added example Spring Boot Starter

spring-boot/starter/application/application.yml

@@ -0,0 +1,4 @@
+eventstarter:
+  listener:
+    enabled-events:
+      - foo

spring-boot/starter/application/build.gradle

@@ -0,0 +1,22 @@
+plugins {
+	id 'org.springframework.boot' version '2.1.7.RELEASE'
+	id 'io.spring.dependency-management' version '1.0.8.RELEASE'
+	id 'java'
+}
+
+group = 'io.reflectoring'
+version = '0.0.1-SNAPSHOT'
+sourceCompatibility = '11'
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation project(':event-starter')
+	implementation 'org.springframework.boot:spring-boot-starter-web'
+	testImplementation 'org.springframework.boot:spring-boot-starter-test'
+
+	compileOnly('org.projectlombok:lombok:1.18.2')
+	annotationProcessor 'org.projectlombok:lombok:1.18.2'
+}

spring-boot/starter/application/src/main/java/io/reflectoring/starter/EventGenerator.java

@@ -0,0 +1,21 @@
+package io.reflectoring.starter;
+
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+@Component
+class EventGenerator {
+
+	private final EventPublisher eventPublisher;
+
+	public EventGenerator(EventPublisher eventPublisher) {
+		this.eventPublisher = eventPublisher;
+	}
+
+	@Scheduled(fixedRate = 2000)
+	void generateEvent() {
+		Event event = new Event("foo", "This is a foo event");
+		eventPublisher.publishEvent(event);
+	}
+
+}

spring-boot/starter/application/src/main/java/io/reflectoring/starter/FooEventListener.java

@@ -0,0 +1,23 @@
+package io.reflectoring.starter;
+
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
+
+@Slf4j
+@Component
+class FooEventListener extends EventListener {
+
+	public FooEventListener(EventListenerProperties properties) {
+		super(properties);
+	}
+
+	@Override
+	public String getSubscribedEventType() {
+		return "foo";
+	}
+
+	@Override
+	public void onEvent(Event event) {
+		log.info("received event {}", event);
+	}
+}

spring-boot/starter/application/src/main/java/io/reflectoring/starter/StarterApplication.java

@@ -0,0 +1,15 @@
+package io.reflectoring.starter;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.scheduling.annotation.EnableScheduling;
+
+@SpringBootApplication
+@EnableScheduling
+public class StarterApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(StarterApplication.class, args);
+	}
+
+}

spring-boot/starter/application/src/main/resources/application.properties

@@ -0,0 +1,2 @@
+eventstarter.enabled=true
+event

spring-boot/starter/application/src/test/java/io/reflectoring/starter/StarterApplicationTests.java

@@ -0,0 +1,22 @@
+package io.reflectoring.starter;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import static org.assertj.core.api.Assertions.*;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class StarterApplicationTests {
+
+	@Autowired(required = false)
+	private EventPublisher eventPublisher;
+
+	@Test
+	public void eventPublisherIsAvailable() {
+		assertThat(eventPublisher).isNotNull();
+	}
+
+}

spring-boot/starter/event-starter/build.gradle

@@ -0,0 +1,30 @@
+plugins {
+    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
+    id 'java'
+}
+
+group = 'io.reflectoring'
+version = '0.0.1-SNAPSHOT'
+sourceCompatibility = '11'
+
+repositories {
+    mavenCentral()
+}
+
+dependencyManagement {
+    imports {
+        mavenBom("org.springframework.boot:spring-boot-dependencies:2.1.7.RELEASE")
+    }
+}
+
+dependencies {
+    compileOnly 'org.springframework.boot:spring-boot-starter'
+    annotationProcessor 'org.springframework.boot:spring-boot-autoconfigure-processor'
+    annotationProcessor 'org.springframework.boot:spring-boot-configuration-processor'
+    testImplementation 'org.springframework.boot:spring-boot-starter-test'
+
+    compileOnly('org.projectlombok:lombok:1.18.2')
+    annotationProcessor 'org.projectlombok:lombok:1.18.2'
+}
+
+compileJava.dependsOn(processResources)

spring-boot/starter/event-starter/src/main/java/io/reflectoring/starter/Event.java

@@ -0,0 +1,13 @@
+package io.reflectoring.starter;
+
+import lombok.ToString;
+import lombok.Value;
+
+@Value
+@ToString
+class Event {
+
+	private String type;
+	private String payload;
+
+}

spring-boot/starter/event-starter/src/main/java/io/reflectoring/starter/EventAutoConfiguration.java

@@ -0,0 +1,20 @@
+package io.reflectoring.starter;
+
+import java.util.List;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ConditionalOnProperty(value = "eventstarter.enabled", havingValue = "true")
+@EnableConfigurationProperties(EventListenerProperties.class)
+class EventAutoConfiguration {
+
+	@Bean
+	EventPublisher eventPublisher(List<EventListener> listeners){
+		return new EventPublisher(listeners);
+	}
+
+}

spring-boot/starter/event-starter/src/main/java/io/reflectoring/starter/EventListener.java

@@ -0,0 +1,32 @@
+package io.reflectoring.starter;
+
+import lombok.RequiredArgsConstructor;
+
+/**
+ * Interface to be implemented for all event types that the application should react to.
+ * EventListeners will be automatically included when they are part of the application context.
+ */
+@RequiredArgsConstructor
+public abstract class EventListener {
+
+	private final EventListenerProperties properties;
+
+	public void receive(Event event) {
+		if(isEnabled(event) && isSubscribed(event)){
+			onEvent(event);
+		}
+	}
+
+	private boolean isSubscribed(Event event) {
+		return event.getType().equals(getSubscribedEventType());
+	}
+
+	private boolean isEnabled(Event event) {
+		return properties.getEnabledEvents().contains(event.getType());
+	}
+
+	protected abstract String getSubscribedEventType();
+
+	protected abstract void onEvent(Event event);
+
+}

spring-boot/starter/event-starter/src/main/java/io/reflectoring/starter/EventListenerProperties.java

@@ -0,0 +1,19 @@
+package io.reflectoring.starter;
+
+import java.util.Collections;
+import java.util.List;
+
+import lombok.Data;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+@ConfigurationProperties(prefix = "eventstarter.listener")
+@Data
+class EventListenerProperties {
+
+	/**
+	 * List of event types that will be passed to {@link EventListener} implementations. All other events
+	 * will be ignored.
+	 */
+	private List<String> enabledEvents = Collections.emptyList();
+
+}

spring-boot/starter/event-starter/src/main/java/io/reflectoring/starter/EventPublisher.java

@@ -0,0 +1,28 @@
+package io.reflectoring.starter;
+
+
+import java.util.List;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * Dummy implementation of an event publisher. Simply publishes an event to all listeners that
+ * are subscribed to that event. This solution obviously doesn't work
+ * across JVM-boundaries... .
+ */
+@Slf4j
+@RequiredArgsConstructor
+public class EventPublisher {
+
+	private final List<EventListener> listeners;
+
+	public void publishEvent(Event event) {
+		log.info("publishing event: {}", event);
+		for (EventListener listener : listeners) {
+			listener.receive(event);
+		}
+	}
+
+
+}

spring-boot/starter/event-starter/src/main/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
+  io.reflectoring.starter.EventAutoConfiguration

spring-boot/starter/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-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

spring-boot/starter/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-boot/starter/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-boot/starter/settings.gradle

@@ -0,0 +1,2 @@
+include 'event-starter'
+include 'application'