GH-218: Add initial support for Kotlin DSL

Fixes https://github.com/spring-projects/spring-integration-extensions/issues/218

spring-integration-kotlin-dsl/.gitignore

@@ -0,0 +1,12 @@
+target
+.settings
+.springBeans
+.classpath
+.project
+/.idea
+/.gradle
+/build
+/*.iml
+/*.ipr
+/*.iws
+/bin/

spring-integration-kotlin-dsl/CODE_OF_CONDUCT.adoc

@@ -0,0 +1,44 @@
+= Contributor Code of Conduct
+
+As contributors and maintainers of this project, and in the interest of fostering an open
+and welcoming community, we pledge to respect all people who contribute through reporting
+issues, posting feature requests, updating documentation, submitting pull requests or
+patches, and other activities.
+
+We are committed to making participation in this project a harassment-free experience for
+everyone, regardless of level of experience, gender, gender identity and expression,
+sexual orientation, disability, personal appearance, body size, race, ethnicity, age,
+religion, or nationality.
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery
+* Personal attacks
+* Trolling or insulting/derogatory comments
+* Public or private harassment
+* Publishing other's private information, such as physical or electronic addresses,
+  without explicit permission
+* Other unethical or unprofessional conduct
+
+Project maintainers have the right and responsibility to remove, edit, or reject comments,
+commits, code, wiki edits, issues, and other contributions that are not aligned to this
+Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors
+that they deem inappropriate, threatening, offensive, or harmful.
+
+By adopting this Code of Conduct, project maintainers commit themselves to fairly and
+consistently applying these principles to every aspect of managing this project. Project
+maintainers who do not follow or enforce the Code of Conduct may be permanently removed
+from the project team.
+
+This Code of Conduct applies both within project spaces and in public spaces when an
+individual is representing the project or its community.
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by
+contacting a project maintainer at spring-code-of-conduct@pivotal.io . All complaints will
+be reviewed and investigated and will result in a response that is deemed necessary and
+appropriate to the circumstances. Maintainers are obligated to maintain confidentiality
+with regard to the reporter of an incident.
+
+This Code of Conduct is adapted from the
+https://contributor-covenant.org[Contributor Covenant], version 1.3.0, available at
+https://contributor-covenant.org/version/1/3/0/[contributor-covenant.org/version/1/3/0/]

spring-integration-kotlin-dsl/README.md

@@ -0,0 +1,6 @@
+Spring Integration Kotlin DSL
+===============================
+
+This project is a Kotlin extension for [Spring Integration Java DSL].
+
+[Spring Integration Java DSL]: https://docs.spring.io/spring-integration/docs/current/reference/html/#java-dsl

