/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package io.undertow;

import io.undertow.attribute.ExchangeAttribute;
import io.undertow.predicate.Predicate;
import io.undertow.predicate.PredicateParser;
import io.undertow.predicate.PredicatesHandler;
import io.undertow.server.HttpHandler;
import io.undertow.server.JvmRouteHandler;
import io.undertow.server.RoutingHandler;
import io.undertow.server.handlers.SetErrorHandler;
import io.undertow.server.handlers.AccessControlListHandler;
import io.undertow.server.handlers.LearningPushHandler;
import io.undertow.server.handlers.DateHandler;
import io.undertow.server.handlers.DisableCacheHandler;
import io.undertow.server.handlers.ExceptionHandler;
import io.undertow.server.handlers.GracefulShutdownHandler;
import io.undertow.server.handlers.HttpContinueAcceptingHandler;
import io.undertow.server.handlers.HttpContinueReadHandler;
import io.undertow.server.handlers.HttpTraceHandler;
import io.undertow.server.handlers.IPAddressAccessControlHandler;
import io.undertow.server.handlers.NameVirtualHostHandler;
import io.undertow.server.handlers.PathHandler;
import io.undertow.server.handlers.PathTemplateHandler;
import io.undertow.server.handlers.PredicateContextHandler;
import io.undertow.server.handlers.PredicateHandler;
import io.undertow.server.handlers.ProxyPeerAddressHandler;
import io.undertow.server.handlers.RedirectHandler;
import io.undertow.server.handlers.RequestDumpingHandler;
import io.undertow.server.handlers.RequestLimit;
import io.undertow.server.handlers.RequestLimitingHandler;
import io.undertow.server.handlers.ResponseRateLimitingHandler;
import io.undertow.server.handlers.SetAttributeHandler;
import io.undertow.server.handlers.SetHeaderHandler;
import io.undertow.server.handlers.URLDecodingHandler;
import io.undertow.server.handlers.builder.PredicatedHandler;
import io.undertow.server.handlers.proxy.ProxyClient;
import io.undertow.server.handlers.proxy.ProxyHandler;
import io.undertow.server.handlers.resource.ResourceHandler;
import io.undertow.server.handlers.resource.ResourceManager;
import io.undertow.server.handlers.sse.ServerSentEventConnectionCallback;
import io.undertow.server.handlers.sse.ServerSentEventHandler;
import io.undertow.websockets.WebSocketConnectionCallback;
import io.undertow.websockets.WebSocketProtocolHandshakeHandler;

import java.util.List;
import java.util.concurrent.TimeUnit;

Utility class with convenience methods for dealing with handlers
Author:
Stuart Douglas/**
 * Utility class with convenience methods for dealing with handlers
 *
 * @author Stuart Douglas
 */
public class Handlers {

    
Creates a new path handler, with the default handler specified
Params:
defaultHandler – The default handler
Returns:
A new path handler/**
     * Creates a new path handler, with the default handler specified
     *
     * @param defaultHandler The default handler
     * @return A new path handler
     */
    public static PathHandler path(final HttpHandler defaultHandler) {
        return new PathHandler(defaultHandler);
    }

    
Creates a new path handler
Returns:
A new path handler/**
     * Creates a new path handler
     *
     * @return A new path handler
     */
    public static PathHandler path() {
        return new PathHandler();
    }

    
Returns:
a new path template handler/**
     *
     * @return a new path template handler
     */
    public static PathTemplateHandler pathTemplate() {
        return new PathTemplateHandler();
    }

    
Params:
rewriteQueryParams – If the query params should be rewritten
Returns:
The routing handler/**
     *
     * @param rewriteQueryParams If the query params should be rewritten
     * @return The routing handler
     */
    public static RoutingHandler routing(boolean rewriteQueryParams) {
        return new RoutingHandler(rewriteQueryParams);
    }

    
Returns:
a new routing handler/**
     *
     * @return a new routing handler
     */
    public static RoutingHandler routing() {
        return new RoutingHandler();
    }

