feat(web): batched xtext websocket prototype

22 files changed, 402 insertions, 103 deletions

diff --git a/gradle.properties b/gradle.properties
index 5c0df1d3..1020bfc9 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -5,6 +5,7 @@ hamcrestVersion=2.2
 jettyVersion=11.0.6
 jmhVersion=1.32
 junitVersion=5.8.1
+mockitoVersion=4.0.0
 mweVersion=1.6.2.M1
 mwe2Version=2.12.2.M1
 nodeVersion=14.18.0
diff --git a/gradle/junit.gradle b/gradle/junit.gradle
index da0cea8c..44a463c7 100644
--- a/gradle/junit.gradle
+++ b/gradle/junit.gradle
@@ -5,6 +5,8 @@ dependencies {
         testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:${junitVersion}"
         testImplementation "org.junit.jupiter:junit-jupiter-params:${junitVersion}"
         testImplementation "org.hamcrest:hamcrest:${hamcrestVersion}"
+        testImplementation "org.mockito:mockito-core:${mockitoVersion}"
+        testImplementation "org.mockito:mockito-junit-jupiter:${mockitoVersion}"
 }
 
 def jacocoTestReport = tasks.named('jacocoTestReport')
diff --git a/language-web/build.gradle b/language-web/build.gradle
index df23bc91..fc2c9bba 100644
--- a/language-web/build.gradle
+++ b/language-web/build.gradle
@@ -1,5 +1,6 @@
 apply plugin: 'java'
 apply from: "${rootDir}/gradle/xtext-common.gradle"
+apply from: "${rootDir}/gradle/junit.gradle"
 
 dependencies {
         implementation project(':refinery-language')
@@ -11,6 +12,7 @@ dependencies {
         implementation "org.eclipse.jetty.websocket:websocket-jetty-server:${jettyVersion}"
         implementation "org.slf4j:slf4j-simple:${slf4JVersion}"
         implementation "org.slf4j:log4j-over-slf4j:${slf4JVersion}"
+        testImplementation "org.eclipse.xtext:org.eclipse.xtext.testing:${xtextVersion}"
 }
 
 def generateXtextLanguage = project(':refinery-language').tasks.named('generateXtextLanguage')
diff --git a/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java b/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
index 799a9c64..04f38414 100644
--- a/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
+++ b/language-web/src/main/java/tools/refinery/language/web/ProblemWebModule.java
@@ -3,9 +3,15 @@
  */
 package tools.refinery.language.web;
 
+import org.eclipse.xtext.web.server.XtextServiceDispatcher;
+
+import tools.refinery.language.web.xtext.server.NoPrecomputedServicesXtextServiceDispatcher;
 
 /**
  * Use this class to register additional components to be used within the web application.
  */
 public class ProblemWebModule extends AbstractProblemWebModule {
+        public Class<? extends XtextServiceDispatcher> bindXtextServiceDispatcher() {
+                return NoPrecomputedServicesXtextServiceDispatcher.class;
+        }
 }
diff --git a/language-web/src/main/java/tools/refinery/language/web/ProblemWebSocketServlet.java b/language-web/src/main/java/tools/refinery/language/web/ProblemWebSocketServlet.java
index 9ffd6557..df67b521 100644
--- a/language-web/src/main/java/tools/refinery/language/web/ProblemWebSocketServlet.java
+++ b/language-web/src/main/java/tools/refinery/language/web/ProblemWebSocketServlet.java
@@ -3,7 +3,7 @@ package tools.refinery.language.web;
 import org.eclipse.xtext.util.DisposableRegistry;
 
 import jakarta.servlet.ServletException;
-import tools.refinery.language.web.xtext.XtextWebSocketServlet;
+import tools.refinery.language.web.xtext.servlet.XtextWebSocketServlet;
 
 public class ProblemWebSocketServlet extends XtextWebSocketServlet {
 
diff --git a/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java b/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
index f6311070..a71d8e93 100644
--- a/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
+++ b/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java
@@ -23,7 +23,7 @@ import org.slf4j.LoggerFactory;
 