spring-integration-kotlin-dsl/build.gradle

@@ -0,0 +1,188 @@
+plugins {
+    id 'java'
+    id 'eclipse'
+    id 'idea'
+    id 'jacoco'
+    id 'org.sonarqube' version '2.7.1'
+    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
+    id "org.jetbrains.kotlin.jvm" version "$kotlinVersion"
+    id "org.jetbrains.kotlin.plugin.spring" version "$kotlinVersion"
+}
+
+apply from: "${rootProject.projectDir}/publish-maven.gradle"
+
+description = 'Spring Integration Kotlin DSL'
+
+group = 'org.springframework.integration'
+
+repositories {
+    if (version.endsWith('BUILD-SNAPSHOT')) {
+        maven { url 'https://repo.spring.io/libs-snapshot' }
+    }
+    maven { url 'https://repo.spring.io/libs-milestone' }
+//	maven { url 'https://repo.spring.io/libs-staging-local' }
+}
+
+ext {
+    assertkVersion = '0.20'
+    jacksonVersion = '2.10.0.pr3'
+    junitVersion = '5.5.2'
+    log4jVersion = '2.12.1'
+    springIntegrationVersion = '5.2.0.BUILD-SNAPSHOT'
+
+    idPrefix = 'kotlin-dsl'
+
+    linkHomepage = 'https://github.com/spring-projects/spring-integration-extensions'
+    linkCi = 'https://build.spring.io/browse/INTEXT'
+    linkIssue = 'https://github.com/spring-projects/spring-integration-extensions/issues'
+    linkScmUrl = 'https://github.com/spring-projects/spring-integration-extensions'
+    linkScmConnection = 'https://github.com/spring-projects/spring-integration-extensions.git'
+    linkScmDevConnection = 'git@github.com:spring-projects/spring-integration-extensions.git'
+
+}
+
+dependencyManagement {
+    resolutionStrategy {
+        cacheChangingModulesFor 0, 'seconds'
+    }
+    applyMavenExclusions = false
+    generatedPomCustomization {
+        enabled = false
+    }
+
+    imports {
+        mavenBom "com.fasterxml.jackson:jackson-bom:$jacksonVersion"
+        mavenBom "org.junit:junit-bom:$junitVersion"
+        mavenBom "org.springframework.integration:spring-integration-bom:$springIntegrationVersion"
+        mavenBom "org.apache.logging.log4j:log4j-bom:$log4jVersion"
+    }
+
+}
+
+compileKotlin {
+    kotlinOptions {
+        jvmTarget = '1.8'
+        freeCompilerArgs = ["-Xjsr305=strict"]
+        allWarningsAsErrors = true
+    }
+}
+compileTestKotlin {
+    kotlinOptions {
+        freeCompilerArgs = ['-Xjsr305=strict']
+        jvmTarget = '1.8'
+    }
+}
+
+
+eclipse.project.natures += 'org.springframework.ide.eclipse.core.springnature'
+
+
+jacoco {
+    toolVersion = '0.8.4'
+}
+
+dependencies {
+    implementation 'org.jetbrains.kotlin:kotlin-reflect'
+    implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
+    implementation 'org.springframework.integration:spring-integration-core'
+
+    testImplementation 'org.springframework.integration:spring-integration-test'
+    testImplementation 'org.junit.jupiter:junit-jupiter-api'
+    testImplementation "com.willowtreeapps.assertk:assertk-jvm:$assertkVersion"
+
+    testRuntime 'com.fasterxml.jackson.module:jackson-module-kotlin'
+    testRuntime 'org.junit.jupiter:junit-jupiter-engine'
+    testRuntime 'org.junit.platform:junit-platform-launcher'
+    testRuntime 'org.apache.logging.log4j:log4j-jcl'
+    testRuntime 'org.apache.logging.log4j:log4j-core'
+}
+
+test {
+    // suppress all console output during testing unless running `gradle -i`
+    logging.captureStandardOutput(LogLevel.INFO)
+    jacoco {
+        append = false
+        destinationFile = file("$buildDir/jacoco.exec")
+    }
+    useJUnitPlatform()
+}
+
+jacocoTestReport {
+    reports {
+        xml.enabled false
+        csv.enabled false
+        html.destination file("${buildDir}/reports/jacoco/html")
+    }
+}
+
+check.dependsOn javadoc
+build.dependsOn jacocoTestReport
+
+
+task sourcesJar(type: Jar) {
+    archiveClassifier = 'sources'
+    from sourceSets.main.kotlin
+}
+
+task javadocJar(type: Jar) {
+    archiveClassifier = 'javadoc'
+    from javadoc
+}
+
+sonarqube {
+    properties {
+        property 'sonar.jacoco.reportPath', "${buildDir.name}/jacoco.exec"
+        property 'sonar.links.homepage', linkHomepage
+        property 'sonar.links.ci', linkCi
+        property 'sonar.links.issue', linkIssue
+        property 'sonar.links.scm', linkScmUrl
+        property 'sonar.links.scm_dev', linkScmDevConnection
+        property 'sonar.java.coveragePlugin', 'jacoco'
+    }
+}
+
+task api(type: Javadoc) {
+    group = 'Documentation'
+    description = 'Generates the Javadoc API documentation.'
+    title = "${rootProject.description} ${version} API"
+    options.memberLevel = org.gradle.external.javadoc.JavadocMemberLevel.PROTECTED
+    options.author = true
+    options.header = rootProject.description
+    options.overview = 'src/api/overview.html'
+
+    source = sourceSets.main.kotlin
+    classpath = project.sourceSets.main.compileClasspath
+    destinationDir = new File(buildDir, 'api')
+}
+
+task distZip(type: Zip) {
+    group = 'Distribution'
+    archiveClassifier = 'dist'
+    description = "Builds -${archiveClassifier} archive, containing all jars and docs, " +
+            "suitable for community download page."
+
+    ext.baseDir = "${project.name}-${project.version}";
+
+    from('src/dist') {
+        include 'readme.txt'
+        include 'license.txt'
+        into "${baseDir}"
+    }
+
+    into("${baseDir}/libs") {
+        from project.jar
+        from project.sourcesJar
+        from project.javadocJar
+    }
+}
+
+artifacts {
+    archives sourcesJar
+    archives javadocJar
+    archives distZip
+}
+
+task dist(dependsOn: assemble) {
+    group = 'Distribution'
+    description = 'Builds -dist, -docs and -schema distribution archives.'
+}