    
Params:
rewriteQueryParams – If the query params should be rewritten
Returns:
The path template handler/**
     *
     * @param rewriteQueryParams If the query params should be rewritten
     * @return The path template handler
     */
    public static PathTemplateHandler pathTemplate(boolean rewriteQueryParams) {
        return new PathTemplateHandler(rewriteQueryParams);
    }


    
Creates a new virtual host handler
Returns:
A new virtual host handler/**
     * Creates a new virtual host handler
     *
     * @return A new virtual host handler
     */
    public static NameVirtualHostHandler virtualHost() {
        return new NameVirtualHostHandler();
    }

    
Creates a new virtual host handler using the provided default handler
Returns:
A new virtual host handler/**
     * Creates a new virtual host handler using the provided default handler
     *
     * @return A new virtual host handler
     */
    public static NameVirtualHostHandler virtualHost(final HttpHandler defaultHandler) {
        return new NameVirtualHostHandler().setDefaultHandler(defaultHandler);
    }

    
Creates a new virtual host handler that uses the provided handler as the root handler for the given hostnames.
Params:
hostHandler – The host handler
hostnames –   The host names
Returns:
A new virtual host handler/**
     * Creates a new virtual host handler that uses the provided handler as the root handler for the given hostnames.
     *
     * @param hostHandler The host handler
     * @param hostnames   The host names
     * @return A new virtual host handler
     */
    public static NameVirtualHostHandler virtualHost(final HttpHandler hostHandler, String... hostnames) {
        NameVirtualHostHandler handler = new NameVirtualHostHandler();
        for (String host : hostnames) {
            handler.addHost(host, hostHandler);
        }
        return handler;
    }

    
Creates a new virtual host handler that uses the provided handler as the root handler for the given hostnames.
Params:
defaultHandler – The default handler
hostHandler –    The host handler
hostnames –      The host names
Returns:
A new virtual host handler/**
     * Creates a new virtual host handler that uses the provided handler as the root handler for the given hostnames.
     *
     * @param defaultHandler The default handler
     * @param hostHandler    The host handler
     * @param hostnames      The host names
     * @return A new virtual host handler
     */
    public static NameVirtualHostHandler virtualHost(final HttpHandler defaultHandler, final HttpHandler hostHandler, String... hostnames) {
        return virtualHost(hostHandler, hostnames).setDefaultHandler(defaultHandler);
    }

    
Params:
sessionHandler – The web socket session handler
Returns:
The web socket handler/**
     * @param sessionHandler The web socket session handler
     * @return The web socket handler
     */
    public static WebSocketProtocolHandshakeHandler websocket(final WebSocketConnectionCallback sessionHandler) {
        return new WebSocketProtocolHandshakeHandler(sessionHandler);
    }

    
Params:
sessionHandler – The web socket session handler
next –           The handler to invoke if the web socket connection fails
Returns:
The web socket handler/**
     * @param sessionHandler The web socket session handler
     * @param next           The handler to invoke if the web socket connection fails
     * @return The web socket handler
     */
    public static WebSocketProtocolHandshakeHandler websocket(final WebSocketConnectionCallback sessionHandler, final HttpHandler next) {
        return new WebSocketProtocolHandshakeHandler(sessionHandler, next);
    }

    
A handler for server sent events
Params:
callback – The server sent events callback
Returns:
A new server sent events handler/**
     * A handler for server sent events
     *
     *
     * @param callback The server sent events callback
     * @return A new server sent events handler
     */
    public static ServerSentEventHandler serverSentEvents(ServerSentEventConnectionCallback callback) {
        return new ServerSentEventHandler(callback);
    }

    
A handler for server sent events
Returns:
A new server sent events handler/**
     * A handler for server sent events
     *
     * @return A new server sent events handler
     */
    public static ServerSentEventHandler serverSentEvents() {
        return new ServerSentEventHandler();
    }
    
