fix: handle case where HTTP response is not valid JSON

CHANGELOG.md

@@ -5,6 +5,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## [Unreleased]
+### Fixed
+* Handle case where HTTP response is not valid JSON.
+
+
 ## [0.2.0] - 2022-09-26
 ### Added
 * Add new `Formality` options: `PreferLess` and `PreferMore`.
@@ -40,6 +45,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Initial version.
 
 
+[Unreleased]: https://github.com/DeepLcom/deepl-java/compare/v0.2.0...HEAD
 [0.2.0]: https://github.com/DeepLcom/deepl-java/compare/v0.1.3...v0.2.0
 [0.1.3]: https://github.com/DeepLcom/deepl-java/compare/v0.1.2...v0.1.3
 [0.1.2]: https://github.com/DeepLcom/deepl-java/compare/v0.1.1...v0.1.2

deepl-java/src/main/java/com/deepl/api/Translator.java

@@ -10,6 +10,7 @@
 import com.deepl.api.http.HttpResponseStream;
 import com.deepl.api.parsing.Parser;
 import com.deepl.api.utils.*;
+import com.google.gson.*;
 import java.io.*;
 import java.net.HttpURLConnection;
 import java.util.*;
@@ -766,10 +767,16 @@ private void checkResponse(HttpResponse response, boolean inDocumentDownload)
       return;
     }
 
-    String messageSuffix = jsonParser.parseErrorMessage(response.getBody());
-    if (!messageSuffix.isEmpty()) {
-      messageSuffix = ", " + messageSuffix;
+    String messageSuffix = "";
+    String body = response.getBody();
+    if (body != null && !body.isEmpty()) {
+      try {
+        messageSuffix = ", error message: " + jsonParser.parseErrorMessage(body);
+      } catch (JsonSyntaxException ignored) {
+        messageSuffix = ", response: " + body;
+      }
     }
+
     switch (response.getCode()) {
       case HttpURLConnection.HTTP_BAD_REQUEST:
         throw new DeepLException("Bad request" + messageSuffix);