spring-integration-kotlin-dsl/gradle.properties

@@ -0,0 +1,3 @@
+version=0.0.1.BUILD-SNAPSHOT
+
+kotlinVersion=1.3.50

spring-integration-kotlin-dsl/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

spring-integration-kotlin-dsl/gradlew

@@ -0,0 +1,188 @@
+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# 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"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+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="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$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
+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
+
+# 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
+    # 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`="\"$arg\""
+        fi
+        i=$((i+1))
+    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, 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"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

spring-integration-kotlin-dsl/gradlew.bat

@@ -0,0 +1,100 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="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
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

spring-integration-kotlin-dsl/publish-maven.gradle

@@ -0,0 +1,84 @@
+apply plugin: 'maven'
+
+ext.optionalDeps = []
+ext.providedDeps = []
+
+ext.optional = { optionalDeps << it }
+ext.provided = { providedDeps << it }
+
+install {
+	repositories.mavenInstaller {
+		customizePom(pom, project)
+	}
+}
+
+def customizePom(pom, gradleProject) {
+	pom.whenConfigured { generatedPom ->
+
+		// sort to make pom dependencies order consistent to ease comparison of older poms
+		generatedPom.dependencies = generatedPom.dependencies.sort { dep ->
+			"$dep.scope:$dep.groupId:$dep.artifactId"
+		}
+
+		def managedVersions = dependencyManagement.managedVersions
+		generatedPom.dependencies.findAll{dep -> !dep.version }.each { dep ->
+			dep.version = managedVersions["${dep.groupId}:${dep.artifactId}"]
+		}
+
+		// respect 'optional' and 'provided' dependencies
+		gradleProject.optionalDeps.each { dep ->
+			generatedPom.dependencies.find { it.artifactId == dep.name }?.optional = true
+		}
+		gradleProject.providedDeps.each { dep ->
+			generatedPom.dependencies.find { it.artifactId == dep.name }?.scope = 'provided'
+		}
+
+		// eliminate test-scoped dependencies (no need in maven central poms)
+		generatedPom.dependencies.removeAll { dep ->
+			dep.scope == 'test'
+		}
+
+		// add all items necessary for maven central publication
+		generatedPom.project {
+			name = gradleProject.description
+			description = gradleProject.description
+			url = linkHomepage
+			organization {
+				name = 'SpringIO'
+				url = 'https://spring.io'
+			}
+			licenses {
+				license {
+					name 'The Apache Software License, Version 2.0'
+					url 'https://www.apache.org/licenses/LICENSE-2.0.txt'
+					distribution 'repo'
+				}
+			}
+
+			scm {
+				url = linkScmUrl
+				connection = "scm:git:$linkScmConnection"
+				developerConnection = "scm:git:$linkScmDevConnection"
+			}
+
+			issueManagement {
+				system = 'GutHub'
+				url = linkIssue
+			}
+
+			developers {
+				developer {
+					id = 'garyrussell'
+					name = 'Gary Russell'
+					email = 'grussell@pivotal.io'
+					roles = ['project lead']
+				}
+				developer {
+					id = 'abilan'
+					name = 'Artem Bilan'
+					email = 'abilan@pivotal.io'
+				}
+			}
+		}
+	}
+}

