com.squareup.moshi.adapters.EnumJsonAdapter Maven / Gradle / Ivy

Go to download
/*
 * 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() + ")";
    }
}