Moves core/docs to root of project for compatibility

Resolves https://github.com/spring-cloud/spring-cloud-stream/issues/2312

docs/src/main/asciidoc/README.adoc

@@ -0,0 +1,27 @@
+:jdkversion: 17
+:github-tag: master
+:github-repo: spring-cloud/spring-cloud-stream
+
+:github-raw: https://raw.githubusercontent.com/{github-repo}/{github-tag}
+:github-code: https://github.com/{github-repo}/tree/{github-tag}
+
+image::https://circleci.com/gh/spring-cloud/spring-cloud-stream.svg?style=svg["CircleCI", link="https://circleci.com/gh/spring-cloud/spring-cloud-stream"]
+image::https://codecov.io/gh/spring-cloud/spring-cloud-stream/branch/{github-tag}/graph/badge.svg["codecov", link="https://codecov.io/gh/spring-cloud/spring-cloud-stream"]
+image::https://badges.gitter.im/spring-cloud/spring-cloud-stream.svg[Gitter, link="https://gitter.im/spring-cloud/spring-cloud-stream?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge"]
+
+// ======================================================================================
+
+== Introuduction
+include::intro.adoc[]
+
+== Resources
+
+For more information, please visit the https://spring.io/projects/spring-cloud-stream[project website]:
+
+== Building
+
+include::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/building.adoc[]
+
+== Contributing
+
+include::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing.adoc[]

docs/src/main/asciidoc/_configprops.adoc

@@ -0,0 +1,23 @@
+|===
+|Name | Default | Description
+
+|spring.cloud.stream.binders |  | Additional per-binder properties (see {@link BinderProperties}) if more then one binder of the same type is used (i.e., connect to multiple instances of RabbitMq). Here you can specify multiple binder configurations, each with different environment settings. For example; spring.cloud.stream.binders.rabbit1.environment. . . , spring.cloud.stream.binders.rabbit2.environment. . .
+|spring.cloud.stream.binding-retry-interval | `30` | Retry interval (in seconds) used to schedule binding attempts. Default: 30 sec.
+|spring.cloud.stream.bindings |  | Additional binding properties (see {@link BinderProperties}) per binding name (e.g., 'input`). For example; This sets the content-type for the 'input' binding of a Sink application: 'spring.cloud.stream.bindings.input.contentType=text/plain'
+|spring.cloud.stream.default-binder |  | The name of the binder to use by all bindings in the event multiple binders available (e.g., 'rabbit').
+|spring.cloud.stream.dynamic-destination-cache-size | `10` | The maximum size of Least Recently Used (LRU) cache of dynamic destinations. Once this size is reached, new destinations will trigger the removal of old destinations. Default: 10
+|spring.cloud.stream.dynamic-destinations | `[]` | A list of destinations that can be bound dynamically. If set, only listed destinations can be bound.
+|spring.cloud.stream.function.batch-mode | `false` | 
+|spring.cloud.stream.function.bindings |  | 
+|spring.cloud.stream.input-bindings |  | A semi-colon delimited string to explicitly define input bindings (specifically for cases when there is no implicit trigger to create such bindings such as Function, Supplier or Consumer).
+|spring.cloud.stream.instance-count | `1` | The number of deployed instances of an application. Default: 1. NOTE: Could also be managed per individual binding "spring.cloud.stream.bindings.foo.consumer.instance-count" where 'foo' is the name of the binding.
+|spring.cloud.stream.instance-index | `0` | The instance id of the application: a number from 0 to instanceCount-1. Used for partitioning and with Kafka. NOTE: Could also be managed per individual binding "spring.cloud.stream.bindings.foo.consumer.instance-index" where 'foo' is the name of the binding.
+|spring.cloud.stream.instance-index-list |  | A list of instance id's from 0 to instanceCount-1. Used for partitioning and with Kafka. NOTE: Could also be managed per individual binding "spring.cloud.stream.bindings.foo.consumer.instance-index-list" where 'foo' is the name of the binding. This setting will override the one set in 'spring.cloud.stream.instance-index'
+|spring.cloud.stream.integration.message-handler-not-propagated-headers |  | Message header names that will NOT be copied from the inbound message.
+|spring.cloud.stream.output-bindings |  | A semi-colon delimited string to explicitly define output bindings (specifically for cases when there is no implicit trigger to create such bindings such as Function, Supplier or Consumer).
+|spring.cloud.stream.override-cloud-connectors | `false` | This property is only applicable when the cloud profile is active and Spring Cloud Connectors are provided with the application. If the property is false (the default), the binder detects a suitable bound service (for example, a RabbitMQ service bound in Cloud Foundry for the RabbitMQ binder) and uses it for creating connections (usually through Spring Cloud Connectors). When set to true, this property instructs binders to completely ignore the bound services and rely on Spring Boot properties (for example, relying on the spring.rabbitmq.* properties provided in the environment for the RabbitMQ binder). The typical usage of this property is to be nested in a customized environment when connecting to multiple systems.
+|spring.cloud.stream.pollable-source | `none` | A semi-colon delimited list of binding names of pollable sources. Binding names follow the same naming convention as functions. For example, name '...pollable-source=foobar' will be accessible as 'foobar-iin-0'' binding
+|spring.cloud.stream.sendto.destination | `none` | The name of the header used to determine the name of the output destination
+|spring.cloud.stream.source |  | A semi-colon delimited string representing the names of the sources based on which source bindings will be created.  This is primarily to support cases where source binding may be required without providing a corresponding Supplier.  (e.g., for cases where the actual source of data is outside of scope of spring-cloud-stream - HTTP -> Stream)  @deprecated use {@link #outputBindings}
+
+|===

