title: maven compiler error with javac at release:prepare
body: <p>i am having this issue. I saw many posts like this but i still can't solve this problem. This error appears when i put mvn release:prepare at the shell</p>
  
  <pre><code>[INFO] [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3:compile (default-compile) on project birthday-greeting-card-sender: Compilation failure
  [INFO] [ERROR] Unable to locate the Javac Compiler in:
  [INFO] [ERROR] /usr/lib/jvm/java-6-openjdk-amd64/jre/../lib/tools.jar
  [INFO] [ERROR] Please ensure you are using JDK 1.4 or above and
  [INFO] [ERROR] not a JRE (the com.sun.tools.javac.Main class is required).
  [INFO] [ERROR] In most cases you can change the location of your Java
  [INFO] [ERROR] installation by setting the JAVA_HOME environment variable.
  [INFO] [ERROR] -&gt; [Help 1]
  [INFO] [ERROR] 
  [INFO] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
  [INFO] [ERROR] Re-run Maven using the -X switch to enable full debug logging.
  [INFO] [ERROR] 
  [INFO] [ERROR] For more information about the errors and possible solutions, please read the following articles:
  [INFO] [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
  </code></pre>
  
  <p>I have set JDK at /usr/lib/jvm/java-7-openjdk-amd64 (Preferences-->Java-->Installed JRE). I also add this line into eclipse.ini, but it couldn't work either:</p>
  
  <pre><code>-vm /usr/lib/jvm/java-7-openjdk-amd64
  </code></pre>
  
  <p>Does anybody have an idea about what is going on?</p>