# Abstract serialization services
-The serialization services are centered around the `serialize` annotation,
+The serialization services are based on the `serialize` and the `noserialize` annotations,
the `Serializable` interface and the implementations of `Serializer` and `Deserializer`.
## The `serialize` annotation
redef fun ==(o) do return o isa SELF and partner_a == o.partner_a and partner_b == o.partner_b
redef fun hash do return partner_a.hash + 1024*partner_b.hash
end
+class Person
+end
~~~
-The `serialize` applies only to the class definition,
-only attributes declared locally will be serialized.
-However, each definition of a class (a refinement or specialization)
-can declare `serialize`.
+### Scope of the `serialize` annotation
+
+`serialize` can annotate class definitions, modules and attributes:
+
+* The annotation on a class applies only to the class definition,
+ only attributes declared locally will be serialized.
+ However, each definition of a class (a refinement or specialization) can be annotated with `serialize`.
+
+* A module declaration annotated with `serialize` states that all its class definitions
+ and locally declared attributes are serializable.
+
+ ~~~nitish
+ module shared_between_clients is serialize
+ ~~~
+
+* Attribute annotated with `serialize` states that it is to be serialized, when the rest of the class does not.
+ The class will become subclass to `Serializable` but its attributes are not to be serialized by default.
+ Only the attributes with the `serialize` annotation will be serialized.
+
+ ~~~
+ # Only serialize the `name`
+ class UserCredentials
+ var name: String is serialize
+ var avatar_path: String = "/somepath/"+name is lazy
+ end
+ ~~~
+
+## The `noserialize` annotation
+
+The `noserialize` annotation mark an exception in a `serialize` module or class definition.
+
+* By default a module is `noserialize`. There is no need to declare it as such.
+
+* A class definition annotated with `noserialize` within a `serialize` module will not be made serializable.
+
+* A `noserialize` attribute within a class or module annotated with `serialize` will not serialize this attribute.
+ The class will still be made subclass of `Serializable` and it won't affect the other attributes.
+ The `noserialize` attribute will not be set at deserialization.
+ Usually, it will also be annotated with `lazy` to get its value by another mean after the object has been deserialized.
+
+ ~~~
+ # Once again, only serialize the `name`
+ class UserCredentials
+ serialize
+
+ var name: String
+ var avatar_path: String = "/somepath/"+name is noserialize, lazy
+ end
+ ~~~
+
+## The `serialize_as` annotation
+
+By default, an attribute is identified in the serialization format by its Nit name.
+The `serialize_as` attribute changes this behavior and sets the name of an attribute in the serialization format.
+
+This annotation can be useful to change the name of an attribute to what is expected by a remote service.
+Or to use identifiers in the serialization format that are reserved keywords in Nit (like `class` and `type`).
+
+~~~
+class UserCredentials
+ serialize
+
+ # Rename to "username" in JSON for compatibility with remote service
+ var name: String is serialize_as "username"
+
+ # Rename to a shorter "ap" for a smaller JSON file
+ var avatar_path: String = "/somepath/"+name is lazy, serialize_as "ap"
+end
+~~~
## Custom serializable classes
two serialization services: `User::core_serialize_to` and
`Deserializer::deserialize_class`.
-~~~
+~~~nitish
module user_credentials
# User credentials for a website
The main implementations of these services are `JsonSerializer` and `JsonDeserializer`,
from the `json_serialization` module.
-~~~
-import json_serialization
+~~~nitish
+import json
import user_credentials
# Data to be serialized and deserialized
The serialization has some limitations:
-* Not enough classes from the standard library are supported.
- This only requires someone to actually code the support.
- It should not be especially hard for most classes, some can
- simply declare the `serialize` annotation.
-
-* A limitation of the Json parser prevents deserializing from files
+* A limitation of the JSON parser prevents deserializing from files
with more than one object.
This could be improved in the future, but for now you should
- serialize a single object to each filesand use different instances of
+ serialize a single object to each files and use different instances of
serializer and deserializer each time.
-* The `serialize` annotation does not handle very well
- complex constructors. This could be improved in the compiler.
- For now, you may prefer to use `serialize` on simple classes,
- of by using custom `Serializable`.
-
* The serialization uses only the short name of a class, not its qualified name.
This will cause problem when different classes using the same name.
This could be solved partially in the compiler and the library.
the different programs sharing the serialized data.
* The serialization support in the compiler need some help to
- deal with generic types. The solution is to use `nitserial`,
+ deal with generic types. A solution is to use `nitserial`,
the next section explores this subject.
## Dealing with generic types
nitlanguage / nit.git / blobdiff