You must download several jar files before you can build Middlegen. Execute the "download-deps" target. Then try to build again. If you are behind a proxy, you should define the properties http.proxyHost and http.proxyPort. Example: ant -Dhttp.proxyHost=foo.com -Dhttp.proxyPort=8080 It's also possible to download the jars manually. Copying web files Generating Java source from JSP pages Compiling JSP classes Copying web resources Copying web resources