PredicatesHandler.java
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* 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.predicate;
import io.undertow.UndertowLogger;
import io.undertow.server.HandlerWrapper;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.server.handlers.builder.HandlerBuilder;
import io.undertow.server.handlers.builder.PredicatedHandler;
import io.undertow.util.AttachmentKey;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
/**
* Handler that can deal with a large number of predicates. chaining together a large number of {@link io.undertow.predicate.PredicatesHandler.Holder}
* instances will make the stack grow to large, so this class is used that can deal with a large number of predicates.
*
* @author Stuart Douglas
*/
public class PredicatesHandler implements HttpHandler {
/**
* static done marker. If this is attached to the exchange it will drop out immediately.
*/
public static final AttachmentKey<Boolean> DONE = AttachmentKey.create(Boolean.class);
public static final AttachmentKey<Boolean> RESTART = AttachmentKey.create(Boolean.class);
private static final boolean traceEnabled;
static {
traceEnabled = UndertowLogger.PREDICATE_LOGGER.isTraceEnabled();
}
private volatile Holder[] handlers = new Holder[0];
private volatile HttpHandler next;
private final boolean outerHandler;
//non-static, so multiple handlers can co-exist
private final AttachmentKey<Integer> CURRENT_POSITION = AttachmentKey.create(Integer.class);
public PredicatesHandler(HttpHandler next) {
this.next = next;
this.outerHandler = true;
}
public PredicatesHandler(HttpHandler next, boolean outerHandler) {
this.next = next;
this.outerHandler = outerHandler;
}
@Override
public String toString() {
return "PredicatesHandler with " + handlers.length + " predicates";
}
@Override
public void handleRequest(HttpServerExchange exchange) throws Exception {
final int length = handlers.length;
Integer current = exchange.getAttachment(CURRENT_POSITION);
do {
int pos;
if (current == null) {
if (outerHandler) {
exchange.removeAttachment(RESTART);
exchange.removeAttachment(DONE);
if (exchange.getAttachment(Predicate.PREDICATE_CONTEXT) == null) {
exchange.putAttachment(Predicate.PREDICATE_CONTEXT, new TreeMap<String, Object>());
}
}
pos = 0;
} else {
//if it has been marked as done
if (exchange.getAttachment(DONE) != null) {
if (traceEnabled && outerHandler) {
UndertowLogger.PREDICATE_LOGGER.tracef("Predicate chain marked done. Next handler is [%s] for %s.", next.toString(), exchange);
}
exchange.removeAttachment(CURRENT_POSITION);
next.handleRequest(exchange);
return;
}
pos = current;
}
for (; pos < length; ++pos) {
final Holder handler = handlers[pos];
if (handler.predicate.resolve(exchange)) {
if(traceEnabled) {
if( handler.predicate.toString().equals("true") ) {
UndertowLogger.PREDICATE_LOGGER.tracef("Executing handler [%s] for %s.", handler.handler.toString(), exchange);
} else {
UndertowLogger.PREDICATE_LOGGER.tracef("Predicate [%s] resolved to true. Next handler is [%s] for %s.", handler.predicate.toString(), handler.handler.toString(), exchange);
}
}
exchange.putAttachment(CURRENT_POSITION, pos + 1);
handler.handler.handleRequest(exchange);
if(shouldRestart(exchange, current)) {
if(traceEnabled) {
UndertowLogger.PREDICATE_LOGGER.tracef("Restarting predicate resolution for %s.", exchange);
}
break;
} else {
return;
}
} else if(handler.elseBranch != null) {
if(traceEnabled) {
UndertowLogger.PREDICATE_LOGGER.tracef("Predicate [%s] resolved to false. Else branch is [%s] for %s.", handler.predicate.toString(), handler.elseBranch.toString(), exchange);
}
exchange.putAttachment(CURRENT_POSITION, pos + 1);
handler.elseBranch.handleRequest(exchange);
if(shouldRestart(exchange, current)) {
if(traceEnabled) {
UndertowLogger.PREDICATE_LOGGER.tracef("Restarting predicate resolution for %s.", exchange);
}
break;
} else {
return;
}
} else if(traceEnabled) {
UndertowLogger.PREDICATE_LOGGER.tracef("Predicate [%s] resolved to false for %s.", handler.predicate.toString(), exchange);
}
}
} while (shouldRestart(exchange, current));
next.handleRequest(exchange);
}
private boolean shouldRestart(HttpServerExchange exchange, Integer current) {
return exchange.getAttachment(RESTART) != null && outerHandler && current == null;
}
/**
* Adds a new predicated handler.
