Play 2 EBean SnakeYaml Constructor

products.yaml

#
# Products
#

- !!models.Product
  name: Product 1
  state: !!models.ProductState 'SPECIFY'
  rooms:
    - &kitchen !!models.Room
      name: Kitchen
      detailGroups:
        - &floors !id models.DetailGroup(1)
        - &fridges !id models.DetailGroup(2)

    - &bathroom !!models.Room
      name: Bathroom
      detailGroups:
        - *floors

YamlEBeanConstructor.java

package utils;

import com.avaje.ebean.Ebean;
import org.yaml.snakeyaml.constructor.AbstractConstruct;
import org.yaml.snakeyaml.constructor.CustomClassLoaderConstructor;
import org.yaml.snakeyaml.nodes.Node;
import org.yaml.snakeyaml.nodes.ScalarNode;
import org.yaml.snakeyaml.nodes.Tag;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
	
/**
 * Usage
 * Since we can't use the built in play Yaml.load we need to create the yaml instance and pass it our custom constructor
 * 
 * org.yaml.snakeyaml.Yaml yaml = new org.yaml.snakeyaml.Yaml(new YamlEBeanConstructor(play.Play.application().classloader()));
 * InputStream is = play.Play.application().resourceAsStream("products.yml");
 * Map<String, Product> productMap = (Map<String, Product>) yaml.load(is);
 */
public class YamlEBeanConstructor extends CustomClassLoaderConstructor {

	public YamlEBeanConstructor(ClassLoader cLoader) {
		super(cLoader);
		yamlConstructors.put(new Tag("!id"), new ConstructEBeanById("default"));
	}

	private class ConstructEBeanById extends AbstractConstruct {

		private String server;

		private ConstructEBeanById(String server) {
			this.server = server;
		}

		final Pattern classPattern = Pattern.compile("([a-zA-Z.]+)\\((\\d+)\\).*");

		public Object construct(Node node) {
			String val = ((ScalarNode) node).getValue();
			Matcher m = classPattern.matcher(val);
			if (!m.matches()) return null;

			String className = m.group(1);
			String id = m.group(2);

			try {
				return Ebean.getServer(server).getReference(getClassForName(className), Long.parseLong(id));
			} catch (ClassNotFoundException e) {
				return null;
			}
		}
	}
}

YamlEBeanConstructorUsage.java

private static List<Product> products = null;

public static List<Product> getProducts() {
	if (products == null) {
		org.yaml.snakeyaml.Yaml yaml = new org.yaml.snakeyaml.Yaml(new YamlEBeanConstructor(play.Play.application().classloader()));
		InputStream is = play.Play.application().resourceAsStream("products.yml");
		products = (List<Product>) yaml.load(is);
	}
	return products;
}