Filtering: Advanced techniques

The following features are described in this document:

  • Escaping properties that should not be filtered
  • Ignoring files based on its extension

Escaping properties

It may be necessary to filters some properties in a file and ignore another. The filtering mechanism won't touch a token that is not recognized (i.e. that represents an unknown property). This won't work if the property is known obviously so it should be escaped explicitely.

The following configuration defines the value of the escapeString which will stop the interpolation of a property if it starts with that value

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-ear-plugin</artifactId>
        <version>3.1.0</version>
        <configuration>
           <filtering>true</filtering>
           <escapeString>\</escapeString>
           [...]
        </configuration>
      </plugin>
    </plugins>
  </build>

Assuming the following file

jdbc.url=${db.url}
jdbc.user=${db.username}
jdbc.password=${db.password}

Filtering the content of such a file with this config will produce this content. Note that that the escaped property can now be filtered the usual way later if necessary!

jdbc.url=jdbc:oracle:thin:@localhost:1521:orcl
jdbc.user=someuser
jdbc.password=${db.password}

Ignoring files based on its extension

Filtering binary files corrupt them so it may be necessary to exclude files from filtering based on the extension. To do so, configure the plugin as follow

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-ear-plugin</artifactId>
        <version>3.1.0</version>
        <configuration>
           <filtering>true</filtering>
           <nonFilteredFileExtensions>
             <nonFilteredFileExtension>png</nonFilteredFileExtension>
             <nonFilteredFileExtension>jpeg</nonFilteredFileExtension>
           </nonFilteredFileExtensions>
           [...]
        </configuration>
      </plugin>
    </plugins>
  </build>