Added Log4j bindings for SLF4J. Test log output is redirected to the console, and demo output is now additionally stored in a rolling log file.

build.gradle

@@ -25,8 +25,8 @@ buildscript {
     ext.jetty_version = '9.3.9.v20160517'
     ext.jersey_version = '2.23.1'
 	ext.jolokia_version = '2.0.0-M1'
-    ext.slf4j_version = '1.7.21'
     ext.assertj_version = '3.5.1'
+    ext.log4j_version = '2.6.2'
 
     repositories {
         mavenCentral()
@@ -63,6 +63,16 @@ sourceSets {
             srcDir file('src/integration-test/kotlin')
         }
     }
+    main {
+        resources {
+            srcDir "config/dev"
+        }
+    }
+    test {
+        resources {
+            srcDir "config/test"
+        }
+    }
 }
 
 //noinspection GroovyAssignabilityCheck

config/dev/log4j2.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="info">
+
+    <Properties>
+        <Property name="log-path">logs</Property>
+        <Property name="log-name">main</Property>
+        <Property name="archive">${log-path}/archive</Property>
+    </Properties>
+
+    <ThresholdFilter level="trace"/>
+
+    <Appenders>
+        <Console name="Console-Appender" target="SYSTEM_OUT">
+            <PatternLayout>
+                <pattern>
+                    [%-5level] %d{HH:mm:ss.SSS} [%t] %c{1}.%M - %msg%n
+                </pattern>>
+            </PatternLayout>
+        </Console>
+
+        <!-- Will generate up to 10 log files for a given day. During every rollover it will delete
+             those that are older than 60 days, but keep the most recent 10 GB -->
+        <RollingFile name="RollingFile-Appender"
+                     fileName="${log-path}/${log-name}.log"
+                     filePattern="${archive}/${log-name}.%d{yyyy-MM-dd}-%i.log.gz">
+
+            <PatternLayout pattern="[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n"/>
+
+            <Policies>
+                <TimeBasedTriggeringPolicy/>
+                <SizeBasedTriggeringPolicy size="10MB"/>
+            </Policies>
+
+            <DefaultRolloverStrategy min="1" max="10">
+                <Delete basePath="${archive}" maxDepth="1">
+                    <IfFileName glob="${log-name}*.log.gz"/>
+                    <IfLastModified age="60d">
+                        <IfAny>
+                            <IfAccumulatedFileSize exceeds="10 GB"/>
+                        </IfAny>
+                    </IfLastModified>
+                </Delete>
+            </DefaultRolloverStrategy>
+
+        </RollingFile>
+    </Appenders>
+
+    <Loggers>
+        <Root level="trace">
+            <AppenderRef ref="Console-Appender" level="info"/>
+            <AppenderRef ref="RollingFile-Appender" level="debug"/>
+        </Root>
+    </Loggers>
+
+</Configuration>

config/test/log4j2.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="info">
+    <Appenders>
+        <Console name="Console-Appender" target="SYSTEM_OUT">
+            <PatternLayout>
+                <pattern>
+                    [%-5level] %d{HH:mm:ss.SSS} [%t] %c{1}.%M - %msg%n
+                </pattern>>
+            </PatternLayout>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Root level="info">
+            <AppenderRef ref="Console-Appender" level="info"/>
+        </Root>
+    </Loggers>
+</Configuration>

contracts/build.gradle

@@ -80,4 +80,12 @@ dependencies {
     compile project(':core')
 
     testCompile 'junit:junit:4.12'
+}
+
+sourceSets {
+    test {
+        resources {
+            srcDir "../config/test"
+        }
+    }
 }

contracts/isolated/build.gradle

@@ -78,4 +78,12 @@ repositories {
 
 dependencies {
     compile project(':core')
+}
+
+sourceSets {
+    test {
+        resources {
+            srcDir "../../config/test"
+        }
+    }
 }

core/build.gradle

@@ -21,6 +21,14 @@ repositories {
     }
 }
 
+sourceSets {
+    test {
+        resources {
+            srcDir "../config/test"
+        }
+    }
+}
+
 dependencies {
     testCompile 'junit:junit:4.12'
     testCompile "commons-fileupload:commons-fileupload:1.3.2"
@@ -35,12 +43,13 @@ dependencies {
     // Thread safety annotations
     compile "com.google.code.findbugs:jsr305:3.0.1"
 
+    // Log4J: logging framework (wth SLF4J bindings)
+    compile "org.apache.logging.log4j:log4j-slf4j-impl:${log4j_version}"
+    compile "org.apache.logging.log4j:log4j-core:${log4j_version}"
+
     // AssertJ: for fluent assertions for testing
     testCompile "org.assertj:assertj-core:${assertj_version}"
 
-    // SLF4J: Logging framework.
-    compile "org.slf4j:slf4j-jdk14:${slf4j_version}"
-
     // Guava: Google utilities library.
     compile "com.google.guava:guava:19.0"
 

node/build.gradle

@@ -19,6 +19,14 @@ configurations {
     runtime.exclude module: 'isolated'
 }
 
+sourceSets {
+    test {
+        resources {
+            srcDir "../config/test"
+        }
+    }
+}
+
 // To find potential version conflicts, run "gradle htmlDependencyReport" and then look in
 // build/reports/project/dependencies/index.html for green highlighted parts of the tree.
 
@@ -26,7 +34,10 @@ dependencies {
     compile project(':contracts')
 
     compile "com.google.code.findbugs:jsr305:3.0.1"
-    compile "org.slf4j:slf4j-jdk14:${slf4j_version}"
+
+    // Log4J: logging framework (wth SLF4J bindings)
+    compile "org.apache.logging.log4j:log4j-slf4j-impl:${log4j_version}"
+    compile "org.apache.logging.log4j:log4j-core:${log4j_version}"
 
     compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
     compile "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"