Streamline all APIs

.github/workflows/maven.yml

@@ -16,7 +16,7 @@ env:
   MAVEN_OPTS: -Dio.netty.tryReflectionSetAccessible=true
 
 jobs:
-  JDK17:
+  JDK21:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

backend/src/main/java/com/shieldblaze/expressgateway/backend/Connection.java

@@ -195,15 +195,15 @@ public void backlogQueue(ConcurrentLinkedQueue<Object> newQueue) {
      * Close this {@link Connection}
      */
     public synchronized void close() {
-        // If Backlog Queue contains something then clear it before closing connection.
+        // If Backlog Queue contains something, then clear it before closing the connection.
         if (backlogQueue != null && !backlogQueue.isEmpty()) {
             clearBacklog();
         }
 
         // Remove this connection from Node
         node.removeConnection(this);
 
-        // If Channel is not null then close it.
+        // If Channel is not null, then close it.
         // Channel can be null if the connection is not initialized.
         if (channel != null) {
             channel.close();

common/src/main/java/com/shieldblaze/expressgateway/common/utils/ObjectUtils.java

@@ -6,14 +6,50 @@ private ObjectUtils() {
         // Prevent outside initialization
     }
 
+    /**
+     * Check if the object is not null and throw a {@link NullPointerException} if it is.
+     * </p>
+     * Exception message will be "Object cannot be 'null'"
+     *
+     * @param obj   The object to check
+     * @param clazz The class of the object
+     * @param <T>   The type of the object
+     * @return The object if it is not null
+     */
     public static <T> T nonNull(T obj, Class<?> clazz) {
         return nonNull(obj, clazz.getSimpleName());
     }
 
+    /**
+     * Check if the object is not null and throw a {@link NullPointerException} if it is.
+     *
+     * @param obj     The object to check
+     * @param message The message to throw with the exception
+     * @param <T>     The type of the object
+     * @return The object if it is not null
+     */
     public static <T> T nonNull(T obj, String message) {
         if (obj == null) {
             throw new NullPointerException(message);
         }
         return obj;
     }
+
+    /**
+     * Check if the object is not null and throw a {@link NullPointerException} if it is.
+     * </p>
+     * Exception message will be "Object cannot be 'null'"
+     *
+     * @param obj    The object to check
+     * @param object The name of the object
+     * @param <T>    The type of the object
+     * @return The object if it is not null
+     * @throws NullPointerException If the object is null
+     */
+    public static <T> T nonNullObject(T obj, String object) {
+        if (obj == null) {
+            throw new NullPointerException(object + " cannot be 'null'");
+        }
+        return obj;
+    }
 }

concurrent/src/main/java/com/shieldblaze/expressgateway/concurrent/GlobalExecutors.java

@@ -54,10 +54,10 @@ private GlobalExecutors() {
     }
 
     /**
-     * Submit a new {@link Runnable} task to executed
+     * Submit a new {@link Runnable} task to execute
      *
      * @param runnable {@link Runnable} to be executed
-     * @return {@link CompletableFuture} Instance of task to be executed
+     * @return {@link CompletableFuture} Instance of a task to be executed
      */
     public static CompletableFuture<Void> submitTask(Runnable runnable) {
         return CompletableFuture.runAsync(runnable, EXECUTOR_SERVICE);
@@ -66,9 +66,9 @@ public static CompletableFuture<Void> submitTask(Runnable runnable) {
     /**
      * Submit a new task to be executed
      *
-     * @param supplier {@link Supplier} implementing task to be executed
+     * @param supplier {@link Supplier} implementing a task to be executed
      * @param <T>      Class implementing {@link Supplier}
-     * @return {@link CompletableFuture} Instance of task to be executed
+     * @return {@link CompletableFuture} Instance of a task to be executed
      */
     public static <T> CompletableFuture<T> submitTask(Supplier<T> supplier) {
         return CompletableFuture.supplyAsync(supplier, EXECUTOR_SERVICE);
@@ -78,7 +78,7 @@ public static <T> CompletableFuture<T> submitTask(Supplier<T> supplier) {
      * Submit and schedule a new {@link Runnable} task to be executed with a fixed delay
      *
      * @param runnable {@link Runnable} to be executed
-     * @return {@link CompletableFuture} Instance of task to be executed
+     * @return {@link CompletableFuture} Instance of a task to be executed
      */
     public static ScheduledFuture<?> submitTaskAndRunEvery(Runnable runnable, int initialDelay, int period, TimeUnit timeUnit) {
         return SCHEDULED_EXECUTOR_SERVICE.scheduleWithFixedDelay(runnable, initialDelay, period, timeUnit);

concurrent/src/main/java/com/shieldblaze/expressgateway/concurrent/event/DefaultEvent.java

