diff --git a/build.gradle b/build.gradle
index eb8af51..1424055 100644
--- a/build.gradle
+++ b/build.gradle
@@ -12,30 +12,33 @@ buildscript {
   }
 
   dependencies {
-  	// usage: gradle dependencyUpdates -Drevision=release
+  	// usage: gradlew dependencyUpdates -Drevision=release
     classpath 'com.github.ben-manes:gradle-versions-plugin:0.21.0'
   }
 }
 
 ext {
     
+    version_log4j2= '2.11.2'
+    version_spring = '2.1.5.RELEASE'
+    
     lib_antlr = "org.antlr:antlr4:4.7.2"
     
     lib_commons_collections4 = 'org.apache.commons:commons-collections4:4.3'
     lib_commons_lang3 = 'org.apache.commons:commons-lang3:3.9'
     lib_guava = 'com.google.guava:guava:27.1-jre'
-    lib_jackson_databind = 'com.fasterxml.jackson.core:jackson-databind:2.9.8'
+    lib_jackson_databind = 'com.fasterxml.jackson.core:jackson-databind:2.9.9'
     
-    lib_log4j2_api = 'org.apache.logging.log4j:log4j-api:2.11.2'
-    lib_log4j2_core = 'org.apache.logging.log4j:log4j-core:2.11.2'
-    lib_log4j2_slf4j_impl = 'org.apache.logging.log4j:log4j-slf4j-impl:2.11.2'
+    lib_log4j2_api = "org.apache.logging.log4j:log4j-api:${version_log4j2}"
+    lib_log4j2_core = "org.apache.logging.log4j:log4j-core:${version_log4j2}"
+    lib_log4j2_slf4j_impl = "org.apache.logging.log4j:log4j-slf4j-impl:${version_log4j2}"
     
     lib_primitive_collections='org.lucares:primitiveCollections:0.1.20190428124907'
     
-    lib_spring_boot_log4j2='org.springframework.boot:spring-boot-starter-log4j2:2.1.4.RELEASE'
-    lib_spring_boot_mustache='org.springframework.boot:spring-boot-starter-mustache:2.1.4.RELEASE'
-    lib_spring_boot_test='org.springframework.boot:spring-boot-starter-test:2.1.4.RELEASE'
-    lib_spring_boot_web='org.springframework.boot:spring-boot-starter-web:2.1.4.RELEASE'
+    lib_spring_boot_log4j2="org.springframework.boot:spring-boot-starter-log4j2:${version_spring}"
+    lib_spring_boot_mustache="org.springframework.boot:spring-boot-starter-mustache:${version_spring}"
+    lib_spring_boot_test="org.springframework.boot:spring-boot-starter-test:${version_spring}"
+    lib_spring_boot_web="org.springframework.boot:spring-boot-starter-web:${version_spring}"
     
     eclipseAccessRestrictions = [
         'org.eclipse.jdt.launching.JRE_CONTAINER': [