 import jakarta.servlet.DispatcherType;
 import jakarta.servlet.SessionTrackingMode;
-import tools.refinery.language.web.xtext.XtextWebSocketServlet;
+import tools.refinery.language.web.xtext.servlet.XtextWebSocketServlet;
 
 public class ServerLauncher {
         public static final String DEFAULT_LISTEN_ADDRESS = "localhost";
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/server/NoPrecomputedServicesXtextServiceDispatcher.java b/language-web/src/main/java/tools/refinery/language/web/xtext/server/NoPrecomputedServicesXtextServiceDispatcher.java
new file mode 100644
index 00000000..6660d6ac
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/server/NoPrecomputedServicesXtextServiceDispatcher.java
@@ -0,0 +1,16 @@
+package tools.refinery.language.web.xtext.server;
+
+import org.eclipse.xtext.web.server.XtextServiceDispatcher;
+import org.eclipse.xtext.web.server.model.PrecomputedServiceRegistry;
+
+import com.google.inject.Singleton;
+
+@Singleton
+public class NoPrecomputedServicesXtextServiceDispatcher extends XtextServiceDispatcher {
+        @Override
+        protected void registerPreComputedServices(PrecomputedServiceRegistry registry) {
+                // Do not register any precomputed services, because we will always send
+                // requests for any pre-computation in the same websocket message as the
+                // document update request.
+        }
+}
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/ResponseHandler.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/ResponseHandler.java
new file mode 100644
index 00000000..b1fcbc8b
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/ResponseHandler.java
@@ -0,0 +1,8 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import java.io.IOException;
+
+@FunctionalInterface
+public interface ResponseHandler {
+        void onResponse(XtextWebSocketResponse response) throws IOException;
+}
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/SimpleServiceContext.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/SimpleServiceContext.java
index 8036b749..945d5db0 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/SimpleServiceContext.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/SimpleServiceContext.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.util.Map;
 import java.util.Set;
@@ -8,6 +8,7 @@ import org.eclipse.xtext.web.server.ISession;
 import org.eclipse.xtext.web.server.InvalidRequestException;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 
 record SimpleServiceContext(ISession session, Map<String, String> parameters) implements IServiceContext {
 
@@ -17,13 +18,9 @@ record SimpleServiceContext(ISession session, Map<String, String> parameters) im
 
         public static final String STATE_ID_PARAMETER = "requiredStateId";
 
-        public SimpleServiceContext(ISession session, XtextWebSocketRequest request, String stateId, int index) {
-                this(session, addPerTransactionData(request, stateId, request.getRequestData().get(index)));
-        }
-
         @Override
         public Set<String> getParameterKeys() {
-                return parameters.keySet();
+                return ImmutableSet.copyOf(parameters.keySet());
         }
 
         @Override
@@ -36,8 +33,9 @@ record SimpleServiceContext(ISession session, Map<String, String> parameters) im
                 return session;
         }
 
-        private static Map<String, String> addPerTransactionData(XtextWebSocketRequest request, String stateId,
-                        Map<String, String> parameters) {
+        public static IServiceContext ofTransaction(ISession session, XtextWebSocketRequest request, String stateId,
+                        int index) {
+                var parameters = request.getRequestData().get(index);
                 checkParameters(parameters, RESOURCE_NAME_PARAMETER);
                 checkParameters(parameters, CONTENT_TYPE_PARAMETER);
                 checkParameters(parameters, STATE_ID_PARAMETER);
@@ -52,7 +50,8 @@ record SimpleServiceContext(ISession session, Map<String, String> parameters) im
                 if (stateId != null) {
                         builder.put(STATE_ID_PARAMETER, stateId);
                 }
-                return builder.build();
+                var allParameters = builder.build();
+                return new SimpleServiceContext(session, allParameters);
         }
 
         private static void checkParameters(Map<String, String> parameters, String perTransactionParameter) {
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/SimpleSession.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/SimpleSession.java
index 691077d0..09c055a2 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/SimpleSession.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/SimpleSession.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.util.HashMap;
 import java.util.Map;
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocket.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/TransactionExecutor.java
index 0849ccb7..08687097 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocket.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/TransactionExecutor.java
@@ -1,17 +1,8 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.io.IOException;
-import java.io.Reader;
 
