Unable to find a javac compiler

Question

I am trying to package my web application into war file using Ant.

When I build, I am getting the following error:

C:\Documents and Settings\Administrator\workspace\Assignment7\build.xml:67: Unable to find a javac compiler; com.sun.tools.javac.Main is not on the classpath. Perhaps JAVA_HOME does not point to the JDK. It is currently set to "C:\Program Files\Java\jre6" 

The following is my build.xml

<?xml version="1.0" encoding="UTF-8"?> <project name="Generate War" default="install" basedir=".">       <property name="build.dir" value="build"/>     <property name="dir.name" value="Assignment7"/>     <property name="package.name" value="${dir.name}.war"/>      <property name="content" value="webContent"/>     <property name="web-inf" value="${content}\WEB-INF"/>     <property name="meta-inf" value="${content}\META-INF"/>     <property name="jsp.dir.name" value="${content}"/>      <property name="lib" value="${web-inf}\lib"/>     <property name="src" value="src"/>     <property name="dest.dir" value="target"/>      <!-- Setting path to the server webapp folder -->      <property name="webapp.dir" value="C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps"/>      <!--  Using temp folder for convinence -->      <property name="temp.dir" value="temp"/>     <property name="temp.dir.web-inf" value="${temp.dir}\WEB-INF"/>     <property name="temp.dir.meta-inf" value="${temp.dir}\META-INF"/>     <property name="temp.dir.lib" value="${temp.dir.web-inf}\lib"/>     <property name="temp.dir.classes" value="${temp.dir.web-inf}\classes"/>     <!--<property name="temp.dir.classes.dir" value="${temp.dir.classes}\**"/>-->      <property name="package.file" value="${dest.dir}\${package.name}"/>      <path id="build.class.path">         <fileset dir="${lib}">             <include name="**/*.jar"/>         </fileset>     </path>     <path id="build.class.path1">         <fileset dir="C:\program files\java\jre6\lib">             <include name="**/*.jar"/>         </fileset>      </path>      <target name="clean">         <delete>             <fileset dir="${dest.dir}" includes="**/*"/>         </delete>         <delete dir="${temp.dir}"/>         <delete dir="${temp.dir.classes}"/>         <delete dir="${temp.dir.web-inf}"/>         <delete dir="${temp.dir.meta-inf}"/>     </target>       <target name="prepare" depends="clean">         <mkdir dir="${dest.dir}"/>         <mkdir dir="${temp.dir}"/>         <mkdir dir="${temp.dir.web-inf}"/>         <mkdir dir="${temp.dir.lib}"/>         <mkdir dir="${temp.dir.classes}"/>         <mkdir dir="${temp.dir.meta-inf}"/>     </target>      <target name="compile" depends="prepare">         <echo>==="complie"===</echo>         <javac srcdir="${src}" destdir="${temp.dir.classes}" debug="on">             <classpath refid="build.class.path"></classpath>          </javac>         <!--<copydir src="${build.dir}\classes" dest="${temp.dir.classes}"/>-->     </target>      <target name="package" depends="compile">         <echo>"PACKAGING THE FILES"</echo>             <copy file="${meta-inf}\MANIFEST.MF" tofile="${temp.dir.meta-inf}\MANIFEST.MF" overwrite="true"/>             <copy file="${web-inf}\web.xml" tofile="${temp.dir.web-inf}\web.xml" overwrite="true"/>             <copy file="${web-inf}\tiles.xml" tofile="${temp.dir.web-inf}\tiles.xml" overwrite="true"/>             <copy todir="${temp.dir.classes}">                 <fileset dir="${src}">                     <include  name="**/*.xml"/>                 </fileset>             </copy>              <war destfile="${package.file}" webxml="${temp.dir.web-inf}\web.xml" basedir="${temp.dir}">                 <fileset dir="${jsp.dir.name}"/>                 <lib dir="${lib}"></lib>                 <classes dir="${temp.dir.classes}"></classes>             </war>     </target>      <target name="jsps">             <copy todir="${webapp.dir}\${dir.name}">                 <fileset dir="${content}">                     <include name="**/*.jsp"/>                     <include name="**/*.html"/>                     <include name="**/*.css"/>                     <include name="**/*.gif"/>                     <include name="**/*.jpg"/>                     <include name="**/*.png"/>                     <include name="**/*.js"/>                 </fileset>             </copy>     </target>      <target name="install" depends="package">             <copy file="${package.file}" todir="${webapp.dir}" overwrite="true"/>     </target>  </project> 

How can I compile a class file that does not have a main class?

How do I set the class path?

For reference, I am using Eclipse.

Answer 1

All your ant stuff will work fine except the javac task which needs the tools.jar, located in the /lib directory from the JDK, JRE is not sufficient in that case. Therefore the hint from ant : "Unable to find a javac compiler;..."

When working with Eclipse the default setting points to your JRE installation.
So, one of your first steps after starting Eclipse for the first time should be :
Window > Preferences > Java > Installed JREs and change the settings from JRE to JDK.
Alternatively use :
Window > Preferences > Ant > Runtime > Classpath > Global Entries
and add the tools.jar from your JDK/lib folder

Answer 2

I had the same problem. In my case, I fixed it by pointing JAVA_HOME to the JDK folder, rather than the JDK\bin folder.