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Add JsonUtils in particular @JsonIo annotation
Typed<T> instances of any T with a @JsonIo-annotated adapter are serialized as json objects with a "type" attribute with the value of the JsonIo.type() annotation, and an "obj" attribute, which is serialized using the annotated adapter. For deserialization, the correct adapter is looked up via the "type" attribute.
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‎src/main/java/bdv/img/remote/AffineTransform3DJsonSerializer.java‎

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import java.lang.reflect.Type;
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import bdv.tools.JsonUtils;
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import net.imglib2.realtransform.AffineTransform3D;
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import com.google.gson.JsonDeserializationContext;
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import com.google.gson.JsonSerializationContext;
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import com.google.gson.JsonSerializer;
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@JsonUtils.JsonIo( jsonType = "AffineTransform3D.Anchor", type = AffineTransform3D.class )
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public class AffineTransform3DJsonSerializer implements JsonDeserializer< AffineTransform3D >, JsonSerializer< AffineTransform3D >
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{
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@Override

‎src/main/java/bdv/tools/JsonUtils.java‎

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package bdv.tools;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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import java.lang.reflect.Type;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Map;
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import java.util.Objects;
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import java.util.concurrent.ConcurrentHashMap;
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import org.scijava.Priority;
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import org.scijava.annotations.Index;
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import org.scijava.annotations.IndexItem;
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import org.scijava.annotations.Indexable;
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import com.google.gson.Gson;
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import com.google.gson.GsonBuilder;
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import com.google.gson.JsonArray;
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import com.google.gson.JsonDeserializationContext;
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import com.google.gson.JsonDeserializer;
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import com.google.gson.JsonElement;
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import com.google.gson.JsonObject;
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import com.google.gson.JsonSerializationContext;
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import com.google.gson.JsonSerializer;
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public class JsonUtils
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{
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public static Gson gson()
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{
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GsonBuilder gsonBuilder = new GsonBuilder();
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JsonIos.registerTypeAdapters( gsonBuilder );
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return gsonBuilder.create();
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}
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/**
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* Annotation for classes that de/serialize instances of {@code T} from/to JSON.
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*/
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@Retention( RetentionPolicy.RUNTIME )
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@Target( ElementType.TYPE )
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@Indexable
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public @interface JsonIo
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{
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/**
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* The value of the "type" attribute in serialized instances.
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* <p>
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* This should be unique, because it is used to pick the correct {@code
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* JsonIo} for deserialization of polymorphic {@link Typed} attributes.
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*/
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String jsonType();
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/**
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* The class of un-serialized instances.
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*/
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Class< ? > type();
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double priority() default Priority.NORMAL;
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}
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/**
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* {@code Typed<T>} instances of any {@code T} with a {@code @JsonIo}-
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* annotated adapter are serialized as json objects with a "type" attribute
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* with the value of the {@link JsonIo#type()} annotation, and an "obj"
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* attribute, which is serialized using the annotated adapter. For
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* deserialization, the correct adapter is looked up via the "type"
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* attribute.
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*/
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public static class Typed< T >
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{
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private final T obj;
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Typed( T obj )
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{
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Objects.requireNonNull( obj );
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this.obj = obj;
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}
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public T get()
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{
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return obj;
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}
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@Override
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public String toString()
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{
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return "Typed{" +
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"obj=" + obj +
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'}';
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}
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@JsonIo( jsonType = "JsonUtils.Typed", type = Typed.class )
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static class JsonAdapter implements JsonSerializer< Typed< ? > >, JsonDeserializer< Typed< ? > >
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{
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@Override
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public Typed< ? > deserialize(
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final JsonElement json,
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final Type typeOfT,
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final JsonDeserializationContext context )
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{
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final JsonObject obj = json.getAsJsonObject();
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final String jsonType = obj.get( "type" ).getAsString();
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final Type type = JsonIos.typeFor( jsonType );
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return typed( context.deserialize( obj.get( "data" ), type ) );
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}
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@Override
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public JsonElement serialize(
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final Typed< ? > src,
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final Type typeOfSrc,
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final JsonSerializationContext context )
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{
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final JsonObject obj = new JsonObject();
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final String jsonType = JsonIos.jsonTypeFor( src.get().getClass() );
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obj.addProperty( "type", jsonType );
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obj.add( "data", context.serialize( src.get() ) );
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return obj;
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}
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}
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}
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public static class TypedList< T >
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{
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private final List< T > list;
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public TypedList()
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{
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list = new ArrayList<>();
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}
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public TypedList( final List< T > list )
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{
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this.list = list;
