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<h1>ConfigSlurper</h1><p><a href="http://groovy.codehaus.org/gapi/groovy/util/ConfigSlurper.html">ConfigSlurper</a> is a utility class within Groovy for writing properties file like scripts for performing configuration. Unlike regular Java properties files ConfigSlurper scripts support native Java types and are structured like a tree.</p><p>Below is an example of how you could configure Log4j with a ConfigSlurper script:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>log4j.appender.stdout = "org.apache.log4j.ConsoleAppender"
log4j.appender."stdout.layout"="org.apache.log4j.PatternLayout"
log4j.rootLogger="error,stdout"
log4j.logger.org.springframework="info,stdout"
log4j.additivity.org.springframework=false
</pre></td></tr></table><p>To load this into a readable config you can do:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def config = new ConfigSlurper().parse(new File('myconfig.groovy').toURL())

assert "info,stdout" == config.log4j.logger.org.springframework
assert false == config.log4j.additivity.org.springframework
</pre></td></tr></table><p>As you can see from the example above you can navigate the config using dot notation and the return values are Java types like strings and booleans.</p><p>You can also use scoping in config scripts to avoid repeating yourself. So the above config could also be written as:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>log4j {
    appender.stdout = "org.apache.log4j.ConsoleAppender"
    appender."stdout.layout"="org.apache.log4j.PatternLayout"
    rootLogger="error,stdout"
    logger {
        org.springframework="info,stdout"
    }
    additivity {
        org.springframework=false
    }
}
</pre></td></tr></table><h2>Converting to and from Java properties files</h2><p>You can convert ConfigSlurper configs to and from Java properties files. For example:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>java.util.Properties props = // load from somewhere

def config = new ConfigSlurper().parse(props)

props = config.toProperties()
</pre></td></tr></table><h2>Merging configurations</h2><p>You can merge config objects so if you have multiple config files and want to create one central config object you can do:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def config1 = new ConfigSlurper().parse(..)
def config2 = new ConfigSlurper().parse(..)

config1 = config1.merge(config2)
</pre></td></tr></table><h2>Serializing a configuration to disk</h2><p>You can serialize a config object to disk. Each config object implements the groovy.lang.Writable interface that allows you to write out the config to any java.io.Writer:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def config = new ConfigSlurper().parse(..)

new File("..").withWriter { writer ->
     config.writeTo(writer)
}
</pre></td></tr></table><h2>Special &quot;environments&quot; Configuration</h2><p>The ConfigSlurper class has a special constructor other than the default constructor that takes an &quot;environment&quot; parameter. This special constructor works in concert with a property setting called environments. This allows a default setting to exist in the property file that can be superceded by a setting in the appropriate environments closure. This allows multiple related configurations to be stored in the same file.</p><p>Given this groovy property file:</p><table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="language=groovy|title=Sample.groovy" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6dGl0bGU9U2FtcGxlLmdyb292eXxsYW5ndWFnZT1ncm9vdnl9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>sample {
  foo = "default_foo"
  bar = "default_bar"
}

environments {
  development {
    sample {
      foo = "dev_foo"
    }
  }
  test {
    sample {
      bar = "test_bar"
    }
  }
}
</pre></td></tr></table><p>Here is the demo code that exercises this configuration:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def config = new ConfigSlurper("development").parse(new File('Sample.groovy').toURL())

assert config.sample.foo == "dev_foo"
assert config.sample.bar == "default_bar"

config = new ConfigSlurper("test").parse(new File('Sample.groovy').toURL())

assert config.sample.foo == "default_foo"
assert config.sample.bar == "test_bar"
</pre></td></tr></table><p>Note: the environments closure is not directly parsable. Without using the special environment constructor the closure is ignored.</p><p>The value of the environment constructor is also available in the configuration file, allowing you to build the configuration like this:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre> switch (environment) {
  case 'development':
    baseUrl = "devServer/"
    break
  case 'test':
    baseUrl = "testServer/"
    break
  default:
    baseUrl = "localhost/"
}
</pre></td></tr></table><h1>Further information</h1><p><a href="http://jroller.com/page/0xcafebabe?entry=using_groovy_configslurper_to_configure">Using Groovy ConfigSlurper to Configure Spring Beans</a></p>