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sphere-java-client
There is a newer version: 0.72.1
package io.sphere.client.model;

import javax.annotation.Nonnull;
import io.sphere.client.ReferenceException;
import org.codehaus.jackson.annotate.JsonCreator;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.annotate.JsonIgnoreProperties;
import org.codehaus.jackson.annotate.JsonProperty;

/** Link to an object using its id and type id.
 *  If the reference has been expanded, the linked object can be obtained using the {@link #get} method. */
@JsonIgnoreProperties({"expanded"})
public class Reference {
    @Nonnull private String id;
    @Nonnull private String typeId;
    private T obj;

    @JsonIgnore
    private Reference(@Nonnull String typeId, @Nonnull String id) {
        this.id = id;
        this.typeId = typeId;
    }

    @JsonCreator
    private Reference(@Nonnull @JsonProperty("typeId") final String typeId, @Nonnull @JsonProperty("id") final String id,
                      @JsonProperty("obj") final T obj) {
        this.id = id;
        this.typeId = typeId;
        this.obj = obj;
    }

    protected Reference() {
    }

    @JsonIgnore
    public static  Reference create(String typeId, String id) {
        return new Reference(typeId, id);
    }

    /** Creates a reference. */
    @JsonIgnore
    static  Reference create(final String typeId, final String id, final T obj) {
        return new Reference(typeId, id, obj);
    }

    /** Returns the object represented by this reference.
     *
     *  If the reference has not been expanded, throws a {@link ReferenceException}. Never returns null.
     *  @throws ReferenceException If this reference has not been expanded. */
    public T get() throws ReferenceException {
        if (obj == null)
            throw new ReferenceException(
                    "Reference has not been expanded: [" + typeId + "]" + id + ". " +
                    "Consider requesting reference expansion (using expand()) when fetching data from the Sphere backend.");
        return obj;
    }

    /** True if this reference has been expanded.
     *
     * If {@link #isExpanded} returns true, {@link #get} is guaranteed to return a non-null object.
     * User code should always check for {@link #isExpanded} before calling {@link #get}. */
    @JsonIgnore
    public boolean isExpanded() { return obj != null; }

    /** True if this reference has no value in the parent object.
     *
     * If {@link #isEmpty} returns true, there's not much to do with this reference - {@link #isExpanded}
     * will return false and all other methods will throw a {@link ReferenceException}. */

    @JsonIgnore
    public boolean isEmpty() { return false; }

    /** Id of the object this reference represents. */
    @Nonnull public String getId() { return id; }

    /** Type id of the object this reference represents, e.g. "customer". */
    @Nonnull public String getTypeId() { return typeId; }

    @Override
    public String toString() {
        return "Reference{" +
                "id='" + id + '\'' +
                ", typeId='" + typeId + '\'' +
                ", obj=" + obj +
                '}';
    }

    public ReferenceId toReferenceIdOrNull() {
        return ReferenceId.create(getTypeId(), getId());
    }

    public Reference toUnexpandedReference() {
        return Reference.create(getTypeId(), getId());
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Reference reference = (Reference) o;

        if (!id.equals(reference.id)) return false;
        if (obj != null ? !obj.equals(reference.obj) : reference.obj != null) return false;
        if (!typeId.equals(reference.typeId)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = id.hashCode();
        result = 31 * result + typeId.hashCode();
        result = 31 * result + (obj != null ? obj.hashCode() : 0);
        return result;
    }
}