feat: Add dead letter topic to a subscription topic.

sdk-springboot/src/main/java/io/dapr/springboot/DaprBeanPostProcessor.java

@@ -107,6 +107,7 @@ private static void subscribeToTopics(
       Rule rule = topic.rule();
       String topicName = stringValueResolver.resolveStringValue(topic.name());
       String pubSubName = stringValueResolver.resolveStringValue(topic.pubsubName());
+      String deadLetterTopic = stringValueResolver.resolveStringValue(topic.deadLetterTopic());
       String match = stringValueResolver.resolveStringValue(rule.match());
       if ((topicName != null) && (topicName.length() > 0) && pubSubName != null && pubSubName.length() > 0) {
         try {
@@ -116,7 +117,7 @@ private static void subscribeToTopics(
           List<String> routes = getAllCompleteRoutesForPost(clazz, method, topicName);
           for (String route : routes) {
             daprRuntime.addSubscribedTopic(
-                pubSubName, topicName, match, rule.priority(), route, metadata, bulkSubscribe);
+                pubSubName, topicName, match, rule.priority(), route,deadLetterTopic, metadata, bulkSubscribe);
           }
         } catch (JsonProcessingException e) {
           throw new IllegalArgumentException("Error while parsing metadata: " + e);

sdk-springboot/src/main/java/io/dapr/springboot/DaprRuntime.java

@@ -22,6 +22,7 @@
  * Internal Singleton to handle Dapr configuration.
  */
 class DaprRuntime {
+
   /**
    * The singleton instance.
    */
@@ -33,8 +34,8 @@ class DaprRuntime {
   private final Map<DaprTopicKey, DaprSubscriptionBuilder> subscriptionBuilders = new HashMap<>();
 
   /**
-   * DaprRuntime should be used as a singleton, using {@link DaprRuntime#getInstance()}.
-   * The constructor's default scope is available for unit tests only.
+   * DaprRuntime should be used as a singleton, using {@link DaprRuntime#getInstance()}. The
+   * constructor's default scope is available for unit tests only.
    */
   private DaprRuntime() {
   }
@@ -59,40 +60,45 @@ public static DaprRuntime getInstance() {
   /**
    * Adds a topic to the list of subscribed topics.
    *
-   * @param pubSubName PubSub name to subscribe to.
-   * @param topicName Name of the topic being subscribed to.
-   * @param match Match expression for this route.
-   * @param priority Priority for this match relative to others.
-   * @param route Destination route for requests.
-   * @param metadata Metadata for extended subscription functionality.
+   * @param pubSubName      PubSub name to subscribe to.
+   * @param topicName       Name of the topic being subscribed to.
+   * @param match           Match expression for this route.
+   * @param priority        Priority for this match relative to others.
+   * @param route           Destination route for requests.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages. 
+   * @param metadata        Metadata for extended subscription functionality.
    */
   public synchronized void addSubscribedTopic(String pubSubName,
-                                              String topicName,
-                                              String match,
-                                              int priority,
-                                              String route,
-                                              Map<String,String> metadata) {
-    this.addSubscribedTopic(pubSubName, topicName, match, priority, route, metadata, null);
+      String topicName,
+      String match,
+      int priority,
+      String route,
+      String deadLetterTopic,
+      Map<String, String> metadata) {
+    this.addSubscribedTopic(pubSubName, topicName, match, priority, route, deadLetterTopic,
+        metadata, null);
   }
 
