15 files changed, 148 insertions, 102 deletions

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 80d6b4f3..62f74f13 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -21,10 +21,11 @@ jobs:
         uses: actions/checkout@v2
         with:
           fetch-depth: ${{ !steps.check-secret.outputs.is_SONAR_TOKEN_set && 1 || 0 }}  # Shallow clones should be disabled for a better relevancy of SonarCloud analysis
-      - name: Set up JDK 17
-        uses: actions/setup-java@v1
+      - name: Set up JDK 19
+        uses: actions/setup-java@v2
         with:
-          java-version: 17
+          java-version: 19
+          distribution: temurin
       - name: Cache Gradle packages
         uses: actions/cache@v2
         with:
diff --git a/README.md b/README.md
index dfb4685e..33d89786 100644
--- a/README.md
+++ b/README.md
@@ -6,27 +6,28 @@
 
 ### With Eclipse IDE
 
-1. Download and install a _Java 17_ compatible JDK. For Windows, prefer OpenJDK builds from [Adoptium](https://adoptium.net/).
+1. Download and install a _Java 19_ compatible JDK. For Windows, prefer OpenJDK builds from [Adoptium](https://adoptium.net/).
 
-2. Download and extract the [Eclipse IDE for Java and DSL Developers 2021-12](https://www.eclipse.org/downloads/packages/release/2021-12/r/eclipse-ide-java-and-dsl-developers) package.
+2. Download and extract the [Eclipse IDE for Java and DSL Developers 2022-09](https://www.eclipse.org/downloads/packages/release/2022-09/r/eclipse-ide-java-and-dsl-developers) package.
 
 3. Launch Eclipse and create a new workspace.
 
-4. Open _Help > Install New Software..._ and install the following software from the _2021-12_ update site:
+4. Open _Help > Install New Software..._ and install the following software from the _2022-09_ update site:
     * _Modeling > Ecore Diagram Editor (SDK)_
 
 5. Open _Help > Eclipse Marketplace_ and install the following software:
     * _EclEmma Java Code Coverage_
+    * _Java 19 Support for Eclipse 2022-09 (4.25)_
     * _SonarLint_
 
 6. Open _Window > Preferences_ and set the following preferences:
     * _General > Workspace > Text file encoding_ should be _UTF-8_.
     * _General > Workspace > New text file line delimiter_ should be _Unix_.
-    * Add the JDK 17 to _Java > Installed JREs_.
-    * Make sure JDK 17 is selected for _JavaSE-17_ at _Java > Installed JREs > Execution Environments_.
+    * Add the JDK 19 to _Java > Installed JREs_.
+    * Make sure JDK 19 is selected for _JavaSE-19_ at _Java > Installed JREs > Execution Environments_.
     * Set _Gradle > Java home_ to the `JAVA_HOME` directory (the directory which contains the `bin` directory) of JDK 17. Here, Buildship will show a yellow warning sign, which can be safely ignored.
-    * Set _Java > Compiler > JDK Compliance > Compiler compliance level_ to _17_. The warning about using Java 16 system libraries during compilation should disappear.
-          
+    * Set _Java > Compiler > JDK Compliance > Compiler compliance level_ to _19_. The warning about using Java 16 system libraries during compilation should disappear.
+
 7. Clone the project Git repository but do not import it into Eclipse yet.
 
 8. Open a new terminal an run `./gradlew prepareEclipse` (`.\gradlew prepareEclipse` on Windows) in the cloned repository.
@@ -36,11 +37,11 @@
 
 9. Select _File > Import... > Gradle > Existing Gradle Project_ and import the cloned repository in Eclipse.
     * Make sure to select the root of the repository (containing this file) as the _Project root directory_ and that the _Gradle distribution_ is _Gradle wrapper_.
-    * If you have previously imported the project into Eclipse, this step will likely fail. In that case, you should remove the projects from Eclipse, run `git clean -fxd` in the repository, and start over from step 8. 
+    * If you have previously imported the project into Eclipse, this step will likely fail. In that case, you should remove the projects from Eclipse, run `git clean -fxd` in the repository, and start over from step 8.
 
