Creating new annotation to exclude beans fields and classes from the GSON Serialization #763

renatorroliveira · 2014-08-27T06:55:21Z

This is a feature that is extremely desirable.
Creating an annotation (@GsonOmitField) that marks a field or a class to be skipped at the JSON serialization reduces a lot the duplication of exclude() calls in some cases.
Imagine a User model where are some private information like password and phone number stored.
Today you have to add a .exclude() call for those fields every time you want to serialize a user object.
With this feature, you just annotate those fields with @GsonOmitField and the job is done, you don't need to worry about those informations ending up at the client side.

It is a very simple implementation and adds a wonderful feature.

…GSON serialization.

Turini · 2014-08-27T10:32:18Z

vraptor-core/src/main/java/br/com/caelum/vraptor/serialization/gson/Exclusions.java

@@ -68,6 +73,7 @@ private boolean isCompatiblePath(Entry<String, Class<?>> path, Class<?> definedI

 	@Override
 	public boolean shouldSkipClass(Class<?> clazz) {
-		return false;
+		GsonOmitField annotation = clazz.getAnnotation(GsonOmitField.class);
+		return (annotation != null);


return clazz.isAnnotationPresent(GsonOmitField)?

Turini · 2014-08-27T10:36:09Z

this is a really nice PR, thanks doing it @renatorroliveira! Two points:

(1) Can you add a simple example of usage at VRaptor's site?
(2) And what about deserialisation? (it doesn't, but should affect both?)

garcia-jj · 2014-08-27T12:55:43Z

Where are the tests?

garcia-jj · 2014-08-27T13:00:57Z

vraptor-core/src/main/java/br/com/caelum/vraptor/serialization/gson/Exclusions.java

+		GsonOmitField annotation = f.getAnnotation(GsonOmitField.class);
+		if (annotation != null)
+			return true;
+


The same here for isAnnotationPresent.

GSON FieldAttributes don't have this method

Here it has, with GSON 2.2.4.
I even tested my app with this implementation and works fine.
The unit tests passed like a charm =)

I mean the isAnnotationPresent, this is not present on FieldAttributes. right?

Right, it isn't. The Class<?> type has it, but FieldAttributes hasn't.

garcia-jj · 2014-08-27T13:05:11Z

I like this feature, thank you for coding. After changing the code with suggestions, are ready to merge (by my mind).

renatorroliveira · 2014-08-27T15:15:27Z

Yes, it should be isAnnotationPresent, my mistake =)

@Turini I can add the example of usage. I should do this in this same PR?
@garcia-jj I will add the unit tests too.

garcia-jj · 2014-08-27T15:38:31Z

Same PR.

Turini · 2014-08-27T16:04:41Z

sorry my delay, please add docs at the same PR. thanks

renatorroliveira · 2014-08-27T17:26:30Z

I looking at the site.
I noticed that there isn't a page specific for serialization content.
Should i create a new page? If not, in which page you suggest to add this content?

lucascs · 2014-08-27T19:52:07Z

Cool PR. I just don't like the name @GsonOmitField.

You are tying the feature to the implementation. If we choose to replace GSon to another framework in the future, the annotation will be awkward.

Rename to something like @OmitField or @NotSerializable and move it to b.c.c.v.serialization package.

garcia-jj · 2014-08-27T20:00:58Z

Great Lucas. I like your suggestion.

renatorroliveira · 2014-08-27T20:01:03Z

You is right @lucascs i will modify these points.

lucascs · 2014-08-27T20:08:59Z

Have you tried this?
http://www.javacreed.com/gson-annotations-example/

renatorroliveira · 2014-08-27T23:26:16Z

Yes @lucascs, i've looked at the Expose annotation, but it has 2 problems:

To use the Expose annotation, you need to change the behavior of Gson object, calling GsonBuilder.excludeFieldsWithoutExposeAnnotation(). If you call this method it will serialize and deserialize only the fields annotated.
In most cases, fields to be ommited are fewer than the fields to be exposed. Another advantage is that the OmitField annotation doesn't require to change the default behavior of Gson, increasing the flexibility in some cases.

