GsonValue

General

Category
Free
Tag
APT
License
Apache License, Version 2.0
Registered
Mar 22, 2016
Favorites
0
Link
https://github.com/evant/gsonvalue
See also
Registry
PrefData
AIDL2
Green Annotations
auto-droid

Additional

Language
Java
Version
N/A
Created
Feb 21, 2016
Updated
Jun 15, 2020
Owner
Evan Tatarka (evant)
Contributors
Evan Tatarka (evant)
naixx
Toby Hsieh (tobyhs)
3
Activity
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Source code

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GsonValue

Compile-time generation of gson TypeAdapters to preserve class encapsulation.

By default, gson uses reflection to read and write fields of you class from json. The problem with this is that it breaks encapsulation. This prevents you from enforcing invariants when you class is constructed and properly hide implementation details from serialization. This library will generate TypeAdapters the call your constructor, factory method, or builder to construct you an instance of your class and will only use accessible fields and methods to write it out.

This library is a nice companion with google's AutoValue, but you may use it with any class you choose. It's nice with kotlin's data classes too!

Download

Gradle

Java

You may want to use a gradle plugin for easier management of apt dependencies. For example, gradle-apt-plugin.

apt 'me.tatarka.gsonvalue:gsonvalue-processor:0.9'
compile 'me.tatarka.gsonvalue:gsonvalue:0.9'

Android

annotationProcessor 'me.tatarka.gsonvalue:gsonvalue-processor:0.9'
compile 'me.tatarka.gsonvalue:gsonvalue:0.9'

Maven

<dependency>
  <groupId>me.tatarka.gsonvalue</groupId>
  <artifactId>gsonvalue</artifactId>
  <version>0.9</version>
</dependency>
<dependency>
  <groupId>me.tatarka.gsonvalue</groupId>
  <artifactId>gsonvalue-processor</artifactId>
  <version>0.9</version>
  <scope>provided</scope>
</dependency>

Usage

Annotate your constructor or factory method with @GsonConstructor. Json will be deserialized using the parameter names and serialized using public fields or getters. The following classes will map to the json

{"arg":1}

POJO

import me.tatarka.gsonvalue.annotations.GsonConstructor;

public class Foo {
    @GsonConstructor
    public Foo(int arg) {
        ...
    }
    
    public int arg() {
        ...
    }
}

public class Bar {
    @GsonConstructor
    public static Bar newInstance(int arg) {
        ...
    }
    
    public int getArg() {
        ...
    }
}

AutoValue

@AutoValue
public abstract class Foo {
    @GsonConstructor
    public static Foo newInstance(int arg) {
        return new AutoValue_Foo(arg);
    }
    
    public abstract int arg();
}

Kotlin Data Class

@GsonConstructor data class Foo(val arg: Int)

Note that both bare getters and bean-style prefixes are supported. Like AutoValue, prefixes only apply if all getters follow that style.

Builders

Alternatively, you can create a builder class. Annotate either the builder's constructor or the factory method that returns the builder with @GsonBuilder.

POJO

import me.tatarka.gsonvalue.annotations.GsonConstructor;

public class Foo {
    public static class Builder {
        @GsonBuilder
        public Builder(int arg1) {
            ...
        }
        
        public Builder arg2(String arg2) {
            ...
        }
        
        public Foo build() {
            ...
        }
    }
}

public class Bar {
    @GsonBuilder
    public static Builder builder() {
        ...
    }
    
    public static class Builder {
        ...
    }
}

AutoValue

@AutoValue
public abstract class Foo {

    @GsonBuilder
    public static Builder builder() {
        return new AutoValue_Foo.Builder();
    }

    @AutoValue.Builder
    public interface Builder {        
        Builder arg(int arg);
        
        Foo build();
    }
}

Gson

Create an abstract TypeAdapterFactory class an annotate it.

import com.google.gson.TypeAdapterFactory;
import me.tatarka.gsonvalue.annotations.GsonValueTypeAdapterFactory;

@GsonValueTypeAdapterFactory
public abstract class MyTypeAdapterFactory implements TypeAdapterFactory {
    public static MyTypeAdapterFactory create() {
        return new GsonValue_MyTypeAdapterFactory();
    }
}

Then register it to your gson builder.

gson = new GsonBuilder()
        .registerTypeAdapterFactory(MyTypeAdapterFactory.create())
        .create();

Supported Gson features.

  • @SerializeName is supported on fields or getters. It will map to both the constructor parameter on deserialization and the field or getter on serialization.
  • Transient fields are ignored.
  • @JsonAdapter is supported with either a TypeAdapter or TypeAdapterFactory as long as it has a public no-args constructor. Since gson's version cannot be placed on a getter method, you may use @me.tatarka.gsonvalue.annotations.JsonAdapter instead if necessary.

Unsupported features.

The following features are not supported. They may be added if there is enough demand.

  • @Since and @Until versioning support.
  • @Expose and exclusion strategies.
  • Field naming policies.

License

Copyright 2016 Evan Tatarka

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.