@@ -20,7 +20,7 @@
 import java.util.concurrent.CompletableFuture;
 
 /**
- * Default implementation of {@link Event}
+ * Default implementation of an {@link Event}
  */
 public class DefaultEvent<T> implements Event<T> {
 
@@ -30,8 +30,7 @@ public class DefaultEvent<T> implements Event<T> {
     private Throwable throwable;
 
     /**
-     * Mark this event as successful with 'null' successful
-     * completion object
+     * Mark this event as successful with 'null' successfulcompletion object
      */
     public void markSuccess() {
         markSuccess(null);

concurrent/src/main/java/com/shieldblaze/expressgateway/concurrent/event/Event.java

@@ -19,6 +19,11 @@
 
 import java.util.concurrent.CompletableFuture;
 
+/**
+ * {@link Event} is an object which is created as a result of an operation.
+ *
+ * @param <T> Type of the operation result
+ */
 public interface Event<T> {
 
     /**
@@ -28,12 +33,17 @@ public interface Event<T> {
 
     /**
      * Set to {@code true} if the event has finished else set to {@code false}.
+     * </p>
+     * Note: This does not mean that the operation was successful. Use {@link #isSuccess()} to check that.
      */
     boolean isFinished();
 
     /**
      * Set to {@code true} if the event has finished and operation was successful else
      * set to {@code false}.
+     * <p>
+     * </p>
+     * {@link #isFinished()} will always return {@code true} if this method returns {@code true}.
      */
     boolean isSuccess();
 

core/src/main/java/com/shieldblaze/expressgateway/core/cluster/CoreContext.java

@@ -18,81 +18,92 @@
 package com.shieldblaze.expressgateway.core.cluster;
 
 import com.shieldblaze.expressgateway.backend.Node;
+import com.shieldblaze.expressgateway.core.exceptions.NotFoundException;
+import com.shieldblaze.expressgateway.core.loadbalancer.L4LoadBalancer;
 
 import java.util.Map;
-import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 
+import static com.shieldblaze.expressgateway.common.utils.ObjectUtils.nonNullObject;
+
 /**
- * This class holds all information about all load balancers.
+ * {@link CoreContext} holds all the {@link L4LoadBalancer} instances
  */
 public final class CoreContext {
 
     /**
-     * Mapping of Load Balancer ID with {@link LoadBalancerContext}
+     * Mapping of Load Balancer ID with {@link L4LoadBalancer}
      */
-    private static final Map<String, LoadBalancerContext> REGISTRY = new ConcurrentHashMap<>();
+    private static final Map<String, L4LoadBalancer> REGISTRY = new ConcurrentHashMap<>();
 
     /**
-     * Get mapped {@link LoadBalancerContext} using Load Balancer ID
+     * Get mapped {@link L4LoadBalancer} using Load Balancer ID
      *
      * @param id Load Balancer ID
-     * @return {@link LoadBalancerContext} Instance
-     * @throws NullPointerException If {@link LoadBalancerContext} is not found with the ID
+     * @return {@link L4LoadBalancer} Instance
+     * @throws NotFoundException    If {@link L4LoadBalancer} is not found with the ID
+     * @throws NullPointerException If {@code id} is {@code null}
      */
-    public static LoadBalancerContext get(String id) {
-        Objects.requireNonNull(id, "ID cannot be 'null'");
+    public static L4LoadBalancer getContext(String id) {
+        nonNullObject(id, "ID");
+
+        L4LoadBalancer property = REGISTRY.get(id);
 