Return a new resource handler
Params:
resourceManager – The resource manager to use
Returns:
A new resource handler/**
     * Return a new resource handler
     *
     * @param resourceManager The resource manager to use
     * @return A new resource handler
     */
    public static ResourceHandler resource(final ResourceManager resourceManager) {
        return new ResourceHandler(resourceManager).setDirectoryListingEnabled(false);
    }

    
Returns a new redirect handler
Params:
location – The redirect location
Returns:
A new redirect handler/**
     * Returns a new redirect handler
     *
     * @param location The redirect location
     * @return A new redirect handler
     */
    public static RedirectHandler redirect(final String location) {
        return new RedirectHandler(location);
    }

    
Returns a new HTTP trace handler. This handler will handle HTTP TRACE
requests as per the RFC.

WARNING: enabling trace requests may leak information, in general it is recommended that
these be disabled for security reasons.
Params:
next – The next handler in the chain
Returns:
A HTTP trace handler/**
     * Returns a new HTTP trace handler. This handler will handle HTTP TRACE
     * requests as per the RFC.
     * <p>
     * WARNING: enabling trace requests may leak information, in general it is recommended that
     * these be disabled for security reasons.
     *
     * @param next The next handler in the chain
     * @return A HTTP trace handler
     */
    public static HttpTraceHandler trace(final HttpHandler next) {
        return new HttpTraceHandler(next);
    }

    
Returns a new HTTP handler that sets the Date: header.
This is no longer necessary, as it is handled by the connectors directly.
Params:
next – The next handler in the chain
Returns:
A new date handler/**
     * Returns a new HTTP handler that sets the Date: header.
     *
     * This is no longer necessary, as it is handled by the connectors directly.
     *
     * @param next The next handler in the chain
     * @return A new date handler
     */
    @Deprecated
    public static DateHandler date(final HttpHandler next) {
        return new DateHandler(next);
    }

    
Returns a new predicate handler, that will delegate to one of the two provided handlers based on the value of the
provided predicate.
Params:
predicate –    The predicate
trueHandler –  The handler that will be executed if the predicate is true
falseHandler – The handler that will be exected if the predicate is false
See Also:
Predicate
Predicates
Returns:
A new predicate handler/**
     * Returns a new predicate handler, that will delegate to one of the two provided handlers based on the value of the
     * provided predicate.
     *
     * @param predicate    The predicate
     * @param trueHandler  The handler that will be executed if the predicate is true
     * @param falseHandler The handler that will be exected if the predicate is false
     * @return A new predicate handler
     * @see Predicate
     * @see io.undertow.predicate.Predicates
     */
    public static PredicateHandler predicate(final Predicate predicate, final HttpHandler trueHandler, final HttpHandler falseHandler) {
        return new PredicateHandler(predicate, trueHandler, falseHandler);
    }

    
Params:
next – The next handler
Returns:
a handler that sets up a new predicate context/**
     * @param next The next handler
     * @return a handler that sets up a new predicate context
     */
    public static HttpHandler predicateContext(HttpHandler next) {
        return new PredicateContextHandler(next);
    }

    public static PredicatesHandler predicates(final List<PredicatedHandler> handlers, HttpHandler next) {
        final PredicatesHandler predicatesHandler = new PredicatesHandler(next);
        for(PredicatedHandler handler : handlers) {
            predicatesHandler.addPredicatedHandler(handler);
        }
        return predicatesHandler;
    }

    
Returns a handler that sets a response header
Params:
next –        The next handler in the chain
headerName –  The name of the header
headerValue – The header value
Returns:
A new set header handler/**
     * Returns a handler that sets a response header
     *
     * @param next        The next handler in the chain
     * @param headerName  The name of the header
     * @param headerValue The header value
     * @return A new set header handler
     */
    public static SetHeaderHandler header(final HttpHandler next, final String headerName, final String headerValue) {
        return new SetHeaderHandler(next, headerName, headerValue);
    }


