liquibase.change.Change Interface Reference

Inheritance diagram for liquibase.change.Change:

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List of all members.

Detailed Description

Interface all changes (refactorings) implement.

How changes are constructed and run when reading changelogs:

As the changelog handler gets to each element inside a changeSet, it passes the tag name to liquibase.change.ChangeFactory which looks through all the registered changes until it finds one with matching specified tag name
The ChangeFactory then constructs a new instance of the change
For each attribute in the XML node, reflection is used to call a corresponding set* method on the change class
The correct generateStatements(*) method is called for the current database

To implement a new change:

Create a new class that implements Change (normally extend AbstractChange)
Implement the abstract generateStatements(*) methods which return the correct SQL calls for each database
Implement the createMessage() method to create a descriptive message for logs and dialogs
Implement the createNode() method to generate an XML element based on the values in this change
Add the new class to the liquibase.change.ChangeFactory

Implementing automatic rollback support

The easiest way to allow automatic rollback support is by overriding the createInverses() method. If there are no corresponding inverse changes, you can override the generateRollbackStatements(*) and canRollBack() methods.

Notes for generated SQL:
Because migration and rollback scripts can be generated for execution at a different time, or against a different database, changes you implement cannot directly reference data in the database. For example, you cannot implement a change that selects all rows from a database and modifies them based on the primary keys you find because when the SQL is actually run, those rows may not longer exist and/or new rows may have been added.

We chose the name "change" over "refactoring" because changes will sometimes change functionality whereas true refactoring will not.

See also:: ChangeFactory
Database

Definition at line 51 of file Change.java.


Public Member Functions
String	getChangeName ()
	Returns the name of this change.
String	getTagName ()
	Returns the tag name of this change.
void	executeStatements (Database database) throws JDBCException, UnsupportedChangeException
	Executes the statements in this change against the database passed in the argument.
void	saveStatements (Database database, Writer writer) throws IOException, UnsupportedChangeException, StatementNotSupportedOnDatabaseException
	Outputs the SQL statements generated by this change.
void	executeRollbackStatements (Database database) throws JDBCException, UnsupportedChangeException, RollbackImpossibleException
	Rolls back the statements in this change against the Database passed as argument.
void	saveRollbackStatement (Database database, Writer writer) throws IOException, UnsupportedChangeException, RollbackImpossibleException, StatementNotSupportedOnDatabaseException
	Outputs the statements necessary to roll back this change.
SqlStatement[]	generateStatements (Database database) throws UnsupportedChangeException
	Generates the SQL statements required to run the change.
SqlStatement[]	generateRollbackStatements (Database database) throws UnsupportedChangeException, RollbackImpossibleException
	Generates the SQL statements required to roll back the change.
boolean	canRollBack ()
	Can this change be rolled back.
String	getConfirmationMessage ()
	Confirmation message to be displayed after the change is executed.
Element	createNode (Document currentChangeLogDOM)
	Creates an XML element (of type Element) of the change object, and adds it to the Document object passed as argument.
String	getMD5Sum ()
	Calculates the MD5 hash for the string representation of the XML element of this change.
void	setFileOpener (FileOpener fileOpener)
	Sets the fileOpener that should be used for any file loading and resource finding for files that are provided by the user.
void	setUp () throws SetupException
	This method will be called after the no arg constructor and all of the properties have been set to allow the task to do any heavy tasks or more importantly generate any exceptions to report to the user about the settings provided.

Member Function Documentation

String liquibase.change.Change.getChangeName ( )

Returns the name of this change.

Returns:: the name of the change

Implemented in liquibase.change.AbstractChange.

String liquibase.change.Change.getTagName ( )

Returns the tag name of this change.

Returns:: the tag name of the change

Implemented in liquibase.change.AbstractChange.

void liquibase.change.Change.executeStatements ( Database database ) throws JDBCException, UnsupportedChangeException

Executes the statements in this change against the database passed in the argument.

Parameters:

database

the reference to the target Database to which the statements are executed

Exceptions:

	JDBCException	if there were problems executing the statements
	UnsupportedChangeException	if this change is not supported by the Database passed as argument

Implemented in liquibase.change.AbstractChange.

void liquibase.change.Change.saveStatements	(	Database	database,
		Writer	writer
	)			throws IOException, UnsupportedChangeException, StatementNotSupportedOnDatabaseException

Outputs the SQL statements generated by this change.

Parameters:

	database	the target Database associated to this change's statements
	writer	the target Writer to which the statements are appended

Exceptions:

	IOException	if there were problems appending the statements to the writer
	UnsupportedChangeException	if this change is not supported by the Database passed as argument

Implemented in liquibase.change.AbstractChange.

void liquibase.change.Change.executeRollbackStatements ( Database database ) throws JDBCException, UnsupportedChangeException, RollbackImpossibleException

Rolls back the statements in this change against the Database passed as argument.

Parameters:

database

the target Database associated to this change's rollback statements

Exceptions:

	JDBCException	if there were problems executing the rollback statements
	UnsupportedChangeException	if this change is not supported by the Database passed as argument
	RollbackImpossibleException	if rollback is not supported for this change

Implemented in liquibase.change.AbstractChange.

void liquibase.change.Change.saveRollbackStatement	(	Database	database,
		Writer	writer
	)			throws IOException, UnsupportedChangeException, RollbackImpossibleException, StatementNotSupportedOnDatabaseException

Outputs the statements necessary to roll back this change.

Parameters:

	database	the target Database associated to this change's rollback statements
	writer	writer the target Writer to which the rollback statements are appended

Exceptions:

	IOException	if there were problems appending the rollback statements to the writer
	UnsupportedChangeException	if this change is not supported by the Database passed as argument
	RollbackImpossibleException	if rollback is not supported for this change

Implemented in liquibase.change.AbstractChange.

SqlStatement [] liquibase.change.Change.generateStatements ( Database database ) throws UnsupportedChangeException

Generates the SQL statements required to run the change.

Parameters:

database

databasethe target Database associated to this change's statements

Returns:: an array of Strings with the statements

Exceptions:

UnsupportedChangeException

if this change is not supported by the Database passed as argument

Referenced by liquibase.change.AbstractChange.executeStatements(), and liquibase.change.AbstractChange.saveStatements().

SqlStatement [] liquibase.change.Change.generateRollbackStatements ( Database database ) throws UnsupportedChangeException, RollbackImpossibleException

Generates the SQL statements required to roll back the change.

Parameters:

database

database databasethe target Database associated to this change's rollback statements

Returns:: an array of Strings with the rollback statements

Exceptions:

	UnsupportedChangeException	if this change is not supported by the Database passed as argument
	RollbackImpossibleException	if rollback is not supported for this change

Implemented in liquibase.change.AbstractChange, and liquibase.change.custom.CustomChangeWrapper.

boolean liquibase.change.Change.canRollBack ( )

Can this change be rolled back.