jspwiki-main/src/main/java/org/apache/wiki/workflow/Step.java

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package org.apache.wiki.workflow;

import org.apache.wiki.api.exceptions.WikiException;

import java.io.Serializable;
import java.security.Principal;
import java.util.Collection;
import java.util.Date;
import java.util.List;
import java.util.Map;


/**
 * <p>
 * Discrete unit of work in a Workflow, such as a {@link Decision} or a {@link Task}. Decisions require user input, while Tasks do not.
 * All Steps, however, possess these properties:
 * </p>
 * <ul>
 * <li><strong>actor</strong>: the Principal responsible for executing the Step; returned by {@link Step#getActor()}.</li>
 * <li><strong>availableOutcomes</strong>: a collection of possible "outcomes," such as "approve decision" ({@link Outcome#DECISION_APPROVE}),
 * "reassign decision" ({@link Outcome#DECISION_REASSIGN}), "abort step" ({@link Outcome#STEP_ABORT}) and others. The range of possible
 * Outcomes for the Step is returned by {@link Step#getAvailableOutcomes()}; see the Outcome class for more details.</li>
 * <li><strong>errors</strong>: an collection of Strings indicating errors returned by the Step. These values are returned by
 * {@link Step#getErrors()}.</li>
 * <li><strong>started</strong> and <strong>completed</strong>: whether the Step has started/finished. These values are returned by
 * {@link Step#isStarted()} and {@link Step#isCompleted()}.</li>
 * <li><strong>startTime</strong> and <strong>endTime</strong>: the time when the Step started and finished. These values are returned by
 * {@link Step#getStartTime()} and {@link Step#getEndTime()}, respectively.</li>
 * <li><strong>workflow</strong>: the parent Workflow. </li>
 * </ul>
 * <p>
 * Steps contain a {@link #getMessageKey()} method that returns a key that can be used with the {@link org.apache.wiki.i18n.InternationalizationManager}.
 * See also {@link Workflow#getMessageArguments()}, which is a convenience method that returns message arguments.
 * </p>
 * 
 * @since 2.5
 */
public interface Step extends Serializable {

    /** Time value: the start or end time has not been set. */
    public static final Date TIME_NOT_SET = new Date( 0 );

    /**
     * Adds a successor Step to this one, which will be triggered by a supplied Outcome. Implementations should respect the order in which
     * Outcomes are added; {@link #getAvailableOutcomes()} should return them in the same order they were added.
     * 
     * @param outcome the Outcome triggering a particular successor Step
     * @param step the Step to associated with this Outcomes (<code>null</code> denotes no Steps)
     */
    void addSuccessor( Outcome outcome, Step step );

    /**
     * Returns a Collection of available outcomes, such as "approve", "deny" or "reassign", in the order in which they were added via
     * {@link #addSuccessor(Outcome, Step)}. Concrete implementations should always return a defensive copy of the outcomes, not the
     * original backing collection.
     * 
     * @return the set of outcomes
     */
    Collection< Outcome > getAvailableOutcomes();

    /**
     * Returns a List of error strings generated by this Step. If this Step generated no errors, this method returns a zero-length array.
     * 
     * @return the errors
     */
    List< String > getErrors();

    /**
     * <p>
     * Executes the processing for this Step and returns an Outcome indicating if it succeeded ({@link Outcome#STEP_COMPLETE} or
     * {@link Outcome#STEP_ABORT}). Processing instructions can do just about anything, such as executing custom business logic or
     * changing the Step's final outcome via {@link #setOutcome(Outcome)}. A return value of <code>STEP_COMPLETE</code> indicates
     * that the instructions executed completely, without errors; <code>STEP_ABORT</code> indicates that the Step and its parent
     * Workflow should be aborted (that is, fail silently without error). If the execution step encounters any errors, it should throw a
     * WikiException or a subclass.
     * </p>
     * <p>
     * Note that successful execution of this methods does not necessarily mean that the Step is considered "complete"; rather, it just
     * means that it has executed. Therefore, it is possible that <code>execute</code> could run multiple times.
     * </p>
     * 
     * @return the result of the Step, expressed as an Outcome
     * @throws WikiException if the step encounters errors while executing
     */
    Outcome execute() throws WikiException;

    /**
     * The Principal responsible for completing this Step, such as a system user or actor assigned to a Decision.
     * 
     * @return the responsible Principal
     */
    Principal getActor();

    /**
     * The end time for this Step. This value should be set when the step completes. Returns {@link #TIME_NOT_SET} if not completed
     * yet.
     * 
     * @return the end time
     */
    Date getEndTime();

    /**
     * Message key for human-friendly name of this Step, including any parameter substitutions. By convention, the message prefix should be
     * a lower-case version of the Step's type, plus a period (<em>e.g.</em>, <code>task.</code> and <code>decision.</code>).
     * 
     * @return the message key for this Step.
     */
    String getMessageKey();

    /**
     * Returns the Outcome of this Step's processing; by default, {@link Outcome#STEP_CONTINUE}.
     * 
     * @return the outcome
     */
    Outcome getOutcome();

    /**
     * The start time for this Step. Returns {@link #TIME_NOT_SET} if not started yet.
     * 
     * @return the start time
     */
    Date getStartTime();

    /**
     * Determines whether the Step is completed; if not, it is by definition awaiting action by the owner or in process. If a Step has
     * completed, it <em>must also</em> return a non-<code>null</code> result for {@link #getOutcome()}.
     * 
     * @return <code>true</code> if the Step has completed; <code>false</code> if not.
     */
    boolean isCompleted();

    /**
     * Determines whether the Step has started.
     * 
     * @return <code>true</code> if the Step has started; <code>false</code> if not.
     */
    boolean isStarted();

    /**
     * Starts the Step, and sets the start time to the moment when this method is first invoked. If this Step has already been started,
     * this method throws an {@linkplain IllegalStateException}. If the Step cannot be started because the underlying implementation
     * encounters an error, it the implementation should throw a WikiException.
     * 
     * @throws WikiException if the step encounters errors while starting
     */
    void start() throws WikiException;

    /**
     * Sets the current Outcome for the step. If the Outcome is a "completion" Outcome, it should also sets the completon time and mark the
     * Step as complete. Once a Step has been marked complete, this method cannot be called again. If the supplied Outcome is not in the
     * set returned by {@link #getAvailableOutcomes()}, or is not  {@link Outcome#STEP_CONTINUE} or {@link Outcome#STEP_ABORT}, this method
     * returns an IllegalArgumentException. If the caller attempts to set an Outcome and the Step has already completed, this method throws
     * an IllegalStateException.
     * 
     * @param outcome whether the step should be considered completed
     */
    void setOutcome( Outcome outcome );

    /**
     * Identifies the next Step for a particular Outcome; if there is no next Step for this Outcome, this method returns <code>null</code>.
     * 
     * @param outcome the outcome
     * @return the next step
     */
    Step getSuccessor( Outcome outcome );

    /**
     * Sets the parent Workflow post-construction. Should be called after building a {@link Step}.
     *
     * @param workflowId the parent workflow id to set
     * @param workflowContext the parent workflow context to set
     */
    void setWorkflow( final int workflowId, final Map< String, Object > workflowContext );

}