   /**
    * Adds a topic to the list of subscribed topics.
    *
-   * @param pubSubName PubSub name to subscribe to.
-   * @param topicName Name of the topic being subscribed to.
-   * @param match Match expression for this route.
-   * @param priority Priority for this match relative to others.
-   * @param route Destination route for requests.
-   * @param metadata Metadata for extended subscription functionality.
-   * @param bulkSubscribe Bulk subscribe configuration.
+   * @param pubSubName      PubSub name to subscribe to.
+   * @param topicName       Name of the topic being subscribed to.
+   * @param match           Match expression for this route.
+   * @param priority        Priority for this match relative to others.
+   * @param route           Destination route for requests.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages.
+   * @param metadata        Metadata for extended subscription functionality.
+   * @param bulkSubscribe   Bulk subscribe configuration.
    */
   public synchronized void addSubscribedTopic(String pubSubName,
-                                              String topicName,
-                                              String match,
-                                              int priority,
-                                              String route,
-                                              Map<String,String> metadata,
-                                              DaprTopicBulkSubscribe bulkSubscribe) {
+      String topicName,
+      String match,
+      int priority,
+      String route,
+      String deadLetterTopic,
+      Map<String, String> metadata,
+      DaprTopicBulkSubscribe bulkSubscribe) {
     DaprTopicKey topicKey = new DaprTopicKey(pubSubName, topicName);
 
     DaprSubscriptionBuilder builder = subscriptionBuilders.get(topicKey);
@@ -111,14 +117,18 @@ public synchronized void addSubscribedTopic(String pubSubName,
       builder.setMetadata(metadata);
     }
 
+    if (deadLetterTopic != null && !deadLetterTopic.isEmpty()) {
+      builder.setDeadLetterTopic(deadLetterTopic);
+    }
+
     if (bulkSubscribe != null) {
       builder.setBulkSubscribe(bulkSubscribe);
     }
   }
 
   public synchronized DaprTopicSubscription[] listSubscribedTopics() {
     List<DaprTopicSubscription> values = subscriptionBuilders.values().stream()
-            .map(b -> b.build()).collect(Collectors.toList());
+        .map(b -> b.build()).collect(Collectors.toList());
     return values.toArray(new DaprTopicSubscription[0]);
   }
 }

sdk-springboot/src/main/java/io/dapr/springboot/DaprSubscriptionBuilder.java

@@ -21,65 +21,91 @@
 import java.util.stream.Collectors;
 
 class DaprSubscriptionBuilder {
+
   private final String pubsubName;
   private final String topic;
   private final List<TopicRule> rules;
+  private String deadLetterTopic;
   private String defaultPath;
   private Map<String, String> metadata;
 
   private DaprTopicBulkSubscribe bulkSubscribe;
 
   /**
    * Create a subscription topic.
+   *
    * @param pubsubName The pubsub name to subscribe to.
-   * @param topic The topic to subscribe to.
+   * @param topic      The topic to subscribe to.
    */
   DaprSubscriptionBuilder(String pubsubName, String topic) {
     this.pubsubName = pubsubName;
     this.topic = topic;
     this.rules = new ArrayList<>();
+    this.deadLetterTopic = null;
     this.defaultPath = null;
     this.metadata = Collections.emptyMap();
   }
 
   /**
    * Sets the default path for the subscription.
+   *
    * @param path The default path.
    * @return this instance.
    */
   DaprSubscriptionBuilder setDefaultPath(String path) {
     if (defaultPath != null) {
       if (!defaultPath.equals(path)) {
         throw new RuntimeException(
-                String.format(
-                        "a default route is already set for topic %s on pubsub %s (current: '%s', supplied: '%s')",
-                        this.topic, this.pubsubName, this.defaultPath, path));
+            String.format(
+                "a default route is already set for topic %s on pubsub %s (current: '%s', supplied: '%s')",
+                this.topic, this.pubsubName, this.defaultPath, path));
       }
     }
     defaultPath = path;
     return this;
   }
 
