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The Drools and jBPM public API which is backwards compatible between releases.

There is a newer version: 6.5.0.Final

/*
 * Copyright 2010 JBoss Inc
 *
 * 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.drools.runtime.process;

/**
 * A work item handler is responsible for executing work items
 * of a specific type.  They represent the glue code between an
 * abstract, high-level work item that is used inside the process
 * and the implementation of this work item.  Work item handlers
 * should be registered with the WorkItemManager for
 * each type of work that can be executed in the engine.
 * 
 * A work item handler is responsible for executing a work item whenever
 * the work item manager delegates one to it.  It should also notify
 * the work item manager when the work item has been completed.
 * 
 * It is also possible that a work item handler is requested to abort
 * an existing work item (that is still executing) because it is no longer
 * necessary.  This might for example be because the process instance
 * (or a part of the process instance) that is was executing in is being
 * aborted.  The work item handler should then try to abort this work item
 * (if possible) and if necessary clean up runtime state related to its
 * execution.
 * 
 * For example, a work item handler that is responsible for executing
 * email work items will retrieve the necessary information from the
 * work item (from, to, body, etc.) and invoke the mail server.  Afterwards,
 * it will notify the WorkItemManager that the work item was completed.
 */
public interface WorkItemHandler {

    /**
     * The given work item should be executed.
     * @param workItem the work item that should be executed
     * @param manager the manager that requested the work item to be executed
     */
    void executeWorkItem(WorkItem workItem,
                         WorkItemManager manager);

    /**
     * The given work item should be aborted.
     * @param workItem the work item that should be aborted
     * @param manager the manager that requested the work item to be aborted
     */
    void abortWorkItem(WorkItem workItem,
                       WorkItemManager manager);

}