Moved logic from specific serializer to shared code

Author: onufryk

core-api/src/main/java/com/optimizely/ab/Optimizely.java

@@ -498,6 +498,13 @@ private void track(@Nonnull String eventName,
      * @return a {@link ProjectConfig} instance given a json string
      */
     private static ProjectConfig getProjectConfig(String datafile) throws ConfigParseException {
+        if (datafile == null) {
+            throw new ConfigParseException("Unable to parse null datafile.");
+        }
+        if (datafile.length() == 0) {
+            throw new ConfigParseException("Unable to parse empty datafile.");
+        }
+
         return DefaultConfigParser.getInstance().parseProjectConfig(datafile);
     }
 

core-api/src/main/java/com/optimizely/ab/config/parser/GsonConfigParser.java

@@ -33,9 +33,6 @@ final class GsonConfigParser implements ConfigParser {
 
     @Override
     public ProjectConfig parseProjectConfig(@Nonnull String json) throws ConfigParseException {
-        if (json == null || json.length() == 0) {
-            throw new ConfigParseException("Unable to parse datafile: " + json);
-        }
         Gson gson = new GsonBuilder()
             .registerTypeAdapter(ProjectConfig.class, new ProjectConfigGsonDeserializer())
             .registerTypeAdapter(Audience.class, new AudienceGsonDeserializer())

core-api/src/test/java/com/optimizely/ab/config/parser/GsonConfigParserTest.java

@@ -22,6 +22,8 @@
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
+import static junit.framework.Assert.assertNull;
+
 
 import static com.optimizely.ab.config.ProjectConfigTestUtils.validConfigJsonV1;
 import static com.optimizely.ab.config.ProjectConfigTestUtils.validProjectConfigV1;
@@ -90,24 +92,22 @@ public void validJsonRequiredFieldMissingExceptionWrapping() throws Exception {
 
     /**
      * Verify that empty string JSON results in a {@link ConfigParseException} being thrown.
+     * This serializer doesn't throw exceptions on null or empty string
      */
     @Test
     public void emptyJsonExceptionWrapping() throws Exception {
-        thrown.expect(ConfigParseException.class);
-
         GsonConfigParser parser = new GsonConfigParser();
-        parser.parseProjectConfig("");
+        assertNull(parser.parseProjectConfig(""));
     }
 
     /**
      * Verify that null JSON results in a {@link ConfigParseException} being thrown.
+     * This serializer doesn't throw exceptions on null or empty string
      */
     @Test
     @SuppressFBWarnings(value="NP_NONNULL_PARAM_VIOLATION", justification="Testing nullness contract violation")
     public void nullJsonExceptionWrapping() throws Exception {
-        thrown.expect(ConfigParseException.class);
-
         GsonConfigParser parser = new GsonConfigParser();
-        parser.parseProjectConfig(null);
+        assertNull(parser.parseProjectConfig(null));
     }
 }