+  /**
+   * Sets the dead letter topic for the subscription.
+   *
+   * @param deadLetterTopic Name of dead letter topic.
+   * @return this instance.
+   */
+  DaprSubscriptionBuilder setDeadLetterTopic(String deadLetterTopic) {
+    if (this.deadLetterTopic != null) {
+      if (!this.deadLetterTopic.equals(deadLetterTopic)) {
+        throw new RuntimeException(
+            String.format(
+                "a default dead letter topic is already set for topic %s on pubsub %s (current: '%s', supplied: '%s')",
+                this.topic, this.pubsubName, this.deadLetterTopic, deadLetterTopic));
+      }
+    }
+    this.deadLetterTopic = deadLetterTopic;
+    return this;
+  }
+
   /**
    * Adds a rule to the subscription.
-   * @param path The path to route to.
-   * @param match The CEL expression the event must match.
+   *
+   * @param path     The path to route to.
+   * @param match    The CEL expression the event must match.
    * @param priority The priority of the rule.
    * @return this instance.
    */
   public DaprSubscriptionBuilder addRule(String path, String match, int priority) {
     if (rules.stream().anyMatch(e -> e.getPriority() == priority)) {
       throw new RuntimeException(
-              String.format(
-                      "a rule priority of %d is already used for topic %s on pubsub %s",
-                      priority, this.topic, this.pubsubName));
+          String.format(
+              "a rule priority of %d is already used for topic %s on pubsub %s",
+              priority, this.topic, this.pubsubName));
     }
     rules.add(new TopicRule(path, match, priority));
     return this;
   }
 
   /**
    * Sets the metadata for the subscription.
+   *
    * @param metadata The metadata.
    * @return this instance.
    */
@@ -90,6 +116,7 @@ public DaprSubscriptionBuilder setMetadata(Map<String, String> metadata) {
 
   /**
    * Sets the bulkSubscribe configuration for the subscription.
+   *
    * @param bulkSubscribe The bulk subscribe configuration.
    * @return this instance.
    */
@@ -100,6 +127,7 @@ public DaprSubscriptionBuilder setBulkSubscribe(DaprTopicBulkSubscribe bulkSubsc
 
   /**
    * Builds the DaprTopicSubscription that is returned by the application to Dapr.
+   *
    * @return The DaprTopicSubscription.
    */
   public DaprTopicSubscription build() {
@@ -109,16 +137,19 @@ public DaprTopicSubscription build() {
     if (!rules.isEmpty()) {
       Collections.sort(rules, Comparator.comparingInt(TopicRule::getPriority));
       List<DaprTopicRule> topicRules = rules.stream()
-              .map(e -> new DaprTopicRule(e.match, e.path)).collect(Collectors.toList());
+          .map(e -> new DaprTopicRule(e.match, e.path)).collect(Collectors.toList());
       routes = new DaprTopicRoutes(topicRules, defaultPath);
     } else {
       route = defaultPath;
     }
 
-    return new DaprTopicSubscription(this.pubsubName, this.topic, route, routes, metadata, bulkSubscribe);
+    return new DaprTopicSubscription(this.pubsubName, this.topic, route, this.deadLetterTopic,
+        routes, metadata,
+        bulkSubscribe);
   }
 
   private static class TopicRule {
+
     private final String path;
     private final String match;
     private final int priority;

sdk-springboot/src/main/java/io/dapr/springboot/DaprTopicSubscription.java

@@ -20,64 +20,78 @@
  * Class to represent a subscription topic along with its metadata.
  */
 class DaprTopicSubscription {
+
   private final String pubsubName;
   private final String topic;
   private final String route;
+  private final String deadLetterTopic;
   private final DaprTopicRoutes routes;
   private final Map<String, String> metadata;
   private final DaprTopicBulkSubscribe bulkSubscribe;
 
   /**
    * Create a subscription topic.
-   * @param pubsubName The pubsub name to subscribe to.
-   * @param topic The topic to subscribe to.
-   * @param route Destination route for messages.
-   * @param metadata Metdata for extended subscription functionality.
+   *
+   * @param pubsubName      The pubsub name to subscribe to.
+   * @param topic           The topic to subscribe to.
+   * @param route           Destination route for messages.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages.
+   * @param metadata        Metdata for extended subscription functionality.
    */
-  DaprTopicSubscription(String pubsubName, String topic, String route, Map<String, String> metadata) {
-    this(pubsubName, topic, route, metadata, null);
+  DaprTopicSubscription(String pubsubName, String topic, String route, String deadLetterTopic,
+      Map<String, String> metadata) {
+    this(pubsubName, topic, route, deadLetterTopic, metadata, null);
   }
 
