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Support for servlets

There is a newer version: 3.18.0.CR1

package io.quarkus.undertow.runtime;

import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.util.List;

import jakarta.servlet.ServletContext;

import io.undertow.Handlers;
import io.undertow.server.HandlerWrapper;
import io.undertow.server.HttpHandler;
import io.undertow.server.handlers.builder.PredicatedHandler;
import io.undertow.server.handlers.builder.PredicatedHandlersParser;
import io.undertow.servlet.ServletExtension;
import io.undertow.servlet.api.DeploymentInfo;

/**
 * Registers the Undertow handlers configured in the app's META-INF/undertow-handlers.conf
 */
public class UndertowHandlersConfServletExtension implements ServletExtension {

    public static final String META_INF_UNDERTOW_HANDLERS_CONF = "META-INF/undertow-handlers.conf";

    @Override
    public void handleDeployment(DeploymentInfo deploymentInfo, ServletContext servletContext) {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        try (InputStream handlers = classLoader.getResourceAsStream(META_INF_UNDERTOW_HANDLERS_CONF)) {
            if (handlers != null) {
                // From Stuart Douglas: Ideally these would be parsed at deployment time and passed into a recorder,
                // however they are likely not bytecode serialisable. Even though this approach
                // does not 100% align with the Quarkus ethos I think it is ok in this case as
                // the gains would be marginal compared to the cost of attempting to make
                // every predicate bytecode serialisable.
                List handlerList = PredicatedHandlersParser.parse(handlers, classLoader);
                if (!handlerList.isEmpty()) {
                    deploymentInfo.addOuterHandlerChainWrapper(new RewriteCorrectingHandlerWrappers.PostWrapper());
                    deploymentInfo.addOuterHandlerChainWrapper(new HandlerWrapper() {
                        @Override
                        public HttpHandler wrap(HttpHandler handler) {
                            return Handlers.predicates(handlerList, handler);
                        }
                    });
                    deploymentInfo.addOuterHandlerChainWrapper(new RewriteCorrectingHandlerWrappers.PreWrapper());
                }
            }
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }
}