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    • com.arpnetworking.jackson.BuilderDeserializer Maven / Gradle / Ivy

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    /**
 * Copyright 2014 Groupon.com
 *
 * 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.arpnetworking.jackson;

import com.arpnetworking.commons.builder.Builder;
import com.arpnetworking.steno.Logger;
import com.arpnetworking.steno.LoggerFactory;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.google.common.base.Objects;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;

import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Map;
import java.util.Set;

/**
 * Deserialize JSON into an instance of a specified type T given a
 * builder that creates instances of that type (or a subtype). In order to use
 * this deserializer with an ObjectMapper be sure to register the
 * transitive closure of builder deserializers (e.g. type-builder pairs) that
 * are required to deserialize an instance of the root type.
 *
 * TODO(vkoskela): This is _duplicated_ from tsd-core and should find its way to a common utility package.
 *
 * @param  The type this deserializer supports.
 *
 * @author Ville Koskela (vkoskela at groupon dot com)
 */
public final class BuilderDeserializer extends JsonDeserializer {

    /**
     * Static factory method.
     *
     * @param  The type this deserializer supports.
     * @param builderClass The builder class for the supported type.
     * @return Instance of BuilderDeserializer.
     */
    public static  BuilderDeserializer of(final Class> builderClass) {
        // TODO(vkoskela): Add caching to avoid unnecessary instances [MAI-114]
        return new BuilderDeserializer(builderClass);
    }

    /**
     * Register builder deserializers for the the transitive closure of builders
     * anchored by the target class in the provided SimpleModule.
     *
     * @param targetModule The SimpleModule to register in.
     * @param targetClass The root of the type tree to traverse.
     */
    public static void addTo(final SimpleModule targetModule, final Class targetClass) {
        final Map, JsonDeserializer> typeToDeserializer = Maps.newHashMap();
        addTo(Sets.newHashSet(), typeToDeserializer, targetClass);
        for (final Map.Entry, JsonDeserializer> entry : typeToDeserializer.entrySet()) {
            @SuppressWarnings("unchecked")
            final Class clazz = (Class) entry.getKey();
            targetModule.addDeserializer(clazz, entry.getValue());
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public T deserialize(final JsonParser parser, final DeserializationContext context) throws IOException {
        final Builder builder = parser.readValueAs(_builderClass);
        return builder.build();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(final Object object) {
        if (this == object) {
            return true;
        }
        if (object == null || getClass() != object.getClass()) {
            return false;
        }

        final BuilderDeserializer other = (BuilderDeserializer) object;

        return Objects.equal(_builderClass, other._builderClass);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        return Objects.hashCode(_builderClass);
    }

    private static void addTo(final Set visited, final Map, JsonDeserializer> deserializerMap, final Type targetType) {
        if (visited.contains(targetType)) {
            return;
        }
        visited.add(targetType);

        if (targetType instanceof Class) {
            @SuppressWarnings("unchecked")
            final Class targetClass = (Class) targetType;
            try {
                // Look-up and register the builder for this class
                final Class> builderClass = getBuilderForClass(targetClass);
                deserializerMap.put(targetClass, BuilderDeserializer.of(builderClass));

                LOGGER.trace()
                        .setMessage("Registered builder for class")
                        .addData("targetClass", targetClass)
                        .addData("targetClassBuilder", builderClass)
                        .log();

                // Process all setters on the builder
                for (final Method method : builderClass.getMethods()) {
                    if (isSetterMethod(builderClass, method)) {
                        final Type setterArgumentType = method.getGenericParameterTypes()[0];
                        // Recursively register builders for each setter's type
                        addTo(visited, deserializerMap, setterArgumentType);
                    }
                }
            } catch (final ClassNotFoundException e) {
                // Log that the class is not build-able
                LOGGER.trace()
                        .setMessage("Ignoring class without builder")
                        .addData("targetClass", targetClass)
                        .log();
            }

            // Support for JsonSubTypes annotation
            if (targetClass.isAnnotationPresent(JsonSubTypes.class)) {
                final JsonSubTypes.Type[] subTypes = targetClass.getAnnotation(JsonSubTypes.class).value();
                for (final JsonSubTypes.Type subType : subTypes) {
                    addTo(visited, deserializerMap, subType.value());
                }
            }

            // Support for JsonTypeInfo annotation
            // TODO(vkoskela): Support JsonTypeInfo classpath scan [MAI-116]
        }

        if (targetType instanceof ParameterizedType) {
            // Recursively register builders for each parameterized type
            final ParameterizedType targetParameterizedType = (ParameterizedType) targetType;
            final Type rawType = targetParameterizedType.getRawType();
            addTo(visited, deserializerMap, rawType);
            for (final Type argumentActualType : targetParameterizedType.getActualTypeArguments()) {
                addTo(visited, deserializerMap, argumentActualType);
            }
        }
    }

    // NOTE: Package private for testing.
    @SuppressWarnings("unchecked")
    static  Class> getBuilderForClass(final Class clazz)
            throws ClassNotFoundException {
        return (Class>) (Class.forName(
                clazz.getName() + "$Builder",
                true, // initialize
                clazz.getClassLoader()));
    }

    // NOTE: Package private for testing.
    static boolean isSetterMethod(final Class builderClass, final Method method) {
        return method.getName().startsWith(SETTER_PREFIX)
                &&
                builderClass.equals(method.getReturnType())
                &&
                !method.isVarArgs()
                &&
                method.getParameterTypes().length == 1;
    }

    private BuilderDeserializer(final Class> builderClass) {
        _builderClass = builderClass;
    }

    private final Class> _builderClass;

    private static final String SETTER_PREFIX = "set";
    private static final Logger LOGGER = LoggerFactory.getLogger(BuilderDeserializer.class);
}
    
    
    
    

    




    
    
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