Centralize Gson creation and registration

5 files changed, 49 insertions, 20 deletions

diff --git a/src/data/Tweet.java b/src/data/Tweet.java
index 3caae6a..04b5f2c 100644
--- a/src/data/Tweet.java
+++ b/src/data/Tweet.java
@@ -1,7 +1,5 @@
 package data;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
 
 /**
  * Represents the tweet object as returned by the twitter API.
@@ -32,8 +30,8 @@ public class Tweet {
 
     @Override
     public String toString() {
-        Gson gson = new GsonBuilder().setPrettyPrinting().create();
-        return gson.toJson(this);
+        return TwitterJsonDeserializer.getGsonBuilder()
+                .setPrettyPrinting().create().toJson(this);
     }
 
     public static class Place {
diff --git a/src/data/TwitterJsonDeserializer.java b/src/data/TwitterJsonDeserializer.java
new file mode 100644
index 0000000..47506d0
--- /dev/null
+++ b/src/data/TwitterJsonDeserializer.java
@@ -0,0 +1,27 @@
+package data;
+
+import com.google.gson.GsonBuilder;
+
+/**
+ * Deserializer for Twitter objects.
+ *
+ * @author Peter Wu
+ */
+public class TwitterJsonDeserializer extends ValidatingJsonDeserializer {
+
+    public TwitterJsonDeserializer() {
+        super(getBaseGsonBuilder()
+                .create());
+    }
+
+    private static GsonBuilder getBaseGsonBuilder() {
+        return new GsonBuilder();
+    }
+
+    public static GsonBuilder getGsonBuilder() {
+        TwitterJsonDeserializer tjd = new TwitterJsonDeserializer();
+        return getBaseGsonBuilder()
+                .registerTypeAdapter(Tweet.class, tjd)
+                .registerTypeAdapter(User.class, tjd);
+    }
+}
diff --git a/src/data/ValidatingJsonDeserializer.java b/src/data/ValidatingJsonDeserializer.java
index d5a8dbc..6fd9dc7 100644
--- a/src/data/ValidatingJsonDeserializer.java
+++ b/src/data/ValidatingJsonDeserializer.java
@@ -21,12 +21,22 @@ import java.lang.reflect.Type;
  */
 public class ValidatingJsonDeserializer<T> implements JsonDeserializer<T> {
 
+    private final Gson gson;
+
+    public ValidatingJsonDeserializer() {
+        this(new Gson());
+    }
+
+    public ValidatingJsonDeserializer(Gson gson) {
+        this.gson = gson;
+    }
+
     @Override
     public T deserialize(JsonElement je, Type type,
             JsonDeserializationContext jdc) throws JsonParseException {
         T obj;
         try {
-            obj = new Gson().fromJson(je, type);
+            obj = gson.fromJson(je, type);
         } catch (JsonParseException jpe) {
             DebuggingJsonDeserializer.tryValidate(je.toString(), (Class) type);
             throw new JsonParseException("Debugger could not find a bug", jpe);
@@ -35,7 +45,7 @@ public class ValidatingJsonDeserializer<T> implements JsonDeserializer<T> {
         return obj;
     }
 
-    void checkObject(String path, JsonElement je, Class type)
+    protected final void checkObject(String path, JsonElement je, Class type)
             throws JsonParseException {
         JsonObject jsonObj = je.getAsJsonObject();
         for (Field f : type.getDeclaredFields()) {
@@ -53,15 +63,14 @@ public class ValidatingJsonDeserializer<T> implements JsonDeserializer<T> {
                 }
             }
             tryValidateProperty(path, val, f);
-            // TODO: validate type?
         }
     }
 
     private void tryValidateProperty(String path, JsonElement je, Field f)
             throws JsonParseException {
         Class<?> type = f.getType();
-        // assume that this annotation is only applied to objects
-        Validator v = f.getAnnotation(Validator.class);
+
+        // validates arrays
         ArrayValidator av = f.getAnnotation(ArrayValidator.class);
         path += f.getName();
         if (av != null) {
@@ -83,6 +92,9 @@ public class ValidatingJsonDeserializer<T> implements JsonDeserializer<T> {
                         + maxLen + ": " + path);
             }
         }
+
+        // validates objects, recursively
+        Validator v = f.getAnnotation(Validator.class);
         if (v != null) {
             if (type.isArray()) {
                 // the class expects an array, so the value must have one too.
diff --git a/src/io/TweetReader.java b/src/io/TweetReader.java
index 8968b84..15ddcea 100644
--- a/src/io/TweetReader.java
+++ b/src/io/TweetReader.java
@@ -1,10 +1,9 @@
 package io;
 
 import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
 import com.google.gson.JsonSyntaxException;
 import data.Tweet;
-import data.ValidatingJsonDeserializer;
+import data.TwitterJsonDeserializer;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
@@ -27,9 +26,7 @@ public class TweetReader implements ITweetReader {
         }
         this.is = is;
         reader = new BufferedReader(new InputStreamReader(is));
-        gson = new GsonBuilder()
-                .registerTypeAdapter(Tweet.class, new ValidatingJsonDeserializer())
-                .create();
+        gson = TwitterJsonDeserializer.getGsonBuilder().create();
     }
 
     @Override
diff --git a/test/data/ValidatingJsonDeserializerTest.java b/test/data/ValidatingJsonDeserializerTest.java
index b51631a..73523f4 100644
--- a/test/data/ValidatingJsonDeserializerTest.java
+++ b/test/data/ValidatingJsonDeserializerTest.java
@@ -1,7 +1,6 @@
 package data;
 
 import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonNull;
@@ -278,9 +277,7 @@ public class ValidatingJsonDeserializerTest {
             + "}";
 
     private Object deserializeJson(String json, Class cls) {
-        Gson gson = new GsonBuilder()
-                .registerTypeAdapter(cls, new ValidatingJsonDeserializer<>())
-                .create();
+        Gson gson = TwitterJsonDeserializer.getGsonBuilder().create();
         return gson.fromJson(json, cls);
     }
 
@@ -312,8 +309,6 @@ public class ValidatingJsonDeserializerTest {
     @Test
     public void testDeserializeTweet() {
         Tweet tweet = (Tweet) deserializeJson(exampleTweet, Tweet.class);
-        Gson gson = new GsonBuilder().setPrettyPrinting().create();
-        //System.out.println(gson.toJson(tweet));
         assertEquals(461441338630619136L, tweet.id);
         assertNotNull(tweet.retweeted_status);
         assertEquals("Wed Apr 30 09:46:02 +0000 2014", tweet.created_at);