docs/src/main/asciidoc/binders.adoc

@@ -0,0 +1,16 @@
+*{spring-cloud-stream-version}*
+
+[[binders]]
+== Binder Implementations
+
+The following binder implementations are available:
+
+* https://cloud.spring.io/spring-cloud-stream-binder-rabbit/[RabbitMQ]
+* https://cloud.spring.io/spring-cloud-stream-binder-kafka/[Apache Kafka]
+* https://github.com/spring-cloud/spring-cloud-stream-binder-aws-kinesis[Amazon Kinesis]
+* https://github.com/spring-cloud/spring-cloud-gcp/tree/master/spring-cloud-gcp-pubsub-stream-binder[Google PubSub _(partner maintained)_]
+* https://github.com/SolaceProducts/spring-cloud-stream-binder-solace[Solace PubSub+ _(partner maintained)_]
+* https://github.com/Azure/azure-sdk-for-java/tree/master/sdk/spring/azure-spring-cloud-stream-binder-eventhubs [Azure Event Hubs _(partner maintained)_]
+* https://github.com/Azure/azure-sdk-for-java/tree/master/sdk/spring/azure-spring-cloud-stream-binder-servicebus-queue [Azure Service Bus Queue Binder _(partner maintained)_]
+* https://github.com/Azure/azure-sdk-for-java/tree/master/sdk/spring/azure-spring-cloud-stream-binder-servicebus-topic [Azure Service Bus Topic Binder _(partner maintained)_]
+* https://github.com/alibaba/spring-cloud-alibaba/wiki/RocketMQ-en[Apache RocketMQ _(partner maintained)_]