   /**
    * Create a subscription topic.
-   * @param pubsubName The pubsub name to subscribe to.
-   * @param topic The topic to subscribe to.
-   * @param route Destination route for messages.
-   * @param metadata Metdata for extended subscription functionality.
+   *
+   * @param pubsubName      The pubsub name to subscribe to.
+   * @param topic           The topic to subscribe to.
+   * @param route           Destination route for messages.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages.
+   * @param metadata        Metadata for extended subscription functionality.
    */
-  DaprTopicSubscription(String pubsubName, String topic, String route,
-                        Map<String, String> metadata, DaprTopicBulkSubscribe bulkSubscribe) {
-    this(pubsubName, topic, route, null, metadata, bulkSubscribe);
+  DaprTopicSubscription(String pubsubName, String topic, String route, String deadLetterTopic,
+      Map<String, String> metadata, DaprTopicBulkSubscribe bulkSubscribe) {
+    this(pubsubName, topic, route, deadLetterTopic,null, metadata, bulkSubscribe);
   }
 
   /**
    * Create a subscription topic.
-   * @param pubsubName The pubsub name to subscribe to.
-   * @param topic The topic to subscribe to.
-   * @param route Destination route for messages.
-   * @param routes Destination routes with rules for messages.
-   * @param metadata Metadata for extended subscription functionality.
+   *
+   * @param pubsubName      The pubsub name to subscribe to.
+   * @param topic           The topic to subscribe to.
+   * @param route           Destination route for messages.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages.
+   * @param routes          Destination routes with rules for messages.
+   * @param metadata        Metadata for extended subscription functionality.
    */
-  DaprTopicSubscription(String pubsubName, String topic, String route, DaprTopicRoutes routes,
-                        Map<String, String> metadata) {
-    this(pubsubName, topic, route, routes, metadata, null);
+  DaprTopicSubscription(String pubsubName, String topic, String route, String deadLetterTopic,
+      DaprTopicRoutes routes,
+      Map<String, String> metadata) {
+    this(pubsubName, topic, route, deadLetterTopic, routes, metadata, null);
   }
 
   /**
    * Create a subscription topic.
-   * @param pubsubName The pubsub name to subscribe to.
-   * @param topic The topic to subscribe to.
-   * @param route Destination route for messages.
-   * @param routes Destination routes with rules for messages.
-   * @param metadata Metadata for extended subscription functionality.
-   * @param bulkSubscribe Bulk subscribe configuration.
+   *
+   * @param pubsubName      The pubsub name to subscribe to.
+   * @param topic           The topic to subscribe to.
+   * @param route           Destination route for messages.
+   * @param deadLetterTopic Name of topic to forward undeliverable messages.
+   * @param routes          Destination routes with rules for messages.
+   * @param metadata        Metadata for extended subscription functionality.
+   * @param bulkSubscribe   Bulk subscribe configuration.
    */
-  DaprTopicSubscription(String pubsubName, String topic, String route, DaprTopicRoutes routes,
-                        Map<String, String> metadata, DaprTopicBulkSubscribe bulkSubscribe) {
+  DaprTopicSubscription(String pubsubName, String topic, String route, String deadLetterTopic,
+      DaprTopicRoutes routes,
+      Map<String, String> metadata, DaprTopicBulkSubscribe bulkSubscribe) {
     this.pubsubName = pubsubName;
     this.topic = topic;
     this.route = route;
     this.routes = routes;
+    this.deadLetterTopic = deadLetterTopic;
     this.metadata = Collections.unmodifiableMap(metadata);
     this.bulkSubscribe = bulkSubscribe;
   }
@@ -94,6 +108,10 @@ public String getRoute() {
     return route;
   }
 
+  public String getDeadLetterTopic() {
+    return deadLetterTopic;
+  }
+
   public DaprTopicRoutes getRoutes() {
     return routes;
   }