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  package org.apache.cayenne.reflect;
  
  import org.apache.cayenne.exp.path.CayennePath;
  import org.apache.cayenne.map.ObjRelationship;
  
  /**
   * A base implementation of the {@link ArcProperty}.
   * 
   * @since 3.0
   */
  public abstract class BaseArcProperty extends BaseProperty implements ArcProperty {
  
      protected String complimentaryReverseArcName;
      protected ClassDescriptor targetDescriptor;
      protected ObjRelationship relationship;
      protected CayennePath reverseDbPath;
  
      public BaseArcProperty(ClassDescriptor owner, ClassDescriptor targetDescriptor, Accessor accessor,
              String reverseName) {
  
          super(owner, accessor);
  
          this.targetDescriptor = targetDescriptor;
          this.complimentaryReverseArcName = reverseName;
          this.relationship = owner.getEntity().getRelationship(getName());
      }
  
      @Override
      public abstract boolean visit(PropertyVisitor visitor);
  
      public abstract boolean isFault(Object source);
      
      @Override
      public String getComplimentaryReverseDbRelationshipPath() {
          if (reverseDbPath == null) {
              reverseDbPath = relationship.getReverseDbRelationshipPath();
          }
  
          return reverseDbPath.value();
      }
  
      public ObjRelationship getRelationship() {
          return relationship;
      }
  
      public ArcProperty getComplimentaryReverseArc() {
          return (ArcProperty) targetDescriptor.getProperty(complimentaryReverseArcName);
      }
  
      public ClassDescriptor getTargetDescriptor() {
          return targetDescriptor;
      }
  
      /**
       * A convenience method to set the reverse arc used by subclasses.
       */
      protected void setReverse(final Object source, final Object oldTarget, final Object newTarget) {
  
          ArcProperty reverseArc = getComplimentaryReverseArc();
  
          if (reverseArc != null) {
  
              // unset old
              if (oldTarget != null) {
  
                  PropertyVisitor visitor = new PropertyVisitor() {
  
                      public boolean visitToMany(ToManyProperty property) {
                          property.removeTarget(oldTarget, source, false);
                          return false;
                      }
  
                      public boolean visitToOne(ToOneProperty property) {
                          property.setTarget(oldTarget, null, false);
                          return false;
                      }
  
                      public boolean visitAttribute(AttributeProperty property) {
                          return false;
                      }
                  };
  
                  reverseArc.visit(visitor);
              }
  
              // set new reverse
              if (newTarget != null) {
                  PropertyVisitor visitor = new PropertyVisitor() {
  
                      public boolean visitToMany(ToManyProperty property) {
                          property.addTarget(newTarget, source, false);
                          return false;
                      }
  
                      public boolean visitToOne(ToOneProperty property) {
                          property.setTarget(newTarget, source, false);
                          return false;
                      }
  
                      public boolean visitAttribute(AttributeProperty property) {
                          return false;
                      }
                  };
  
                  reverseArc.visit(visitor);
              }
          }
      }
  }
  