 ### With IntelliJ IDEA
 
-It is possible to import the project into IntelliJ IDEA, but it gives no editing help for Xtext (`*.xtext`), MWE2 (`*.mwe2`), and Xtend (`*.xtend`) and Ecore class diagrams (`*.aird`, `*.ecore`, `*.genmodel`). 
+It is possible to import the project into IntelliJ IDEA, but it gives no editing help for Xtext (`*.xtext`), MWE2 (`*.mwe2`), and Xtend (`*.xtend`) and Ecore class diagrams (`*.aird`, `*.ecore`, `*.genmodel`).
 
 ## License
 
diff --git a/buildSrc/src/main/groovy/refinery-java-application.gradle b/buildSrc/src/main/groovy/refinery-java-application.gradle
index c38ccdb3..9abfc2b3 100644
--- a/buildSrc/src/main/groovy/refinery-java-application.gradle
+++ b/buildSrc/src/main/groovy/refinery-java-application.gradle
@@ -4,6 +4,10 @@ plugins {
         id 'refinery-java-conventions'
 }
 
+application {
+        applicationDefaultJvmArgs += '--enable-preview'
+}
+
 for (taskName in ['distTar', 'distZip', 'shadowDistTar', 'shadowDistZip']) {
         tasks.named(taskName) {
                 enabled = false
diff --git a/buildSrc/src/main/groovy/refinery-java-conventions.gradle b/buildSrc/src/main/groovy/refinery-java-conventions.gradle
index b95153ce..eedefdf8 100644
--- a/buildSrc/src/main/groovy/refinery-java-conventions.gradle
+++ b/buildSrc/src/main/groovy/refinery-java-conventions.gradle
@@ -21,7 +21,7 @@ dependencies {
 }
 
 java.toolchain {
-        languageVersion = JavaLanguageVersion.of(17)
+        languageVersion = JavaLanguageVersion.of(19)
 }
 
 def jacocoTestReport = tasks.named('jacocoTestReport')
@@ -53,6 +53,18 @@ tasks.named('jar') {
         }
 }
 
+tasks.withType(JavaCompile) {
+        options.compilerArgs += '--enable-preview'
+}
+
+tasks.withType(Test) {
+        jvmArgs += '--enable-preview'
+}
+
+tasks.withType(JavaExec) {
+        jvmArgs += '--enable-preview'
+}
+
 def generateEclipseSourceFolders = tasks.register('generateEclipseSourceFolders')
 
 tasks.register('prepareEclipse') {
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index d8b3d4d8..e8b7f5dd 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,6 +1,6 @@
 [versions]
 eclipseCollections = "11.1.0"
-jetty = "11.0.12"
+jetty = "12.0.0.alpha2"
 jmh = "1.36"
 junit = "5.9.1"
 mockito = "4.9.0"
@@ -19,9 +19,9 @@ gradlePlugin-shadow = { group = "gradle.plugin.com.github.johnrengelman", name =
 gradlePlugin-sonarqube = { group = "org.sonarsource.scanner.gradle", name = "sonarqube-gradle-plugin", version = "3.3" }
 hamcrest = { group = "org.hamcrest", name = "hamcrest", version = "2.2" }
 jetty-server = { group = "org.eclipse.jetty", name = "jetty-server", version.ref = "jetty" }
-jetty-servlet = { group = "org.eclipse.jetty", name = "jetty-servlet", version.ref = "jetty" }
-jetty-websocket-client = { group = "org.eclipse.jetty.websocket", name = "websocket-jetty-client", version.ref = "jetty" }
-jetty-websocket-server = { group = "org.eclipse.jetty.websocket", name = "websocket-jetty-server", version.ref = "jetty" }
+jetty-servlet = { group = "org.eclipse.jetty.ee10", name = "jetty-ee10-servlet", version.ref = "jetty" }
+jetty-websocket-client = { group = "org.eclipse.jetty.ee10.websocket", name = "jetty-ee10-websocket-jetty-client", version.ref = "jetty" }
+jetty-websocket-server = { group = "org.eclipse.jetty.ee10.websocket", name = "jetty-ee10-websocket-jetty-server", version.ref = "jetty" }
 jmh-core = { group = "org.openjdk.jmh", name = "jmh-core", version.ref = "jmh" }
 jmh-annprocess = { group = "org.openjdk.jmh", name = "jmh-generator-annprocess", version.ref = "jmh" }
 junit-api = { group = "org.junit.jupiter", name = "junit-jupiter-api", version.ref = "junit" }
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index ae04661e..f88321a2 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6-rc-4-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/subprojects/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java b/subprojects/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
index ec55036f..706413a9 100644
--- a/subprojects/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
+++ b/subprojects/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
@@ -3,12 +3,13 @@
  */
 package tools.refinery.language.web;
 
