com.j256.ormlite.dao.LazyForeignCollection Maven / Gradle / Ivy

package com.j256.ormlite.dao;

import java.io.Serializable;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import com.j256.ormlite.field.ForeignCollectionField;

/**
 * Collection that is set on a field that as been marked with the {@link ForeignCollectionField} annotation when an
 * object is refreshed or queried (i.e. not created). Most of the methods here require a pass through the database.
 * Operations such as size() therefore should most likely not be used because of their expense. Chances are you only
 * want to use the {@link #iterator()}, {@link #toArray()}, and {@link #toArray(Object[])} methods.
 * 
 * 
 * WARNING: Most likely for(;;) loops should not be used here since we need to be careful about closing the
 * iterator.
 * 
 * 
 * @author graywatson
 */
public class LazyForeignCollection extends BaseForeignCollection implements ForeignCollection,
		Serializable {

	private static final long serialVersionUID = -5460708106909626233L;

	private transient CloseableIterator lastIterator;

	public LazyForeignCollection(Dao dao, Object parent, Object parentId, String columnName, String orderColumn) {
		super(dao, parent, parentId, columnName, orderColumn);
	}

	/**
	 * The iterator returned from a lazy collection keeps a connection open to the database as it iterates across the
	 * collection. You will need to call {@link CloseableIterator#close()} or go all the way through the loop to ensure
	 * that the connection has been closed. You can also call {@link #closeLastIterator()} on the collection itself
	 * which will close the last iterator returned. See the reentrant warning.
	 */
	public CloseableIterator iterator() {
		return closeableIterator();
	}

	public CloseableIterator closeableIterator() {
		try {
			return iteratorThrow();
		} catch (SQLException e) {
			throw new IllegalStateException("Could not build lazy iterator for " + dao.getDataClass(), e);
		}
	}

	/**
	 * This is the same as {@link #iterator()} except it throws.
	 */
	public CloseableIterator iteratorThrow() throws SQLException {
		lastIterator = seperateIteratorThrow();
		return lastIterator;
	}

	/**
	 * Same as {@link #iteratorThrow()} except this doesn't set the last iterator which can be closed with the
	 * {@link #closeLastIterator()}.
	 */
	public CloseableIterator seperateIteratorThrow() throws SQLException {
		// check state to make sure we have a DAO in case we have a deserialized collection
		if (dao == null) {
			throw new IllegalStateException(
					"Internal DAO object is null.  Lazy collections cannot be used if they have been deserialized.");
		} else {
			return dao.iterator(getPreparedQuery());
		}
	}

	public CloseableWrappedIterable getWrappedIterable() {
		return new CloseableWrappedIterableImpl(new CloseableIterable() {
			public CloseableIterator iterator() {
				return closeableIterator();
			}
			public CloseableIterator closeableIterator() {
				try {
					return LazyForeignCollection.this.seperateIteratorThrow();
				} catch (Exception e) {
					throw new IllegalStateException("Could not build lazy iterator for " + dao.getDataClass(), e);
				}
			}
		});
	}

	public void closeLastIterator() throws SQLException {
		if (lastIterator != null) {
			lastIterator.close();
			lastIterator = null;
		}
	}

	public boolean isEager() {
		return false;
	}

	public int size() {
		CloseableIterator iterator = iterator();
		try {
			int sizeC;
			for (sizeC = 0; iterator.hasNext(); sizeC++) {
				// move to next without constructing the object
				iterator.moveToNext();
			}
			return sizeC;
		} finally {
			try {
				iterator.close();
			} catch (SQLException e) {
				// ignored
			}
		}
	}

	public boolean isEmpty() {
		CloseableIterator iterator = iterator();
		try {
			return !iterator.hasNext();
		} finally {
			try {
				iterator.close();
			} catch (SQLException e) {
				// ignored
			}
		}
	}

	public boolean contains(Object obj) {
		CloseableIterator iterator = iterator();
		try {
			while (iterator.hasNext()) {
				if (iterator.next().equals(obj)) {
					return true;
				}
			}
			return false;
		} finally {
			try {
				iterator.close();
			} catch (SQLException e) {
				// ignored
			}
		}
	}

	public boolean containsAll(Collection collection) {
		Set