docs/src/main/asciidoc/ghpages.sh

@@ -0,0 +1,330 @@
+#!/bin/bash -x
+
+set -e
+
+# Set default props like MAVEN_PATH, ROOT_FOLDER etc.
+function set_default_props() {
+    # The script should be run from the root folder
+    ROOT_FOLDER=`pwd`
+    echo "Current folder is ${ROOT_FOLDER}"
+
+    if [[ ! -e "${ROOT_FOLDER}/.git" ]]; then
+        echo "You're not in the root folder of the project!"
+        exit 1
+    fi
+
+    # Prop that will let commit the changes
+    COMMIT_CHANGES="no"
+    MAVEN_PATH=${MAVEN_PATH:-}
+    echo "Path to Maven is [${MAVEN_PATH}]"
+    REPO_NAME=${PWD##*/}
+    echo "Repo name is [${REPO_NAME}]"
+    SPRING_CLOUD_STATIC_REPO=${SPRING_CLOUD_STATIC_REPO:-git@github.com:spring-cloud/spring-cloud-static.git}
+    echo "Spring Cloud Static repo is [${SPRING_CLOUD_STATIC_REPO}"
+}
+
+# Check if gh-pages exists and docs have been built
+function check_if_anything_to_sync() {
+    git remote set-url --push origin `git config remote.origin.url | sed -e 's/^git:/https:/'`
+
+    if ! (git remote set-branches --add origin gh-pages && git fetch -q); then
+        echo "No gh-pages, so not syncing"
+        exit 0
+    fi
+
+    if ! [ -d docs/target/generated-docs ] && ! [ "${BUILD}" == "yes" ]; then
+        echo "No gh-pages sources in docs/target/generated-docs, so not syncing"
+        exit 0
+    fi
+}
+
+function retrieve_current_branch() {
+    # Code getting the name of the current branch. For master we want to publish as we did until now
+    # https://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch
+    # If there is a branch already passed will reuse it - otherwise will try to find it
+    CURRENT_BRANCH=${BRANCH}
+    if [[ -z "${CURRENT_BRANCH}" ]] ; then
+      CURRENT_BRANCH=$(git symbolic-ref -q HEAD)
+      CURRENT_BRANCH=${CURRENT_BRANCH##refs/heads/}
+      CURRENT_BRANCH=${CURRENT_BRANCH:-HEAD}
+    fi
+    echo "Current branch is [${CURRENT_BRANCH}]"
+    git checkout ${CURRENT_BRANCH} || echo "Failed to check the branch... continuing with the script"
+}
+
+# Switches to the provided value of the release version. We always prefix it with `v`
+function switch_to_tag() {
+    git checkout v${VERSION}
+}
+
+# Build the docs if switch is on
+function build_docs_if_applicable() {
+    if [[ "${BUILD}" == "yes" ]] ; then
+        ./mvnw clean install -P docs -pl docs -DskipTests
+    fi
+}
+
+# Get the name of the `docs.main` property
+# Get allowed branches - assumes that a `docs` module is available under `docs` profile
+function retrieve_doc_properties() {
+    MAIN_ADOC_VALUE=$("${MAVEN_PATH}"mvn -q \
+        -Dexec.executable="echo" \
+        -Dexec.args='${docs.main}' \
+        --non-recursive \
+        org.codehaus.mojo:exec-maven-plugin:1.3.1:exec)
+    echo "Extracted 'main.adoc' from Maven build [${MAIN_ADOC_VALUE}]"
+
+
+    ALLOW_PROPERTY=${ALLOW_PROPERTY:-"docs.allowed.branches"}
+    ALLOWED_BRANCHES_VALUE=$("${MAVEN_PATH}"mvn -q \
+        -Dexec.executable="echo" \
+        -Dexec.args="\${${ALLOW_PROPERTY}}" \
+        org.codehaus.mojo:exec-maven-plugin:1.3.1:exec \
+        -P docs \
+        -pl docs)
+    echo "Extracted '${ALLOW_PROPERTY}' from Maven build [${ALLOWED_BRANCHES_VALUE}]"
+}
+
+# Stash any outstanding changes
+function stash_changes() {
+    git diff-index --quiet HEAD && dirty=$? || (echo "Failed to check if the current repo is dirty. Assuming that it is." && dirty="1")
+    if [ "$dirty" != "0" ]; then git stash; fi
+}
+
+# Switch to gh-pages branch to sync it with current branch
+function add_docs_from_target() {
+    local DESTINATION_REPO_FOLDER
+    if [[ -z "${DESTINATION}" && -z "${CLONE}" ]] ; then
+        DESTINATION_REPO_FOLDER=${ROOT_FOLDER}
+    elif [[ "${CLONE}" == "yes" ]]; then
+        mkdir -p ${ROOT_FOLDER}/target
+        local clonedStatic=${ROOT_FOLDER}/target/spring-cloud-static
+        if [[ ! -e "${clonedStatic}/.git" ]]; then
+            echo "Cloning Spring Cloud Static to target"
+            git clone ${SPRING_CLOUD_STATIC_REPO} ${clonedStatic} && git checkout gh-pages
+        else
+            echo "Spring Cloud Static already cloned - will pull changes"
+            cd ${clonedStatic} && git checkout gh-pages && git pull origin gh-pages
+        fi
+        DESTINATION_REPO_FOLDER=${clonedStatic}/${REPO_NAME}
+        mkdir -p ${DESTINATION_REPO_FOLDER}
+    else
+        if [[ ! -e "${DESTINATION}/.git" ]]; then
+            echo "[${DESTINATION}] is not a git repository"
+            exit 1
+        fi
+        DESTINATION_REPO_FOLDER=${DESTINATION}/${REPO_NAME}
+        mkdir -p ${DESTINATION_REPO_FOLDER}
+        echo "Destination was provided [${DESTINATION}]"
+    fi
+    cd ${DESTINATION_REPO_FOLDER}
+    git checkout gh-pages
+    git pull origin gh-pages
+
+    # Add git branches
+    ###################################################################
+    if [[ -z "${VERSION}" ]] ; then
+        copy_docs_for_current_version
+    else
+        copy_docs_for_provided_version
+    fi
+    commit_changes_if_applicable
+}
+
+
+# Copies the docs by using the retrieved properties from Maven build
+function copy_docs_for_current_version() {
+    if [[ "${CURRENT_BRANCH}" == "master" ]] ; then
+        echo -e "Current branch is master - will copy the current docs only to the root folder"
+        for f in docs/target/generated-docs/*; do
+            file=${f#docs/target/generated-docs/*}
+            if ! git ls-files -i -o --exclude-standard --directory | grep -q ^$file$; then
+                # Not ignored...
+                cp -rf $f ${ROOT_FOLDER}/
+                git add -A ${ROOT_FOLDER}/$file
+            fi
+        done
+        COMMIT_CHANGES="yes"
+    else
+        echo -e "Current branch is [${CURRENT_BRANCH}]"
+        # https://stackoverflow.com/questions/29300806/a-bash-script-to-check-if-a-string-is-present-in-a-comma-separated-list-of-strin
+        if [[ ",${ALLOWED_BRANCHES_VALUE}," = *",${CURRENT_BRANCH},"* ]] ; then
+            mkdir -p ${ROOT_FOLDER}/${CURRENT_BRANCH}
+            echo -e "Branch [${CURRENT_BRANCH}] is allowed! Will copy the current docs to the [${CURRENT_BRANCH}] folder"
+            for f in docs/target/generated-docs/*; do
+                file=${f#docs/target/generated-docs/*}
+                if ! git ls-files -i -o --exclude-standard --directory | grep -q ^$file$; then
+                    # Not ignored...
+                    # We want users to access 2.0.0.BUILD-SNAPSHOT/ instead of 1.0.0.RELEASE/spring-cloud.sleuth.html
+                    if [[ "${file}" == "${MAIN_ADOC_VALUE}.html" ]] ; then
+                        # We don't want to copy the spring-cloud-sleuth.html
