fix #126, surrogate failed to serialize in gson mode

Author: taowen

src/main/java/com/jsoniter/extra/GsonCompatibilityMode.java

@@ -287,6 +287,8 @@ public void encode(Object obj, JsonStream stream) throws IOException {
                                 if (i >= value.length()) { // unless we hit the end?
                                     break;
                                 }
+                                i++;
+                                c = value.charAt(i);
                                 int firstPart = _surrogate;
                                 _surrogate = 0;
                                 // Ok, then, is the second part valid?

src/main/java/com/jsoniter/output/ReflectionObjectEncoder.java

@@ -35,7 +35,7 @@ public ReflectionObjectEncoder(ClassInfo classInfo) {
     public void encode(Object obj, JsonStream stream) throws IOException {
         try {
             enocde_(obj, stream);
-        } catch (RuntimeException e) {
+        } catch (JsonException e) {
             throw e;
         } catch (Exception e) {
             throw new JsonException(e);

src/test/java/com/jsoniter/output/TestGson.java

@@ -293,4 +293,22 @@ public boolean shouldSkipClass(Class<?> clazz) {
         output = JsonStream.serialize(config, obj);
         assertEquals("{\"field3\":\"field3\"}", output);
     }
+
+
+    private static class TestObject {
+        private String test;
+    }
+
+    public void test_surrogate() {
+        GsonCompatibilityMode gsonConfig =
+                new GsonCompatibilityMode.Builder()
+                        .disableHtmlEscaping()
+                        .build();
+
+        String input = "{\"test\":\"lorem-\uD83D\uDC44\uD83D\uDC40\"}";
+        TestObject testObject = new Gson().fromJson(input, TestObject.class);
+
+        System.out.println("Gson: " + new Gson().toJson(testObject));
+        System.out.println("jsoniter: " + JsonStream.serialize(gsonConfig, testObject));
+    }
 }