-        LoadBalancerContext property = REGISTRY.get(id);
-        Objects.requireNonNull(property, "Load Balancer was not found with the ID: " + id);
+        if (property == null) {
+            throw new NotFoundException("Load Balancer was not found with the ID: " + id);
+        }
 
         return property;
     }
 
     /**
-     * Add mapping to {@link LoadBalancerContext} using Load Balancer ID
+     * Add mapping to {@link L4LoadBalancer} using Load Balancer ID
      *
-     * @param id       Load Balancer ID
-     * @param context {@link LoadBalancerContext} Instance
-     * @throws NullPointerException If {@code id} or {@link LoadBalancerContext} is 'null'
+     * @param id      Load Balancer ID
+     * @param context {@link L4LoadBalancer} Instance
+     * @throws NullPointerException If {@code id} or {@link L4LoadBalancer} is 'null'
      */
-    public static void add(String id, LoadBalancerContext context) {
-        Objects.requireNonNull(id, "ID cannot be 'null'");
-        Objects.requireNonNull(context, "Property cannot be 'null'");
+    public static void add(String id, L4LoadBalancer context) {
+        nonNullObject(id, "ID");
+        nonNullObject(context, "LoadBalancerContext");
+
+        if (REGISTRY.containsKey(id)) {
+            throw new IllegalArgumentException("Load Balancer already exists with the ID: " + id);
+        }
 
         REGISTRY.put(id, context);
     }
 
     /**
-     * Remove mapping of {@link LoadBalancerContext} using Load Balancer ID
+     * Remove mapping of {@link L4LoadBalancer} using Load Balancer ID
      *
      * @param id Load Balancer ID
-     * @return {@link LoadBalancerContext} Instance is successfully removed else {@code null}
+     * @return {@link L4LoadBalancer} Instance is successfully removed else {@code null}
      */
-    public static LoadBalancerContext remove(String id) {
-        Objects.requireNonNull(id, "ID cannot be 'null'");
+    public static L4LoadBalancer remove(String id) {
+        nonNullObject(id, "ID");
         return REGISTRY.remove(id);
     }
 
     /**
-     * Get total connections across all load balancers.
+     * Get total active connections across all load balancers.
      */
     public int totalActiveConnections() {
         return REGISTRY.values()
                 .stream()
-                .mapToInt(loadBalancerProperty -> loadBalancerProperty.l4LoadBalancer()
+                .mapToInt(L4LoadBalancer -> L4LoadBalancer
                         .connectionTracker()
                         .connections())
                 .sum();
     }
 
     /**
-     * Get total connections load across all load balancers
+     * Get the total connections load across all load balancers
      */
     public long totalConnections() {
-         return REGISTRY.values()
+        return REGISTRY.values()
                 .stream()
-                .mapToLong(value -> value.l4LoadBalancer()
+                .mapToLong(value -> value
                         .clusters()
                         .values()
                         .stream()

core/src/main/java/com/shieldblaze/expressgateway/core/events/L4FrontListenerShutdownEvent.java

@@ -22,7 +22,10 @@
 import com.shieldblaze.expressgateway.core.L4FrontListener;
 
 /**
- * {@link Event} for {@link L4FrontListener}
+ * {@link Event} for {@link L4FrontListener}.
+ * </p>
+ *
+ * This event is fired when {@link L4FrontListener} is stopped.
  */
 public class L4FrontListenerShutdownEvent extends DefaultEvent<Void> {
     // Empty

core/src/main/java/com/shieldblaze/expressgateway/core/events/L4FrontListenerStartupEvent.java

@@ -22,7 +22,8 @@
 import com.shieldblaze.expressgateway.core.L4FrontListener;
 
 /**
- * <p>{@link Event} for {@link L4FrontListener}</p>
+ * {@link Event} for {@link L4FrontListener}
+ * </p>
  *
  * This event is fired when {@link L4FrontListener} is started.
  */

core/src/main/java/com/shieldblaze/expressgateway/core/events/L4FrontListenerStopEvent.java

@@ -23,6 +23,9 @@
 
 /**
  * {@link Event} for {@link L4FrontListener}
+ * </p>
+ *
+ * This event is fired when {@link L4FrontListener} is stopped.
  */
 public class L4FrontListenerStopEvent extends DefaultEvent<Void> {
     // Empty