 import org.eclipse.emf.common.util.URI;
-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.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.websocket.api.annotations.WebSocket;
 import org.eclipse.xtext.resource.IResourceServiceProvider;
 import org.eclipse.xtext.web.server.IServiceResult;
 import org.eclipse.xtext.web.server.ISession;
@@ -25,87 +16,35 @@ import org.eclipse.xtext.web.server.hover.HoverResult;
 import org.eclipse.xtext.web.server.model.DocumentStateResult;
 import org.eclipse.xtext.web.server.occurrences.OccurrencesResult;
 import org.eclipse.xtext.web.server.persistence.ResourceContentResult;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import com.google.common.base.Strings;
-import com.google.gson.Gson;
-import com.google.gson.JsonIOException;
-import com.google.gson.JsonParseException;
 import com.google.inject.Injector;
 
-@WebSocket
-public class XtextWebSocket {
-        private static final Logger LOG = LoggerFactory.getLogger(XtextWebSocket.class);
-
-        private final Gson gson = new Gson();
-
+public class TransactionExecutor {
         private final ISession session;
 
         private final IResourceServiceProvider.Registry resourceServiceProviderRegistry;
 
-        public XtextWebSocket(ISession session, IResourceServiceProvider.Registry resourceServiceProviderRegistry) {
+        public TransactionExecutor(ISession session, IResourceServiceProvider.Registry resourceServiceProviderRegistry) {
                 this.session = session;
                 this.resourceServiceProviderRegistry = resourceServiceProviderRegistry;
         }
 
-        @OnWebSocketConnect
-        public void onConnect(Session webSocketSession) {
-                LOG.debug("New websocket connection from {}", webSocketSession.getRemoteAddress());
-        }
-
-        @OnWebSocketClose
-        public void onClose(Session webSocketSession, int statusCode, String reason) {
-                if (statusCode == StatusCode.NORMAL) {
-                        LOG.debug("{} closed connection normally: {}", webSocketSession.getRemoteAddress(), reason);
-                } else {
-                        LOG.warn("{} closed connection with status code {}: {}", webSocketSession.getRemoteAddress(), statusCode,
-                                        reason);
-                }
-        }
-
-        @OnWebSocketError
-        public void onError(Session webSocketSession, Throwable error) {
-                LOG.error("Internal websocket error in connection from" + webSocketSession.getRemoteAddress(), error);
-        }
-
-        @OnWebSocketMessage
-        public void onMessage(Session webSocketSession, Reader reader) {
-                XtextWebSocketRequest request;
-                try {
-                        request = gson.fromJson(reader, XtextWebSocketRequest.class);
-                } catch (JsonIOException e) {
-                        LOG.error("Cannot read from websocket from" + webSocketSession.getRemoteAddress(), e);
-                        if (webSocketSession.isOpen()) {
-                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot read payload");
-                        }
-                        return;
-                } catch (JsonParseException e) {
-                        LOG.warn("Malformed websocket request from" + webSocketSession.getRemoteAddress(), e);
-                        webSocketSession.close(XtextStatusCode.INVALID_JSON, "Invalid JSON payload");
-                        return;
-                }
+        public void handleRequest(XtextWebSocketRequest request, ResponseHandler handler) throws IOException {
                 var requestData = request.getRequestData();
                 if (requestData == null || requestData.isEmpty()) {
                         // Nothing to do.
                         return;
                 }
                 int nCalls = requestData.size();
-                try {
-                        int lastCall = handleTransaction(webSocketSession, request);
-                        for (int index = lastCall + 1; index < nCalls; index++) {
-                                sendReply(webSocketSession,
-                                                new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.TRANSACTION_CANCELLED));
-                        }
-                } catch (IOException e) {
-                        LOG.warn("Cannot initiaite async write to websocket " + webSocketSession.getRemoteAddress(), e);
-                        if (webSocketSession.isOpen()) {
-                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot write payload");
-                        }
+                int lastCall = handleTransaction(request, handler);
+                for (int index = lastCall + 1; index < nCalls; index++) {
+                        handler.onResponse(
+                                        new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.TRANSACTION_CANCELLED));
                 }
         }
 
