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   1 /**
   2  * Copyright (c) 2010-2023 Contributors to the openHAB project
   3  *
   4  * See the NOTICE file(s) distributed with this work for additional
   5  * information.
   6  *
   7  * This program and the accompanying materials are made available under the
   8  * terms of the Eclipse Public License 2.0 which is available at
   9  * http://www.eclipse.org/legal/epl-2.0
  10  *
  11  * SPDX-License-Identifier: EPL-2.0
  12  */
  13 package org.openhab.binding.surepetcare.internal.utils;
  14
  15 import java.io.IOException;
  16 import java.util.List;
  17
  18 import org.eclipse.jdt.annotation.NonNullByDefault;
  19 import org.eclipse.jdt.annotation.Nullable;
  20 import org.openhab.binding.surepetcare.internal.dto.SurePetcareDeviceCurfew;
  21 import org.openhab.binding.surepetcare.internal.dto.SurePetcareDeviceCurfewList;
  22
  23 import com.google.gson.Gson;
  24 import com.google.gson.TypeAdapter;
  25 import com.google.gson.TypeAdapterFactory;
  26 import com.google.gson.reflect.TypeToken;
  27 import com.google.gson.stream.JsonReader;
  28 import com.google.gson.stream.JsonToken;
  29 import com.google.gson.stream.JsonWriter;
  30 import com.google.gson.stream.MalformedJsonException;
  31
  32 /**
  33  * The {@link SurePetcareDeviceCurfewListTypeAdapterFactory} class is a custom TypeAdapter factory to ensure
  34  * deserialization always returns a list even if the Json document contains only a single curfew object and
  35  * not an array.
  36  *
  37  * See https://stackoverflow.com/questions/43412261/make-gson-accept-single-objects-where-it-expects-arrays
  38  *
  39  * @author Rene Scherer - Initial contribution
  40  */
  41 @NonNullByDefault
  42 public final class SurePetcareDeviceCurfewListTypeAdapterFactory<E> implements TypeAdapterFactory {
  43
  44     // Gson can instantiate it itself
  45     private SurePetcareDeviceCurfewListTypeAdapterFactory() {
  46     }
  47
  48     @Override
  49     public @Nullable <T> TypeAdapter<T> create(final @Nullable Gson gson, final @Nullable TypeToken<T> typeToken) {
  50         if (gson == null || typeToken == null) {
  51             return null;
  52         }
  53         final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter = gson
  54                 .getAdapter(TypeToken.get(SurePetcareDeviceCurfew.class));
  55         @SuppressWarnings("unchecked")
  56         final TypeAdapter<T> alwaysListTypeAdapter = (TypeAdapter<T>) new SurePetcareDeviceCurfewListTypeAdapter(
  57                 elementTypeAdapter).nullSafe();
  58         return alwaysListTypeAdapter;
  59     }
  60
  61     private static final class SurePetcareDeviceCurfewListTypeAdapter
  62             extends TypeAdapter<List<SurePetcareDeviceCurfew>> {
  63
  64         private final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter;
  65
  66         private SurePetcareDeviceCurfewListTypeAdapter(final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter) {
  67             this.elementTypeAdapter = elementTypeAdapter;
  68         }
  69
  70         @Override
  71         public void write(final @Nullable JsonWriter out, @Nullable final List<SurePetcareDeviceCurfew> list)
  72                 throws IOException {
  73             if (out != null && list != null) {
  74                 out.beginArray();
  75                 for (SurePetcareDeviceCurfew curfew : list) {
  76                     elementTypeAdapter.write(out, curfew);
  77                 }
  78                 out.endArray();
  79             }
  80         }
  81
  82         @Override
  83         public @Nullable List<SurePetcareDeviceCurfew> read(final @Nullable JsonReader in) throws IOException {
  84             // This is where we detect the list "type"
  85             final SurePetcareDeviceCurfewList list = new SurePetcareDeviceCurfewList();
  86             if (in != null) {
  87                 final JsonToken token = in.peek();
  88                 switch (token) {
  89                     case BEGIN_ARRAY:
  90                         // If it's a regular list, just consume [, <all elements>, and ]
  91                         in.beginArray();
  92                         while (in.hasNext()) {
  93                             SurePetcareDeviceCurfew cf = elementTypeAdapter.read(in);
  94                             if (cf != null) {
  95                                 list.add(cf);
  96                             }
  97                         }
  98                         in.endArray();
  99                         break;
 100                     case BEGIN_OBJECT:
 101                         SurePetcareDeviceCurfew cf = elementTypeAdapter.read(in);
 102                         if (cf != null) {
 103                             list.add(cf);
 104                         }
 105                         break;
 106                     case NULL:
 107                         throw new AssertionError(
 108                                 "Must never happen: check if the type adapter configured with .nullSafe()");
 109                     case STRING:
 110                     case NUMBER:
 111                     case BOOLEAN:
 112                     case NAME:
 113                     case END_ARRAY:
 114                     case END_OBJECT:
 115                     case END_DOCUMENT:
 116                         throw new MalformedJsonException("Unexpected token: " + token);
 117                     default:
 118                         throw new AssertionError("Must never happen: " + token);
 119                 }
 120             }
 121             return list;
 122         }
 123     }
 124 }