RewriteHandler.java

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2025 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.server.handlers;

import java.util.Map;
import java.util.Set;

import io.undertow.UndertowLogger;
import io.undertow.attribute.ConstantExchangeAttribute;
import io.undertow.attribute.ExchangeAttribute;
import io.undertow.attribute.ExchangeAttributes;
import io.undertow.attribute.ReadOnlyAttributeException;
import io.undertow.server.HandlerWrapper;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.server.handlers.builder.HandlerBuilder;

/**
 * @author <a href="mailto:bbaranow@ibm.com">Bartosz Baranowski</a>
 * @author Stuart Douglas
 */
public class RewriteHandler extends SetAttributeHandler {

    public RewriteHandler(HttpHandler next, ExchangeAttribute value) {
        super(next, ExchangeAttributes.relativePath(), value);
    }

    @Override
    public void handleRequest(HttpServerExchange exchange) throws Exception {
        UndertowLogger.PREDICATE_LOGGER.debugf("Request rewritten to [%s] for %s.", getValue().readAttribute(exchange),
                exchange);
        super.handleRequest(exchange);
    }

    @Override
    public String toString() {
        return "rewrite( '" + getValue().toString() + "' )";
    }

    public static class Builder implements HandlerBuilder {

        @Override
        public String name() {
            return "rewrite";
        }

        @Override
        public Map<String, Class<?>> parameters() {
            return Map.of("value", ExchangeAttribute.class);
        }

        @Override
        public Set<String> requiredParameters() {
            return Set.of("value");
        }

        @Override
        public String defaultParameter() {
            return "value";
        }

        @Override
        public HandlerWrapper build(final Map<String, Object> config) {
            final ExchangeAttribute configValue = (ExchangeAttribute) config.get("value");
            ExchangeAttribute tmpValue = null;
            if (configValue instanceof ConstantExchangeAttribute) {
                tmpValue = new ConstantExchangeAttribute(normalize(configValue.readAttribute(null)));
            } else {
                tmpValue = new ExchangeAttribute() {

                    @Override
                    public String readAttribute(HttpServerExchange exchange) {
                        return normalize(configValue.readAttribute(exchange));
                    }

                    @Override
                    public void writeAttribute(HttpServerExchange exchange, String newValue) throws ReadOnlyAttributeException {
                        throw new ReadOnlyAttributeException("constant", newValue);
                    }

                    public String toString() {
                        return "NDA";
                    };
                };
            }
            final ExchangeAttribute value = tmpValue;

            return new HandlerWrapper() {
                @Override
                public HttpHandler wrap(HttpHandler handler) {
                    return new RewriteHandler(handler, value);
                }

            };
        }

        @Override
        public int priority() {
            return 0;
        }

        private String normalize(final String readAttribute) {
            if (readAttribute.startsWith("/")) {
                return readAttribute;
            } else {
                return "/" + readAttribute;
            }
        }
    }
}