Esto es muy útil cuando necesitas:

* Tener lógica compartida (la misma lógica de código una y otra vez).
* Compartir conexiones a bases de datos.
* Imponer seguridad, autenticación, requisitos de roles, etc.
* Y muchas otras cosas...

Todo esto, mientras minimizas la repetición de código.

## Primeros Pasos

Veamos un ejemplo muy simple. Será tan simple que no es muy útil, por ahora.

 * This form extends CreateForm to include fields necessary for updating existing Kuromoji dictionary entries.
 * Kuromoji is a Japanese morphological analyzer, and this dictionary manages custom tokenization rules.
 */
public class EditForm extends CreateForm {

    /**
     * Creates a new EditForm instance.
     */
    public EditForm() {
        super();
    }

    /**

import java.io.Serializable;

import org.codelibs.fess.crawler.entity.ResponseData;
import org.codelibs.fess.crawler.processor.ResponseProcessor;

/**
 * The Rule interface defines the contract for implementing rules that can be applied to
 * response data in a web crawler. Implementations of this interface should provide logic
 * to determine if a given response data matches the rule, retrieve the rule's identifier,

## Get started

In this document we will explain in detail on how to configure all the prerequisites.

> NOTE: If you are interested in AssumeRole API only, skip to [here](https://github.com/minio/minio/blob/master/docs/sts/assume-role.md)

### Prerequisites

 * Form class for editing stemmer override dictionary entries in the admin interface.
 * This form extends CreateForm to include fields necessary for updating existing stemmer override entries.
 * Stemmer overrides define custom stemming rules that take precedence over the default stemming algorithm.
 *
 */
public class EditForm extends CreateForm {

    /**
     * Creates a new EditForm instance.
     */
    public EditForm() {
        super();

    /**
     * Sets whether to use robots.txt disallow rules.
     *
     * @param useRobotsTxtDisallows True to use disallow rules, false otherwise
     */
    public void setUseRobotsTxtDisallows(final boolean useRobotsTxtDisallows) {
        this.useRobotsTxtDisallows = useRobotsTxtDisallows;
    }

    /**
     * Sets whether to use robots.txt allow rules.
     *

		</postConstruct>
		<!-- fess_user index -->
		<postConstruct name="addIndexConfig">
			<arg>"fess_user.user/user"</arg>
		</postConstruct>
		<postConstruct name="addIndexConfig">
			<arg>"fess_user.role/role"</arg>
		</postConstruct>
		<postConstruct name="addIndexConfig">
			<arg>"fess_user.group/group"</arg>
		</postConstruct>
		<!-- fess_log index -->
		<postConstruct name="addIndexConfig">

    }

    /**
     * Returns the action role for this admin action.
     *
     * @return the role name
     */
    @Override
    protected String getActionRole() {
        return ROLE;
    }

    // ===================================================================================

    }

    @Override
    protected String getActionRole() {
        return ROLE;
    }

    /**
     * Show the index page.
     * @return The HTML response.
     */
    @Execute
    @Secured({ ROLE, ROLE + VIEW })
    public HtmlResponse index() {
        saveToken();
        return asListHtml();
    }

    /**

func registerSTSRouter(router *mux.Router) {
	// Initialize STS.
	sts := &stsAPIHandlers{}

	// STS Router
	stsRouter := router.NewRoute().PathPrefix(SlashSeparator).Subrouter()

	// Assume roles with no JWT, handles AssumeRole.
	stsRouter.Methods(http.MethodPost).MatcherFunc(func(r *http.Request, rm *mux.RouteMatch) bool {
		ctypeOk := wildcard.MatchSimple("application/x-www-form-urlencoded*", r.Header.Get(xhttp.ContentType))