    
Returns a handler that sets a response header
Params:
next –        The next handler in the chain
headerName –  The name of the header
headerValue – The header value
Returns:
A new set header handler/**
     * Returns a handler that sets a response header
     *
     * @param next        The next handler in the chain
     * @param headerName  The name of the header
     * @param headerValue The header value
     * @return A new set header handler
     */
    public static SetHeaderHandler header(final HttpHandler next, final String headerName, final ExchangeAttribute headerValue) {
        return new SetHeaderHandler(next, headerName, headerValue);
    }


    
Returns a new handler that can allow or deny access to a resource based on IP address
Params:
next –         The next handler in the chain
defaultAllow – Determine if a non-matching address will be allowed by default
Returns:
A new IP access control handler/**
     * Returns a new handler that can allow or deny access to a resource based on IP address
     *
     * @param next         The next handler in the chain
     * @param defaultAllow Determine if a non-matching address will be allowed by default
     * @return A new IP access control handler
     */
    public static final IPAddressAccessControlHandler ipAccessControl(final HttpHandler next, boolean defaultAllow) {
        return new IPAddressAccessControlHandler(next).setDefaultAllow(defaultAllow);
    }

    
Returns a new handler that can allow or deny access to a resource based an at attribute of the exchange
Params:
next –         The next handler in the chain
defaultAllow – Determine if a non-matching user agent will be allowed by default
Returns:
A new user agent access control handler/**
     * Returns a new handler that can allow or deny access to a resource based an at attribute of the exchange
     *
     * @param next         The next handler in the chain
     * @param defaultAllow Determine if a non-matching user agent will be allowed by default
     * @return A new user agent access control handler
     */
    public static final AccessControlListHandler acl(final HttpHandler next, boolean defaultAllow, ExchangeAttribute attribute) {
        return new AccessControlListHandler(next, attribute).setDefaultAllow(defaultAllow);
    }

    
A handler that automatically handles HTTP 100-continue responses, by sending a continue
response when the first attempt is made to read from the request channel.
Params:
next – The next handler in the chain
Returns:
A new continue handler/**
     * A handler that automatically handles HTTP 100-continue responses, by sending a continue
     * response when the first attempt is made to read from the request channel.
     *
     * @param next The next handler in the chain
     * @return A new continue handler
     */
    public static final HttpContinueReadHandler httpContinueRead(final HttpHandler next) {
        return new HttpContinueReadHandler(next);
    }

    
Returns a handler that sends back a HTTP 100 continue response if the given predicate resolves to true. This handler differs from the one returned by httpContinueRead(HttpHandler) in that it will eagerly send the response, and not wait for the first read attempt. 
Params:
next – The next handler
accept – The predicate used to determine if the request should be accepted
Returns:
The accepting handler/**
     * Returns a handler that sends back a HTTP 100 continue response if the given predicate resolves to true.
     *
     * This handler differs from the one returned by {@link #httpContinueRead(io.undertow.server.HttpHandler)} in
     * that it will eagerly send the response, and not wait for the first read attempt.
     *
     * @param next The next handler
     * @param accept The predicate used to determine if the request should be accepted
     * @return The accepting handler
     */
    public static final HttpContinueAcceptingHandler httpContinueAccepting(final HttpHandler next, final Predicate accept) {
        return new HttpContinueAcceptingHandler(next, accept);
    }

    
Returns a handler that sends back a HTTP 100 continue response to all requests. This handler differs from the one returned by httpContinueRead(HttpHandler) in that it will eagerly send the response, and not wait for the first read attempt. 
Params:
next – The next handler
Returns:
The accepting handler/**
     * Returns a handler that sends back a HTTP 100 continue response to all requests.
     *
     * This handler differs from the one returned by {@link #httpContinueRead(io.undertow.server.HttpHandler)} in
     * that it will eagerly send the response, and not wait for the first read attempt.
     *
     * @param next The next handler
     * @return The accepting handler
     */
    public static final HttpContinueAcceptingHandler httpContinueAccepting(final HttpHandler next) {
        return new HttpContinueAcceptingHandler(next);
    }

    
A handler that will decode the URL, query parameters and to the specified charset.
 If you are using this handler you must set the UndertowOptions.DECODE_URL parameter to false. 