+                        # we want it to be converted to index.html
+                        cp -rf $f ${ROOT_FOLDER}/${CURRENT_BRANCH}/index.html
+                        git add -A ${ROOT_FOLDER}/${CURRENT_BRANCH}/index.html
+                    else
+                        cp -rf $f ${ROOT_FOLDER}/${CURRENT_BRANCH}
+                        git add -A ${ROOT_FOLDER}/${CURRENT_BRANCH}/$file
+                    fi
+                fi
+            done
+            COMMIT_CHANGES="yes"
+        else
+            echo -e "Branch [${CURRENT_BRANCH}] is not on the allow list! Check out the Maven [${ALLOW_PROPERTY}] property in
+             [docs] module available under [docs] profile. Won't commit any changes to gh-pages for this branch."
+        fi
+    fi
+}
+
+# Copies the docs by using the explicitly provided version
+function copy_docs_for_provided_version() {
+    local FOLDER=${DESTINATION_REPO_FOLDER}/${VERSION}
+    mkdir -p ${FOLDER}
+    echo -e "Current tag is [v${VERSION}] Will copy the current docs to the [${FOLDER}] folder"
+    for f in ${ROOT_FOLDER}/docs/target/generated-docs/*; do
+        file=${f#${ROOT_FOLDER}/docs/target/generated-docs/*}
+        copy_docs_for_branch ${file} ${FOLDER}
+    done
+    COMMIT_CHANGES="yes"
+    CURRENT_BRANCH="v${VERSION}"
+}
+
+# Copies the docs from target to the provided destination
+# Params:
+# $1 - file from target
+# $2 - destination to which copy the files
+function copy_docs_for_branch() {
+    local file=$1
+    local destination=$2
+    if ! git ls-files -i -o --exclude-standard --directory | grep -q ^${file}$; then
+        # Not ignored...
+        # We want users to access 2.0.0.BUILD-SNAPSHOT/ instead of 1.0.0.RELEASE/spring-cloud.sleuth.html
+        if [[ ("${file}" == "${MAIN_ADOC_VALUE}.html") || ("${file}" == "${REPO_NAME}.html") ]] ; then
+            # We don't want to copy the spring-cloud-sleuth.html
+            # we want it to be converted to index.html
+            cp -rf $f ${destination}/index.html
+            git add -A ${destination}/index.html
+        else
+            cp -rf $f ${destination}
+            git add -A ${destination}/$file
+        fi
+    fi
+}
+
+function commit_changes_if_applicable() {
+    if [[ "${COMMIT_CHANGES}" == "yes" ]] ; then
+        COMMIT_SUCCESSFUL="no"
+        git commit -a -m "Sync docs from ${CURRENT_BRANCH} to gh-pages" && COMMIT_SUCCESSFUL="yes" || echo "Failed to commit changes"
+
+        # Uncomment the following push if you want to auto push to
+        # the gh-pages branch whenever you commit to master locally.
+        # This is a little extreme. Use with care!
+        ###################################################################
+        if [[ "${COMMIT_SUCCESSFUL}" == "yes" ]] ; then
+            git push origin gh-pages
+        fi
+    fi
+}
+
+# Switch back to the previous branch and exit block
+function checkout_previous_branch() {
+    # If -version was provided we need to come back to root project
+    cd ${ROOT_FOLDER}
+    git checkout ${CURRENT_BRANCH} || echo "Failed to check the branch... continuing with the script"
+    if [ "$dirty" != "0" ]; then git stash pop; fi
+    exit 0
+}
+
+# Assert if properties have been properly passed
+function assert_properties() {
+echo "VERSION [${VERSION}], DESTINATION [${DESTINATION}], CLONE [${CLONE}]"
+if [[ "${VERSION}" != "" && (-z "${DESTINATION}" && -z "${CLONE}") ]] ; then echo "Version was set but destination / clone was not!"; exit 1;fi
+if [[ ("${DESTINATION}" != "" && "${CLONE}" != "") && -z "${VERSION}" ]] ; then echo "Destination / clone was set but version was not!"; exit 1;fi
+if [[ "${DESTINATION}" != "" && "${CLONE}" == "yes" ]] ; then echo "Destination and clone was set. Pick one!"; exit 1;fi
+}
+
+# Prints the usage
+function print_usage() {
+cat <<EOF
+The idea of this script is to update gh-pages branch with the generated docs. Without any options
+the script will work in the following manner:
+
+- if there's no gh-pages / target for docs module then the script ends
+- for master branch the generated docs are copied to the root of gh-pages branch
+- for any other branch (if that branch is allowed) a subfolder with branch name is created
+    and docs are copied there
+- if the version switch is passed (-v) then a tag with (v) prefix will be retrieved and a folder
+    with that version number will be created in the gh-pages branch. WARNING! No allow verification will take place
+- if the destination switch is passed (-d) then the script will check if the provided dir is a git repo and then will
+    switch to gh-pages of that repo and copy the generated docs to `docs/<project-name>/<version>`
+- if the destination switch is passed (-d) then the script will check if the provided dir is a git repo and then will
+    switch to gh-pages of that repo and copy the generated docs to `docs/<project-name>/<version>`
+
+USAGE:
+
+You can use the following options:
+
+-v|--version        - the script will apply the whole procedure for a particular library version
+-d|--destination    - the root of destination folder where the docs should be copied. You have to use the full path.
+                        E.g. point to spring-cloud-static folder. Can't be used with (-c)
+-b|--build          - will run the standard build process after checking out the branch
+-c|--clone          - will automatically clone the spring-cloud-static repo instead of providing the destination.
+                        Obviously can't be used with (-d)
+
+EOF
+}
+
+
+# ==========================================
+#    ____   ____ _____  _____ _____ _______
+#  / ____|/ ____|  __ \|_   _|  __ \__   __|
+# | (___ | |    | |__) | | | | |__) | | |
+#  \___ \| |    |  _  /  | | |  ___/  | |
+#  ____) | |____| | \ \ _| |_| |      | |
+# |_____/ \_____|_|  \_\_____|_|      |_|
+#
+# ==========================================
+
+while [[ $# > 0 ]]
+do
+key="$1"
+case ${key} in
+    -v|--version)
+    VERSION="$2"
+    shift # past argument
+    ;;
+    -d|--destination)
+    DESTINATION="$2"
+    shift # past argument
+    ;;
+    -b|--build)
+    BUILD="yes"
+    ;;
+    -c|--clone)
+    CLONE="yes"
+    ;;
+    -h|--help)
+    print_usage
+    exit 0
+    ;;
+    *)
+    echo "Invalid option: [$1]"
+    print_usage
+    exit 1
+    ;;
+esac
+shift # past argument or value
+done
+
+assert_properties
+set_default_props
+check_if_anything_to_sync
+if [[ -z "${VERSION}" ]] ; then
+    retrieve_current_branch
+else
+    switch_to_tag
+fi
+build_docs_if_applicable
+retrieve_doc_properties
+stash_changes
+add_docs_from_target
+checkout_previous_branch