spring-integration-kotlin-dsl/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'spring-integration-kotlin-dsl'

spring-integration-kotlin-dsl/src/api/overview.html

@@ -0,0 +1,22 @@
+<html>
+<body>
+This document is the API specification for Spring Integration Cassandra Extension
+<hr/>
+<div id="overviewBody">
+    <p>
+        For further API reference and developer documentation, see the
+        <a href="https://docs.spring.io/spring-integration/reference/html" target="_top">Spring
+            Integration reference documentation</a>.
+        That documentation contains more detailed, developer-targeted
+        descriptions, with conceptual overviews, definitions of terms,
+        workarounds, and working code examples.
+    </p>
+
+    <p>
+        If you are interested in commercial training, consultancy, and
+        support for Spring Integration, please visit
+        <a href="https://spring.io/" target="_top">https://spring.io/</a>
+    </p>
+</div>
+</body>
+</html>

spring-integration-kotlin-dsl/src/dist/license.txt

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        https://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
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spring-integration-kotlin-dsl/src/main/kotlin/org/springframework/integration/dsl/kotlin/IntegrationFlowBuilderExtensions.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl.kotlin
+
+import org.springframework.integration.dsl.GenericEndpointSpec
+import org.springframework.integration.dsl.IntegrationFlowDefinition
+import org.springframework.integration.transformer.MessageTransformingHandler
+
+/**
+ * Extension for [IntegrationFlowDefinition.convert()] providing a `convert<Foo>()` variant.
+ *
+ * @author Artem Bilan
+ */
+inline fun <reified T> IntegrationFlowDefinition<*>.convert(
+		crossinline consumer: (GenericEndpointSpec<MessageTransformingHandler>) -> Unit = {}): IntegrationFlowDefinition<*> =
+		convert(T::class.java) { consumer(it) }

spring-integration-kotlin-dsl/src/main/kotlin/org/springframework/integration/dsl/kotlin/IntegrationFlowDsl.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl.kotlin
+
+import org.springframework.integration.core.MessageSource
+import org.springframework.integration.dsl.GatewayProxySpec
+import org.springframework.integration.dsl.IntegrationFlow
+import org.springframework.integration.dsl.IntegrationFlowDefinition
+import org.springframework.integration.dsl.IntegrationFlows
+import org.springframework.integration.dsl.SourcePollingChannelAdapterSpec
+import java.util.function.Consumer
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from(Class)]
+ *
+ * @author Artem Bilan
+ */
+inline fun <reified T> integrationFlow(crossinline gateway: (GatewayProxySpec) -> Unit = {},
+									   crossinline flow: (IntegrationFlowDefinition<*>) -> Unit): IntegrationFlow {
+
+	val flowBuilder = IntegrationFlows.from(T::class.java) { gateway(it) }
+	flow.invoke(flowBuilder)
+	return flowBuilder.get()
+}
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from(String,Boolean)]
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(channelName: String, fixedSubscriber: Boolean = false,
+					flow: (IntegrationFlowDefinition<*>) -> Unit): IntegrationFlow {
+
+	val flowBuilder = IntegrationFlows.from(channelName, fixedSubscriber)
+	flow.invoke(flowBuilder)
+	return flowBuilder.get()
+}
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for
+ * [IntegrationFlows.from(MessageSource<*>,Consumer<SourcePollingChannelAdapterSpec>)]
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(messageSource: MessageSource<*>,
+						   options: (SourcePollingChannelAdapterSpec) -> Unit = {},
+					flow: (IntegrationFlowDefinition<*>) -> Unit): IntegrationFlow {
+
+	val flowBuilder = IntegrationFlows.from(messageSource, Consumer {options(it)})
+	flow.invoke(flowBuilder)
+	return flowBuilder.get()
+}
+

spring-integration-kotlin-dsl/src/test/kotlin/org/springframework/integration/dsl/kotlin/test/KotlinDslTests.kt