-        protected int handleTransaction(Session webSocketSession, XtextWebSocketRequest request) throws IOException {
+        protected int handleTransaction(XtextWebSocketRequest request, ResponseHandler handler) throws IOException {
                 var requestData = request.getRequestData();
                 var stateId = request.getRequiredStateId();
                 int index = 0;
@@ -114,10 +53,10 @@ public class XtextWebSocket {
                         var serviceDispatcher = injector.getInstance(XtextServiceDispatcher.class);
                         int nCalls = requestData.size();
                         for (; index < nCalls; index++) {
-                                var serviceContext = new SimpleServiceContext(session, request, stateId, index);
+                                var serviceContext = SimpleServiceContext.ofTransaction(session, request, stateId, index);
                                 var service = serviceDispatcher.getService(serviceContext);
                                 var serviceResult = service.getService().apply();
-                                sendReply(webSocketSession, new XtextWebSocketOkResponse(request, index, serviceResult));
+                                handler.onResponse(new XtextWebSocketOkResponse(request, index, serviceResult));
                                 if (serviceResult instanceof ServiceConflictResult) {
                                         break;
                                 }
@@ -127,25 +66,15 @@ public class XtextWebSocket {
                                 }
                         }
                 } catch (InvalidRequestException e) {
-                        sendReply(webSocketSession,
+                        handler.onResponse(
                                         new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.REQUEST_ERROR, e));
                 } catch (RuntimeException e) {
-                        sendReply(webSocketSession,
+                        handler.onResponse(
                                         new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.SERVER_ERROR, e));
                 }
                 return index;
         }
 
-        protected void sendReply(Session webSocketSession, XtextWebSocketResponse response) throws IOException {
-                var responseString = gson.toJson(response);
-                webSocketSession.getRemote().sendPartialString(responseString, true, new WriteCallback() {
-                        @Override
-                        public void writeFailed(Throwable x) {
-                                LOG.warn("Cannot complete async write to websocket " + webSocketSession.getRemoteAddress(), x);
-                        }
-                });
-        }
-
         /**
          * Get the injector to satisfy the request in the {@code serviceContext}.
          * 
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextStatusCode.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextStatusCode.java
index 8ef60108..0cd229e8 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextStatusCode.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextStatusCode.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 public final class XtextStatusCode {
         public static final int INVALID_JSON = 4007;
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
new file mode 100644
index 00000000..25f67545
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
@@ -0,0 +1,94 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import java.io.IOException;
+import java.io.Reader;
+
+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.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.websocket.api.annotations.WebSocket;
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.web.server.ISession;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonIOException;
+import com.google.gson.JsonParseException;
+
+@WebSocket
+public class XtextWebSocket {
+        private static final Logger LOG = LoggerFactory.getLogger(XtextWebSocket.class);
+
+        private final Gson gson = new Gson();
+
+        private final TransactionExecutor executor;
+
+        public XtextWebSocket(TransactionExecutor executor) {
+                this.executor = executor;
+        }
+
+        public XtextWebSocket(ISession session, IResourceServiceProvider.Registry resourceServiceProviderRegistry) {
+                this(new TransactionExecutor(session, resourceServiceProviderRegistry));
+        }
+
+        @OnWebSocketConnect
+        public void onConnect(Session webSocketSession) {
+                LOG.debug("New websocket connection from {}", webSocketSession.getRemoteAddress());
+        }
+
+        @OnWebSocketClose
+        public void onClose(Session webSocketSession, int statusCode, String reason) {
+                if (statusCode == StatusCode.NORMAL) {
+                        LOG.debug("{} closed connection normally: {}", webSocketSession.getRemoteAddress(), reason);
+                } else {
+                        LOG.warn("{} closed connection with status code {}: {}", webSocketSession.getRemoteAddress(), statusCode,
+                                        reason);
+                }
+        }
+
+        @OnWebSocketError
+        public void onError(Session webSocketSession, Throwable error) {
+                LOG.error("Internal websocket error in connection from" + webSocketSession.getRemoteAddress(), error);
+        }
+
+        @OnWebSocketMessage
+        public void onMessage(Session webSocketSession, Reader reader) {
+                XtextWebSocketRequest request;
+                try {
+                        request = gson.fromJson(reader, XtextWebSocketRequest.class);
+                } catch (JsonIOException e) {
+                        LOG.error("Cannot read from websocket from" + webSocketSession.getRemoteAddress(), e);
+                        if (webSocketSession.isOpen()) {
+                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot read payload");
+                        }
+                        return;
+                } catch (JsonParseException e) {
+                        LOG.warn("Malformed websocket request from" + webSocketSession.getRemoteAddress(), e);
+                        webSocketSession.close(XtextStatusCode.INVALID_JSON, "Invalid JSON payload");
+                        return;
+                }
+                try {
+                        executor.handleRequest(request, response -> sendResponse(webSocketSession, response));
+                } catch (IOException e) {
+                        LOG.warn("Cannot initiaite async write to websocket " + webSocketSession.getRemoteAddress(), e);
+                        if (webSocketSession.isOpen()) {
+                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot write payload");
+                        }
+                }
+        }
+
+        protected void sendResponse(Session webSocketSession, XtextWebSocketResponse response) throws IOException {
+                var responseString = gson.toJson(response);
+                webSocketSession.getRemote().sendPartialString(responseString, true, new WriteCallback() {
+                        @Override
+                        public void writeFailed(Throwable x) {
+                                LOG.warn("Cannot complete async write to websocket " + webSocketSession.getRemoteAddress(), x);
+                        }
+                });
+        }
+}
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketErrorKind.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketErrorKind.java
index 5759f39e..66ea227f 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketErrorKind.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketErrorKind.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import com.google.gson.annotations.SerializedName;
 
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketErrorResponse.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketErrorResponse.java
index 1d2cf08a..3be7df39 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketErrorResponse.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketErrorResponse.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.util.Objects;
 
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketOkResponse.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketOkResponse.java
index aa453544..0a841895 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketOkResponse.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketOkResponse.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.util.Objects;
 
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketRequest.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketRequest.java
index 8aee70a1..8be67bc1 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketRequest.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketRequest.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.util.List;
 import java.util.Map;
@@ -19,6 +19,16 @@ public class XtextWebSocketRequest {
         @SerializedName("request")
         private List<Map<String, String>> requestData;
 
+        public XtextWebSocketRequest(String id, String resourceName, String contentType, String requiredStateId,
+                        List<Map<String, String>> requestData) {
+                super();
+                this.id = id;
+                this.resourceName = resourceName;
+                this.contentType = contentType;
+                this.requiredStateId = requiredStateId;
+                this.requestData = requestData;
+        }
+
         public String getId() {
                 return id;
         }
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketResponse.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketResponse.java
index 9e15aa69..2e7cfbbb 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketResponse.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketResponse.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 public sealed interface XtextWebSocketResponse permits XtextWebSocketOkResponse,XtextWebSocketErrorResponse {
         public String getId();
diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketServlet.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
index 5769e9e7..6d4d2cad 100644
--- a/language-web/src/main/java/tools/refinery/language/web/xtext/XtextWebSocketServlet.java
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocketServlet.java
@@ -1,4 +1,4 @@
-package tools.refinery.language.web.xtext;
+package tools.refinery.language.web.xtext.servlet;
 
 import java.io.IOException;
 import java.time.Duration;
diff --git a/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/AwaitTerminationExecutorServiceProvider.java b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/AwaitTerminationExecutorServiceProvider.java
new file mode 100644
index 00000000..08230335
--- /dev/null
+++ b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/AwaitTerminationExecutorServiceProvider.java
@@ -0,0 +1,34 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.xtext.ide.ExecutorServiceProvider;
+
+import com.google.inject.Singleton;
+
+@Singleton
+public class AwaitTerminationExecutorServiceProvider extends ExecutorServiceProvider {
+        private List<ExecutorService> servicesToShutDown = new ArrayList<>();
+
+        @Override
+        protected ExecutorService createInstance(String key) {
+                var instance = super.createInstance(key);
+                servicesToShutDown.add(instance);
+                return instance;
+        }
+
+        @Override
+        public void dispose() {
+                super.dispose();
+                for (var executorService : servicesToShutDown) {
+                        try {
+                                executorService.awaitTermination(1, TimeUnit.SECONDS);
+                        } catch (InterruptedException e) {
+                                // Continue normally.
+                        }
+                }
+        }
+}
diff --git a/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/ProblemWebInjectorProvider.java b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/ProblemWebInjectorProvider.java
new file mode 100644
index 00000000..3493c9eb
--- /dev/null
+++ b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/ProblemWebInjectorProvider.java
@@ -0,0 +1,47 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import org.eclipse.xtext.ide.ExecutorServiceProvider;
+import org.eclipse.xtext.util.DisposableRegistry;
+import org.eclipse.xtext.util.Modules2;
+
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+
+import tools.refinery.language.ide.ProblemIdeModule;
+import tools.refinery.language.tests.ProblemInjectorProvider;
+import tools.refinery.language.web.ProblemWebModule;
+import tools.refinery.language.web.ProblemWebSetup;
+
+public class ProblemWebInjectorProvider extends ProblemInjectorProvider {
+
+        protected Injector internalCreateInjector() {
+                return new ProblemWebSetup() {
+                        @Override
+                        public Injector createInjector() {
+                                return Guice.createInjector(
+                                                Modules2.mixin(createRuntimeModule(), new ProblemIdeModule(), createWebModule()));
+                        }
+                }.createInjectorAndDoEMFRegistration();
+        }
+
+        protected ProblemWebModule createWebModule() {
+                // Await termination of the executor service to avoid race conditions between
+                // between the tasks in the service and the {@link
+                // org.eclipse.xtext.testing.extensions.InjectionExtension}.
+                return new ProblemWebModule() {
+                        @SuppressWarnings("unused")
+                        public Class<? extends ExecutorServiceProvider> bindExecutorServiceProvider() {
+                                return AwaitTerminationExecutorServiceProvider.class;
+                        }
+                };
+        }
+
+        @Override
+        public void restoreRegistry() {
+                // Also make sure to dispose any IDisposable instances (that may depend on the
+                // global state) created by Xtext before restoring the global state.
+                var disposableRegistry = getInjector().getInstance(DisposableRegistry.class);
+                disposableRegistry.dispose();
+                super.restoreRegistry();
+        }
+}
diff --git a/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java
new file mode 100644
index 00000000..6ad82d7f
--- /dev/null
+++ b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java
@@ -0,0 +1,151 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.hasProperty;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.junit.jupiter.api.Assertions.fail;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.testing.InjectWith;
+import org.eclipse.xtext.testing.extensions.InjectionExtension;
+import org.eclipse.xtext.web.server.ServiceConflictResult;
+import org.eclipse.xtext.web.server.model.DocumentStateResult;
+import org.eclipse.xtext.web.server.validation.ValidationResult;
+import org.hamcrest.Matcher;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import com.google.inject.Inject;
+
+@ExtendWith(MockitoExtension.class)
+@ExtendWith(InjectionExtension.class)
+@InjectWith(ProblemWebInjectorProvider.class)
+class TransactionExecutorTest {
+        private static final String RESOURCE_NAME = "test.problem";
+
+        private static final String INVALID_STATE_ID = "<invalid_state>";
+
+        private static final String TEST_PROBLEM = """
+                                class Person {
+                                Person friend[0..*] opposite friend
+                        }
+
+                        friend(a, b).
+                        """;
+
+        private static final Map<String, String> UPDATE_FULL_TEXT_PARAMS = Map.of("serviceType", "update", "fullText",
+                        TEST_PROBLEM);
+
+        private static final Map<String, String> VALIDATE_PARAMS = Map.of("serviceType", "validate");
+
+        @Inject
+        private IResourceServiceProvider.Registry resourceServiceProviderRegistry;
+
+        private TransactionExecutor transactionExecutor;
+
+        @BeforeEach
+        void beforeEach() {
+                transactionExecutor = new TransactionExecutor(new SimpleSession(), resourceServiceProviderRegistry);
+        }
+        
+        @Test
+        void emptyBatchTest() {
+                performBatchRequest(null);
+        }
+
+        @Test
+        void fullTextUpdateTest() {
+                var response = performSingleRequest(null, UPDATE_FULL_TEXT_PARAMS);
+                assertThat(response, hasResponseData(instanceOf(DocumentStateResult.class)));
+        }
+
+        @Test
+        void validationAfterFullTextUpdateInSameBatchTest() {
+                var response = performBatchRequest(null, UPDATE_FULL_TEXT_PARAMS, VALIDATE_PARAMS).get(1);
+                assertThat(response, hasResponseData(instanceOf(ValidationResult.class)));
+        }
+
+        @Test
+        void validationAfterFullTextUpdateInDifferentBatchTest() {
+                var stateId = updateFullText();
+                var validateResponse = performSingleRequest(stateId, VALIDATE_PARAMS);
+                assertThat(validateResponse, hasResponseData(instanceOf(ValidationResult.class)));
+        }
+
+        @Test
+        void conflictTest() {
+                updateFullText();
+                var response = performSingleRequest(INVALID_STATE_ID, VALIDATE_PARAMS);
+                assertThat(response, hasResponseData(instanceOf(ServiceConflictResult.class)));
+        }
+
+        @Test
+        void transactionCancelledDueToConflictTest() {
+                updateFullText();
+                var response = performBatchRequest(INVALID_STATE_ID, VALIDATE_PARAMS, VALIDATE_PARAMS).get(1);
+                assertThat(response, hasErrorKind(equalTo(XtextWebSocketErrorKind.TRANSACTION_CANCELLED)));
+        }
+
+        @SafeVarargs
+        private List<XtextWebSocketResponse> performBatchRequest(String requiredStateId, Map<String, String>... params) {
+                var id = UUID.randomUUID().toString();
+                var request = new XtextWebSocketRequest(id, RESOURCE_NAME, null, requiredStateId, List.of(params));
+                
+                var responseHandler = mock(ResponseHandler.class);
+                try {
+                        transactionExecutor.handleRequest(request, responseHandler);
+                } catch (IOException e) {
+                        fail("Unexpected IOException", e);
+                }
+                
+                var captor = ArgumentCaptor.forClass(XtextWebSocketResponse.class);
+                int nParams = params.length;
+                try {
+                        verify(responseHandler, times(nParams)).onResponse(captor.capture());
+                } catch (IOException e) {
+                        throw new RuntimeException("Mockito threw unexcepted exception", e);
+                }
+                var allResponses = captor.getAllValues();
+                for (int i = 0; i < nParams; i++) {
+                        var response = allResponses.get(i);
+                        assertThat(response, hasProperty("id", equalTo(id)));
+                        assertThat(response, hasProperty("index", equalTo(i)));
+                }
+                return allResponses;
+        }
+
+        private XtextWebSocketResponse performSingleRequest(String requiredStateId, Map<String, String> param) {
+                return performBatchRequest(requiredStateId, param).get(0);
+        }
+
+        private String updateFullText() {
+                var updateResponse = (XtextWebSocketOkResponse) performSingleRequest(null, UPDATE_FULL_TEXT_PARAMS);
+                var documentStateResult = (DocumentStateResult) updateResponse.getResponseData();
+                var stateId = documentStateResult.getStateId();
+                if (INVALID_STATE_ID.equals(stateId)) {
+                        throw new RuntimeException("Service returned unexpected stateId: " + stateId);
+                }
+                return stateId;
+        }
+
+        private static Matcher<XtextWebSocketResponse> hasResponseData(Matcher<?> responseDataMatcher) {
+                return hasProperty("responseData", responseDataMatcher);
+        }
+
+        private static Matcher<XtextWebSocketResponse> hasErrorKind(
+                        Matcher<? extends XtextWebSocketErrorKind> errorKindMatcher) {
+                return hasProperty("errorKind", errorKindMatcher);
+        }
+}