toolchains.xml

<?xml version="1.0" encoding="UTF8"?>
<!-- IMPORTANT: toolchain works only with JRE not with JDK directories, define the JRE inside the JDK if you have JDK -->
<!-- JRE version requirements: Java7 u55, Java6 u31 -->
<toolchains>
   <toolchain>
     <type>jdk</type>
     <provides>
         <id>J2SE-1.5</id>
     </provides>
     <configuration>
        <jdkHome>path/to/jre6</jdkHome>
     </configuration>
  </toolchain>
  <toolchain>
     <type>jdk</type>
     <provides>
         <id>JavaSE-1.6</id>
     </provides>
     <configuration>
        <jdkHome>path/to/jre6</jdkHome>
     </configuration>
  </toolchain>
  <toolchain>
     <type>jdk</type>
     <provides>
         <id>JavaSE-1.7</id>
     </provides>
     <configuration>
        <jdkHome>path/to/jre7</jdkHome>
     </configuration>
  </toolchain>
</toolchains>