docs/src/main/asciidoc/index.adoc

@@ -0,0 +1,25 @@
+= Spring Cloud Stream Reference Documentation
+Sabby Anandan; Marius Bogoevici; Eric Bottard; Mark Fisher; Ilayaperumal Gopinathan; Mark Heckler; Gunnar Hillert; Mark Pollack; Patrick Peralta; Glenn Renfro; Thomas Risberg; Dave Syer; David Turanski; Janne Valkealahti; Benjamin Klein; Vinicius Carvalho; Gary Russell; Oleg Zhurakousky; Jay Bryant; Soby Chacko; Domenico Sibilio
+
+*{project-version}*
+
+:docinfo: shared
+
+The reference documentation consists of the following sections:
+
+[horizontal]
+<<spring-cloud-stream.adoc#spring-cloud-stream-reference,Overview>> :: History, Quick Start, Concepts, Architecture Overview, Binder Abstraction, and Core Features
+
+https://docs.spring.io/spring-cloud-stream-binder-rabbit/docs/{project-version}/reference/html/spring-cloud-stream-binder-rabbit.html[Rabbit MQ Binder] :: Spring Cloud Stream binder reference for Rabbit MQ
+https://docs.spring.io/spring-cloud-stream-binder-kafka/docs/{project-version}/reference/html/spring-cloud-stream-binder-kafka.html#_apache_kafka_binder[Apache Kafka Binder] :: Spring Cloud Stream binder reference for Apache Kafka
+https://docs.spring.io/spring-cloud-stream-binder-kafka/docs/{project-version}/reference/html/spring-cloud-stream-binder-kafka.html#_kafka_streams_binder[Apache Kafka Streams Binder] :: Spring Cloud Stream binder reference for Apache Kafka Streams
+<<binders.adoc#binders,Additional Binders>> :: A collection of Partner maintained binder implementations for Spring Cloud Stream (e.g., Azure Event Hubs, Google PubSub, Solace PubSub+)
+https://github.com/spring-cloud/spring-cloud-stream-samples/[Spring Cloud Stream Samples]  :: A curated collection of repeatable Spring Cloud Stream samples to walk through the features
+
+Relevant Links:
+
+[horizontal]
+https://cloud.spring.io/spring-cloud-dataflow/[Spring Cloud Data Flow] :: Spring Cloud Data Flow
+http://www.enterpriseintegrationpatterns.com/[Enterprise Integration Patterns]  :: Patterns and Best Practices for Enterprise Integration
+https://spring.io/projects/spring-integration[Spring Integration]  :: Spring Integration framework
+

