Question

I have read that JARing up Java classes before uploading them to App Engine improves performance. Can anyone explain how that is done? Can that be achieved from within Eclipse?

Answer 1

You can easily use Ant to make the jar

<property name="staging.dir" value="war"/>
<property name="classes.dir" value="${staging.dir}/WEB-INF/classes"/>

<target name="jarClasses">
    <delete file="${staging.dir}/WEB-INF/lib/classes.jar" />
    <echo> ${staging.dir}/WEB-INF/lib/classes.jar DELETED </echo>
    <jar destfile="${staging.dir}/WEB-INF/lib/classes.jar" basedir="${classes.dir}" />
    <echo> ${staging.dir}/WEB-INF/lib/classes.jar JARRED </echo>
    <delete dir="${classes.dir}" />
    <echo> ${classes.dir} DELETED </echo>
</target>

My layout is like:

/war
/build.xml

Alternatively you can use an Ant task to deploy

Configure Eclipse to pre-bundle App Engine classes into a single JAR for faster warm-up

I haven’t done it that way as I’m not sure how to handle the passphrase authentication.