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl.kotlin.test
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
+import assertk.assertions.isNotNull
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.BeanFactory
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import org.springframework.integration.channel.QueueChannel
+import org.springframework.integration.config.EnableIntegration
+import org.springframework.integration.dsl.kotlin.convert
+import org.springframework.integration.dsl.kotlin.integrationFlow
+import org.springframework.integration.endpoint.MessageProcessorMessageSource
+import org.springframework.integration.support.MessageBuilder
+import org.springframework.messaging.MessageChannel
+import org.springframework.messaging.MessageHeaders
+import org.springframework.messaging.PollableChannel
+import org.springframework.test.annotation.DirtiesContext
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig
+import java.util.*
+import java.util.function.Function
+
+/**
+ * @author Artem Bilan
+ */
+@SpringJUnitConfig
+@DirtiesContext
+class KotlinDslTests {
+
+	@Autowired
+	private lateinit var beanFactory: BeanFactory
+
+	@Autowired
+	private lateinit var convertFlowInput: MessageChannel
+
+	@Test
+	fun `test convert extension`() {
+		assertThat(this.beanFactory.containsBean("kotlinConverter"))
+
+		val replyChannel = QueueChannel()
+		val date = Date()
+		val testMessage =
+				MessageBuilder.withPayload("{\"name\": \"Test\",\"date\": " + date.time + "}")
+						.setHeader(MessageHeaders.CONTENT_TYPE, "application/json")
+						.setReplyChannel(replyChannel)
+						.build()
+		this.convertFlowInput.send(testMessage)
+
+		assertThat(replyChannel.receive(10000)?.payload)
+				.isNotNull()
+				.isInstanceOf(TestPojo::class.java)
+				.isEqualTo(TestPojo("Test", date))
+	}
+
+	@Autowired
+	private lateinit var upperCaseFunction: Function<String, String>
+
+	@Test
+	fun `test uppercase function`() {
+		assertThat(this.upperCaseFunction.apply("test")).isEqualTo("TEST")
+	}
+
+	@Autowired
+	private lateinit var fromSupplierQueue: PollableChannel
+
+	@Test
+	fun `verify supplier flow`() {
+		assertThat(this.fromSupplierQueue.receive(10_000)).isNotNull()
+	}
+
+
+	@Configuration
+	@EnableIntegration
+	class Config {
+
+		@Bean
+		fun convertFlow() =
+				integrationFlow("convertFlowInput") {
+					it.convert<TestPojo>()
+							.convert<TestPojo> { it.id("kotlinConverter") }
+				}
+
+		@Bean
+		fun functionFlow() =
+				integrationFlow<Function<String, String>>({ it.beanName("functionGateway") }) {
+					it.transform<String, String> { it.toUpperCase() }
+				}
+
+		@Bean
+		fun messageSourceFlow() =
+				integrationFlow(MessageProcessorMessageSource { "testSource" },
+						{ it.poller { it.fixedDelay(10).maxMessagesPerPoll(1) } }) {
+					it.channel { c -> c.queue("fromSupplierQueue") }
+				}
+	}
+
+	data class TestPojo(val name: String?, val date: Date?)
+
+}

spring-integration-kotlin-dsl/src/test/resources/log4j2-test.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN">
+	<Appenders>
+		<Console name="STDOUT" target="SYSTEM_OUT">
+			<PatternLayout pattern="%d %p [%t] [%c] - %m%n" />
+		</Console>
+	</Appenders>
+	<Loggers>
+		<Logger name="org.springframework.integration" level="warn"/>
+		<Logger name="org.springframework.integration.dsl.kotlin" level="warn"/>
+		<Root level="warn">
+			<AppenderRef ref="STDOUT" />
+		</Root>
+	</Loggers>
+</Configuration>