+import org.eclipse.xtext.ide.ExecutorServiceProvider;
 import org.eclipse.xtext.web.server.XtextServiceDispatcher;
 import org.eclipse.xtext.web.server.model.IWebDocumentProvider;
 import org.eclipse.xtext.web.server.model.XtextWebDocumentAccess;
 import org.eclipse.xtext.web.server.occurrences.OccurrencesService;
-
 import tools.refinery.language.web.occurrences.ProblemOccurrencesService;
+import tools.refinery.language.web.xtext.VirtualThreadExecutorServiceProvider;
 import tools.refinery.language.web.xtext.server.push.PushServiceDispatcher;
 import tools.refinery.language.web.xtext.server.push.PushWebDocumentAccess;
 import tools.refinery.language.web.xtext.server.push.PushWebDocumentProvider;
@@ -20,16 +21,20 @@ public class ProblemWebModule extends AbstractProblemWebModule {
         public Class<? extends IWebDocumentProvider> bindIWebDocumentProvider() {
                 return PushWebDocumentProvider.class;
         }
-        
+
         public Class<? extends XtextWebDocumentAccess> bindXtextWebDocumentAccess() {
                 return PushWebDocumentAccess.class;
         }
-        
+
         public Class<? extends XtextServiceDispatcher> bindXtextServiceDispatcher() {
                 return PushServiceDispatcher.class;
         }
-        
+
         public Class<? extends OccurrencesService> bindOccurrencesService() {
                 return ProblemOccurrencesService.class;
         }
+
+        public Class<? extends ExecutorServiceProvider> bindExecutorServiceProvider() {
+                return VirtualThreadExecutorServiceProvider.class;
+        }
 }
diff --git a/subprojects/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java b/subprojects/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
index 58c8ea4e..5da16850 100644
--- a/subprojects/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
+++ b/subprojects/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
@@ -5,20 +5,21 @@ package tools.refinery.language.web;
 
 import jakarta.servlet.DispatcherType;
 import jakarta.servlet.SessionTrackingMode;
+import org.eclipse.jetty.ee10.servlet.DefaultServlet;
+import org.eclipse.jetty.ee10.servlet.ServletContextHandler;
+import org.eclipse.jetty.ee10.servlet.ServletHolder;
+import org.eclipse.jetty.ee10.servlet.SessionHandler;
+import org.eclipse.jetty.ee10.websocket.server.config.JettyWebSocketServletContainerInitializer;
 import org.eclipse.jetty.server.Server;
-import org.eclipse.jetty.server.session.SessionHandler;
-import org.eclipse.jetty.servlet.DefaultServlet;
-import org.eclipse.jetty.servlet.ServletContextHandler;
-import org.eclipse.jetty.servlet.ServletHolder;
+import org.eclipse.jetty.util.VirtualThreads;
 import org.eclipse.jetty.util.resource.Resource;
-import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
+import org.eclipse.jetty.util.resource.ResourceFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import tools.refinery.language.web.config.BackendConfigServlet;
 import tools.refinery.language.web.xtext.servlet.XtextWebSocketServlet;
 
 import java.io.File;
-import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -42,13 +43,18 @@ public class ServerLauncher {
 
         private final Server server;
 
-        public ServerLauncher(InetSocketAddress bindAddress, Resource baseResource, String[] allowedOrigins,
-                                                  String webSocketUrl) {
+        public ServerLauncher(InetSocketAddress bindAddress, String[] allowedOrigins, String webSocketUrl) {
                 server = new Server(bindAddress);
+                if (server.getThreadPool() instanceof VirtualThreads.Configurable virtualThreadsConfigurable) {
+                        // Change this to setVirtualThreadsExecutor once
+                        // https://github.com/eclipse/jetty.project/commit/83154b4ffe4767ef44981598d6c26e6a5d32e57c gets released.
+                        virtualThreadsConfigurable.setUseVirtualThreads(VirtualThreads.areSupported());
+                }
                 var handler = new ServletContextHandler();
                 addSessionHandler(handler);
                 addProblemServlet(handler, allowedOrigins);
                 addBackendConfigServlet(handler, webSocketUrl);
+                var baseResource = getBaseResource();
                 if (baseResource != null) {
                         handler.setBaseResource(baseResource);
                         handler.setWelcomeFiles(new String[]{"index.html"});
@@ -95,6 +101,35 @@ public class ServerLauncher {
                 handler.addServlet(defaultServletHolder, "/");
         }
 
