Add a part to be implemented in ListenNotifyResource (#20)

lunatech-labs · Jun 15, 2024 · 00c0211 · 00c0211
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diff --git a/code/exercise_013_Listen_and_Notify/README.md b/code/exercise_013_Listen_and_Notify/README.md
@@ -4,7 +4,61 @@ In this exercise, we will play a bit with Postgres’ `LISTEN / NOTIFY` feature,
 
 The `LISTEN / NOTIFY` feature of Postgres allows you to setup a connection to Postgres, and listen for evens that pass by on a channel, as well as notifying such channels. With the reactive sql clients, we can connect to these channels as a `Multi` in Quarkus.
 
-* Get the code for `ListenNotifyResource` by executing this command from the command line: `cmtc pull-template src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java <root folder of exercise repo>`.
+* Create the class `ListenNotifyResource` from the following template:
+
+```java
+import io.smallrye.mutiny.Multi;
+import io.smallrye.mutiny.Uni;
+import io.vertx.core.json.JsonObject;
+import io.vertx.mutiny.pgclient.PgConnection;
+import io.vertx.mutiny.pgclient.PgPool;
+import io.vertx.pgclient.PgNotification;
+import org.jboss.resteasy.reactive.RestStreamElementType;
+
+import jakarta.inject.Inject;
+import jakarta.ws.rs.*;
+import jakarta.ws.rs.core.MediaType;
+
+@Path("/channel")
+public class ListenNotifyResource {
+
+    @Inject
+    PgPool client;
+
+    @Path("{channel}")
+    @GET
+    @Produces(MediaType.SERVER_SENT_EVENTS)
+    @RestStreamElementType(MediaType.APPLICATION_JSON)
+    public Multi<JsonObject> listen(@PathParam("channel") String channel) {
+        return client
+                .getConnection()
+                .map(PgConnection::cast)
+                .toMulti()
+                .flatMap(connection ->
+                    connection.query("LISTEN " + channel)
+                        .execute()
+                        .toMulti()
+                        .flatMap(__ -> streamNotifications(connection))
+                )
+                .map(PgNotification::toJson);
+    }
+
+    @Path("{channel}")
+    @POST
+    @Produces(MediaType.TEXT_PLAIN)
+    @Consumes(MediaType.WILDCARD)
+    public Uni<String> notify(@PathParam("channel") String channel, String stuff) {
+        return client.preparedQuery("NOTIFY " + channel +  ", $$" + stuff + "$$")
+                .execute()
+                .map(rs -> "Posted to " + channel + " channel");
+    }
+
+    // Use PgConnection::notificationHandler to register a handler that emits PgNotification values on a Multi stream
+    private Multi<PgNotification> streamNotifications(PgConnection connection) {
+        // To be implemented
+    }
+}
+```
 
 * Connect to the channel `milkshakes` using the following cURL command.
 

diff --git a/...3_Listen_and_Notify/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java b/...3_Listen_and_Notify/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java
@@ -5,7 +5,6 @@
 import io.vertx.core.json.JsonObject;
 import io.vertx.mutiny.pgclient.PgConnection;
 import io.vertx.mutiny.pgclient.PgPool;
-import io.vertx.mutiny.sqlclient.SqlConnection;
 import io.vertx.pgclient.PgNotification;
 import org.jboss.resteasy.reactive.RestStreamElementType;
 
@@ -26,31 +25,30 @@ public class ListenNotifyResource {
     public Multi<JsonObject> listen(@PathParam("channel") String channel) {
         return client
                 .getConnection()
+                .map(PgConnection::cast)
                 .toMulti()
-                .flatMap(connection -> {
-                    Multi<PgNotification> notifications = Multi.createFrom().
-                            emitter(c -> toPgConnection(connection).notificationHandler(c::emit));
-
-                    return connection.query("LISTEN " + channel)
-                            .execute()
-                            .toMulti()
-                            .flatMap(__ -> notifications);
-                })
+                .flatMap(connection ->
+                    connection.query("LISTEN " + channel)
+                        .execute()
+                        .toMulti()
+                        .flatMap(__ -> streamNotifications(connection))
+                )
                 .map(PgNotification::toJson);
     }
 