docs/src/main/asciidoc/intro.adoc

@@ -0,0 +1,69 @@
+Spring Cloud Stream is a framework for building message-driven microservice applications.
+Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications and uses Spring Integration to provide connectivity to message brokers.
+It provides opinionated configuration of middleware from several vendors, introducing the concepts of persistent publish-subscribe semantics, consumer groups, and partitions.
+These are called binder implementations in the parlance of Spring Cloud Stream.
+Out of the box, Spring Cloud Stream provides binder implementations for Apache Kafka and RabbitMQ.
+While these two binder implementations are based on Message Channels, Spring Cloud Stream also provides another binder implementation for Kafka Streams that does not use message channels, but native Kafka Streams types such as KStream, KTable etc.
+
+Below, you can find more information on how to use these various out-of-the-box binder implementations in your applications.
+
+== Apache Kafka Binder
+
+=== Usage
+
+To use Apache Kafka binder, you need to add `spring-cloud-stream-binder-kafka` as a dependency to your Spring Cloud Stream application, as shown in the following example for Maven:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.cloud</groupId>
+  <artifactId>spring-cloud-stream-binder-kafka</artifactId>
+</dependency>
+----
+
+Alternatively, you can also use the Spring Cloud Stream Kafka Starter, as shown in the following example for Maven:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.cloud</groupId>
+  <artifactId>spring-cloud-starter-stream-kafka</artifactId>
+</dependency>
+----
+
+== Apache Kafka Streams Binder
+
+=== Usage
+
+To use Apache Kafka Streams binder, you need to add `spring-cloud-stream-binder-kafka-streams` as a dependency to your Spring Cloud Stream application, as shown in the following example for Maven:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.cloud</groupId>
+  <artifactId>spring-cloud-stream-binder-kafka-streams</artifactId>
+</dependency>
+----
+
+== RabbitMQ Binder
+=== Usage
+
+To use the RabbitMQ binder, you can add it to your Spring Cloud Stream application, by using the following Maven coordinates:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.cloud</groupId>
+  <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+</dependency>
+----
+
+Alternatively, you can use the Spring Cloud Stream RabbitMQ Starter, as follows:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.cloud</groupId>
+  <artifactId>spring-cloud-starter-stream-rabbit</artifactId>
+</dependency>
+----

