org.apache.openjpa.lib.rop.ResultObjectProvider Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.openjpa.lib.rop;
import org.apache.openjpa.lib.util.Closeable;
/**
* Interface that allows lazy/custom instantiation of input objects.
* {@link ResultList} objects do not necessarily load in data all
* at once. Instead, they may lazily load objects as necessary. So,
* the lifespan of a {@link ResultObjectProvider} instance is
* related to how the application deals with processing the
* {@link ResultList} created with a given
* {@link ResultObjectProvider} instance.
*
* @author Marc Prud'hommeaux
* @author Patrick Linskey
* @author Abe White
*/
public interface ResultObjectProvider extends Closeable {
/**
* Return true if this provider supports random access.
*/
public boolean supportsRandomAccess();
/**
* Open the result. This will be called before
* {@link #next}, {@link #absolute}, or {@link #size}.
*/
public void open() throws Exception;
/**
* Instantiate the current result object. This method will only be
* called after {@link #next} or {@link #absolute}.
*/
public Object getResultObject() throws Exception;
/**
* Advance the input to the next position. Return true if
* there is more data; otherwise false.
*/
public boolean next() throws Exception;
/**
* Move to the given 0-based position. This method is
* only called for providers that support random access.
* Return true if there is data at this position;
* otherwise false. This may be invoked in place of
* {@link #next}.
*/
public boolean absolute(int pos) throws Exception;
/**
* Return the number of items in the input, or {@link Integer#MAX_VALUE}
* if the size in unknown.
*/
public int size() throws Exception;
/**
* Reset this provider. This is an optional operation. If supported,
* it should move the position of the provider to before the first
* element. Non-random-access providers may be able to support this
* method by re-acquiring all resources as if the result were just opened.
*/
public void reset() throws Exception;
/**
* Free the resources associated with this provider.
*/
public void close() throws Exception;
/**
* Any checked exceptions that are thrown will be passed to this method.
* The provider should re-throw the exception as an appropriate unchecked
* exception.
*/
public void handleCheckedException(Exception e);
}