{
   "myprocessor": {
        "surferRoleprocessor": "fr.wedia.confres.core.model.processor.SurferRolePostProcessor/res/postprocessors/myprocessor.groovy",
        "userAgent}
}

{
   "myprocessor": {
            "processor": "fr.wedia.confres.core.model.processor.UserAgentPostProcessorjar:file:/thejarfile.jar!/fr/wedia/mypackage/postprocessors/myprocessorinjar.groovy",
   }
}

{
       "configmyprocessor": [
                {
                    "pattern"processor": ".*Mobi.*jar:file:/other/path/thejarfile.jar!/fr/wedia/mypackage/postprocessors/myprocessorinjar.groovy",
       }
}

package fr.wedia.confref.postprocessor.examples;

import java.util.stream.*;
import java.util.Collection;

import com.google.gson.*;
import com.noheto.plugins.IPlugin;

import fr.wedia.confres.core.model.processor.*;
import fr.wedia.confres.utils.Utils;
import fr.wedia.confres.utils.annot.PostProcessorConfigExclude; 

import fr.wedia.confres.core.model.processor.EngineToolkit.ParameterType; // need to import explicitly the enum (in groovy)

/**
 * A basic example of postprocessor implementation in groovy.
 *
 * <p>This is an example of a postprocessor with interaction with the plugin that declares the postprocessor.
 * The value is a configurable fixed value.</p>
 * <p>There are two types of interactions </p>
 * <ul>
 * <li>We read some configuration properties of the plugin (they are not used, it is just for the example)</li>
 * <li>We invoke a method of the plugin at each call (it doesn't matter what it does, it's just for the example)</li>
 * </ul>
 * 
 * <p></p>
 *
 * @author joel.drigo@wedia-group.com
 *
 */
class CustomProcessorExampleOfInteractionWithThePlugin extends AbstractPostProcessor {
	
	/**
	 * This value is always returned. It is configurable because there isn't any {@link @PostProcessorConfig} annotation.
	 */
	private String value = "fixed";
	
	/**
	 * This is the list of possible returned values. It is initialized at startup, since the returned value is configurable (variable {@code value})
	 * <p>This variable is excluded explicitly from configuration, because there isn't any {@link @PostProcessorConfig} annotation</p>
	 */
	@PostProcessorConfigExclude
	private Set<String> values;

	/**
	 * Stores the plugin that declares the postprocessor (initialized at loading)
	 */
	@PostProcessorConfigExclude
	private IPlugin plugin;
	
	/**
	 * True when the plugin parameters has been effectly loaded
	 */
	@PostProcessorConfigExclude
	private boolean configured;

	/**
	 * This is a string parameter from plugin parameters
	 */
	@PostProcessorConfigExclude
	private String paramExample1;

	/**
	 * This is a JsonObject parameter from plugin parameters
	 */
	@PostProcessorConfigExclude
	private JsonObject paramExample2;

	/**
	 * This method is used when loading the postprocessor to inject the plugin that declares this postprocessor.
	 *
	 * @param plugin the name of the plugin that declares this postprocessor.
	 */
	public void setPlugin(IPlugin plugin) {
		this.plugin = plugin;
		loadConfig(); // lazy loading of plugin parameters
	}
	
	/**
	 * Start the processor.
	 */
	public void start() {
		loadConfig(); // lazy loading of plugin parameters
		value = Utils.withDefault(value, ""); // if value is null or blank, replace with empty string
		values = Utils.unmodifiableSet(value);
	}

	/**
	 * This method reads the configuration from plugin (whose declare this postprocessor).
	 */
	private void loadConfig() {
		if ( !configured ) { // if configuration has not been yet loaded
			if ( plugin==null ) {
				PostProcessorLogger.warn("Plugin has not be set correctly");
				configured = true; // we force this state to avoid trying to load again the configuration
			}
			else if ( plugin.isStarted() ) {
				if ( PostProcessorLogger.debug() ) PostProcessorLogger.debug(CustomProcessorExampleOfInteractionWithThePlugin.class,"Load parameters from plugin " + plugin.getName() );
				try {
					// we read the desired plugin parameters
					Map<String,Object> parameters = new EngineToolkit.PluginParameters()
					 .registerParameter("param_example_1", ParameterType.STRING, "default") // reads parameter_example_1 of type string
					 .registerParameter("param_example_2", ParameterType.JSON, ()-> new JsonObject()) // reads parameter_example_2 of type json
					 .collect(plugin);
					 configured = true;
					 paramExample1 = (String)parameters.get("param_example_1");
					 JsonElement json = (JsonElement)parameters.get("param_example_2");
					 if ( json instanceof JsonObject ) {
						 paramExample2 = (JsonObject)json; 
					 }
					 else {
						 paramExample2 = new JsonObject();
					 }
					if ( PostProcessorLogger.debug() ) {
						PostProcessorLogger.debug(CustomProcessorExampleOfInteractionWithThePlugin.class,"Parameter param_example_1 = " + paramExample1 );
						PostProcessorLogger.debug(CustomProcessorExampleOfInteractionWithThePlugin.class,"Parameter param_example_2 = " + paramExample2 );
					}
				}
				catch(Throwable t) {
					// show stack trace only in debug level
					if ( PostProcessorLogger.debug() ) PostProcessorLogger.debug(CustomProcessorExampleOfInteractionWithThePlugin.class,"Error while loading parameters from plugin " + plugin.getName() +".", t );
				    else if ( PostProcessorLogger.warn() ) PostProcessorLogger.warn(CustomProcessorExampleOfInteractionWithThePlugin.class,"Error while loading parameters from plugin " + plugin.getName() +". Set log to debug to see stacktrace." );
				}
			}
		}
	}