This is not as efficient as using the parsers built in UTF-8 decoder. Unless you need to decode to something other
than UTF-8 you should rely on the parsers decoding instead.
Params:
next –    The next handler in the chain
charset – The charset to decode to
Returns:
a new url decoding handler/**
     * A handler that will decode the URL, query parameters and to the specified charset.
     * <p>
     * If you are using this handler you must set the {@link io.undertow.UndertowOptions#DECODE_URL} parameter to false.
     * <p>
     * This is not as efficient as using the parsers built in UTF-8 decoder. Unless you need to decode to something other
     * than UTF-8 you should rely on the parsers decoding instead.
     *
     * @param next    The next handler in the chain
     * @param charset The charset to decode to
     * @return a new url decoding handler
     */
    public static final URLDecodingHandler urlDecoding(final HttpHandler next, final String charset) {
        return new URLDecodingHandler(next, charset);
    }

    
Returns an attribute setting handler that can be used to set an arbitrary attribute on the exchange.
This includes functions such as adding and removing headers etc.
Params:
next –        The next handler
attribute –  The attribute to set, specified as a string presentation of an ExchangeAttribute
value –  The value to set, specified an a string representation of an ExchangeAttribute
classLoader – The class loader to use to parser the exchange attributes
Returns:
The handler/**
     * Returns an attribute setting handler that can be used to set an arbitrary attribute on the exchange.
     * This includes functions such as adding and removing headers etc.
     *
     * @param next        The next handler
     * @param attribute   The attribute to set, specified as a string presentation of an {@link io.undertow.attribute.ExchangeAttribute}
     * @param value       The value to set, specified an a string representation of an {@link io.undertow.attribute.ExchangeAttribute}
     * @param classLoader The class loader to use to parser the exchange attributes
     * @return The handler
     */
    public static SetAttributeHandler setAttribute(final HttpHandler next, final String attribute, final String value, final ClassLoader classLoader) {
        return new SetAttributeHandler(next, attribute, value, classLoader);
    }

    
Creates the set of handlers that are required to perform a simple rewrite.
Params:
condition – The rewrite condition
target – The rewrite target if the condition matches
next – The next handler
Returns:
/**
     * Creates the set of handlers that are required to perform a simple rewrite.
     * @param condition The rewrite condition
     * @param target The rewrite target if the condition matches
     * @param next The next handler
     * @return
     */
    public static HttpHandler rewrite(final String condition, final String target, final ClassLoader classLoader, final HttpHandler next) {
        return predicateContext(predicate(PredicateParser.parse(condition, classLoader), setAttribute(next, "%R", target, classLoader), next));
    }

    
Returns a new handler that decodes the URL and query parameters into the specified charset, assuming it has not already been done by the connector. For this handler to take effect the parameter UndertowOptions.DECODE_URL must have been set to false. 
Params:
charset – The charset to decode
next – The next handler
Returns:
A handler that decodes the URL/**
     * Returns a new handler that decodes the URL and query parameters into the specified charset, assuming it
     * has not already been done by the connector. For this handler to take effect the parameter
     * {@link UndertowOptions#DECODE_URL} must have been set to false.
     *
     * @param charset The charset to decode
     * @param next The next handler
     * @return A handler that decodes the URL
     */
    public static HttpHandler urlDecodingHandler(final String charset, final HttpHandler next) {
        return new URLDecodingHandler(next, charset);
    }


    
Returns a new handler that can be used to wait for all requests to finish before shutting down the server gracefully.
Params:
next – The next http handler
Returns:
The graceful shutdown handler/**
     * Returns a new handler that can be used to wait for all requests to finish before shutting down the server gracefully.
     *
     * @param next The next http handler
     * @return The graceful shutdown handler
     */
    public static GracefulShutdownHandler gracefulShutdown(HttpHandler next) {
        return new GracefulShutdownHandler(next);
    }

