
 
 javadocJar {
-    from rootProject.file("LICENSE")
+    metaInf {
+        from rootProject.file("LICENSE")
+        from rootProject.file("NOTICE")
+    }
 }
 
 publishing {
@@ -178,6 +187,10 @@ publishing {
 }
 
 signing {
+    if (project.hasProperty("signingKey") && project.hasProperty("signingPassword")) {
+        logger.lifecycle("Signing with an in-memory key.")
+        useInMemoryPgpKeys(signingKey, signingPassword)
+    }
     sign publishing.publications.maven
 }
 
diff --git a/gradle.lockfile b/gradle.lockfile
new file mode 100644
index 0000000..5178d4d
--- /dev/null
+++ b/gradle.lockfile
@@ -0,0 +1,24 @@
+# This is a Gradle generated file for dependency locking.
+# Manual edits can break the build and are not advised.
+# This file is expected to be part of source control.
+com.fasterxml.jackson.core:jackson-annotations:2.6.7=compileClasspath,runtimeClasspath
+com.fasterxml.jackson.core:jackson-core:2.6.7=compileClasspath,runtimeClasspath
+com.fasterxml.jackson.core:jackson-databind:2.6.7=compileClasspath,runtimeClasspath
+com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.6.7=compileClasspath,runtimeClasspath
+javax.validation:validation-api:1.1.0.Final=compileClasspath,runtimeClasspath
+org.eclipse.jetty:jetty-client:9.2.14.v20151106=compileClasspath,runtimeClasspath
+org.eclipse.jetty:jetty-http:9.2.14.v20151106=compileClasspath,runtimeClasspath
+org.eclipse.jetty:jetty-io:9.2.14.v20151106=compileClasspath,runtimeClasspath
+org.eclipse.jetty:jetty-util:9.2.14.v20151106=compileClasspath,runtimeClasspath
+org.embulk:embulk-api:0.10.28=compileClasspath
+org.embulk:embulk-base-restclient:0.10.1=compileClasspath,runtimeClasspath
+org.embulk:embulk-spi:0.10.28=compileClasspath
+org.embulk:embulk-util-config:0.3.2=compileClasspath,runtimeClasspath
+org.embulk:embulk-util-json:0.1.1=compileClasspath,runtimeClasspath
+org.embulk:embulk-util-retryhelper-jetty92:0.8.2=compileClasspath,runtimeClasspath
+org.embulk:embulk-util-retryhelper:0.8.2=compileClasspath,runtimeClasspath
+org.embulk:embulk-util-rubytime:0.3.2=runtimeClasspath
+org.embulk:embulk-util-timestamp:0.2.1=compileClasspath,runtimeClasspath
+org.msgpack:msgpack-core:0.8.11=compileClasspath
+org.slf4j:slf4j-api:1.7.30=compileClasspath
+empty=
diff --git a/gradle/dependency-locks/embulkPluginRuntime.lockfile b/gradle/dependency-locks/embulkPluginRuntime.lockfile
deleted file mode 100644
index 9011472..0000000
--- a/gradle/dependency-locks/embulkPluginRuntime.lockfile
+++ /dev/null
@@ -1,19 +0,0 @@
-# This is a Gradle generated file for dependency locking.
-# Manual edits can break the build and are not advised.
-# This file is expected to be part of source control.
-com.fasterxml.jackson.core:jackson-annotations:2.6.7
-com.fasterxml.jackson.core:jackson-core:2.6.7
-com.fasterxml.jackson.core:jackson-databind:2.6.7
-com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.6.7
-javax.validation:validation-api:1.1.0.Final
-org.eclipse.jetty:jetty-client:9.2.14.v20151106
-org.eclipse.jetty:jetty-http:9.2.14.v20151106
-org.eclipse.jetty:jetty-io:9.2.14.v20151106
-org.eclipse.jetty:jetty-util:9.2.14.v20151106
-org.embulk:embulk-base-restclient:0.10.1
-org.embulk:embulk-util-config:0.3.0
-org.embulk:embulk-util-json:0.1.1
-org.embulk:embulk-util-retryhelper-jetty92:0.8.2
-org.embulk:embulk-util-retryhelper:0.8.2
-org.embulk:embulk-util-rubytime:0.3.2
-org.embulk:embulk-util-timestamp:0.2.1
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index e708b1c..249e583 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 442d913..ae04661 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 4f906e0..a69d9cb 100755
--- a/gradlew
+++ b/gradlew
@@ -1,7 +1,7 @@
-#!/usr/bin/env sh
+#!/bin/sh
 
 #
-# Copyright 2015 the original author or authors.
+# Copyright © 2015-2021 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -17,67 +17,101 @@
 #
 
 ##############################################################################
-##
-##  Gradle start up script for UN*X
-##
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
 ##############################################################################
 
