Update pom.xml

* bump dependencies
* move used JDK to more prominent place
* move non-default build plugin versions to properties section

pom.xml

@@ -15,18 +15,24 @@
 
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<maven.compiler.release>8</maven.compiler.release>
 
 		<!-- dependencies -->
 		<gson.version>2.8.6</gson.version>
-		<guava.version>30.1-jre</guava.version>
+		<guava.version>30.1.1-jre</guava.version>
 		<siv-mode.version>1.4.1</siv-mode.version>
 		<slf4j.version>1.7.30</slf4j.version>
 
 		<!-- test dependencies -->
 		<junit.jupiter.version>5.7.1</junit.jupiter.version>
-		<mockito.version>3.7.7</mockito.version>
+		<mockito.version>3.9.0</mockito.version>
 		<hamcrest.version>2.2</hamcrest.version>
-		<jmh.version>1.27</jmh.version>
+		<jmh.version>1.29</jmh.version>
+
+		<!-- build plugin dependencies -->
+		<dependency-check.version>6.1.6</dependency-check.version>
+		<jacoco.version>0.8.7</jacoco.version>
+		<nexus-staging.version>1.6.8</nexus-staging.version>
 	</properties>
 
 	<licenses>
@@ -138,7 +144,6 @@
 				<artifactId>maven-compiler-plugin</artifactId>
 				<version>3.8.1</version>
 				<configuration>
-					<release>8</release>
 					<encoding>UTF-8</encoding>
 					<showWarnings>true</showWarnings>
 				</configuration>
@@ -222,7 +227,7 @@
 					<plugin>
 						<groupId>org.owasp</groupId>
 						<artifactId>dependency-check-maven</artifactId>
-						<version>6.1.5</version>
+						<version>${dependency-check.version}</version>
 						<configuration>
 							<cveValidForHours>24</cveValidForHours>
 							<failBuildOnCVSS>0</failBuildOnCVSS>
@@ -249,7 +254,7 @@
 					<plugin>
 						<groupId>org.jacoco</groupId>
 						<artifactId>jacoco-maven-plugin</artifactId>
-						<version>0.8.6</version>
+						<version>${jacoco.version}</version>
 						<executions>
 							<execution>
 								<id>prepare-agent</id>
@@ -310,7 +315,7 @@
 					<plugin>
 						<groupId>org.sonatype.plugins</groupId>
 						<artifactId>nexus-staging-maven-plugin</artifactId>
-						<version>1.6.8</version>
+						<version>${nexus-staging.version}</version>
 						<extensions>true</extensions>
 						<configuration>
 							<serverId>ossrh</serverId>