add missing element-id

model/src/main/java/lcsb/mapviewer/model/map/reaction/ReactionNode.java

 package lcsb.mapviewer.model.map.reaction;
 
-import javax.persistence.DiscriminatorValue;
-import javax.persistence.Entity;
-import javax.persistence.FetchType;
-import javax.persistence.ManyToOne;
-
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
-
 import lcsb.mapviewer.model.map.species.Element;
 import lcsb.mapviewer.modelutils.map.ElementUtils;
 import lcsb.mapviewer.modelutils.serializer.model.map.ElementAsIdSerializer;
 
+import javax.persistence.DiscriminatorValue;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.ManyToOne;
+
 /**
  * One of two known types of nodes in the {@link Reaction}. It defines input or
  * output element of the reaction in the map model. {@link #element} define
@@ -21,17 +20,15 @@ import lcsb.mapviewer.modelutils.serializer.model.map.ElementAsIdSerializer;
  * <li>{@link Product} - output of the reaction,</li>
  * <li>{@link Modifier} - some modifier of the reaction.</li>
  * </ul>
- * 
- * 
+ *
  * @author Piotr Gawron
- * 
  */
 @Entity
 @DiscriminatorValue("GENERIC_REACTION_NODE")
 public abstract class ReactionNode extends AbstractNode {
 
   /**
-   * 
+   *
    */
   private static final long serialVersionUID = 1L;
 
@@ -53,9 +50,8 @@ public abstract class ReactionNode extends AbstractNode {
 
   /**
    * Constructor that creates a copy of the object in the parameter.
-   * 
-   * @param node
-   *          original node
+   *
+   * @param node original node
    */
   protected ReactionNode(final ReactionNode node) {
     super(node);
@@ -65,9 +61,8 @@ public abstract class ReactionNode extends AbstractNode {
 
   /**
    * Constructor that creates node for given {@link #element}.
-   * 
-   * @param element
-   *          {@link Element} to which this node refer to
+   *
+   * @param element {@link Element} to which this node refer to
    */
   public ReactionNode(final Element element) {
     this.element = element;
@@ -81,9 +76,15 @@ public abstract class ReactionNode extends AbstractNode {
     return element;
   }
 
+  public String getElementId() {
+    if (element != null) {
+      return element.getElementId();
+    }
+    return null;
+  }
+
   /**
-   * @param element
-   *          the element to set
+   * @param element the element to set
    * @see #element
    */
   public void setElement(final Element element) {