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Liquibase is a tool for managing and executing database changes.
There is a newer version: 4.29.1
package liquibase.command;

import liquibase.exception.CommandValidationException;

import java.util.List;

/**
 * Defines a particular step in a command pipeline.
 * When a command is executed, Liquibase will find all the step whose {@link #defineCommandNames()} matches the command,
 * add the dependencies and run the pipeline.
 *
 * @see CommandScope#execute()
 */
public interface CommandStep {

    /**
     * Returned by {@link #getOrder(CommandDefinition)} if you are unsure where in the pipeline your step should go, use this value.
     */
    @Deprecated
    int ORDER_DEFAULT = 1000;

    /**
     * Returned by {@link #getOrder(CommandDefinition)} if this step should not be a part of the pipeline.
     */
    @Deprecated
    int ORDER_NOT_APPLICABLE = -1;

    /**
     * Defines new command names
     * For example, if it is part of `liquibase update`, this should return new String[][]{ new String[] {"update"}}.
     * If it is a part of `liquibase example init`, this should return {"example", "init"}.
     * 
     * This is used to determine the available command names.
     * 
     * This can return null if this step is not defining a new command but "cross-cutting" existing commands
     */
    String[][] defineCommandNames();

    /**
     * The order in the pipeline that this step should be executed in.
     * Logic is generally based off {@link CommandDefinition#getName()} but it can check other things in the definition such as arguments.
     *
     * @return -1 if this step does not apply to the given command
     */
    @Deprecated
    int getOrder(CommandDefinition commandDefinition);

    /**
     * Called by the command pipeline setup to adjust the {@link CommandDefinition} metadata about the overall command.
     * This method should not be called directly. It is called by the overall pipeline logic in the {@link CommandFactory#getCommandDefinition(String...)}.
     */
    void adjustCommandDefinition(CommandDefinition commandDefinition);

    /**
     * Validates that the {@link CommandScope} is correctly set up for this step to run.
     * Any validation in {@link CommandArgumentDefinition#validate(CommandScope)} will be checked previous to this method being called.
     */
    void validate(CommandScope commandScope) throws CommandValidationException;

    /**
     * Performs the business logic.
     * This method should not be called directly. It is called by the overall pipeline logic in the {@link CommandScope#execute()} order.
     */
    void run(CommandResultsBuilder resultsBuilder) throws Exception;

    /**
     * Return a list of configured Classes that this command requires to be passed as a dependency.
     * @return list with the required classes types
     */
    List> requiredDependencies();

    /**
     * Returns a list of all the dependency Classes that this step provides
     * @return list with the provided classes types
     */
    List> providedDependencies();
}