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:0.7' compile 'me.tatarka.gsonvalue:gsonvalue:0.7'Android
annotationProcessor 'me.tatarka.gsonvalue:gsonvalue-processor:0.7' compile 'me.tatarka.gsonvalue:gsonvalue:0.7'Maven
<dependency>
<groupId>me.tatarka.gsonvalue</groupId>
<artifactId>gsonvalue</artifactId>
<version>0.7</version> </dependency> <dependency>
<groupId>me.tatarka.gsonvalue</groupId>
<artifactId>gsonvalue-processor</artifactId>
<version>0.7</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();
}
}
In most cases the class being built will be discovered from the builder. However, it's possible that it is ambiguous. In that case, you can provide the built class in the annotation @GsonBuilder(Foo.class).
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();
Alternatively, you can use the old reflection-based ValueTypeAdapterFactory.
gson = new GsonBuilder()
.registerTypeAdapterFactory(new ValueTypeAdapterFactory())
.create();
Supported Gson features.
@SerializeNameis 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.
@JsonAdapteris supported with either aTypeAdapterorTypeAdapterFactoryas 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.JsonAdapterinstead if necessary.
Unsupported features.
The following features are not supported. They may be added if there is enough demand.
@Sinceand@Untilversioning support.@Exposeand 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.