ebean/src/main/java/com/avaje/ebean/bean/NodeUsageCollector.java

package com.avaje.ebean.bean;

import java.lang.ref.WeakReference;
import java.util.HashSet;

/**
 * Collects profile information for a bean (or reference/proxy bean) at a given
 * AutoFetchNode.
 * <p>
 * The AutoFetchNode identifies the location of the bean in the object graph.
 * </p>
 * <p>
 * It has to use a weak reference so as to ensure that it does not stop the
 * associated bean from being garbage collected.
 * </p>
 */
public final class NodeUsageCollector {

  /**
   * The point in the object graph for a specific query and call stack point.
   */
  private final ObjectGraphNode node;

  /**
   * Weak to allow garbage collection.
   */
  private final WeakReference<NodeUsageListener> managerRef;

  /**
   * The properties used at this profile point.
   */
  private final HashSet<String> used = new HashSet<String>();

  /**
   * set to true if the bean is modified (setter called)
   */
  private boolean modified;

  /**
   * The property that cause a reference to lazy load.
   */
  private String loadProperty;

  public NodeUsageCollector(ObjectGraphNode node, WeakReference<NodeUsageListener> managerRef) {
    this.node = node;
    // weak to allow garbage collection.
    this.managerRef = managerRef;
  }

  /**
   * The bean has been modified by a setter method.
   */
  public void setModified() {
    modified = true;
  }

  /**
   * Add the name of a property that has been used.
   */
  public void addUsed(String property) {
    used.add(property);
  }

  /**
   * The property that invoked a lazy load.
   */
  public void setLoadProperty(String loadProperty) {
    this.loadProperty = loadProperty;
  }

  /**
   * Publish the usage info to the manager.
   */
  private void publishUsageInfo() {
    NodeUsageListener manager = managerRef.get();
    if (manager != null) {
      manager.collectNodeUsage(this);
    }
  }

  /**
   * publish the collected usage information when garbage collection occurs.
   */
  @Override
  protected void finalize() throws Throwable {
    publishUsageInfo();
    super.finalize();
  }

  /**
   * Return the associated node which identifies the location in the object
   * graph of the bean/reference.
   */
  public ObjectGraphNode getNode() {
    return node;
  }

  /**
   * Return true if no properties where used.
   */
  public boolean isEmpty() {
    return used.isEmpty();
  }

  /**
   * Return the set of used properties.
   */
  public HashSet<String> getUsed() {
    return used;
  }

  /**
   * Return true if the bean was modified by a setter.
   */
  public boolean isModified() {
    return modified;
  }

  public String getLoadProperty() {
    return loadProperty;
  }

  public String toString() {
    return node + " read:" + used + " modified:" + modified;
  }
}