Line data    Source code

       1             : // Copyright (C) 2019 The Android Open Source Project
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.json;
      16             : 
      17             : import com.google.gerrit.common.Nullable;
      18             : import com.google.gson.Gson;
      19             : import com.google.gson.JsonSyntaxException;
      20             : import com.google.gson.TypeAdapter;
      21             : import com.google.gson.TypeAdapterFactory;
      22             : import com.google.gson.internal.bind.TypeAdapters;
      23             : import com.google.gson.reflect.TypeToken;
      24             : import com.google.gson.stream.JsonReader;
      25             : import com.google.gson.stream.JsonToken;
      26             : import com.google.gson.stream.JsonWriter;
      27             : import java.io.IOException;
      28             : 
      29             : /**
      30             :  * A {@code TypeAdapterFactory} for enums.
      31             :  *
      32             :  * <p>This factory introduces a wrapper around Gson's own default enum handler to add the following
      33             :  * special behavior: log when input which doesn't match any existing enum value is encountered.
      34             :  */
      35         158 : public class EnumTypeAdapterFactory implements TypeAdapterFactory {
      36             : 
      37             :   @SuppressWarnings({"rawtypes", "unchecked"})
      38             :   @Nullable
      39             :   @Override
      40             :   public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
      41         112 :     TypeAdapter<T> defaultEnumAdapter = TypeAdapters.ENUM_FACTORY.create(gson, typeToken);
      42         112 :     if (defaultEnumAdapter == null) {
      43             :       // Not an enum. -> Enum type adapter doesn't apply.
      44         112 :       return null;
      45             :     }
      46             : 
      47         108 :     return new EnumTypeAdapter(defaultEnumAdapter, typeToken);
      48             :   }
      49             : 
      50             :   private static class EnumTypeAdapter<T extends Enum<T>> extends TypeAdapter<T> {
      51             : 
      52             :     private final TypeAdapter<T> defaultEnumAdapter;
      53             :     private final TypeToken<T> typeToken;
      54             : 
      55         108 :     public EnumTypeAdapter(TypeAdapter<T> defaultEnumAdapter, TypeToken<T> typeToken) {
      56         108 :       this.defaultEnumAdapter = defaultEnumAdapter;
      57         108 :       this.typeToken = typeToken;
      58         108 :     }
      59             : 
      60             :     @Override
      61             :     public T read(JsonReader in) throws IOException {
      62             :       // Still handle null values. -> Check them first.
      63         106 :       if (in.peek() == JsonToken.NULL) {
      64           1 :         in.nextNull();
      65           1 :         return null;
      66             :       }
      67         106 :       T enumValue = defaultEnumAdapter.read(in);
      68         106 :       if (enumValue == null) {
      69           1 :         throw new JsonSyntaxException(
      70           1 :             String.format("Expected an existing value for enum %s.", typeToken));
      71             :       }
      72         106 :       return enumValue;
      73             :     }
      74             : 
      75             :     @Override
      76             :     public void write(JsonWriter out, T value) throws IOException {
      77         107 :       defaultEnumAdapter.write(out, value);
      78         107 :     }
      79             :   }
      80             : }