Add json containers for Tweet and User objects

3 files changed, 147 insertions, 0 deletions

diff --git a/src/data/Tweet.java b/src/data/Tweet.java
new file mode 100644
index 0000000..0d529d6
--- /dev/null
+++ b/src/data/Tweet.java
@@ -0,0 +1,57 @@
+package data;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+/**
+ * Represents the tweet object as returned by the twitter API.
+ */
+public class Tweet {
+
+    public String lang;
+    public long id;
+    public long in_reply_to_user_id;
+    public String created_at;
+    public long favorite_count;
+    public String place;
+    public String coordinates;
+    public String text;
+    @ValidatingJsonDeserializer.Nullable
+    public Tweet retweeted_status;
+    public Entities entities;
+    public long retweet_count;
+    @ValidatingJsonDeserializer.Validator()
+    public User user;
+
+    @Override
+    public String toString() {
+        Gson gson = new GsonBuilder().setPrettyPrinting().create();
+        return gson.toJson(this);
+    }
+
+    public class Entities {
+
+        public Hashtag[] hashtags;
+        public Url[] urls;
+        public Mention[] user_mentions;
+    }
+
+    public class Hashtag {
+
+        public String text;
+    }
+
+    public class Url {
+
+        public String expanded_url;
+        //public String display_url;
+        //public String url;
+    }
+
+    public class Mention {
+
+        public long id; // user ID
+        //public String name; // display name
+        //public String screen_name; // Screen name (at-name)
+    }
+}
diff --git a/src/data/User.java b/src/data/User.java
new file mode 100644
index 0000000..054fa54
--- /dev/null
+++ b/src/data/User.java
@@ -0,0 +1,18 @@
+package data;
+
+/**
+ * Represents the user object from the Twitter API as contained in a tweet.
+ */
+public class User {
+
+    public long id;
+    public String name;
+    public String time_zone;
+    public long statuses_count;
+    public long followers_count;
+    public long friends_count;
+    public String location;
+    public String screen_name;
+    public String created_at;
+    public String lang;
+}
diff --git a/src/data/ValidatingJsonDeserializer.java b/src/data/ValidatingJsonDeserializer.java
new file mode 100644
index 0000000..91c1709
--- /dev/null
+++ b/src/data/ValidatingJsonDeserializer.java
@@ -0,0 +1,72 @@
+package data;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.reflect.Field;
+import java.lang.reflect.Type;
+
+/**
+ * JSON deserializer which validates that all fields are present.
+ *
+ * @author Peter Wu.
+ */
+public class ValidatingJsonDeserializer<T> implements JsonDeserializer<T> {
+
+    @Override
+    public T deserialize(JsonElement je, Type type,
+            JsonDeserializationContext jdc) throws JsonParseException {
+        T obj = new Gson().fromJson(je, type);
+        JsonObject jsonObj = je.getAsJsonObject();
+        for (Field f : obj.getClass().getDeclaredFields()) {
+            if (!jsonObj.has(f.getName())) {
+                if (f.getAnnotation(Nullable.class) != null) {
+                    // null allowed, skip
+                    continue;
+                }
+                throw new JsonParseException("Missing field: " + f.getName());
+            }
+            // TODO: validate type?
+        }
+        return obj;
+    }
+
+    public static GsonBuilder addValidation(GsonBuilder gson, Type type) {
+        GsonBuilder gb = new GsonBuilder();
+        gson.registerTypeAdapter(type, new ValidatingJsonDeserializer());
+        for (Field f : type.getClass().getDeclaredFields()) {
+            Validator v = f.getAnnotation(Validator.class);
+            if (v != null) {
+                addValidation(gson, v.deserializer());
+            }
+        }
+        return gb;
+    }
+
+    /**
+     * Marks a member as object that should be validated too.
+     */
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target(ElementType.FIELD)
+    public @interface Validator {
+
+        Class deserializer() default ValidatingJsonDeserializer.class;
+    }
+
+    /**
+     * Marks a member as nullable, that is, it can be missing from the JSON
+     * object.
+     */
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target(ElementType.FIELD)
+    public @interface Nullable {
+    }
+}