Accept only 200 HTTP status code / check for empty response body (#68)

* Accept only 200 HTTP status code / check for empty response body

* Throw exception in case of invalid JSON

* Update src/main/java/com/configcat/Utils.java

Co-authored-by: adams85 <31276480+adams85@users.noreply.github.com>

* Proposed changes

* Potential further improvements that may help error diagnostics

* Bump versions

---------

Co-authored-by: adams85 <31276480+adams85@users.noreply.github.com>
Co-authored-by: Adam Simon <adamosimoni@gmail.com>

Author: z4kn4fein

gradle.properties

@@ -1 +1 @@
-version=9.4.3
+version=9.4.4

src/main/java/com/configcat/Config.java

@@ -13,7 +13,7 @@ public class Config {
     @SerializedName(value = "p")
     private Preferences preferences;
     @SerializedName(value = "f")
-    private final Map<String, Setting> entries = new HashMap<>();
+    private Map<String, Setting> entries = new HashMap<>();
     @SerializedName(value = "s")
     private Segment[] segments;
 
@@ -35,7 +35,9 @@ public Segment[] getSegments() {
      * The map of settings.
      */
     public Map<String, Setting> getEntries() {
-        return entries;
+        // NOTE: Deserializing a JSON like '{ "f": null }' overwrites entries with null.
+        // However, we want to treat null as an empty map in that case too.
+        return entries != null ? entries : (entries = new HashMap<>());
     }
 
     boolean isEmpty() {

src/main/java/com/configcat/ConfigFetcher.java

@@ -113,8 +113,8 @@ public void onFailure(@NotNull Call call, @NotNull IOException e) {
             public void onResponse(@NotNull Call call, @NotNull Response response) {
                 try (ResponseBody body = response.body()) {
                     String cfRayId = response.header("CF-RAY");
-                    if (response.isSuccessful() && body != null) {
-                        String content = body.string();
+                    if (response.code() == 200) {
+                        String content = body != null ? body.string() : null;
                         String eTag = response.header("ETag");
                         Result<Config> result = deserializeConfig(content, cfRayId);
                         if (result.error() != null) {
@@ -190,4 +190,3 @@ private Result<Config> deserializeConfig(String json, String cfRayId) {
         }
     }
 }
-

src/main/java/com/configcat/Constants.java

@@ -7,7 +7,7 @@ private Constants() { /* prevent from instantiation*/ }
     static final long DISTANT_PAST = 0;
     static final String CONFIG_JSON_NAME = "config_v6.json";
     static final String SERIALIZATION_FORMAT_VERSION = "v2";
-    static final String VERSION = "9.4.3";
+    static final String VERSION = "9.4.4";
 
     static final String SDK_KEY_PROXY_PREFIX = "configcat-proxy/";
     static final String SDK_KEY_PREFIX = "configcat-sdk-1";

src/main/java/com/configcat/RolloutEvaluator.java

@@ -45,7 +45,7 @@ public EvaluationResult evaluate(Setting setting, String key, User user, Map<Str
     @NotNull
     private EvaluationResult evaluateSetting(Setting setting, EvaluateLogger evaluateLogger, EvaluationContext context) {
         EvaluationResult evaluationResult = null;
-        if (setting.getTargetingRules() != null) {
+        if (setting.getTargetingRules() != null && setting.getTargetingRules().length > 0) {
             evaluationResult = evaluateTargetingRules(setting, context, evaluateLogger);
         }
         if (evaluationResult == null && setting.getPercentageOptions() != null && setting.getPercentageOptions().length > 0) {

src/main/java/com/configcat/Utils.java

@@ -37,8 +37,17 @@ public static DecimalFormat getDecimalFormat() {
     }
 
     public static Config deserializeConfig(String json) {
+        if (json == null || json.isEmpty()) {
+            throw new IllegalArgumentException("Config JSON content cannot be null or empty.");
+        }
+
         Config config = Utils.gson.fromJson(json, Config.class);
-        String salt = config.getPreferences().getSalt();
+
+        if (config == null) {
+            throw new IllegalArgumentException("Invalid config JSON content: " + json);
+        }
+
+        String salt = config.getPreferences() != null ? config.getPreferences().getSalt() : null;
         Segment[] segments = config.getSegments();
         if (segments == null) {
             segments = new Segment[]{};

src/test/java/com/configcat/ConfigFetcherTest.java

@@ -8,12 +8,16 @@
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
 
 import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.anyString;
@@ -155,6 +159,32 @@ public void fetchSuccess() throws Exception {
         fetcher.close();
     }
 
+    private static Stream<Arguments> emptyFetchTestData() {
+        return Stream.of(
+                Arguments.of(""),
+                Arguments.of("null")
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource("emptyFetchTestData")
+    public void fetchEmpty(String body) throws Exception {
+        this.server.enqueue(new MockResponse().setResponseCode(200).setBody(body));
+
+        ConfigFetcher fetcher = new ConfigFetcher(new OkHttpClient.Builder().build(),
+                logger,
+                "",
+                this.server.url("/").toString(),
+                false,
+                PollingModes.manualPoll().getPollingIdentifier());
+
+        FetchResponse response = fetcher.fetchAsync(null).get();
+        assertFalse(response.isFetched());
+        assertEquals("Fetching config JSON was successful but the HTTP response content was invalid.", response.error().toString());
+
+        fetcher.close();
+    }
+
     @Test
     public void testIntegration() throws IOException, ExecutionException, InterruptedException {
         ConfigFetcher fetch = new ConfigFetcher(new OkHttpClient.Builder()