	/**
	 * This method invoke a method of a class of the plugin (whose declare this postprocessor).
	 */
	private void invokePlugin(ProcessorContext context) { 
		if ( PostProcessorLogger.trace() ) {
			PostProcessorLogger.trace("Invoking " + plugin.getName() + " / fr.wedia.confref.postprocessor.examples.Example.helloPlugin()");
		}

		String pluginMessage = EngineToolkit.invokePlugin(plugin, t->{
			if ( t!=null ) { // if t is null plugin is not started
			    // show stack trace only in debug level
				if ( PostProcessorLogger.debug() ) PostProcessorLogger.debug(CustomProcessorExampleOfInteractionWithThePlugin.class,"Error while invoking plugin " + plugin.getName() +".", t );
				else if ( PostProcessorLogger.warn() ) PostProcessorLogger.warn(CustomProcessorExampleOfInteractionWithThePlugin.class,"Error while invoking plugin " + plugin.getName() +". Set log to debug to see stacktrace." );
			}
		}, "fr.wedia.confref.postprocessor.examples.Example","helloPlugin", context.getProcessorName() );
		if ( pluginMessage!=null ) {
			if ( PostProcessorLogger.info() ) {
				PostProcessorLogger.info("The plugin " + plugin.getName() + " says: \"" + pluginMessage + "\"");
			}
		}
		else {
			if ( PostProcessorLogger.debug() ) {
				PostProcessorLogger.debug("Invoking " + plugin.getName() + "... seems to be not started.");
			}
		}
	}

	/**
	 * {@inheritDoc}
	 * Returns the postprocessor value corresponding (always the value {@code value}.
	 */
	@Override
	String getValue(ProcessorContext context) {
		loadConfig(); // lazy loading of plugin parameters
		if ( PostProcessorLogger.trace() ) {
			PostProcessorLogger.trace("Invoking " + plugin.getName() + "...");
		}
		invokePlugin(context); // invoke plugin
		return value;
	}
	
	/**
	 * Returns all possible values.
	 *
	 * @return all possible values.
	 */
	@Override
	public Collection<String> getAvailableValues() {
		loadConfig(); // lazy loading of plugin parameters
		return values;
	}
	
	/**
	 * Returns a hash code value for this postprocessor.
	 */
	public int hashCode() {
		return Objects.hash(value);
	}
		
	/**
	 * Returns true if the specified object is equals to this processor, i.e. the classes of both are equals and indexes are equals.
	 *
	 * return true if the specified object is equalis to this processor.
	 */
	@Override
	public boolean equals(Object obj) {
	   return fr.wedia.confres.utils.Utils.equals(CustomProcessorExampleOfInteractionWithThePlugin.class, this, obj, (o1,o2)-> Objects.equals(o1.value,o2.value));
	}
	
}

{
    "mappings": {
        "portal": "_portal@club-wed@:surferRole@:userAgent",
        "picker": "_portal@club-wed@:picker"
    },
    "postProcessors": {
        "surferRole": "fr.wedia.confres.core.model.processor.SurferRolePostProcessor",
        "userAgent": {
            "processor": "fr.wedia.confres.core.model.processor.UserAgentPostProcessor",
            "config": [
                {
                    "pattern": ".*Mobi.*",
                    "name": "mobile"
                }
            ]
        }
    }
}

Avoid using the query to retrieve context information (like the surfer for example). Always prefer to use the context when possible. Simulation queries can pass context information (like the surfer, or a header) as parameters, and this information is put in ProcessorContext, the query cannot be modified. Moreover, during unit tests your postprocessor could be called without request with a mocked server. In this case, the request instance will be null. If the context does not give you access to the information you want, you can use the request, but in this case your postprocessor cannot be used in simulation for this information nor in testing.