liquibase.snapshot.SnapshotGenerator Maven / Gradle / Ivy
package liquibase.snapshot;
import liquibase.database.Database;
import liquibase.exception.DatabaseException;
import liquibase.structure.DatabaseObject;
/*
* A class that implements the SnapshotGenerator interface is capable of creating an object representation
* ("a snapshot") of one (or more?) object types in one (or more) DBMSs.
*
*/
public interface SnapshotGenerator {
int PRIORITY_NONE = -1;
int PRIORITY_DEFAULT = 1;
int PRIORITY_DATABASE = 5;
int PRIORITY_ADDITIONAL = 50;
/**
* Inquire if this SnapshotGenerator is capable of snapshotting objects of type
* objectType (e.g. Table, Index, View etc.) in the DBMS database (e.g. Oracle, Postgres, HyperSQL etc.)
* A return priority of > 0 will be interpreted as capable. The highest priority for an objectType-database
* combination wins.
*
* @param objectType The object type we are asked to snapshot
* @param database The DBMS for which the snapshotting should be done
* @return An integer of PRIORITY_... constants indicating our capability and willingness to snapshot
*/
int getPriority(Class objectType, Database database);
/**
* Commands the SnapshotGenerator to create a snapshot (a representation of a database object in Java object form)
* of a specific database object.
* @param example The object we should try to snapshot
* @param snapshot The Snapshot object representating the result of the snapshot operations so far
* @param chain A list of other SnapshotGenerators that might be asked to try the same
* @param The Java object type in which we are to return the snapshot result
* @return An object of type T if our snapshot attempt is successful
* @throws DatabaseException If an operation on the database fails
* @throws InvalidExampleException If, for some reason, we cannot work on the example object (ambiguous naming etc.)
*/
T snapshot(T example, DatabaseSnapshot snapshot, SnapshotGeneratorChain chain)
throws DatabaseException, InvalidExampleException;
/**
* When snapshotting a certain object type (e.g. a table), different types of objects might be discovered in the
* process.
* (TODO: Which ones? Needs a more precise description.)
* @return an array of classes that this SnapshotGenerator might return upon snapshotting a given
* DatabaseObject type.
*/
Class[] addsTo();
/**
* Returns classes (and superclasses) that this SnapshotGenerator replaces. Return null or empty array to not
* affect the SnapshotGeneratorChain.
*/
Class[] replaces();
}