Why does this large Java Project need common-ant.xml for building?

This is the error when trying to build the Pet Store example:

C:\Users\user\workspace\common-ant.xml could not be found
BUILD FAILED
java.io.FileNotFoundException: C:\Users\user\workspace\common-ant.xml
(The system cannot find the file specified)

The common-ant.xml part is making no 开发者_开发问答sense. I have no idea why it says common-ant.

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The install_dir/samples/common-ant.xml file defines properties common to all sample applications and implements targets needed to compile, assemble, deploy and undeploy sample applications. In most sample applications, the build.xml file includes common-ant.xml.

Found on a tutorial here

Have a look at your build.xml file, the location may be declared inside. Then, read the pet store tutorial carefully (again), maybe there's a sentence where you're asked to copy some predefined common-ant.xml to some location.

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Is this a GWT project? If so, it requires to have a common-ant.xml. Google that file, and you'll see examples online.