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}
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public List< T > list()
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{
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return list;
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}
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@Override
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public String toString()
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{
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return "TypedList{" + list + '}';
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}
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@JsonUtils.JsonIo( jsonType = "TypedList", type = TypedList.class )
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static class JsonAdapter implements JsonDeserializer< TypedList< ? > >, JsonSerializer< TypedList< ? > >
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{
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@Override
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public TypedList< ? > deserialize(
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final JsonElement json,
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final Type typeOfT,
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final JsonDeserializationContext context )
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{
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return deserializeT( json, typeOfT, context );
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}
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private < T > TypedList< T > deserializeT(
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final JsonElement json,
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final Type typeOfT,
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final JsonDeserializationContext context )
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{
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final List< T > list = new ArrayList<>();
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for ( JsonElement element : json.getAsJsonArray() )
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{
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final Typed< T > typed = context.deserialize( element, Typed.class );
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list.add( typed.get() );
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}
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return new TypedList<>( list );
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}
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@Override
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public JsonElement serialize(
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final TypedList< ? > src,
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final Type typeOfSrc,
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final JsonSerializationContext context )
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{
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final JsonArray array = new JsonArray();
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for ( final Object spec : src.list() ) {
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array.add( context.serialize( typed( spec ) ) );
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}
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return array;
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}
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}
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}
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/**
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* Wrap {@code obj} into a {@code Typed<T>} for serialization of polymorphic objects.
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*/
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public static < T > Typed< T > typed( T obj )
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{
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return new Typed<>( obj );
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}
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static class JsonIos
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{
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static void registerTypeAdapters( final GsonBuilder gsonBuilder )
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{
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build();
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type_to_JsonAdapterClassName.forEach( ( type, adapterClassName ) -> {
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if ( adapterClassName == null )
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{
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throw new RuntimeException( "could not find JsonAdapter for " + type );
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}
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final Object adapter;
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try
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{
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adapter = Class.forName( adapterClassName ).newInstance();
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}
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catch ( final Exception e )
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{
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throw new RuntimeException( "could not create \"" + adapterClassName + "\" instance", e );
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}
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gsonBuilder.registerTypeAdapter( type, adapter );
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} );
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}
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private static String jsonTypeFor( final Type type )
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{
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build();
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final String jsonType = type_to_JsonType.get( type );
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if ( jsonType == null )
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throw new RuntimeException( "could not find JsonIo implementation for " + type );
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return jsonType;
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}
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private static Type typeFor( final String jsonType )
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{
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build();
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final Type type = jsonType_to_Type.get( jsonType );
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if ( type == null )
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throw new RuntimeException( "could not find JsonIo implementation for " + jsonType );
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return type;
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}
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private static final Map< Type, String > type_to_JsonType = new ConcurrentHashMap<>();
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private static final Map< String, Type > jsonType_to_Type = new ConcurrentHashMap<>();
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private static final Map< Type, String > type_to_JsonAdapterClassName = new ConcurrentHashMap<>();
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private static volatile boolean buildWasCalled = false;
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private static void build()
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{
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if ( !buildWasCalled )
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{
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synchronized ( JsonUtils.class )
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{
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if ( !buildWasCalled )
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{
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try
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{
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final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
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final Index< JsonIo > annotationIndex = Index.load( JsonUtils.JsonIo.class, classLoader );
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for ( final IndexItem< JsonIo > item : annotationIndex )
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{
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final JsonUtils.JsonIo io = item.annotation();
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type_to_JsonType.put( io.type(), io.jsonType() );
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jsonType_to_Type.put( io.jsonType(), io.type() );
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type_to_JsonAdapterClassName.put( io.type(), item.className() );
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}
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}
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catch ( final Exception e )
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{
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throw new RuntimeException( "problem accessing annotation index", e );
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}
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buildWasCalled = true;
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}
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}
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}
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}
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}
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public static String prettyPrint( final JsonElement jsonElement )
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{
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Gson gson = new GsonBuilder().setPrettyPrinting().create();
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return gson.toJson( jsonElement );
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}
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}

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