    
Returns a new handler that sets the peer address based on the X-Forwarded-For and
X-Forwarded-Proto header
Params:
next – The next http handler
Returns:
The handler/**
     * Returns a new handler that sets the peer address based on the X-Forwarded-For and
     * X-Forwarded-Proto header
     * @param next The next http handler
     * @return The handler
     */
    public static ProxyPeerAddressHandler proxyPeerAddress(HttpHandler next) {
        return new ProxyPeerAddressHandler(next);
    }

    
Handler that appends the JVM route to the session cookie
Params:
sessionCookieName – The session cookie name
jvmRoute – The JVM route to append
next – The next handler
Returns:
The handler/**
     * Handler that appends the JVM route to the session cookie
     * @param sessionCookieName The session cookie name
     * @param jvmRoute The JVM route to append
     * @param next The next handler
     * @return The handler
     */
    public static JvmRouteHandler jvmRoute(final String sessionCookieName, final String jvmRoute, HttpHandler next) {
        return new JvmRouteHandler(next, sessionCookieName, jvmRoute);
    }

    
Returns a handler that limits the maximum number of requests that can run at a time.
Params:
maxRequest – The maximum number of requests
queueSize –  The maximum number of queued requests
next –       The next handler
Returns:
          The handler/**
     * Returns a handler that limits the maximum number of requests that can run at a time.
     *
     * @param maxRequest The maximum number of requests
     * @param queueSize  The maximum number of queued requests
     * @param next       The next handler
     * @return           The handler
     */
    public static RequestLimitingHandler requestLimitingHandler(final int maxRequest, final int queueSize, HttpHandler next) {
        return new RequestLimitingHandler(maxRequest, queueSize, next);
    }

    
Returns a handler that limits the maximum number of requests that can run at a time.
Params:
requestLimit – The request limit object that can be shared between handlers, to apply the same limits across multiple handlers
next –         The next handler
Returns:
            The handler/**
     * Returns a handler that limits the maximum number of requests that can run at a time.
     *
     * @param requestLimit The request limit object that can be shared between handlers, to apply the same limits across multiple handlers
     * @param next         The next handler
     * @return             The handler
     */
    public static RequestLimitingHandler requestLimitingHandler(final RequestLimit requestLimit, HttpHandler next) {
        return new RequestLimitingHandler(requestLimit, next);
    }

    
Returns a handler that can act as a load balancing reverse proxy.
Params:
proxyClient – The proxy client to use to connect to the remote server
maxRequestTime – The maximum amount of time a request can be in progress before it is forcibly closed
next – The next handler to invoke if the proxy client does not know how to proxy the request
Returns:
The proxy handler/**
     * Returns a handler that can act as a load balancing reverse proxy.
     *
     * @param proxyClient The proxy client to use to connect to the remote server
     * @param maxRequestTime The maximum amount of time a request can be in progress before it is forcibly closed
     * @param next The next handler to invoke if the proxy client does not know how to proxy the request
     * @return The proxy handler
     */
    public static ProxyHandler proxyHandler(ProxyClient proxyClient, int maxRequestTime, HttpHandler next) {
        return ProxyHandler.builder().setProxyClient(proxyClient).setNext(next).setMaxRequestTime(maxRequestTime).build();
    }
    
Returns a handler that can act as a load balancing reverse proxy.
Params:
proxyClient – The proxy client to use to connect to the remote server
next – The next handler to invoke if the proxy client does not know how to proxy the request
Returns:
The proxy handler/**
     * Returns a handler that can act as a load balancing reverse proxy.
     *
     * @param proxyClient The proxy client to use to connect to the remote server
     * @param next The next handler to invoke if the proxy client does not know how to proxy the request
     * @return The proxy handler
     */
    public static ProxyHandler proxyHandler(ProxyClient proxyClient, HttpHandler next) {
        return ProxyHandler.builder().setProxyClient(proxyClient).setNext(next).build();
    }

