com.hazelcast.query.impl.getters.Getter Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2021, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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 com.hazelcast.query.impl.getters;
/**
* Base class for extraction of values from object instances.
* Each sub-class encapsulates extraction strategy.
*/
abstract class Getter {
protected final Getter parent;
Getter(final Getter parent) {
this.parent = parent;
}
/**
* Method for attribute-specific getters that can extract from one path only
*/
abstract Object getValue(Object obj) throws Exception;
/**
* Method for generic getters that are not bound to a specific path only, but can get any attributePath
* and extract from it.
*/
Object getValue(Object obj, String attributePath) throws Exception {
return getValue(obj);
}
/**
* Method for generic getters that can make use of metadata if available. These getters must
* gracefully fallback to not using metadata if unavailable.
*/
Object getValue(Object obj, String attributePath, Object metadata) throws Exception {
return getValue(obj, attributePath);
}
/**
* Returns extracted object type for non-generic getters. It is only applicable when
* extracted object type can be determined before running the getter.
*
* @return The type of extracted attribute
*/
abstract Class getReturnType();
/**
* A getter instance may be re-used for all predicates that has the same target object
* type and attribute path.
*
* Generic getters such as {@link PortableGetter} should not be cached because the same
* getter is used for all entries regardless of attribute path. Instead, generic getters
* should use a singleton instance.
*
* @return {@code true} if this getter is cacheable, {@code false} otherwise.
*/
abstract boolean isCacheable();
}