* <p>
*
* @param predicate
* @param handlerWrapper
*/
public PredicatesHandler addPredicatedHandler(final Predicate predicate, final HandlerWrapper handlerWrapper, final HandlerWrapper elseBranch) {
Holder[] old = handlers;
Holder[] handlers = new Holder[old.length + 1];
System.arraycopy(old, 0, handlers, 0, old.length);
HttpHandler elseHandler = elseBranch != null ? elseBranch.wrap(this) : null;
handlers[old.length] = new Holder(predicate, handlerWrapper.wrap(this), elseHandler);
this.handlers = handlers;
return this;
}
/**
* Adds a new predicated handler.
* <p>
*
* @param predicate
* @param handlerWrapper
*/
public PredicatesHandler addPredicatedHandler(final Predicate predicate, final HandlerWrapper handlerWrapper) {
this.addPredicatedHandler(predicate, handlerWrapper, null);
return this;
}
public PredicatesHandler addPredicatedHandler(final PredicatedHandler handler) {
return addPredicatedHandler(handler.getPredicate(), handler.getHandler(), handler.getElseHandler());
}
public void setNext(HttpHandler next) {
this.next = next;
}
public HttpHandler getNext() {
return next;
}
private static final class Holder {
final Predicate predicate;
final HttpHandler handler;
final HttpHandler elseBranch;
private Holder(Predicate predicate, HttpHandler handler, HttpHandler elseBranch) {
this.predicate = predicate;
this.handler = handler;
this.elseBranch = elseBranch;
}
}
public static final class DoneHandlerBuilder implements HandlerBuilder {
@Override
public String name() {
return "done";
}
@Override
public Map<String, Class<?>> parameters() {
return Collections.emptyMap();
}
@Override
public Set<String> requiredParameters() {
return Collections.emptySet();
}
@Override
public String defaultParameter() {
return null;
}
@Override
public HandlerWrapper build(Map<String, Object> config) {
return new HandlerWrapper() {
@Override
public HttpHandler wrap(final HttpHandler handler) {
return new HttpHandler() {
@Override
public void handleRequest(HttpServerExchange exchange) throws Exception {
exchange.putAttachment(DONE, true);
handler.handleRequest(exchange);
}
@Override
public String toString() {
return "done";
}
};
}
};
}
@Override
public int priority() {
return 0;
}
}
public static final class RestartHandlerBuilder implements HandlerBuilder {
private static final AttachmentKey<Integer> RESTART_COUNT = AttachmentKey.create(Integer.class);
private static final int MAX_RESTARTS = Integer.getInteger("io.undertow.max_restarts", 1000);
@Override
public String name() {
return "restart";
}
@Override
public Map<String, Class<?>> parameters() {
return Collections.emptyMap();
}
@Override
public Set<String> requiredParameters() {
return Collections.emptySet();
}
@Override
public String defaultParameter() {
return null;
}
@Override
public HandlerWrapper build(Map<String, Object> config) {
return new HandlerWrapper() {
@Override
public HttpHandler wrap(final HttpHandler handler) {
return new HttpHandler() {
@Override
public void handleRequest(HttpServerExchange exchange) throws Exception {
Integer restarts = exchange.getAttachment(RESTART_COUNT);
if(restarts == null) {
restarts = 1;
} else {
restarts++;
}
exchange.putAttachment(RESTART_COUNT, restarts);
if(restarts > MAX_RESTARTS) {
throw UndertowLogger.ROOT_LOGGER.maxRestartsExceeded(MAX_RESTARTS);
}
exchange.putAttachment(RESTART, true);
}
@Override
public String toString() {
return "restart";
}
};
}
};
}
@Override
public int priority() {
return 0;
}
}
public static class Wrapper implements HandlerWrapper {
private final List<PredicatedHandler> handlers;
private final boolean outerHandler;
public Wrapper(List<PredicatedHandler> handlers, boolean outerHandler) {
this.handlers = handlers;
this.outerHandler = outerHandler;
}
@Override
public HttpHandler wrap(HttpHandler handler) {
PredicatesHandler h = new PredicatesHandler(handler, outerHandler);
for(PredicatedHandler pred : handlers) {
h.addPredicatedHandler(pred.getPredicate(), pred.getHandler());
}
return h;
}
}
}