     @Path("{channel}")
     @POST
     @Produces(MediaType.TEXT_PLAIN)
     @Consumes(MediaType.WILDCARD)
-    public Uni<String> notif(@PathParam("channel") String channel, String stuff) {
+    public Uni<String> notify(@PathParam("channel") String channel, String stuff) {
         return client.preparedQuery("NOTIFY " + channel +  ", $$" + stuff + "$$")
                 .execute()
                 .map(rs -> "Posted to " + channel + " channel");
     }
 
-    // We have to do some type juggling here. Solved in the mutiny client v2.
-    PgConnection toPgConnection(SqlConnection sqlConnection) {
-        return new PgConnection((io.vertx.pgclient.PgConnection) sqlConnection.getDelegate());
+    // Use PgConnection::notificationHandler to register a handler that emits PgNotification values on a Multi stream
+    private Multi<PgNotification> streamNotifications(PgConnection connection) {
+        return Multi.createFrom()
+            .emitter(multiEmitter -> connection.notificationHandler(multiEmitter::emit));
     }
 }
diff --git a/...4_Internal_Channels/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java b/...4_Internal_Channels/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java
@@ -5,7 +5,6 @@
 import io.vertx.core.json.JsonObject;
 import io.vertx.mutiny.pgclient.PgConnection;
 import io.vertx.mutiny.pgclient.PgPool;
-import io.vertx.mutiny.sqlclient.SqlConnection;
 import io.vertx.pgclient.PgNotification;
 import org.jboss.resteasy.reactive.RestStreamElementType;
 
@@ -26,31 +25,30 @@ public class ListenNotifyResource {
     public Multi<JsonObject> listen(@PathParam("channel") String channel) {
         return client
                 .getConnection()
+                .map(PgConnection::cast)
                 .toMulti()
-                .flatMap(connection -> {
-                    Multi<PgNotification> notifications = Multi.createFrom().
-                            emitter(c -> toPgConnection(connection).notificationHandler(c::emit));
-
-                    return connection.query("LISTEN " + channel)
-                            .execute()
-                            .toMulti()
-                            .flatMap(__ -> notifications);
-                })
+                .flatMap(connection ->
+                    connection.query("LISTEN " + channel)
+                        .execute()
+                        .toMulti()
+                        .flatMap(__ -> streamNotifications(connection))
+                )
                 .map(PgNotification::toJson);
     }
 
     @Path("{channel}")
     @POST
     @Produces(MediaType.TEXT_PLAIN)
     @Consumes(MediaType.WILDCARD)
-    public Uni<String> notif(@PathParam("channel") String channel, String stuff) {
+    public Uni<String> notify(@PathParam("channel") String channel, String stuff) {
         return client.preparedQuery("NOTIFY " + channel +  ", $$" + stuff + "$$")
                 .execute()
                 .map(rs -> "Posted to " + channel + " channel");
     }
 
-    // We have to do some type juggling here. Solved in the mutiny client v2.
-    PgConnection toPgConnection(SqlConnection sqlConnection) {
-        return new PgConnection((io.vertx.pgclient.PgConnection) sqlConnection.getDelegate());
+    // Use PgConnection::notificationHandler to register a handler that emits PgNotification values on a Multi stream
+    private Multi<PgNotification> streamNotifications(PgConnection connection) {
+        return Multi.createFrom()
+            .emitter(multiEmitter -> connection.notificationHandler(multiEmitter::emit));
     }
 }
diff --git a/...Connecting_to_Kafka/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java b/...Connecting_to_Kafka/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java
@@ -5,7 +5,6 @@
 import io.vertx.core.json.JsonObject;
 import io.vertx.mutiny.pgclient.PgConnection;
 import io.vertx.mutiny.pgclient.PgPool;
-import io.vertx.mutiny.sqlclient.SqlConnection;
 import io.vertx.pgclient.PgNotification;
 import org.jboss.resteasy.reactive.RestStreamElementType;
 
