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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.google.cloud.datastore.Cursor;
import com.googlecode.objectify.cmd.QueryKeys;
import com.googlecode.objectify.cmd.SimpleQuery;


/**
 * Base for command classes that include methods for defining a query (filter, order, limit, etc).
 * Does not include the methods for executing a query.
 *
 * @author Jeff Schnitzer 
 */
public abstract class SimpleQueryImpl implements SimpleQuery
{
	/** Constant seems to have disappeared from the SDK */
	private final String KEY_RESERVED_PROPERTY = "__key__";

	/** */
	protected final LoaderImpl loader;

	/**
	 * There is a special case - if loader is null, use 'this' as the LoaderImpl. It's a bit of a hack
	 * but we can't pass in 'this' to super constructors.
	 */
	SimpleQueryImpl(final LoaderImpl loader) {
		this.loader = loader == null ? (LoaderImpl)this : loader;
	}

	/**
	 * Create an initial query object; for a typed query this will have a class, otherwise it will be generic.
	 * For the real QueryImpl itself this is a clone() operation.
	 */
	abstract QueryImpl createQuery();

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.QueryCommon#filterKey(java.lang.String, java.lang.Object)
	 */
	@Override
	public QueryImpl filterKey(String condition, Object value) {
		QueryImpl q = createQuery();
		q.addFilter(KEY_RESERVED_PROPERTY + " " + condition.trim(), value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.SimpleQuery#filterKey(java.lang.Object)
	 */
	@Override
	public QueryImpl filterKey(Object value) {
		return filterKey("=", value);
	}

	@Override
	public QueryImpl orderKey(boolean descending) {
		String prefix = descending ? "-" : "";

		QueryImpl q = createQuery();
		q.addOrder(prefix + KEY_RESERVED_PROPERTY);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#ancestor(java.lang.Object)
	 */
	@Override
	public QueryImpl ancestor(Object keyOrEntity) {
		QueryImpl q = createQuery();
		q.setAncestor(keyOrEntity);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#limit(int)
	 */
	@Override
	public QueryImpl limit(int value) {
		QueryImpl q = createQuery();
		q.setLimit(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#offset(int)
	 */
	@Override
	public QueryImpl offset(int value) {
		QueryImpl q = createQuery();
		q.setOffset(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#startCursor(com.google.cloud.datastore.Cursor)
	 */
	@Override
	public QueryImpl startAt(Cursor value) {
		QueryImpl q = createQuery();
		q.setStartCursor(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#endCursor(com.google.cloud.datastore.Cursor)
	 */
	@Override
	public QueryImpl endAt(Cursor value) {
		QueryImpl q = createQuery();
		q.setEndCursor(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#chunk(int)
	 */
	@Override
	public QueryImpl chunk(int value) {
		QueryImpl q = createQuery();
		q.setChunk(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.SimpleQuery#hybrid(boolean)
	 */
	@Override
	public QueryImpl hybrid(boolean force) {
		QueryImpl q = createQuery();
		q.setHybrid(force);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.SimpleQuery#chunkAll()
	 */
	@Override
	public QueryImpl chunkAll()
	{
		return chunk(Integer.MAX_VALUE);
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.Query#keys()
	 */
	@Override
	public QueryKeys keys() {
		QueryImpl q = createQuery();
		q.checkKeysOnlyOk();
		return new QueryKeysImpl<>(q);
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.SimpleQuery#distinct(boolean)
	 */
	@Override
	public QueryImpl distinct(boolean value) {
		QueryImpl q = createQuery();
		q.setDistinct(value);
		return q;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.cmd.SimpleQuery#project(String...)
	 */
	@Override
	public QueryImpl project(String... fields) {
		QueryImpl q = createQuery();
		q.addProjection(fields);
		return q;
	}

}