docs/src/main/asciidoc/preface.adoc

@@ -0,0 +1,186 @@
+=== A Brief History of Spring's Data Integration Journey
+
+Spring's journey on Data Integration started with https://projects.spring.io/spring-integration/[Spring Integration]. With its programming model, it provided a consistent developer experience to build applications that can embrace http://www.enterpriseintegrationpatterns.com/[Enterprise Integration Patterns] to connect with external systems such as, databases, message brokers, and among others.
+
+Fast forward to the cloud-era, where microservices have become prominent in the enterprise setting. https://projects.spring.io/spring-boot/[Spring Boot] transformed the way how developers built Applications. With Spring's programming model and the runtime responsibilities handled by Spring Boot, it became seamless to develop stand-alone, production-grade Spring-based microservices.
+
+To extend this to Data Integration workloads, Spring Integration and Spring Boot were put together into a new project. Spring Cloud Stream was born.
+
+[%hardbreaks]
+With Spring Cloud Stream, developers can:
+
+- Build, test and deploy data-centric applications in isolation.
+- Apply modern microservices architecture patterns, including composition through messaging.
+- Decouple application responsibilities with event-centric thinking. An event can represent something that has happened in time, to which the downstream consumer applications can react without knowing where it originated or the producer's identity.
+- Port the business logic onto message brokers (such as RabbitMQ, Apache Kafka, Amazon Kinesis).
+- Rely on the framework's automatic content-type support for common use-cases. Extending to different data conversion types is possible.
+- and many more. . .
+
+=== Quick Start
+
+You can try Spring Cloud Stream in less than 5 min even before you jump into any details by following this three-step guide.
+
+We show you how to create a Spring Cloud Stream application that receives messages coming from the messaging middleware of your choice (more on this later) and logs received messages to the console.
+We call it `LoggingConsumer`.
+While not very practical, it provides a good introduction to some of the main concepts
+and abstractions, making it easier to digest the rest of this user guide.
+
+The three steps are as follows:
+
+. <<spring-cloud-stream-preface-creating-sample-application>>
+. <<spring-cloud-stream-preface-importing-project>>
+. <<spring-cloud-stream-preface-adding-message-handler>>
+
+[[spring-cloud-stream-preface-creating-sample-application]]
+==== Creating a Sample Application by Using Spring Initializr
+To get started, visit the https://start.spring.io[Spring Initializr]. From there, you can generate our `LoggingConsumer` application. To do so:
+
+. In the *Dependencies* section, start typing `stream`.
+When the "`Cloud Stream`" option should appears, select it.
+. Start typing either 'kafka' or 'rabbit'.
+. Select "`Kafka`" or "`RabbitMQ`".
++
+Basically, you choose the messaging middleware to which your application binds.
+We recommend using the one you have already installed or feel more comfortable with installing and running.
+Also, as you can see from the Initilaizer screen, there are a few other options you can choose.
+For example, you can choose Gradle as your build tool instead of Maven (the default).
+. In the *Artifact* field, type 'logging-consumer'.
++
+The value of the *Artifact* field becomes the application name.
+If you chose RabbitMQ for the middleware, your Spring Initializr should now be as follows:
+
+[%hardbreaks]
+[%hardbreaks]
+[%hardbreaks]
+image::/docs/src/main/asciidoc/images/spring-initializr.png[align="center"]
+
+[%hardbreaks]
+[%hardbreaks]
+
+. Click the *Generate Project* button.
++
+Doing so downloads the zipped version of the generated project to your hard drive.
+. Unzip the file into the folder you want to use as your project directory.
+
+TIP: We encourage you to explore the many possibilities available in the Spring Initializr.
+It lets you create many different kinds of Spring applications.
+
+[[spring-cloud-stream-preface-importing-project]]
+==== Importing the Project into Your IDE
+
+Now you can import the project into your IDE.
+Keep in mind that, depending on the IDE, you may need to follow a specific import procedure.
+For example, depending on how the project was generated (Maven or Gradle), you may need to follow specific import procedure (for example, in Eclipse or STS, you need to use File -> Import -> Maven -> Existing Maven Project).
+
+Once imported, the project must have no errors of any kind. Also, `src/main/java` should contain `com.example.loggingconsumer.LoggingConsumerApplication`.
+
+Technically, at this point, you can run the application's main class.
+It is already a valid Spring Boot application.
+However, it does not do anything, so we want to add some code.
+
+[[spring-cloud-stream-preface-adding-message-handler]]
+==== Adding a Message Handler, Building, and Running
+
+Modify the `com.example.loggingconsumer.LoggingConsumerApplication` class to look as follows:
+
+[source, java]
+----
+@SpringBootApplication
+public class LoggingConsumerApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(LoggingConsumerApplication.class, args);
+	}
+
+	@Bean
+	public Consumer<Person> log() {
+	    return person -> {
+	        System.out.println("Received: " + person);
+	    };
+	}
+
+	public static class Person {
+		private String name;
+		public String getName() {
+			return name;
+		}
+		public void setName(String name) {
+			this.name = name;
+		}
+		public String toString() {
+			return this.name;
+		}
+	}
+}
+----
+
+As you can see from the preceding listing:
+
+* We are using functional programming model (see <<Spring Cloud Function support>>) to define a single message handler as `Consumer`.
+* We are relying on framework conventions to bind such handler to the input destination binding exposed by the binder.
+
+Doing so also lets you see one of the core features of the framework: It tries to automatically convert incoming message payloads to type `Person`.
+
+You now have a fully functional Spring Cloud Stream application that does listens for messages.
+From here, for simplicity, we assume you selected RabbitMQ in <<spring-cloud-stream-preface-creating-sample-application,step one>>.
+Assuming you have RabbitMQ installed and running, you can start the application by running its `main` method in your IDE.
+
+You should see following output:
+
+[source]
+----
+	--- [ main] c.s.b.r.p.RabbitExchangeQueueProvisioner : declaring queue for inbound: input.anonymous.CbMIwdkJSBO1ZoPDOtHtCg, bound to: input
+	--- [ main] o.s.a.r.c.CachingConnectionFactory       : Attempting to connect to: [localhost:5672]
+	--- [ main] o.s.a.r.c.CachingConnectionFactory       : Created new connection: rabbitConnectionFactory#2a3a299:0/SimpleConnection@66c83fc8. . .
+	. . .
+	--- [ main] o.s.i.a.i.AmqpInboundChannelAdapter      : started inbound.input.anonymous.CbMIwdkJSBO1ZoPDOtHtCg
+	. . .
+	--- [ main] c.e.l.LoggingConsumerApplication         : Started LoggingConsumerApplication in 2.531 seconds (JVM running for 2.897)
+----
+
+Go to the RabbitMQ management console or any other RabbitMQ client and send a message to `input.anonymous.CbMIwdkJSBO1ZoPDOtHtCg`.
+The `anonymous.CbMIwdkJSBO1ZoPDOtHtCg` part represents the group name and is generated, so it is bound to be different in your environment.
+For something more predictable, you can use an explicit group name by setting `spring.cloud.stream.bindings.input.group=hello` (or whatever name you like).
+
+The contents of the message should be a JSON representation of the `Person` class, as follows:
+
+	{"name":"Sam Spade"}
+
+Then, in your console, you should see:
+
+`Received: Sam Spade`
+
+You can also build and package your application into a boot jar (by using `./mvnw clean install`) and run the built JAR by using the `java -jar` command.
+
+Now you have a working (albeit very basic) Spring Cloud Stream application.
+
+
+[[spring-cloud-stream-preface-notable-deprecations]]
+== Notable Deprecations
+
+- Annotation-based programming model. Basically the @EnableBInding, @StreamListener and all related annotations are now deprecated in 
+favor of the functional programming model. See <<Spring Cloud Function support>> for more details.
+- _Reactive module_ (`spring-cloud-stream-reactive`) is discontinued and no longer distributed in favor of native support via spring-cloud-function.
+For backward
+compatibility you can still bring `spring-cloud-stream-reactive` from previous versions.
+- _Test support binder_ `spring-cloud-stream-test-support` with MessageCollector in favor of a new test binder. See <<Testing>> for more details.
+- _@StreamMessageConverter_ - deprecated as it is no longer required.
+- The `original-content-type` header references have been removed after it's been deprecated in v2.0.
+- The `BinderAwareChannelResolver` is deprecated in favor if providing `spring.cloud.stream.sendto.destination` property.
+This is primarily for function-based programming model. For StreamListener it would still be required and thus will stay until we deprecate and eventually discontinue StreamListener
+and annotation-based programming model.
+
+[[spel-and-streaming-data]]
+
+== Spring Expression Language (SpEL) in the context of Streaming data
+
+Throughout this reference manual you will encounter many features and examples where you can utilize Spring Expression Language (SpEL). It is important to understand certain limitations when it comes to using it.
+
+SpEL gives you access to the current Message as well as the Application Context you are running in. 
+However it is important to understand what type of data SpEL can see especially in the context of the incoming Message.
+From the broker, the message arrives in a form of a byte[]. It is then transformed to a `Message<byte[]>` by the binders where as you can see the payload of the message maintains its raw form. The headers of the message are `<String, Object>`, where values are typically another primitive or a collection/array of primitives, hence Object.
+That is because binder does not know the required input type as it has no access to the user code (function). So effectively binder delivered an envelope with the payload and some readable meta-data in the form of message headers, just like the letter delivered by mail. 
+This means that while accessing payload of the message is possible you will only have access to it as raw data (i.e., byte[]). And while it may be very common for developers to ask for ability to have SpEL access to fields of a payload object as concrete type (e.g., Foo, Bar etc), you can see how difficult or even impossible would it be to achieve. 
+Here is one example to demonstrate the problem; Imagine you have a routing expression to route to different functions based on payload type. This requirement would imply payload conversion from byte[] to a specific type and then applying the SpEL. However, in order to perform such conversion we would need to know the actual type to pass to converter and that comes from function's signature which we don’t know which one. A better approach to solve this requirement would be to pass the type information as message headers (e.g., `application/json;type=foo.bar.Baz` ). You’ll get a clear readable String value that could be accessed and evaluated in a year and easy to read SpEL expression.
+
+Additionally it is considered very bad practice to use payload for routing decisions, since the payload is considered to be privileged data - data only to be read by its final recipient. Again, using the mail delivery analogy you would not want the mailman to open your envelope and read the contents of the letter to make some delivery decisions. The same concept applies here, especially when it is relatively easy to include such information when generating a Message. It enforces certain level of discipline related to the design of data to be transmitted over the network and which pieces of such data can be considered as public and which are privileged. 

