Maven: Non Existing Library jdk.tools.jar

The Problem
Today,after add some dependencies to maven,  I found that maven refuses to compile. In Problems view, it shows error:
The container 'Maven Dependencies' references non existing library 'C:\Users\administrator\.m2\repository\jdk\tools\jdk.tools\1.6\jdk.tools-1.6.jar'

Check my pom.xml, there is no direct dependency of jdk.tools-1.6.jar, then use maven dependency:tree tool to figure out which lib indirectly depends on it.
mvn dependency:tree -Dverbose -Dincludes=jdk.tools

[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ learningLucene ---

[INFO] org.lifelongprogrammer:learningLucene:jar:1.0

[INFO] \- org.apache.solr:solr-core:jar:4.9.0:compile

[INFO]    \- org.apache.hadoop:hadoop-annotations:jar:2.2.0:compile

[INFO]       \- jdk.tools:jdk.tools:jar:1.7:system

Turn out, solr-code depends on hadoop-annotation which then need jdk.tools.jar.

The Solution

Google search, find this page: 

http://maven.apache.org/general.html#tools-jar-dependency

<dependency>
  <groupId>jdk.tools</groupId>
  <artifactId>jdk.tools</artifactId>
  <scope>system</scope>
  <systemPath>C:/Program Files/Java/jdk1.8.0/lib/tools.jar</systemPath>
  <!-- have to include the version, otherwise eclipse throws exception: 
    Errors running builder 'Maven Project Builder' on project 'learningLucene'. 
    java.lang.NullPointerException -->
  <version>8.0</version>
</dependency>
</dependencies>
<build>
<plugins>
  <plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
      <source>1.8</source>
      <target>1.8</target>
    </configuration>
  </plugin>
</plugins>
</build>

Ant: Different Ways to Call Another Target

AntCall Task
Call another target within the same buildfile optionally specifying some properties.

<target name="default">
  <antcall target="doSomethingElse">
    <param name="param1" value="value"/>
  </antcall>
</target>

Ant antfile
Call target in another file.

<ant antfile="${liteLucene-project-basedir}/shrink-solr.xml" target="shrink">
<property name="original.home" value="${main-build-path}\${application-name}" />
<property name="shrinked.home" value="${main-build-path}\shrinked-${application-name}" />
<property name="shrinked.tmp" value="${main-build-path}\shrinked-tmp" />
</ant>

Ant Include
Include another build file into the current project.

<include file="${parent-project-build-imp-xml}" as="parent"/>
<target name="package" depends="parent.init, parent.build-package, overwrite-solr-home, create-template, parent.post-clean"/>

How is <import> different from <include>?
The short version: Use import if you intend to override a target, otherwise use include.

Subant Task
Calls a given target for all defined sub-builds.
Example-Solr's build file:

<target name="compile" description="Compile Lucene and Solr">
    <sequential>
      <subant target="compile" inheritall="false" failonerror="true">
        <fileset dir="lucene" includes="build.xml" />
        <fileset dir="solr" includes="build.xml" />
      </subant>
    </sequential>
</target>