Mark execute as Nullable and add convenience method for safe calls.

Author: rubengees

library/src/main/java/me/proxer/library/api/ProxerCall.java

@@ -33,6 +33,7 @@ public final class ProxerCall<T> implements Cloneable {
      * Upon success, the result entity is returned. If an error occurs, the respective {@link ProxerException} is
      * thrown.
      */
+    @Nullable
     public T execute() throws ProxerException {
         try {
             return processResponse(internalCall.execute());
@@ -43,6 +44,16 @@ public T execute() throws ProxerException {
         }
     }
 
+    public T safeExecute() throws ProxerException {
+        final T result = execute();
+
+        if (result == null) {
+            throw processNonProxerError(new NullPointerException("Response is null."));
+        } else {
+            return result;
+        }
+    }
+
     /**
      * Executes the request asynchronous.
      * <p>
@@ -112,6 +123,7 @@ public Request request() {
         return internalCall.request();
     }
 
+    @Nullable
     private T processResponse(final Response<ProxerResponse<T>> response) throws ProxerException {
         if (response.isSuccessful()) {
             final ProxerResponse<T> proxerResponse = response.body();

library/src/main/java/me/proxer/library/api/ProxerCallback.java

@@ -1,5 +1,7 @@
 package me.proxer.library.api;
 
+import javax.annotation.Nullable;
+
 /**
  * A callback for a successful request.
  *
@@ -11,5 +13,5 @@ public interface ProxerCallback<T> {
     /**
      * Called upon success for each Request with the {@code result}.
      */
-    void onSuccess(T result);
+    void onSuccess(@Nullable T result);
 }

library/src/main/java/me/proxer/library/api/ProxerResponse.java

@@ -3,6 +3,8 @@
 import com.squareup.moshi.Json;
 import lombok.*;
 
+import javax.annotation.Nullable;
+
 /**
  * @author Ruben Gees
  */
@@ -27,6 +29,7 @@ final class ProxerResponse<T> {
     @Json(name = "code")
     private int code;
 
+    @Nullable
     @SuppressWarnings("unused")
     @Getter(AccessLevel.PACKAGE)
     @Json(name = "data")

library/src/test/java/me/proxer/library/api/messenger/SendMessageEndpointTest.java

@@ -66,11 +66,9 @@ public void testActionParameters() throws ProxerException, IOException, Interrup
 
     @Test
     public void testInvalidAction() throws ProxerException, IOException, InterruptedException {
-        //noinspection CodeBlock2Expr
-        assertThatThrownBy(() -> {
-            api.messenger().sendMessage("id", MessageAction.NONE, "")
-                    .build()
-                    .execute();
-        }).isInstanceOf(IllegalArgumentException.class);
+        assertThatThrownBy(() -> api.messenger().sendMessage("id", MessageAction.NONE, "")
+                .build()
+                .execute())
+                .isInstanceOf(IllegalArgumentException.class);
     }
 }

sample/src/main/java/me/proxer/sample/News.java

@@ -17,7 +17,7 @@ public static void main(String[] args) {
         try {
             final String news = api.notifications().news()
                     .build()
-                    .execute()
+                    .safeExecute()
                     .stream()
                     .map(newsArticle -> newsArticle.getSubject() + " written by " + newsArticle.getAuthor())
                     .collect(Collectors.joining("\n"));