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/*
 * Copyright 2015 Ignacio del Valle Alles [email protected].
 *
 * 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 org.brutusin.jsonsrv;

import org.brutusin.jsonsrv.caching.CachingInfo;

/**
 * Used to define business operations considered safe according to the
 * HTTP definition, meaning that the action "... defined semantics are
 * essentially read-only; i.e., the client does not request, and does not
 * expect, any state change on the origin server as a result of applying a safe
 * method to a target resource. Likewise, reasonable use of a safe method is not
 * expected to cause any harm, loss of property, or unusual burden on the origin
 * server."
 * 

Threading issues: Instances of this class will be accessed
 * by several threads concurrently, so implementing subclasses must be
 * thread-safe.
 * 

Instance life-cycle: For each request received the following
 * methods are (can be) executed:
 * 
 *  {@link #getCachingInfo(java.lang.Object)}: That returns caching
 * information for this request.
 *  {@link #execute(java.lang.Object)}: Depending on the client request
 * being conditional, and on the value returned by the previous method, this
 * method is or is not executed.
 * 
 * 

 * See section 4.2.1 of rfc7231 for more
 * details.
 *
 * @see UnsafeAction
 * @author Ignacio del Valle Alles [email protected]
 * @param  Input POJO class.
 * @param  Output POJO class
 */
public abstract class SafeAction extends JsonAction {

    /**
     * Returns the caching information of the request, based on the input data.
     * 

For conditional-cacheable executions this method must perform a
     * lightweight computation (in fact, for all kind of executions),
     * since its objective is to avoid the potentially heavyweight computation
     * performed by {@link #execute(java.lang.Object)}
     * 

Default implementations returns {@code null}, meaning that not
     * caching is performed.
     *
     * @param input
     * @return
     */
    public CachingInfo getCachingInfo(I input) {
        return null;
    }

    @Override
    public final boolean isIdempotent(){
        return true;
    }
}