+        private Resource getBaseResource() {
+                var factory = ResourceFactory.of(server);
+                var baseResourceOverride = System.getenv("BASE_RESOURCE");
+                if (baseResourceOverride != null) {
+                        // If a user override is provided, use it.
+                        return factory.newResource(baseResourceOverride);
+                }
+                var indexUrlInJar = ServerLauncher.class.getResource("/webapp/index.html");
+                if (indexUrlInJar != null) {
+                        // If the app is packaged in the jar, serve it.
+                        URI webRootUri = null;
+                        try {
+                                webRootUri = URI.create(indexUrlInJar.toURI().toASCIIString().replaceFirst("/index.html$", "/"));
+                        } catch (URISyntaxException e) {
+                                throw new IllegalStateException("Jar has invalid base resource URI", e);
+                        }
+                        return factory.newResource(webRootUri);
+                }
+                // Look for unpacked production artifacts (convenience for running from IDE).
+                var unpackedResourcePathComponents = new String[]{System.getProperty("user.dir"), "build", "webpack",
+                                "production"};
+                var unpackedResourceDir = new File(String.join(File.separator, unpackedResourcePathComponents));
+                if (unpackedResourceDir.isDirectory()) {
+                        return factory.newResource(unpackedResourceDir.toPath());
+                }
+                // Fall back to just serving a 404.
+                return null;
+        }
+
         public void start() throws Exception {
                 server.start();
                 LOG.info("Server started on {}", server.getURI());
@@ -104,10 +139,9 @@ public class ServerLauncher {
         public static void main(String[] args) {
                 try {
                         var bindAddress = getBindAddress();
-                        var baseResource = getBaseResource();
                         var allowedOrigins = getAllowedOrigins();
                         var webSocketUrl = getWebSocketUrl();
-                        var serverLauncher = new ServerLauncher(bindAddress, baseResource, allowedOrigins, webSocketUrl);
+                        var serverLauncher = new ServerLauncher(bindAddress, allowedOrigins, webSocketUrl);
                         serverLauncher.start();
                 } catch (Exception exception) {
                         LOG.error("Fatal server error", exception);
@@ -137,29 +171,6 @@ public class ServerLauncher {
                 return new InetSocketAddress(listenAddress, listenPort);
         }
 
