com.getperka.flatpack.codexes.DynamicCodex.java Source code

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Here is the source code for com.getperka.flatpack.codexes.DynamicCodex.java

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/*
 * #%L
 * FlatPack serialization code
 * %%
 * Copyright (C) 2012 Perka 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.
 * #L%
 */
package com.getperka.flatpack.codexes;

import java.io.IOException;
import java.math.BigDecimal;
import java.util.UUID;
import java.util.regex.Pattern;

import javax.inject.Inject;
import javax.inject.Provider;

import com.getperka.flatpack.HasUuid;
import com.getperka.flatpack.ext.Codex;
import com.getperka.flatpack.ext.DeserializationContext;
import com.getperka.flatpack.ext.JsonKind;
import com.getperka.flatpack.ext.SerializationContext;
import com.getperka.flatpack.ext.Type;
import com.getperka.flatpack.ext.TypeContext;
import com.google.gson.JsonElement;
import com.google.gson.JsonPrimitive;

/**
 * Allows arbitrary objects to be written by examining their type and read by inferring a type from
 * the payload.
 */
public class DynamicCodex extends Codex<Object> {
    private static final Pattern UUID_PATTERN = Pattern
            .compile("[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}");

    // Use Provider to prevent cyclic reference
    private Provider<ListCodex<Object>> listCodex;
    private Provider<StringMapCodex<Object>> mapCodex;
    private TypeContext typeContext;

    protected DynamicCodex() {
    }

    @Override
    public Type describe() {
        return new Type.Builder().withJsonKind(JsonKind.ANY).build();
    }

    /**
     * Attempt to infer the type from the JsonElement presented.
     * <ul>
     * <li>boolean -> {@link Boolean}
     * <li>number -> {@link BigDecimal}
     * <li>string -> {@link HasUuid} or {@link String}
     * <li>array -> {@link ListCodex}
     * <li>object -> {@link StringMapCodex}
     * </ul>
     */
    @Override
    public Object readNotNull(JsonElement element, DeserializationContext context) throws Exception {
        if (element.isJsonPrimitive()) {
            JsonPrimitive primitive = element.getAsJsonPrimitive();
            if (primitive.isBoolean()) {
                return primitive.getAsBoolean();
            } else if (primitive.isNumber()) {
                // Always return numbers as BigDecimals for consistency
                return primitive.getAsBigDecimal();
            } else {
                String value = primitive.getAsString();

                // Interpret UUIDs as entity references
                if (UUID_PATTERN.matcher(value).matches()) {
                    UUID uuid = UUID.fromString(value);
                    HasUuid entity = context.getEntity(uuid);
                    if (entity != null) {
                        return entity;
                    }
                }

                return value;
            }
        } else if (element.isJsonArray()) {
            return listCodex.get().readNotNull(element, context);
        } else if (element.isJsonObject()) {
            return mapCodex.get().readNotNull(element, context);
        }
        context.fail(new UnsupportedOperationException("Cannot infer data type for " + element.toString()));
        return null;
    }

    @Override
    public void scanNotNull(Object object, SerializationContext context) {
        Codex<Object> actual = typeContext.getCodex(object.getClass());
        if (actual == this) {
            context.fail(new UnsupportedOperationException(object.getClass().getName()));
        }
        actual.scan(object, context);
    }

    @Override
    public void writeNotNull(Object object, SerializationContext context) throws IOException {
        Codex<Object> actual = typeContext.getCodex(object.getClass());
        actual.write(object, context);
    }

    @Inject
    void inject(TypeContext typeContext, Provider<ListCodex<Object>> listCodex,
            Provider<StringMapCodex<Object>> mapCodex) {
        this.listCodex = listCodex;
        this.mapCodex = mapCodex;
        this.typeContext = typeContext;
    }
}