com.googlecode.objectify.impl.LoadConditions Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of objectify Show documentation

The simplest convenient interface to the Google App Engine datastore

There is a newer version: 6.1.2

package com.googlecode.objectify.impl;

import com.googlecode.objectify.annotation.Load;
import com.googlecode.objectify.annotation.Parent;
import java.util.Set;

/** 
 * A 'brain' class that determines whether or not refs should be loaded.
 */
public class LoadConditions
{
	/** The states are important - null means none, empty means "all" */
	Class[] loadGroups;

	/** This will never be empty - either null or have some values */
	Class[] loadUnlessGroups;

	/** Whether or not this field is a @Parent field */
	boolean parent;

	/**
	 * @param load can be null; it's "whatever was specified on the field", possibly nothing
	 * @param parent will be null for nonparent fields
	 */
	public LoadConditions(Load load, Parent parent) {
		// Get @Load groups
		if (load != null) {
			loadGroups = load.value();
			
			if (load.unless().length > 0)
				loadUnlessGroups = load.unless();
		}

		this.parent = parent != null;
	}

	/**
	 * @return true if the property should be loaded when the given loadgroups are active
	 */
	public boolean shouldLoad(Set> groups, boolean inTransaction) {
		if (loadGroups == null)
			return false;
		
		if (loadGroups.length > 0 && !matches(groups, loadGroups))
			return false;

		if (loadUnlessGroups != null && matches(groups, loadUnlessGroups))
			return false;

		if (inTransaction) {
			if (parent) {
				return true;	// even in transactions, it's always safe to load the parent - same entity group
			} else {
				// Let explicitly specified load groups work in transactions, otherwise not at all - too dangerous
				return loadGroups.length > 0;
			}
		} else {
			return true;
		}
	}

	/**
	 */
	private boolean matches(Set> groups, Class[] loadGroups) {
		for (Class propertyGroup: loadGroups)
			for (Class enabledGroup: groups)
				if (propertyGroup.isAssignableFrom(enabledGroup))
					return true;
		
		return false;
	}
}