In a Filters class, you can specify any other Filters classes that should first be executed using the dependsOn property. The dependsOn property is used when a Filters class depends on the behavior of another Filters class (e.g. setting up the environment, modifying the request/session, etc.) and is defined as an array of Filters classes.

Take the following example Filters classes:

class MyFilters {
    def dependsOn = [MyOtherFilters]

def filters = { checkAwesome(uri:"/*") { before = { if (request.isAwesome) { // do something awesome } } }

checkAwesome2(uri:"/*") { before = { if (request.isAwesome) { // do something else awesome } } } } }

class MyOtherFilters { def filters = { makeAwesome(uri:"/*") { before = { request.isAwesome = true; } } doNothing(uri:"/*") { before = { // do nothing } } } }

MyFilters specifically dependsOn MyOtherFilters. This will cause all the filters in MyOtherFilters to be executed before those in MyFilters, given their scope matches the current request. For a request of "/test", which will match the scope of every filter in the example, the execution order would be as follows:

The filters within the MyOtherFilters class are processed in order first, followed by the filters in the MyFilters class. Execution order between Filters classes are enabled and the execution order of filters within each Filters class are preserved.

If any cyclical dependencies are detected, the filters with cyclical dependencies will be added to the end of the filter chain and processing will continue. Information about any cyclical dependencies that are detected will be written to the logs. Ensure that your root logging level is set to at least WARN or configure an appender for the Grails Filters Plugin (org.codehaus.groovy.grails.plugins.web.filters.FiltersGrailsPlugin) when debugging filter dependency issues.