Example realworldapp backend (#737)

* WIP initial implementation, User crud, half Article crud

* WIP more article crud (update, complete fav/unfav) some refactor

* WIP various bugfixes, making responses compatible with API

* WIP finished articles + comments + tags crud. not bug checked though

* minimal bugfix, added waitFor and refresh to post and delete methods

* minor refactor, WIP documentation, added license

* major refactor, added validation to user controller, WIP testcontainer unit test example

* working testcontainer unit test

* the rest of the test

* style refactor, more documentation

* fully documented user service, linting

* code style

* code style, a e s t e t h i c s

* quick bug fixes

* putting java instant directly into db

* logic optimizations, hashing passwords

* fixed unit test

* more documentation

* finished documenting methods, added README.md, set up gradle correctly, minor refactors

* fixed readme, added license to all files

* fixed readme

* feed follow fix, shortened comment id

examples/realworld-app/README.md

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+# ![RealWorld Example App](rw-logo.png)
+
+> ### Spring Boot + Elasticsearch codebase containing real world examples (CRUD, auth, advanced patterns, etc) that adheres to the [RealWorld](https://github.com/gothinkster/realworld) spec and API
+
+### [RealWorld](https://github.com/gothinkster/realworld)
+
+This codebase was created to demonstrate a fully fledged fullstack application built with **Java + Spring Boot +
+Elasticsearch** including CRUD operations, authentication, routing, pagination, and more.
+
+We've gone to great lengths to adhere to the **Java + Spring Boot + Elasticsearch** community styleguides & best
+practices.
+
+For more information on how to this works with other frontends/backends, head over to
+the [RealWorld](https://github.com/gothinkster/realworld) repo.
+
+# How it works
+
+The application was made mainly demonstrate the
+new [Elasticsearch Java API Client](https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/current/index.html).
+
+The application was built with:
+
+- [Java](https://www.java.com/en/) as programming language
+- [Spring Boot](https://spring.io/projects/spring-boot) as dependency injection framework
+- [Gradle](https://github.com/gradle/gradle) as build tool
+- [Elasticsearch](https://github.com/elastic/elasticsearch) as database
+- [Jackson](https://github.com/FasterXML/jackson-core) as data bind serialization/deserialization
+- [Java JWT](https://github.com/jwtk/jjwt) for JWT implementation
+- [Jaxb](https://github.com/jakartaee/jaxb-api) for JWT parsing
+- [Slugify](https://github.com/slugify/slugify) for slug
+
+Tests:
+
+- [Junit](https://github.com/junit-team/junit4)
+- [Testcontainers](https://github.com/testcontainers) to create an Elasticsearch instance
+
+#### Structure
+
+This is a multimodule gradle project:
+
+- rw-database
+    - Elasticsearch client connection, queries, document classes
+- rw-rest
+    - Spring rest controllers
+- rw-server
+    - Configuration and entrypoint. Main class: [SpringBootApp.java](rw-server/src/main/java/realworld/SpringBootApp.java)
+
+# Getting started
+
+#### JVM
+
+A version of the JVM has to be installed, openjdk version "21.0.2" was used during development.
+
+#### Elasticsearch
+
+An Elasticsearch instance needs to be running for the application to start successfully.
+To start one easily, a [docker-compose](docker-compose.yaml) is provided, it will start Elasticsearch on port 9200 and
+Kibana on [5601](http://localhost:5601/app/home#/); otherwise, the connection properties can be changed in [application.properties](rw-server/src/main/resources/application.properties).
+
+### Build:
+
+> ./gradlew clean build
+
+#### Start the server:
+
+> ./gradlew run
+
+#### Run
+
+The application will start on [8080](http://localhost:8080/api) with `api` context, it can be changed
+in [application.properties](rw-server/src/main/resources/application.properties).
+
+### Unit tests
+
+A basic [unit test](rw-database/src/test/java/realworld/db/UserServiceTest.java) using testcontainer (docker is
+required).

examples/realworld-app/build.gradle

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+plugins {
+  id 'java'
+  id 'org.springframework.boot' version '3.2.1'
+  id 'io.spring.dependency-management' version '1.1.4'
+  id 'application'
+}
+
+group = 'realworldapp'
+version = '0.0.1-SNAPSHOT'
+
+java {
+  sourceCompatibility = '21'
+}
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  implementation('org.springframework.boot:spring-boot-starter-parent:3.2.0')
+  implementation('realworldapp:rw-server')
+}
+
+mainClassName = 'rw-server/src/main/java/realworld/SpringBootApp.java'
+

examples/realworld-app/docker-compose.yaml

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+services:
+  es:
+    image: docker.elastic.co/elasticsearch/elasticsearch:8.11.1
+    container_name: es
+    environment:
+      "discovery.type": "single-node"
+      "xpack.security.enabled": "false"
+      "xpack.security.http.ssl.enabled": "false"
+    ports:
+      - "9200:9200"
+    networks:
+      - elastic
+  kibana:
+    image: docker.elastic.co/kibana/kibana:8.7.1
+    container_name: kibana
+    environment:
+      XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY: d1a66dfd-c4d3-4a0a-8290-2abcb83ab3aa
+    ports:
+      - 5601:5601
+    networks:
+      - elastic
+    deploy:
+      resources:
+        limits:
+          cpus: '2.0'
+        reservations:
+          cpus: '1.0'
+networks:
+  elastic:

examples/realworld-app/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

examples/realworld-app/gradlew

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+#!/bin/sh
+
+#
+# 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.
+# 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 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/HEAD/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
+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
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&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  ;; #(
+  MSYS* | 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: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( 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
+    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
+        # 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
+fi
+
+
+# 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"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+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.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"