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OptaPlanner solves planning problems. This lightweight, embeddable planning engine implements powerful and scalable algorithms to optimize business resource scheduling and planning. This module contains the examples which demonstrate how to use it in a normal Java application.

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package org.optaplanner.examples.common.persistence.jackson;

import java.util.Objects;

import org.optaplanner.examples.common.domain.AbstractPersistable;
import org.optaplanner.examples.common.persistence.AbstractJsonSolutionFileIO;

import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.KeyDeserializer;

/**
 * Deserializes map key defined by {@link JacksonUniqueIdGenerator} to a child of {@link AbstractPersistable}.
 * 
 * Deserialization will create new instances of the map key type.
 * Duplicate instances will be created if any other part of the JSON is also referencing the same type.
 * In that case, a custom implementation of {@link AbstractJsonSolutionFileIO} must be used later
 * to resolve the duplicates by comparing IDs of such objects and making sure only one instance exists with each ID.
 * 
 * Example: let us consider a "Location" object that has a field of type Map<Location, Distance>.
 * When the outer Location object gets deserialized from List<Location>,
 * the nested map needs to be deserialized as well.
 * However, at this point, the Location objects used as keys in the map do not yet exist.
 * (The rest of the list has not been read yet.)
 * Therefore the deserializer needs to create a temporary dummy Location object to use as the map key.
 * This object later needs to be replaced by the actual Location object by the {@link AbstractJsonSolutionFileIO}.
 *
 * @param  The type must have a {@link com.fasterxml.jackson.annotation.JsonIdentityInfo} annotation with
 *        {@link JacksonUniqueIdGenerator} as its generator.
 */
public abstract class AbstractKeyDeserializer extends KeyDeserializer {

    private final Class persistableClass;

    protected AbstractKeyDeserializer(Class persistableClass) {
        this.persistableClass = Objects.requireNonNull(persistableClass);
    }

    @Override
    public final E deserializeKey(String value, DeserializationContext deserializationContext) {
        String[] parts = value.split("#");
        String className = parts[0];
        if (!Objects.equals(className, persistableClass.getSimpleName())) {
            throw new IllegalStateException("Impossible state: not the correct type (" + value + ").");
        }
        String idString = parts[1];
        try {
            long id = Long.parseLong(idString);
            return createInstance(id); // Need to be de-duplicated in solution IO.
        } catch (NumberFormatException e) {
            throw new IllegalStateException("Impossible state: id is not a number (" + idString + ")");
        }
    }

    protected abstract E createInstance(long id);

}