-        private static Resource getBaseResource() throws IOException, URISyntaxException {
-                var baseResourceOverride = System.getenv("BASE_RESOURCE");
-                if (baseResourceOverride != null) {
-                        // If a user override is provided, use it.
-                        return Resource.newResource(baseResourceOverride);
-                }
-                var indexUrlInJar = ServerLauncher.class.getResource("/webapp/index.html");
-                if (indexUrlInJar != null) {
-                        // If the app is packaged in the jar, serve it.
-                        var webRootUri = URI.create(indexUrlInJar.toURI().toASCIIString().replaceFirst("/index.html$", "/"));
-                        return Resource.newResource(webRootUri);
-                }
-                // Look for unpacked production artifacts (convenience for running from IDE).
-                var unpackedResourcePathComponents = new String[]{System.getProperty("user.dir"), "build", "webpack",
-                                "production"};
-                var unpackedResourceDir = new File(String.join(File.separator, unpackedResourcePathComponents));
-                if (unpackedResourceDir.isDirectory()) {
-                        return Resource.newResource(unpackedResourceDir);
-                }
-                // Fall back to just serving a 404.
-                return null;
-        }
-
         private static String getPublicHost() {
                 var publicHost = System.getenv("PUBLIC_HOST");
                 if (publicHost != null) {
diff --git a/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/VirtualThreadExecutorServiceProvider.java b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/VirtualThreadExecutorServiceProvider.java
new file mode 100644
index 00000000..ead98927
--- /dev/null
+++ b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/VirtualThreadExecutorServiceProvider.java
@@ -0,0 +1,20 @@
+package tools.refinery.language.web.xtext;
+
+import org.eclipse.xtext.ide.ExecutorServiceProvider;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class VirtualThreadExecutorServiceProvider extends ExecutorServiceProvider {
+        private static final String THREAD_POOL_NAME = "xtextWeb";
+
+        @Override
+        protected ExecutorService createInstance(String key) {
+                var name = key == null ? THREAD_POOL_NAME : THREAD_POOL_NAME + "-" + key;
+                return Executors.newThreadPerTaskExecutor(Thread.ofVirtual()
+                                .allowSetThreadLocals(true)
+                                .inheritInheritableThreadLocals(false)
+                                .name(name + "-", 0)
+                                .factory());
+        }
+}
diff --git a/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
index 82391d8b..1d9e0463 100644
--- a/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
+++ b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
@@ -3,10 +3,10 @@ package tools.refinery.language.web.xtext.servlet;
 import com.google.gson.Gson;
 import com.google.gson.JsonIOException;
 import com.google.gson.JsonParseException;
-import org.eclipse.jetty.websocket.api.Session;
-import org.eclipse.jetty.websocket.api.StatusCode;
-import org.eclipse.jetty.websocket.api.WriteCallback;
-import org.eclipse.jetty.websocket.api.annotations.*;
+import org.eclipse.jetty.ee10.websocket.api.Session;
+import org.eclipse.jetty.ee10.websocket.api.StatusCode;
+import org.eclipse.jetty.ee10.websocket.api.WriteCallback;
+import org.eclipse.jetty.ee10.websocket.api.annotations.*;
 import org.eclipse.xtext.resource.IResourceServiceProvider;
 import org.eclipse.xtext.web.server.ISession;
 import org.slf4j.Logger;
@@ -17,7 +17,6 @@ import tools.refinery.language.web.xtext.server.TransactionExecutor;
 import tools.refinery.language.web.xtext.server.message.XtextWebRequest;
 import tools.refinery.language.web.xtext.server.message.XtextWebResponse;
 
-import java.io.IOException;
 import java.io.Reader;
 
 @WebSocket
@@ -108,12 +107,7 @@ public class XtextWebSocket implements WriteCallback, ResponseHandler {
                         throw new ResponseHandlerException("Trying to send message when websocket is disconnected");
                 }
                 var responseString = gson.toJson(response);
-                try {
-                        webSocketSession.getRemote().sendPartialString(responseString, true, this);
-                } catch (IOException e) {
-                        throw new ResponseHandlerException(
-                                        "Cannot initiate async write to websocket " + webSocketSession.getRemoteAddress(), e);
-                }
+                webSocketSession.getRemote().sendPartialString(responseString, true, this);
         }
 
         @Override
diff --git a/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
index a2ad2943..9a32b937 100644
--- a/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
+++ b/subprojects/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
@@ -2,7 +2,7 @@ package tools.refinery.language.web.xtext.servlet;
 
 import jakarta.servlet.ServletConfig;
 import jakarta.servlet.ServletException;
-import org.eclipse.jetty.websocket.server.*;
+import org.eclipse.jetty.ee10.websocket.server.*;
 import org.eclipse.xtext.resource.IResourceServiceProvider;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
diff --git a/subprojects/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java b/subprojects/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
index 652fc13b..6dfce780 100644
--- a/subprojects/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
+++ b/subprojects/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
@@ -1,17 +1,17 @@
 package tools.refinery.language.web;
 
+import org.eclipse.jetty.ee10.servlet.ServletContextHandler;
+import org.eclipse.jetty.ee10.servlet.ServletHolder;
+import org.eclipse.jetty.ee10.websocket.api.Session;
+import org.eclipse.jetty.ee10.websocket.api.StatusCode;
+import org.eclipse.jetty.ee10.websocket.api.annotations.WebSocket;
+import org.eclipse.jetty.ee10.websocket.api.exceptions.UpgradeException;
+import org.eclipse.jetty.ee10.websocket.client.ClientUpgradeRequest;
+import org.eclipse.jetty.ee10.websocket.client.WebSocketClient;
+import org.eclipse.jetty.ee10.websocket.server.config.JettyWebSocketServletContainerInitializer;
 import org.eclipse.jetty.http.HttpHeader;
 import org.eclipse.jetty.http.HttpStatus;
 import org.eclipse.jetty.server.Server;
-import org.eclipse.jetty.servlet.ServletContextHandler;
-import org.eclipse.jetty.servlet.ServletHolder;
-import org.eclipse.jetty.websocket.api.Session;
-import org.eclipse.jetty.websocket.api.StatusCode;
-import org.eclipse.jetty.websocket.api.annotations.WebSocket;
-import org.eclipse.jetty.websocket.api.exceptions.UpgradeException;
-import org.eclipse.jetty.websocket.client.ClientUpgradeRequest;
-import org.eclipse.jetty.websocket.client.WebSocketClient;
-import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
 import org.eclipse.xtext.testing.GlobalRegistries;
 import org.eclipse.xtext.testing.GlobalRegistries.GlobalStateMemento;
 import org.junit.jupiter.api.AfterEach;
diff --git a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/AwaitTerminationExecutorServiceProvider.java b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/AwaitTerminationExecutorServiceProvider.java
index b70d0ed5..ebf36f13 100644
--- a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/AwaitTerminationExecutorServiceProvider.java
+++ b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/AwaitTerminationExecutorServiceProvider.java
@@ -1,16 +1,15 @@
 package tools.refinery.language.web.tests;
 
