org.eclipse.scada.base.json.VariantJsonDeserializer.java Source code

Introduction

Here is the source code for org.eclipse.scada.base.json.VariantJsonDeserializer.java

Source

/*******************************************************************************
 * Copyright (c) 2013 IBH SYSTEMS GmbH and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBH SYSTEMS GmbH - initial API and implementation
 *******************************************************************************/
package org.eclipse.scada.base.json;

import java.lang.reflect.Type;

import org.eclipse.scada.core.Variant;
import org.eclipse.scada.core.VariantEditor;
import org.eclipse.scada.core.VariantType;
import org.eclipse.scada.utils.str.StringHelper;

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;

public class VariantJsonDeserializer implements JsonDeserializer<Variant> {

    @Override
    public Variant deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context)
            throws JsonParseException {
        if (json.isJsonNull()) {
            return null;
        }

        if (json instanceof JsonPrimitive) {
            return decodeFromPrimitive(json);
        }

        if (json instanceof JsonObject) {
            final JsonObject jsonObj = (JsonObject) json;
            final JsonElement type = jsonObj.get(VariantJson.FIELD_TYPE);
            final JsonElement value = jsonObj.get(VariantJson.FIELD_VALUE);

            if (type == null || type.isJsonNull()) {
                if (value == null) {
                    throw new JsonParseException(String.format("Variant encoded as object must have a field '%s'",
                            VariantJson.FIELD_VALUE));
                }
                return Variant.valueOf(value.getAsString());
            }

            if (!type.isJsonPrimitive()) {
                throw new JsonParseException(
                        String.format("Variant field '%s' must be a string containing the variant type (%s)",
                                VariantJson.FIELD_TYPE, StringHelper.join(VariantType.values(), ", ")));
            }

            final String typeStr = type.getAsString();

            if (typeStr.equals("NULL")) {
                return Variant.NULL;
            }

            if (value == null || value.isJsonNull()) {
                throw new JsonParseException(String.format(
                        "The type '%s' does not support a null value. Use variant type NULL instead.", typeStr));
            }

            if (value.isJsonObject() || value.isJsonArray()) {
                throw new JsonParseException(
                        "The variant value must be a JSON primitive matching the type. Arrays and objects are not supported");
            }

            switch (type.getAsString()) {
            case "BOOLEAN":
                return Variant.valueOf(value.getAsBoolean());
            case "STRING":
                return Variant.valueOf(value.getAsString());
            case "DOUBLE":
                return Variant.valueOf(value.getAsDouble());
            case "INT32":
                return Variant.valueOf(value.getAsInt());
            case "INT64":
                return Variant.valueOf(value.getAsLong());
            default:
                throw new JsonParseException(String.format("Type '%s' is unknown (known types: %s)",
                        StringHelper.join(VariantType.values(), ", ")));
            }
        }

        throw new JsonParseException("Unknown serialization of Variant type");
    }

    private Variant decodeFromPrimitive(final JsonElement json) {
        final JsonPrimitive jsonPrim = (JsonPrimitive) json;
        if (jsonPrim.isBoolean()) {
            return Variant.valueOf(jsonPrim.getAsBoolean());
        } else if (jsonPrim.isNumber()) {
            return Variant.valueOf(jsonPrim.getAsNumber());
        } else {
            return VariantEditor.toVariant(jsonPrim.getAsString());
        }
    }
}