Question

Hey guys, I am using Apache Ant and I am wondering how would I edit a variable in a file (e.g. database host, username, password) and pass an argument (e.g. for a subversion commit message)

Basically I want the Apache Ant task to change my database variables and then execute the subversion commit command on my current directory.

This is on Windows 7.

Thanks

Answer 1

— It’s hard to know what you are asking for in detail, so the answer changes —

If you want to copy a new value into a portion of a file (instead of allowing a user to set a variable in ant), then you use ant’s copy task coupled with a filterset.

The copy will produce the output file from the input file, and the filterset will indicate which “tokens” need to be replaced with some value. Often this value is something that was stored in a property, but it could be composed by other means.

<copy todir="build/source">
  <fileset dir="src"/>
  <filterset>
    <filter token="BUILD_NUMBER" value="${build.number}"/>
  </filterset>
</copy>

copies all files from src to build/src replacing @BUILD_NUMBER@ with the value of the property build.number.

— Original post follows —

Create a properties file, then reference it from the build.xml.

An example of a properties file database.properties

database.user=dbuser
database.user.password=supersecret
database.url=jdbc:org:driver:locahost:0000/mydatabase
database.driver=org.example.DatabaseDriver

An example of referencing the file from a build.xml file

<property file="database.properties"/>

This way you can isolate your configuration changes to a specific file. Ant doesn’t have variables, it has properties which are “set once”, so to provide default values, you need to do something like

<property file="database.properties"/>
<property name="database.user" value="default"/>

to ensure that the database.user is always set. If a database user property is defined in the database.properties file, then the second attempt to assign the property will be ignored. If a user removes database.user=bob from the properties file, then the second attempt to set it in the build.xml file will succeed.

In the rare event that you actually want a person to type in some value (perhaps a password), use the input task; however, it again can only set a property. Ant doesn’t have variables.