From c25278b4d6036a0e0ae758b13194813936d9e911 Mon Sep 17 00:00:00 2001
From: Inderjeet Singh
Date: Thu, 11 Oct 2012 03:20:36 +0000
Subject: [PATCH] Created an alpha package that holds experimental feature.
Added support for JsonPostDeserializer that allows you to invoke
postDeserialize methods on an Gson deserialized object.
---
gson/src/main/java/com/google/gson/Gson.java | 24 ++++++-
.../google/gson/internal/alpha/Intercept.java | 64 +++++++++++++++++++
.../internal/alpha/JsonPostDeserializer.java | 33 ++++++++++
.../gson/internal/alpha/package-info.java | 9 +++
.../gson/functional/InterceptorTest.java | 64 +++++++++++++++++++
5 files changed, 192 insertions(+), 2 deletions(-)
create mode 100644 gson/src/main/java/com/google/gson/internal/alpha/Intercept.java
create mode 100644 gson/src/main/java/com/google/gson/internal/alpha/JsonPostDeserializer.java
create mode 100644 gson/src/main/java/com/google/gson/internal/alpha/package-info.java
create mode 100644 gson/src/test/java/com/google/gson/functional/InterceptorTest.java
diff --git a/gson/src/main/java/com/google/gson/Gson.java b/gson/src/main/java/com/google/gson/Gson.java
index 3c2cd3e2..dfe1d158 100644
--- a/gson/src/main/java/com/google/gson/Gson.java
+++ b/gson/src/main/java/com/google/gson/Gson.java
@@ -33,8 +33,11 @@ import java.util.Map;
import com.google.gson.internal.ConstructorConstructor;
import com.google.gson.internal.Excluder;
+import com.google.gson.internal.ObjectConstructor;
import com.google.gson.internal.Primitives;
import com.google.gson.internal.Streams;
+import com.google.gson.internal.alpha.Intercept;
+import com.google.gson.internal.alpha.JsonPostDeserializer;
import com.google.gson.internal.bind.ArrayTypeAdapter;
import com.google.gson.internal.bind.CollectionTypeAdapterFactory;
import com.google.gson.internal.bind.DateTypeAdapter;
@@ -791,8 +794,11 @@ public final class Gson {
try {
reader.peek();
isEmpty = false;
- TypeAdapter typeAdapter = (TypeAdapter) getAdapter(TypeToken.get(typeOfT));
- return typeAdapter.read(reader);
+ TypeToken typeToken = (TypeToken) TypeToken.get(typeOfT);
+ TypeAdapter typeAdapter = (TypeAdapter) getAdapter(typeToken);
+ T object = typeAdapter.read(reader);
+ invokeInterceptorIfNeeded(object, typeToken);
+ return object;
} catch (EOFException e) {
/*
* For compatibility with JSON 1.5 and earlier, we return null for empty
@@ -884,6 +890,20 @@ public final class Gson {
}
}
+ @SuppressWarnings({ "unchecked", "rawtypes" })
+ private void invokeInterceptorIfNeeded(T object, TypeToken type) {
+ Class super T> clazz = type.getRawType();
+ Intercept interceptor = clazz.getAnnotation(Intercept.class);
+ if (interceptor == null) return;
+ // TODO: We don't need to construct an instance of postDeserializer every time. we can
+ // create it once and cache it.
+ Class extends JsonPostDeserializer> postDeserializerClass = interceptor.postDeserialize();
+ ObjectConstructor extends JsonPostDeserializer> objectConstructor =
+ constructorConstructor.get(TypeToken.get(postDeserializerClass));
+ JsonPostDeserializer postDeserializer = objectConstructor.construct();
+ postDeserializer.postDeserialize(object);
+ }
+
@Override
public String toString() {
StringBuilder sb = new StringBuilder("{")
diff --git a/gson/src/main/java/com/google/gson/internal/alpha/Intercept.java b/gson/src/main/java/com/google/gson/internal/alpha/Intercept.java
new file mode 100644
index 00000000..bd00b983
--- /dev/null
+++ b/gson/src/main/java/com/google/gson/internal/alpha/Intercept.java
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2012 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.gson.internal.alpha;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+
+/**
+ * Use this annotation to indicate various interceptors for class instances after
+ * they have been processed by Gson. For example, you can use it to validate an instance
+ * after it has been deserialized from Json.
