Issues with maven compiler - maven

Question

I am trying to use jetty plugin for a grails project. I am currently using jdk 1.6.0_45. It seems that the jre version used by jdk 1.6 is a little old one for jetty plugin and it generates the following error.
Fatal error during compilation org.apache.tools.ant.BuildException: java.lang.UnsupportedClassVersionError: org/eclipse/jetty/plus/webapp/EnvConfiguration : Unsupported major.minor version 51.0 (Use --stacktrace to see the full trace)
To resolve this error I have added a code in the pom.xml to use java source 1.7. The code is something like this.
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
But still I continue to get the same error. Can any body please help me out.
I am posting my entire pom.xml and the error that I am getting
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany</groupId>
<artifactId>grails-mongo-demo</artifactId>
<packaging>grails-app</packaging>
<version>0.1</version>
<name>grails-mongo-demo</name>
<description>grails-mongo-demo</description>
<properties>
<grails.version>2.4.2</grails.version>
<h2.version>1.3.170</h2.version>
</properties>
<dependencies>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-dependencies</artifactId>
<version>${grails.version}</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-test</artifactId>
<version>${grails.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-plugin-testing</artifactId>
<version>${grails.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-core</artifactId>
<version>0.7-groovy-2.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>${h2.version}</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.grails</groupId>
<artifactId>grails-datastore-test-support</artifactId>
<version>1.0-grails-2.4</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>scaffolding</artifactId>
<version>2.1.2</version>
<scope>compile</scope>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>cache</artifactId>
<version>1.1.7</version>
<scope>compile</scope>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>asset-pipeline</artifactId>
<version>1.8.11</version>
<scope>compile</scope>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>jquery</artifactId>
<version>1.11.1</version>
<scope>runtime</scope>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>webxml</artifactId>
<version>1.4.1</version>
<type>zip</type>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>mongodb</artifactId>
<version>3.0.2</version>
<scope>compile</scope>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.grails.plugins</groupId>
<artifactId>jetty</artifactId>
<version>3.0.0</version>
<type>zip</type>
</dependency>
</dependencies>
<build>
<pluginManagement />
<plugins>
<!-- Disables the Maven surefire plugin for Grails applications, as we have our own test runner -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.17</version>
<configuration>
<skip>true</skip>
</configuration>
<executions>
<execution>
<id>surefire-it</id>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<skip>false</skip>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-clean-plugin</artifactId>
<version>2.4.1</version>
<configuration>
<filesets>
<fileset>
<directory>plugins</directory>
<includes>
<include>**/*</include>
</includes>
<followSymlinks>false</followSymlinks>
</fileset>
</filesets>
</configuration>
</plugin>
<plugin>
<groupId>org.grails</groupId>
<artifactId>grails-maven-plugin</artifactId>
<version>2.4.3</version>
<configuration>
<grailsVersion>${grails.version}</grailsVersion>
</configuration>
<extensions>true</extensions>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>grails</id>
<name>grails</name>
<url>http://repo.grails.org/grails/core</url>
</repository>
<repository>
<id>grails-plugins</id>
<name>grails-plugins</name>
<url>http://repo.grails.org/grails/plugins</url>
</repository>
</repositories>
<profiles>
<profile>
<id>tools</id>
<activation>
<property>
<name>java.vendor</name>
<value>Sun Microsystems Inc.</value>
</property>
</activation>
<dependencies>
<dependency>
<groupId>com.sun</groupId>
<artifactId>tools</artifactId>
<version>${java.version}</version>
<scope>system</scope>
<systemPath>${java.home}/../lib/tools.jar</systemPath>
</dependency>
</dependencies>
</profile>
</profiles>
</project>
Error
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building grails-mongo-demo 0.1
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.4.1:clean (default-clean) # grails-mongo-demo ---
[INFO] Deleting /mnt/data/Work/Tutorials/Practice/grails/grails-mongo-demo/target
[INFO] Deleting /mnt/data/Work/Tutorials/Practice/grails/grails-mongo-demo/plugins (includes = [**/*], excludes = [])
[INFO]
[INFO] --- grails-maven-plugin:2.4.3:clean (default-clean) # grails-mongo-demo ---
4 Sep, 2014 6:28:00 PM org.codehaus.groovy.runtime.m12n.MetaInfExtensionModule newModule
WARNING: Module [groovy-all] - Unable to load extension class [org.codehaus.groovy.runtime.NioGroovyMethods]
4 Sep, 2014 6:28:00 PM org.codehaus.groovy.runtime.m12n.MetaInfExtensionModule newModule
WARNING: Module [groovy-all] - Unable to load extension class [org.codehaus.groovy.runtime.NioGroovyMethods]
|Loading Grails 2.4.2
|Configuring classpath
|Running pre-compiled script
.
|Environment set to development
....................
|Application cleaned.
[INFO]
[INFO] --- grails-maven-plugin:2.4.3:validate (default-validate) # grails-mongo-demo ---
[INFO]
[INFO] --- grails-maven-plugin:2.4.3:init (default-init) # grails-mongo-demo ---
[INFO]
[INFO] --- grails-maven-plugin:2.4.3:config-directories (default-config-directories) # grails-mongo-demo ---
[INFO]
[INFO] --- grails-maven-plugin:2.4.3:maven-compile (default-maven-compile) # grails-mongo-demo ---
4 Sep, 2014 6:28:32 PM org.codehaus.groovy.runtime.m12n.MetaInfExtensionModule newModule
WARNING: Module [groovy-all] - Unable to load extension class [org.codehaus.groovy.runtime.NioGroovyMethods]
4 Sep, 2014 6:28:32 PM org.codehaus.groovy.runtime.m12n.MetaInfExtensionModule newModule
WARNING: Module [groovy-all] - Unable to load extension class [org.codehaus.groovy.runtime.NioGroovyMethods]
|Loading Grails 2.4.2
|Configuring classpath
|Running pre-compiled script
.
|Environment set to development
......
|Installing zip jetty-3.0.0.zip...
...
|Installed plugin jetty-3.0.0
.............
|Installing zip webxml-1.4.1.zip...
...
|Installed plugin webxml-1.4.1
.............
|Installing zip asset-pipeline-1.8.11.zip...
...
|Installed plugin asset-pipeline-1.8.11
..................
|Installing zip cache-1.1.7.zip...
...
|Installed plugin cache-1.1.7
..............
|Installing zip scaffolding-2.1.2.zip...
...
|Installed plugin scaffolding-2.1.2
..............
|Installing zip jquery-1.11.1.zip...
...
|Installed plugin jquery-1.11.1
..............
|Installing zip mongodb-3.0.2.zip...
...
|Installed plugin mongodb-3.0.2
...................
|Compiling 87 source files
.Error
|
Fatal error during compilation org.apache.tools.ant.BuildException: java.lang.UnsupportedClassVersionError: org/eclipse/jetty/plus/webapp/EnvConfiguration : Unsupported major.minor version 51.0 (Use --stacktrace to see the full trace)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 47.500 s
[INFO] Finished at: 2014-09-04T18:28:42+05:30
[INFO] Final Memory: 10M/102M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.grails:grails-maven-plugin:2.4.3:maven-compile (default-maven-compile) on project grails-mongo-demo: Forked Grails VM exited with error -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException