Close #353: Register FetchAndLockHandler when initializing the REST a…

…pi so that long polling works, i.e. the if there are currently no tasks then the server will keep the connection open for the given time.

micronaut-camunda-bpm-feature/build.gradle

@@ -44,7 +44,7 @@ dependencies {
 
     // REST API + Webapps
     implementation("com.fasterxml.jackson.jaxrs:jackson-jaxrs-json-provider")
-    implementation("org.camunda.bpm:camunda-engine-rest:$camundaVersion:classes")
+    implementation("org.camunda.bpm:camunda-engine-rest-jaxrs2:$camundaVersion")
     implementation("org.camunda.bpm.webapp:camunda-webapp-webjar:$camundaVersion")
     implementation("org.glassfish.jersey.inject:jersey-hk2:$jerseyVersion")
     implementation("org.glassfish.jersey.containers:jersey-container-servlet-core:$jerseyVersion")

micronaut-camunda-bpm-feature/jetty-webapp-and-rest/build.gradle

@@ -24,6 +24,8 @@ dependencies {
     kaptTest("io.micronaut:micronaut-inject-java:$micronautVersion")
 
     testCompileOnly("io.micronaut.servlet:micronaut-http-server-jetty")
+    testImplementation("org.junit.jupiter:junit-jupiter-params")
+    testImplementation("org.assertj:assertj-core")
     testImplementation("io.micronaut:micronaut-http-client")
     testImplementation("org.eclipse.jetty:jetty-server:$jettyVersion")
     testImplementation("org.eclipse.jetty:jetty-servlet:$jettyVersion")

micronaut-camunda-bpm-feature/jetty-webapp-and-rest/src/test/kotlin/info/novatec/micronaut/camunda/bpm/feature/test/JettyRestTest.kt

@@ -22,9 +22,15 @@ import io.micronaut.http.client.HttpClient
 import io.micronaut.http.client.annotation.Client
 import io.micronaut.test.extensions.junit5.annotation.MicronautTest
 import jakarta.inject.Inject
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.within
 import org.eclipse.jetty.server.Server
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.ValueSource
+import java.time.Duration
+import java.time.Instant
 
 /**
  * Test the REST API on Jetty.
@@ -49,4 +55,30 @@ class JettyRestTest {
 
         assertEquals("""[{"name":"default"}]""", body)
     }
+
+    @ParameterizedTest
+    @ValueSource(longs = [0, 2000, 5000])
+    fun `long polling`(duration: Long) {
+        val request: HttpRequest<String> = HttpRequest.POST(
+            configuration.rest.contextPath + "/external-task/fetchAndLock",
+            """
+                {
+                    "maxTasks": 1,
+                    "workerId": "aWorkerId",
+                    "asyncResponseTimeout": $duration,
+                    "topics": [
+                        {
+                            "topicName": "aTopicName",
+                            "lockDuration": 1000
+                        }
+                    ]
+                }
+            """
+        )
+        val start = Instant.now()
+        val body = client.toBlocking().retrieve(request)
+
+        assertEquals("[]", body)
+        assertThat(Duration.between(start, Instant.now()).toMillis()).isCloseTo(duration, within(500L))
+    }
 }

micronaut-camunda-bpm-feature/src/main/java/info/novatec/micronaut/camunda/bpm/feature/JettyServerCustomizer.java

@@ -22,9 +22,10 @@
 import jakarta.inject.Singleton;
 import org.camunda.bpm.admin.impl.web.bootstrap.AdminContainerBootstrap;
 import org.camunda.bpm.cockpit.impl.web.bootstrap.CockpitContainerBootstrap;
-import org.camunda.bpm.engine.rest.security.auth.ProcessEngineAuthenticationFilter;
 import org.camunda.bpm.engine.rest.filter.CacheControlFilter;
 import org.camunda.bpm.engine.rest.filter.EmptyBodyFilter;
+import org.camunda.bpm.engine.rest.impl.FetchAndLockContextListener;
+import org.camunda.bpm.engine.rest.security.auth.ProcessEngineAuthenticationFilter;
 import org.camunda.bpm.tasklist.impl.web.bootstrap.TasklistContainerBootstrap;
 import org.camunda.bpm.webapp.impl.engine.ProcessEnginesFilter;
 import org.camunda.bpm.webapp.impl.security.auth.AuthenticationFilter;
@@ -50,11 +51,11 @@
 import java.util.HashMap;
 import java.util.Map;
 
-import static java.util.Collections.*;
-import static javax.servlet.DispatcherType.*;
+import static java.util.Collections.singletonMap;
+import static javax.servlet.DispatcherType.REQUEST;
 
 /**
- * Using Micronaut Servlet with Jetty to run the REST API as a servlet.
+ * Using Micronaut Servlet with Jetty to run the REST API/Webapps as a servlet.
  *
  * see https://micronaut-projects.github.io/micronaut-servlet/latest/guide/#jetty
  *
@@ -84,6 +85,13 @@ public Server onCreated(BeanCreatedEvent<Server> event) {
             ServletContextHandler restServletContextHandler = new ServletContextHandler();
             restServletContextHandler.setContextPath(configuration.getRest().getContextPath());
             restServletContextHandler.addServlet(new ServletHolder(new ServletContainer(new RestApp())), "/*");
+            restServletContextHandler.addEventListener(new ServletContextListener() {
+                @Override
+                public void contextInitialized(ServletContextEvent sce) {
+                    // Required for long polling
+                    new FetchAndLockContextListener().contextInitialized(sce);
+                }
+            });
 
             if (configuration.getRest().isBasicAuthEnabled()) {
                 // see https://docs.camunda.org/manual/latest/reference/rest/overview/authentication/
@@ -167,9 +175,6 @@ public void contextInitialized(ServletContextEvent sce) {
             registerFilter("CacheControlFilter", CacheControlFilter.class, "/api/*", "/app/*");
         }
 
-        @Override
-        public void contextDestroyed(ServletContextEvent sce) {}
-
         protected Map<String, String> getCsrfInitParams(){
             Map<String, String> initParams = new HashMap<>();