com.squareup.moshi.adapters.EnumJsonAdapter Maven / Gradle / Ivy
/*
* Copyright (C) 2018 Square, Inc.
*
* 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.
*/
package com.squareup.moshi.adapters;
import com.jn.langx.annotation.Nullable;
import com.squareup.moshi.*;
import java.io.IOException;
import java.util.Arrays;
/**
* A JsonAdapter for enums that allows having a fallback enum value when a deserialized string does
* not match any enum value. To use, add this as an adapter for your enum type on your {@link
* com.squareup.moshi.Moshi.Builder Moshi.Builder}:
*
*
{@code
*
* Moshi moshi = new Moshi.Builder()
* .add(CurrencyCode.class, EnumJsonAdapter.create(CurrencyCode.class)
* .withUnknownFallback(CurrencyCode.USD))
* .build();
* }
*/
public final class EnumJsonAdapter> extends JsonAdapter {
final Class enumType;
final String[] nameStrings;
final T[] constants;
final JsonReader.Options options;
final boolean useFallbackValue;
final @Nullable
T fallbackValue;
public static > EnumJsonAdapter create(Class enumType) {
return new EnumJsonAdapter(enumType, null, false);
}
/**
* Create a new adapter for this enum with a fallback value to use when the JSON string does not
* match any of the enum's constants. Note that this value will not be used when the JSON value is
* null, absent, or not a string. Also, the string values are case-sensitive, and this fallback
* value will be used even on case mismatches.
*/
public EnumJsonAdapter withUnknownFallback(@Nullable T fallbackValue) {
return new EnumJsonAdapter(enumType, fallbackValue, true);
}
EnumJsonAdapter(Class enumType, @Nullable T fallbackValue, boolean useFallbackValue) {
this.enumType = enumType;
this.fallbackValue = fallbackValue;
this.useFallbackValue = useFallbackValue;
try {
constants = enumType.getEnumConstants();
nameStrings = new String[constants.length];
for (int i = 0; i < constants.length; i++) {
String constantName = constants[i].name();
Json annotation = enumType.getField(constantName).getAnnotation(Json.class);
String name = annotation != null ? annotation.name() : constantName;
nameStrings[i] = name;
}
options = JsonReader.Options.of(nameStrings);
} catch (NoSuchFieldException e) {
throw new RuntimeException("Missing field in " + enumType.getName(), e);
}
}
@Override
public @Nullable
T fromJson(JsonReader reader) throws IOException {
int index = reader.selectString(options);
if (index != -1) {
return constants[index];
}
String path = reader.getPath();
if (!useFallbackValue) {
String name = reader.nextString();
throw new JsonDataException("Expected one of "
+ Arrays.asList(nameStrings) + " but was " + name + " at path " + path);
}
if (reader.peek() != JsonReader.Token.STRING) {
throw new JsonDataException(
"Expected a string but was " + reader.peek() + " at path " + path);
}
reader.skipValue();
return fallbackValue;
}
@Override
public void toJson(JsonWriter writer, T value) throws IOException {
if (value == null) {
throw new NullPointerException(
"value was null! Wrap in .nullSafe() to write nullable values.");
}
writer.value(nameStrings[value.ordinal()]);
}
@Override
public String toString() {
return "EnumJsonAdapter(" + enumType.getName() + ")";
}
}