For me these 2 points are enough to justify the creation of a OmitField annotation =)

renatorroliveira · 2014-08-27T23:29:11Z

Another point that i forget, the capability to omit a class is something you don't acomplish with Expose, since all fields are ommited, except those that were annotated. I see the OmitField as a much more clear am easier approach.

lucascs · 2014-08-27T23:34:14Z

I'm not arguing against the OmitField... just to see if gson annotations are already supported by default.

renatorroliveira · 2014-08-27T23:39:50Z

Yes i udnerstood that, i just want to clarify my motivation to create the annotation =)

garcia-jj · 2014-08-28T00:20:08Z

I think that if GSON annotations are supported, may we can do this approaching, changing GSON components to always uses annotations. Why? Because if Google team create another annotations in the future will supported without any modifications in vraptor implementation.

Makes any sense?

renatorroliveira · 2014-08-28T01:03:07Z

Makes sense, but i see two concerns here.
To enable the native Expose annotation of GSON, it must be done by a configuration or something similar, because the side effect of enabling the Expose annotation is a breaking change for most projects.
The second concern is that with native annotations of GSON we can't achieve the "desirable" behavior that we are aiming with this new annotation. We just register a simple logic to the ExclusionStrategy. In theory this should be a very compatible implementation with newer versions of GSON.

Another point is that the version 2.2.4 was released in May of 2013, and next release was two weeks ago, the version 2.3, more than one year without updates. Maybe is not necessary to worry about GSON updates. =D

renatorroliveira · 2014-08-28T01:06:05Z

I believe that we should create a way to enable the Expose annotation without the need to overwrite the GsonBuilderWrapper.

garcia-jj · 2014-08-28T01:09:06Z

As I see with this option (enabling expose annotation), we need to annotate all fields with Expose to serialize/deserialize. So can break existent applications. And its to boring to annotate all fields :).

renatorroliveira · 2014-08-28T01:14:02Z

Yeah, very boring =)
If it is added, it should be an optional behavior

garcia-jj · 2014-08-30T02:16:57Z

@lucascs @Turini Can I merge? I think that the core are good to merge.

Turini · 2014-08-30T18:48:50Z

vraptor-site/content/en/docs/view-and-ajax.html

+public class UserPrivateInfo {
+	String document;
+	String phone;
+	String address;


can you add private on fields and a code comment
about omitted getters and setters? Same for the User.

Turini · 2014-08-30T18:51:10Z

vraptor-site/content/en/docs/view-and-ajax.html

+
+When serialiazing to JSON you can use the annotation 'SkipSerialization' to omit the serialization of a field or class.
+
+~~~ 


we can maybe add an text introducing the situation here, for example:
"The class below has all of your fields omitted for serialization."

renatorroliveira · 2014-09-01T20:23:58Z

I agree, and i will improve the docs.

Turini · 2014-09-04T19:00:43Z

thanks @renatorroliveira!

Creating new annotation to exclude beans fields and classes from the GSON Serialization

Creating new annotation to exclude beans fields and classes from the …

d848134

…GSON serialization.

Turini reviewed Aug 27, 2014
View reviewed changes

Turini added the documentation label Aug 27, 2014

garcia-jj reviewed Aug 27, 2014
View reviewed changes

Changing to isAnnotationPresent()

56c51ad

Unit tests for @GsonOmitField.

a4b6ddc

Renaming annotation to SkipSerialization

a02cb5a

Adding the documentation example of the new annotation.

16b8767

Turini reviewed Aug 30, 2014
View reviewed changes

Improving the SkipSerialization docs

55f10c5

Turini added a commit that referenced this pull request Sep 4, 2014

Merge pull request #763 from progolden/master

7d858fc

Creating new annotation to exclude beans fields and classes from the GSON Serialization

Turini merged commit 7d858fc into caelum:master Sep 4, 2014

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Creating new annotation to exclude beans fields and classes from the GSON Serialization #763

Creating new annotation to exclude beans fields and classes from the GSON Serialization #763

renatorroliveira commented Aug 27, 2014

Turini Aug 27, 2014

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garcia-jj commented Aug 27, 2014

garcia-jj Aug 27, 2014

Turini Aug 27, 2014

renatorroliveira Aug 27, 2014

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lucascs commented Aug 27, 2014

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renatorroliveira commented Aug 28, 2014

garcia-jj commented Aug 30, 2014

Turini Aug 30, 2014

Turini Aug 30, 2014

renatorroliveira commented Sep 1, 2014

Turini commented Sep 4, 2014


		When serialiazing to JSON you can use the annotation 'SkipSerialization' to omit the serialization of a field or class.

		~~~

Creating new annotation to exclude beans fields and classes from the GSON Serialization #763

Creating new annotation to exclude beans fields and classes from the GSON Serialization #763

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