+import com.google.inject.Singleton;
+import org.eclipse.xtext.ide.ExecutorServiceProvider;
+
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.ExecutorService;
 
-import org.eclipse.xtext.ide.ExecutorServiceProvider;
-
-import com.google.inject.Singleton;
-
 @Singleton
 public class AwaitTerminationExecutorServiceProvider extends ExecutorServiceProvider {
-        private List<RestartableCachedThreadPool> servicesToShutDown = new ArrayList<>();
+        private final List<RestartableCachedThreadPool> servicesToShutDown = new ArrayList<>();
 
         @Override
         protected ExecutorService createInstance(String key) {
diff --git a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/RestartableCachedThreadPool.java b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/RestartableCachedThreadPool.java
index 1468273d..8e5038ae 100644
--- a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/RestartableCachedThreadPool.java
+++ b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/RestartableCachedThreadPool.java
@@ -1,45 +1,44 @@
 package tools.refinery.language.web.tests;
 
-import java.util.Collection;
-import java.util.List;
-import java.util.concurrent.Callable;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.*;
+
+@SuppressWarnings("NullableProblems")
 public class RestartableCachedThreadPool implements ExecutorService {
         private static final Logger LOG = LoggerFactory.getLogger(RestartableCachedThreadPool.class);
-        
+
         private ExecutorService delegate;
 
         public RestartableCachedThreadPool() {
                 delegate = createExecutorService();
         }
-        
+
         public void waitForAllTasksToFinish() {
                 delegate.shutdown();
                 waitForTermination();
                 delegate = createExecutorService();
         }
-        
+
         public void waitForTermination() {
+                boolean result = false;
                 try {
-                        delegate.awaitTermination(1, TimeUnit.SECONDS);
+                        result = delegate.awaitTermination(1, TimeUnit.SECONDS);
                 } catch (InterruptedException e) {
                         LOG.warn("Interrupted while waiting for delegate executor to stop", e);
                 }
+                if (!result) {
+                        throw new IllegalStateException("Failed to shut down Xtext thread pool");
+                }
         }
-        
+
         protected ExecutorService createExecutorService() {
                 return Executors.newCachedThreadPool();
         }
-        
+
         @Override
         public boolean awaitTermination(long arg0, TimeUnit arg1) throws InterruptedException {
                 return delegate.awaitTermination(arg0, arg1);
diff --git a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/WebSocketIntegrationTestClient.java b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/WebSocketIntegrationTestClient.java
index 74695c9a..f19c10ca 100644
--- a/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/WebSocketIntegrationTestClient.java
+++ b/subprojects/language-web/src/test/java/tools/refinery/language/web/tests/WebSocketIntegrationTestClient.java
@@ -1,10 +1,10 @@
 package tools.refinery.language.web.tests;
 
-import org.eclipse.jetty.websocket.api.Session;
-import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
-import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
-import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
-import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
+import org.eclipse.jetty.ee10.websocket.api.Session;
+import org.eclipse.jetty.ee10.websocket.api.annotations.OnWebSocketClose;
+import org.eclipse.jetty.ee10.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.ee10.websocket.api.annotations.OnWebSocketError;
+import org.eclipse.jetty.ee10.websocket.api.annotations.OnWebSocketMessage;
 
 import java.io.IOException;
 import java.time.Duration;