Query.java

/*
 * 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.stanbol.entityhub.servicesapi.query;

import org.apache.stanbol.entityhub.servicesapi.site.Site;
import org.apache.stanbol.entityhub.servicesapi.yard.Yard;

/**
 * Common interfaces for all supported queries. The idea is that some query
 * types MUST BE supported by the Entityhub. However some {@link Site} and
 * {@link Yard} implementations may support additional query types.<p>
 *
 * @author Rupert Westenthaler
 *
 */
public interface Query extends Cloneable {
    /**
     * The type of the Query (e.g. "fieldQuery" or "entityQuery"). Typically the
     * type should be defines as String constant in the java interface of the
     * query type.
     * @return return the name of the query (usually the the value as
     *     returned by the {@link Class#getSimpleName()} class object of the
     *     Java Interface for the query type but with a
     *     {@link Character#toLowerCase(char)} for the first character.
     */
    String getQueryType();
    /**
     * Getter for the maximum number of results for this query.
     * @return the maximum number of results or <code>null</code> if no limit
     *    is defined. MUST never return a number <code><= 1</code>
     */
    Integer getLimit();
    /**
     * Setter for the maximum number of results or <code>null</code> if no
     * limit is defined.
     * @param limit the limit as positive integer or <code>null</code> to define
     *    that no limit is defined. Parsing a negative number results in setting
     *    the limit to <code>null</code>.
     */
    void setLimit(Integer limit);
    /**
     * Getter for the offset for the first result of this query.
     * @return the offset for this query. MUST NOT return a value <code> < 0</code>
     */
    int getOffset();
    /**
     * Setter for the offset of the query. Setting the offset to any value
     * <code>< 0</code> MUST result in setting the offset to <code>0</code>
     * @param offset the offset, a positive natural number including <code>0</code>.
     *    Parsing a negative number results to setting the offset to <code>0</code>
     */
    void setOffset(int offset);
    /**
     * Clones the query.
     * @return the clone
     */
    Query clone();
}