+ * Here is an example of how this annotation is used:
+ * Here is an example of how this annotation is used:
+ *
+ * @Intercept(postDeserialize=UserValidator.class)
+ * public class User {
+ * String name;
+ * String password;
+ * String emailAddress;
+ * }
+ *
+ * public class UserValidator implements JsonPostDeserializer<User> {
+ * public void postDeserialize(User user) {
+ * // Do some checks on user
+ * if (user.name == null || user.password == null) {
+ * throw new JsonParseException("name and password are required fields.");
+ * }
+ * if (user.emailAddress == null) {
+ * emailAddress = "unknown"; // assign a default value.
+ * }
+ * }
+ * }
+ *
+ *
+ * @author Inderjeet Singh
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+public @interface Intercept {
+
+ /**
+ * Specify the class that provides the methods that should be invoked after an instance
+ * has been deserialized.
+ */
+ @SuppressWarnings("rawtypes")
+ public Class extends JsonPostDeserializer> postDeserialize();
+}
diff --git a/gson/src/main/java/com/google/gson/internal/alpha/JsonPostDeserializer.java b/gson/src/main/java/com/google/gson/internal/alpha/JsonPostDeserializer.java
new file mode 100644
index 00000000..7a249912
--- /dev/null
+++ b/gson/src/main/java/com/google/gson/internal/alpha/JsonPostDeserializer.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2012 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.gson.internal.alpha;
+
+import com.google.gson.InstanceCreator;
+
+/**
+ * This interface is implemented by a class that wishes to inspect or modify an object
+ * after it has been deserialized. You must define a no-args constructor or register an
+ * {@link InstanceCreator} for such a class.
+ *
+ * @author Inderjeet Singh
+ */
+public interface JsonPostDeserializer {
+
+ /**
+ * This method is called by Gson after the object has been deserialized from Json.
+ */
+ public void postDeserialize(T object);
+}
diff --git a/gson/src/main/java/com/google/gson/internal/alpha/package-info.java b/gson/src/main/java/com/google/gson/internal/alpha/package-info.java
new file mode 100644
index 00000000..919f347f
--- /dev/null
+++ b/gson/src/main/java/com/google/gson/internal/alpha/package-info.java
@@ -0,0 +1,9 @@
+/**
+ * This package provides experimental Gson features that are very likely to change from
+ * release to release. Backwards compatibility will almost certainly be broken in a future
+ * release by either changing the package name (when the feature moves to main Gson) or when
+ * we decide that the feature isn't worth adding.
+ *
+ * @author Inderjeet Singh, Joel Leitch, Jesse Wilson
+ */
+package com.google.gson.internal.alpha;
diff --git a/gson/src/test/java/com/google/gson/functional/InterceptorTest.java b/gson/src/test/java/com/google/gson/functional/InterceptorTest.java
new file mode 100644
index 00000000..eb37da1f
--- /dev/null
+++ b/gson/src/test/java/com/google/gson/functional/InterceptorTest.java
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2012 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.gson.functional;
+
+import junit.framework.TestCase;
+
+import com.google.gson.Gson;
+import com.google.gson.internal.alpha.Intercept;
+import com.google.gson.internal.alpha.JsonPostDeserializer;
+
+/**
+ * Unit tests for {@link Intercept} and {@link JsonPostDeserializer}.
+ *
+ * @author Inderjeet Singh
+ */
+public final class InterceptorTest extends TestCase {
+
+ private Gson gson;
+
+ @Override
+ public void setUp() throws Exception {
+ super.setUp();
+ this.gson = new Gson();
+ }
+
+ public void testPostDeserialize() {
+ MyObject target = gson.fromJson("{}", MyObject.class);
+ assertEquals(MyObject.DEFAULT_VALUE, target.value);
+ assertEquals(MyObject.DEFAULT_MESSAGE, target.message);
+ }
+
+ @Intercept(postDeserialize = MyObjectInterceptor.class)
+ private static final class MyObject {
+ static final int DEFAULT_VALUE = 10;
+ static final String DEFAULT_MESSAGE = "hello";
+
+ int value = 0;
+ String message = null;
+ }
+
+ private static final class MyObjectInterceptor implements JsonPostDeserializer {
+ public void postDeserialize(MyObject o) {
+ if (o.value == 0) {
+ o.value = MyObject.DEFAULT_VALUE;
+ }
+ if (o.message == null) {
+ o.message = MyObject.DEFAULT_MESSAGE;
+ }
+ }
+ }
+}
\ No newline at end of file