build number in pom is empty - maven

Question

I am trying to create a manifest entry "Build" whose value is build number. The generated buildNumber from the following POM is empty and I cannot figure out why. All the other fields in the manifest.mf file are correct.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.edvs</groupId>
<artifactId>EDVSTestJar1</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>EDVSTestJar1</name>
<url>http://maven.apache.org</url>
<scm>
<connection>scm:svn:http://127.0.0.1/dummy</connection>
<developerConnection>scm:svn:https://127.0.0.1/dummy</developerConnection>
<tag>HEAD</tag>
<url>http://127.0.0.1/dummy</url>
</scm>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.build.timestamp.format>yyyy-MM-dd HH:mm:ss</maven.build.timestamp.format>
<maven.build.timestamp>${maven.build.timestamp}</maven.build.timestamp>
<jar.finalName>EDVSTestJar1</jar.finalName>
</properties>
<dependencies>
<!-- Dependency to EDVSCommon -->
<dependency>
<groupId>com.edvs</groupId>
<artifactId>EDVSCommon</artifactId>
<version>0.0.2-SNAPSHOT</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-eclipse-plugin</artifactId>
<version>2.9</version>
<configuration>
<additionalProjectnatures>
<projectnature>org.springframework.ide.eclipse.core.springnature</projectnature>
</additionalProjectnatures>
<additionalBuildcommands>
<buildcommand>org.springframework.ide.eclipse.core.springbuilder</buildcommand>
</additionalBuildcommands>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<compilerArgument>-Xlint:all</compilerArgument>
<showWarnings>true</showWarnings>
<showDeprecation>true</showDeprecation>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<configuration>
<mainClass>org.test.int1.Main</mainClass>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>buildnumber-maven-plugin</artifactId>
<version>1.4</version>
<executions>
<execution>
<phase>validate</phase>
<goals>
<goal>create</goal>
</goals>
</execution>
</executions>
<configuration>
<doCheck>true</doCheck>
<doUpdate>true</doUpdate>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.6</version>
<configuration>
<archive>
<manifest>
<mainClass>com.edvs.main.TestIt</mainClass>
<classpathLayoutType>custom</classpathLayoutType>
<customClasspathLayout>WEB-INF/lib/${artifact.groupIdPath}/${artifact.artifactId}-${artifact.version}${dashClassifier?}.${artifact.extension}</customClasspathLayout>
</manifest>
<manifestEntries>
<Date>${maven.build.timestamp}</Date>
<Version>${project.version}</Version>
<Build>${buildNumber}</Build>
</manifestEntries>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-scm-plugin</artifactId>
<version>1.9.4</version>
<configuration>
<connectionType>developerConnection</connectionType>
</configuration>
</plugin>
</plugins>
</build>