MetaWrapper.java

package de.galan.verjson.util;

import static de.galan.commons.time.Instants.*;
import static de.galan.verjson.util.Transformations.*;
import static org.apache.commons.lang3.StringUtils.*;

import java.util.Date;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.JsonNode;


/**
 * Nests the object to be serialized, adding meta information such as the current version number and namespace. Also
 * provides static accessor to these nodes.
 *
 * @author daniel
 */
public class MetaWrapper {

	public static final String ID_VERSION = "$v";
	public static final String ID_NAMESPACE = "$ns";
	public static final String ID_DATA = "$d";
	public static final String ID_TIMESTAMP = "$ts";

	/** Incremental version */
	@JsonProperty(ID_VERSION)
	private long version;

	/** Namespace for the data object */
	@JsonProperty(ID_NAMESPACE)
	private String namespace;

	/** Timestamp when the object was serialized */
	@JsonProperty(ID_TIMESTAMP)
	private Date timestamp;

	/** Actual payload */
	@JsonProperty(ID_DATA)
	private Object data;


	public MetaWrapper(long version, String namespace, Object data, Date timestamp) {
		this.version = version;
		this.namespace = namespace;
		this.data = data;
		this.timestamp = timestamp;
	}


	/** Returns the data node from a wrapped JsonNode */
	public static JsonNode getData(JsonNode node) {
		return getObj(obj(node), MetaWrapper.ID_DATA);
	}


	/** Returns the namespace from a wrapped JsonNode */
	public static String getNamespace(JsonNode node) {
		JsonNode nodeNs = obj(node).get(ID_NAMESPACE);
		return (nodeNs != null) ? nodeNs.asText() : null;
	}


	/** Returns the source version from a wrapped JsonNode */
	public static Long getVersion(JsonNode node) {
		return obj(node).get(ID_VERSION).asLong();
	}


	/** Sets the version on a wrapped JsonNode */
	public static void setVersion(JsonNode node, Long version) {
		obj(node).put(ID_VERSION, version);
	}


	/** Returns the timestamp from a wrapped JsonNode */
	public static Date getTimestamp(JsonNode node) {
		String text = obj(node).get(ID_TIMESTAMP).asText();
		return isNotBlank(text) ? from(instantUtc(text)).toDate() : null;
	}

}