    
Returns a handler that can act as a load balancing reverse proxy.
Params:
proxyClient – The proxy client to use to connect to the remote server
Returns:
The proxy handler/**
     * Returns a handler that can act as a load balancing reverse proxy.
     *
     * @param proxyClient The proxy client to use to connect to the remote server
     * @return The proxy handler
     */
    public static ProxyHandler proxyHandler(ProxyClient proxyClient) {
        return ProxyHandler.builder().setProxyClient(proxyClient).build();
    }

    
Handler that sets the headers that disable caching of the response
Params:
next – The next handler
Returns:
The handler/**
     * Handler that sets the headers that disable caching of the response
     * @param next The next handler
     * @return The handler
     */
    public static HttpHandler disableCache(final HttpHandler next) {
        return new DisableCacheHandler(next);
    }

    
Returns a handler that dumps requests to the log for debugging purposes.
Params:
next – The next handler
Returns:
The request dumping handler/**
     * Returns a handler that dumps requests to the log for debugging purposes.
     *
     * @param next The next handler
     * @return The request dumping handler
     */
    public static HttpHandler requestDump(final HttpHandler next) {
        return new RequestDumpingHandler(next);
    }

    
Returns a handler that maps exceptions to additional handlers
Params:
next – The next handler
Returns:
The exception handler/**
     * Returns a handler that maps exceptions to additional handlers
     * @param next The next handler
     * @return The exception handler
     */
    public static ExceptionHandler exceptionHandler(final HttpHandler next) {
        return new ExceptionHandler(next);
    }

    
A handler that limits the download speed to a set number of bytes/period
Params:
next – The next handler
bytes – The number of bytes per time period
time – The time period
timeUnit – The units of the time period/**
     *
     * A handler that limits the download speed to a set number of bytes/period
     *
     * @param next The next handler
     * @param bytes The number of bytes per time period
     * @param time The time period
     * @param timeUnit The units of the time period
     */
    public static ResponseRateLimitingHandler responseRateLimitingHandler(HttpHandler next, int bytes,long time, TimeUnit timeUnit) {
        return new ResponseRateLimitingHandler(next, bytes, time, timeUnit);
    }

    
Creates a handler that automatically learns which resources to push based on the referer header
Params:
maxEntries – The maximum number of entries to store
maxAge – The maximum age of the entries
next – The next handler
Returns:
A caching push handler/**
     * Creates a handler that automatically learns which resources to push based on the referer header
     *
     * @param maxEntries The maximum number of entries to store
     * @param maxAge The maximum age of the entries
     * @param next The next handler
     * @return A caching push handler
     */
    public static LearningPushHandler learningPushHandler(int maxEntries, int maxAge, HttpHandler next) {
        return new LearningPushHandler(maxEntries, maxAge, next);
    }

    
A handler that sets response code but continues the exchange so the servlet's
error page can be returned.
Params:
responseCode – The response code to set
next – The next handler
Returns:
A Set Error handler/**
     * A handler that sets response code but continues the exchange so the servlet's
     * error page can be returned.
     *
     * @param responseCode The response code to set
     * @param next The next handler
     * @return A Set Error handler
     */
    public static SetErrorHandler setErrorHandler(int responseCode, HttpHandler next) {
        return new SetErrorHandler(next, responseCode);
    }

    
Creates a handler that automatically learns which resources to push based on the referer header
Params:
maxEntries – The maximum number of entries to store
next – The next handler
Returns:
A caching push handler/**
     * Creates a handler that automatically learns which resources to push based on the referer header
     *
     * @param maxEntries The maximum number of entries to store
     * @param next The next handler
     * @return A caching push handler
     */
    public static LearningPushHandler learningPushHandler(int maxEntries, HttpHandler next) {
        return new LearningPushHandler(maxEntries, -1, next);
    }

    private Handlers() {

    }

    public static void handlerNotNull(final HttpHandler handler) {
        if (handler == null) {
            throw UndertowMessages.MESSAGES.handlerCannotBeNull();
        }
    }
}