Replace gson with Android's org.json.*

lib/build.gradle

@@ -35,7 +35,6 @@ android {
 
 dependencies {
     implementation 'androidx.annotation:annotation:1.1.0'
-    implementation 'com.google.code.gson:gson:2.8.9'
 
     testImplementation 'junit:junit:4.13'
     testImplementation 'org.hamcrest:java-hamcrest:2.0.0.0'
@@ -44,6 +43,7 @@ dependencies {
         exclude group: 'com.google.auto.service', module: 'auto-service'
     }
     testImplementation 'org.mockito:mockito-core:3.2.4'
+    testImplementation project(':jwtdecode')
 }
 
 tasks.withType(Test) {

lib/src/main/java/com/auth0/android/jwt/BaseClaim.java

@@ -1,10 +1,11 @@
 package com.auth0.android.jwt;
 
 import androidx.annotation.Nullable;
-import java.lang.reflect.Array;
-import java.util.Collections;
+
+import org.json.JSONArray;
+import org.json.JSONObject;
+
 import java.util.Date;
-import java.util.List;
 
 /**
  * The BaseClaim class is a Claim implementation that returns null when any of it's methods it's called.
@@ -47,18 +48,13 @@ public Date asDate() {
 
     @SuppressWarnings("unchecked")
     @Override
-    public <T> T[] asArray(Class<T> tClazz) throws DecodeException {
-        return (T[]) Array.newInstance(tClazz, 0);
-    }
-
-    @Override
-    public <T> List<T> asList(Class<T> tClazz) throws DecodeException {
-        return Collections.emptyList();
+    public JSONArray asArray() {
+        return null;
     }
 
     @Nullable
     @Override
-    public <T> T asObject(Class<T> tClazz) throws DecodeException {
+    public JSONObject asObject() {
         return null;
     }
 }

lib/src/main/java/com/auth0/android/jwt/Claim.java

@@ -1,6 +1,10 @@
 package com.auth0.android.jwt;
 
 import androidx.annotation.Nullable;
+
+import org.json.JSONArray;
+import org.json.JSONObject;
+
 import java.util.Date;
 import java.util.List;
 
@@ -69,26 +73,16 @@ public interface Claim {
      * If the value isn't an Array, an empty Array will be returned.
      *
      * @return the value as an Array or an empty Array.
-     * @throws DecodeException if the values inside the Array can't be converted to a class T.
      */
-    <T> T[] asArray(Class<T> tClazz) throws DecodeException;
-
-    /**
-     * Get this Claim as a List of type T.
-     * If the value isn't an Array, an empty List will be returned.
-     *
-     * @return the value as a List or an empty List.
-     * @throws DecodeException if the values inside the List can't be converted to a class T.
-     */
-    <T> List<T> asList(Class<T> tClazz) throws DecodeException;
+    @Nullable
+    JSONArray asArray();
 
     /**
      * Get this Claim as a Object of type T.
      * If the value isn't of type Object, null will be returned.
      *
-     * @return the value as a Object of type T or null.
-     * @throws DecodeException if the value can't be converted to a class T.
+     * @return the value as a Object of type T or null..
      */
     @Nullable
-    <T> T asObject(Class<T> tClazz) throws DecodeException;
+    JSONObject asObject();
 }

lib/src/main/java/com/auth0/android/jwt/JSONObjectClaim.java

@@ -0,0 +1,99 @@
+package com.auth0.android.jwt;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.util.Date;
+
+final class JSONObjectClaim implements Claim {
+    @NonNull
+    private final String name;
+    @NonNull
+    private final JSONObject object;
+
+    JSONObjectClaim(@NonNull JSONObject object, @NonNull String name) {
+        this.object = object;
+        this.name = name;
+    }
+
+    @Nullable
+    @Override
+    public Boolean asBoolean() {
+        try {
+            return object.getBoolean(name);
+        } catch (JSONException exception) {
+            return null;
+        }
+    }
+
+    @Nullable
+    @Override
+    public Integer asInt() {
+        try {
+            return object.getInt(name);
+        } catch (JSONException exception) {
+            return null;
+        }
+    }
+
+    @Nullable
+    @Override
+    public Long asLong() {
+        try {
+            return object.getLong(name);
+        } catch (JSONException exception) {
+            return null;
+        }
+    }
+
+    @Nullable
+    @Override
+    public Double asDouble() {
+        try {
+            return object.getDouble(name);
+        } catch (JSONException exception) {
+            return null;
+        }
+    }
+
+    @Nullable
+    @Override
+    public String asString() {
+        if (object.isNull(name) || object.optJSONArray(name) != null || object.optJSONObject(name) != null) {
+            return null;
+        }
+
+        try {
+            return object.getString(name);
+        } catch (JSONException exception) {
+            return null;
+        }
+    }
+
+    @Nullable
+    @Override
+    public Date asDate() {
+        final Long value = asLong();
+        if (value != null) {
+            return new Date(value * 1000);
+        }
+
+        return null;
+    }
+
+    @Nullable
+    @Override
+    public JSONArray asArray() {
+        return object.optJSONArray(name);
+    }
+
+    @Nullable
+    @Override
+    public JSONObject asObject() {
+        return object.optJSONObject(name);
+    }
+}

lib/src/main/java/com/auth0/android/jwt/JWT.java

@@ -7,11 +7,6 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-import com.google.gson.reflect.TypeToken;
-
-import java.lang.reflect.Type;
 import java.nio.charset.Charset;
 import java.util.Date;
 import java.util.List;
@@ -208,10 +203,8 @@ public JWT[] newArray(int size) {
 
     private void decode(String token) {
         final String[] parts = splitToken(token);
-        Type mapType = new TypeToken<Map<String, String>>() {
-        }.getType();
-        header = parseJson(base64Decode(parts[0]), mapType);
-        payload = parseJson(base64Decode(parts[1]), JWTPayload.class);
+        header = decoder.decodeHeader(base64Decode(parts[0]));
+        payload = decoder.decodePayload(base64Decode(parts[1]));
         signature = parts[2];
     }
 
@@ -239,19 +232,5 @@ private String base64Decode(String string) {
         return decoded;
     }
 
-    private <T> T parseJson(String json, Type typeOfT) {
-        T payload;
-        try {
-            payload = getGson().fromJson(json, typeOfT);
-        } catch (Exception e) {
-            throw new DecodeException("The token's payload had an invalid JSON format.", e);
-        }
-        return payload;
-    }
-
-    static Gson getGson() {
-        return new GsonBuilder()
-                .registerTypeAdapter(JWTPayload.class, new JWTDeserializer())
-                .create();
-    }
+    private static JWTDecoder decoder = new JWTDecoder();
 }