 # Attempt to set APP_HOME
+
 # Resolve links: $0 may be a link
-PRG="$0"
-# Need this for relative symlinks.
-while [ -h "$PRG" ] ; do
-    ls=`ls -ld "$PRG"`
-    link=`expr "$ls" : '.*-> \(.*\)$'`
-    if expr "$link" : '/.*' > /dev/null; then
-        PRG="$link"
-    else
-        PRG=`dirname "$PRG"`"/$link"
-    fi
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
 done
-SAVED="`pwd`"
-cd "`dirname \"$PRG\"`/" >/dev/null
-APP_HOME="`pwd -P`"
-cd "$SAVED" >/dev/null
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
 
 APP_NAME="Gradle"
-APP_BASE_NAME=`basename "$0"`
+APP_BASE_NAME=${0##*/}
 
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
-MAX_FD="maximum"
+MAX_FD=maximum
 
 warn () {
     echo "$*"
-}
+} >&2
 
 die () {
     echo
     echo "$*"
     echo
     exit 1
-}
+} >&2
 
 # OS specific support (must be 'true' or 'false').
 cygwin=false
 msys=false
 darwin=false
 nonstop=false
-case "`uname`" in
-  CYGWIN* )
-    cygwin=true
-    ;;
-  Darwin* )
-    darwin=true
-    ;;
-  MINGW* )
-    msys=true
-    ;;
-  NONSTOP* )
-    nonstop=true
-    ;;
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
 esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
@@ -87,9 +121,9 @@ CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
         # IBM's JDK on AIX uses strange locations for the executables
-        JAVACMD="$JAVA_HOME/jre/sh/java"
+        JAVACMD=$JAVA_HOME/jre/sh/java
     else
-        JAVACMD="$JAVA_HOME/bin/java"
+        JAVACMD=$JAVA_HOME/bin/java
     fi
     if [ ! -x "$JAVACMD" ] ; then
         die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
@@ -98,7 +132,7 @@ Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
     fi
 else
-    JAVACMD="java"
+    JAVACMD=java
     which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
@@ -106,80 +140,101 @@ location of your Java installation."
 fi
 
 # Increase the maximum file descriptors if we can.
-if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
-    MAX_FD_LIMIT=`ulimit -H -n`
-    if [ $? -eq 0 ] ; then
-        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
-            MAX_FD="$MAX_FD_LIMIT"
-        fi
-        ulimit -n $MAX_FD
-        if [ $? -ne 0 ] ; then
-            warn "Could not set maximum file descriptor limit: $MAX_FD"
-        fi
-    else
-        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
-    fi
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
 fi
 
-# For Darwin, add options to specify how the application appears in the dock
-if $darwin; then
-    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
-fi
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
 
 # For Cygwin or MSYS, switch paths to Windows format before running java
-if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
-    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
-    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
-
-    JAVACMD=`cygpath --unix "$JAVACMD"`
-
-    # We build the pattern for arguments to be converted via cygpath
-    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
-    SEP=""
-    for dir in $ROOTDIRSRAW ; do
-        ROOTDIRS="$ROOTDIRS$SEP$dir"
-        SEP="|"
-    done
-    OURCYGPATTERN="(^($ROOTDIRS))"
-    # Add a user-defined pattern to the cygpath arguments
-    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
-        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
-    fi
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
     # Now convert the arguments - kludge to limit ourselves to /bin/sh
-    i=0
-    for arg in "$@" ; do
-        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
-        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
-
-        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
-            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
-        else
-            eval `echo args$i`="\"$arg\""
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
         fi
-        i=`expr $i + 1`
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
     done
-    case $i in
-        0) set -- ;;
-        1) set -- "$args0" ;;
-        2) set -- "$args0" "$args1" ;;
-        3) set -- "$args0" "$args1" "$args2" ;;
-        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
-        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
-        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
-        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
-        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
-        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
-    esac
 fi
 
-# Escape application args
-save () {
-    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
-    echo " "
-}
-APP_ARGS=`save "$@"`
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
 
-# Collect all arguments for the java command, following the shell quoting and substitution rules
-eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
 
 exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
index ac1b06f..53a6b23 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -14,7 +14,7 @@
 @rem limitations under the License.
 @rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
 @rem  Gradle startup script for Windows
@@ -25,7 +25,7 @@
 if "%OS%"=="Windows_NT" setlocal
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,7 +40,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -75,13 +75,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 :end
 @rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
+if %ERRORLEVEL% equ 0 goto mainEnd
 
 :fail
 rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
 rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
 
 :mainEnd
 if "%OS%"=="Windows_NT" endlocal
diff --git a/settings.gradle b/settings.gradle
index 426d76e..9ce2844 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -1 +1 @@
-rootProject.name = 'embulk-output-elasticsearch'
+rootProject.name = "embulk-output-elasticsearch"