@@ -26,31 +25,30 @@ public class ListenNotifyResource {
     public Multi<JsonObject> listen(@PathParam("channel") String channel) {
         return client
                 .getConnection()
+                .map(PgConnection::cast)
                 .toMulti()
-                .flatMap(connection -> {
-                    Multi<PgNotification> notifications = Multi.createFrom().
-                            emitter(c -> toPgConnection(connection).notificationHandler(c::emit));
-
-                    return connection.query("LISTEN " + channel)
-                            .execute()
-                            .toMulti()
-                            .flatMap(__ -> notifications);
-                })
+                .flatMap(connection ->
+                    connection.query("LISTEN " + channel)
+                        .execute()
+                        .toMulti()
+                        .flatMap(__ -> streamNotifications(connection))
+                )
                 .map(PgNotification::toJson);
     }
 
     @Path("{channel}")
     @POST
     @Produces(MediaType.TEXT_PLAIN)
     @Consumes(MediaType.WILDCARD)
-    public Uni<String> notif(@PathParam("channel") String channel, String stuff) {
+    public Uni<String> notify(@PathParam("channel") String channel, String stuff) {
         return client.preparedQuery("NOTIFY " + channel +  ", $$" + stuff + "$$")
                 .execute()
                 .map(rs -> "Posted to " + channel + " channel");
     }
 
-    // We have to do some type juggling here. Solved in the mutiny client v2.
-    PgConnection toPgConnection(SqlConnection sqlConnection) {
-        return new PgConnection((io.vertx.pgclient.PgConnection) sqlConnection.getDelegate());
+    // Use PgConnection::notificationHandler to register a handler that emits PgNotification values on a Multi stream
+    private Multi<PgNotification> streamNotifications(PgConnection connection) {
+        return Multi.createFrom()
+            .emitter(multiEmitter -> connection.notificationHandler(multiEmitter::emit));
     }
 }
diff --git a/...nd_Stream_filtering/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java b/...nd_Stream_filtering/src/main/java/com/lunatech/training/quarkus/ListenNotifyResource.java
@@ -5,7 +5,6 @@
 import io.vertx.core.json.JsonObject;
 import io.vertx.mutiny.pgclient.PgConnection;
 import io.vertx.mutiny.pgclient.PgPool;
-import io.vertx.mutiny.sqlclient.SqlConnection;
 import io.vertx.pgclient.PgNotification;
 import org.jboss.resteasy.reactive.RestStreamElementType;
 
@@ -26,31 +25,30 @@ public class ListenNotifyResource {
     public Multi<JsonObject> listen(@PathParam("channel") String channel) {
         return client
                 .getConnection()
+                .map(PgConnection::cast)
                 .toMulti()
-                .flatMap(connection -> {
-                    Multi<PgNotification> notifications = Multi.createFrom().
-                            emitter(c -> toPgConnection(connection).notificationHandler(c::emit));
-
-                    return connection.query("LISTEN " + channel)
-                            .execute()
-                            .toMulti()
-                            .flatMap(__ -> notifications);
-                })
+                .flatMap(connection ->
+                    connection.query("LISTEN " + channel)
+                        .execute()
+                        .toMulti()
+                        .flatMap(__ -> streamNotifications(connection))
+                )
                 .map(PgNotification::toJson);
     }
 
     @Path("{channel}")
     @POST
     @Produces(MediaType.TEXT_PLAIN)
     @Consumes(MediaType.WILDCARD)
-    public Uni<String> notif(@PathParam("channel") String channel, String stuff) {
+    public Uni<String> notify(@PathParam("channel") String channel, String stuff) {
         return client.preparedQuery("NOTIFY " + channel +  ", $$" + stuff + "$$")
                 .execute()
                 .map(rs -> "Posted to " + channel + " channel");
     }
 
-    // We have to do some type juggling here. Solved in the mutiny client v2.
-    PgConnection toPgConnection(SqlConnection sqlConnection) {
-        return new PgConnection((io.vertx.pgclient.PgConnection) sqlConnection.getDelegate());
+    // Use PgConnection::notificationHandler to register a handler that emits PgNotification values on a Multi stream
+    private Multi<PgNotification> streamNotifications(PgConnection connection) {
+        return Multi.createFrom()
+            .emitter(multiEmitter -> connection.notificationHandler(multiEmitter::emit));
     }
 }