docs/src/main/asciidoc/sagan-index.adoc

@@ -0,0 +1,25 @@
+Spring Cloud Stream is a framework for building highly scalable event-driven microservices connected with shared messaging systems.
+
+The framework provides a flexible programming model built on already established and familiar Spring idioms and best practices, including support
+for persistent pub/sub semantics, consumer groups, and stateful partitions.
+
+## Binder Implementations
+
+Spring Cloud Stream supports a variety of binder implementations and the following table includes the link to the GitHub projects.
+
+* https://github.com/spring-cloud/spring-cloud-stream-binder-rabbit[RabbitMQ]
+* https://github.com/spring-cloud/spring-cloud-stream-binder-kafka[Apache Kafka]
+* https://github.com/spring-cloud/spring-cloud-stream-binder-kafka/tree/master/spring-cloud-stream-binder-kafka-streams[Kafka Streams]
+* https://github.com/spring-cloud/spring-cloud-stream-binder-aws-kinesis[Amazon Kinesis]
+* https://github.com/GoogleCloudPlatform/spring-cloud-gcp/tree/main/spring-cloud-gcp-pubsub-stream-binder[Google PubSub _(partner maintained)_]
+* https://github.com/SolaceProducts/spring-cloud-stream-binder-solace[Solace PubSub+ _(partner maintained)_]
+* https://github.com/microsoft/spring-cloud-azure/tree/master/spring-cloud-azure-stream-binder/spring-cloud-azure-eventhubs-stream-binder[Azure Event Hubs _(partner maintained)_]
+* https://github.com/alibaba/spring-cloud-alibaba/wiki/RocketMQ-en[Apache RocketMQ _(partner maintained)_]
+
+The core building blocks of Spring Cloud Stream are:
+
+* *Destination Binders*: Components responsible to provide integration with the external messaging systems.
+* *Destination Bindings*: Bridge between the external messaging systems and application provided Producers and Consumers of messages (created by the Destination Binders).
+* *Message*: The canonical data structure used by producers and consumers to communicate with Destination Binders (and thus other applications via external messaging systems).
+
+

docs/src/main/ruby/generate_readme.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env ruby
+
+base_dir = File.join(File.dirname(__FILE__),'../../..')
+src_dir = File.join(base_dir, "/src/main/asciidoc")
+require 'asciidoctor'
+require 'optparse'
+
+options = {}
+file = "#{src_dir}/README.adoc"
+
+OptionParser.new do |o|
+  o.on('-o OUTPUT_FILE', 'Output file (default is stdout)') { |file| options[:to_file] = file unless file=='-' }
+  o.on('-h', '--help') { puts o; exit }
+  o.parse!
+end
+
+file = ARGV[0] if ARGV.length>0
+
+# Copied from https://github.com/asciidoctor/asciidoctor-extensions-lab/blob/master/scripts/asciidoc-coalescer.rb
+doc = Asciidoctor.load_file file, safe: :unsafe, header_only: true, attributes: options[:attributes]
+header_attr_names = (doc.instance_variable_get :@attributes_modified).to_a
+header_attr_names.each {|k| doc.attributes[%(#{k}!)] = '' unless doc.attr? k }
+attrs = doc.attributes
+attrs['allow-uri-read'] = true
+puts attrs
+
+out = "// Do not edit this file (e.g. go instead to src/main/asciidoc)\n\n"
+doc = Asciidoctor.load_file file, safe: :unsafe, parse: false, attributes: attrs
+out << doc.reader.read
+
+unless options[:to_file]
+  puts out
+else
+  File.open(options[:to_file],'w+') do |file|
+    file.write(out)
+  end
+end