com.puppycrawl.tools.checkstyle.checks.design

Class DesignForExtensionCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.api.AutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.puppycrawl.tools.checkstyle.checks.design.DesignForExtensionCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class DesignForExtensionCheck
extends AbstractCheck

The check finds classes that are designed for extension (subclass creation).

Nothing wrong could be with founded classes. This check makes sense only for library projects (not application projects) which care of ideal OOP-design to make sure that class works in all cases even misusage. Even in library projects this check most likely will find classes that are designed for extension by somebody. User needs to use suppressions extensively to got a benefit from this check, and keep in suppressions all confirmed/known classes that are deigned for inheritance intentionally to let the check catch only new classes, and bring this to team/user attention.

ATTENTION: Only user can decide whether a class is designed for extension or not. The check just shows all classes which are possibly designed for extension. If smth inappropriate is found please use suppression.

ATTENTION: If the method which can be overridden in a subclass has a javadoc comment (a good practice is to explain its self-use of overridable methods) the check will not rise a violation. The violation can also be skipped if the method which can be overridden in a subclass has one or more annotations that are specified in ignoredAnnotations option. Note, that by default @Override annotation is not included in the ignoredAnnotations set as in a subclass the method which has the annotation can also be overridden in its subclass.

More specifically, the check enforces a programming style where superclasses provide empty "hooks" that can be implemented by subclasses.

The check finds classes that have overridable methods (public or protected methods that are non-static, not-final, non-abstract) and have non-empty implementation.

This protects superclasses against being broken by subclasses. The downside is that subclasses are limited in their flexibility, in particular, they cannot prevent execution of code in the superclass, but that also means that subclasses cannot forget to call their super method.

The check has the following options:

• ignoredAnnotations - annotations which allow the check to skip the method from validation. Default value is Test, Before, After, BeforeClass, AfterClass.

Author:

lkuehne, Andrei Selkin

Nested Class Summary

Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

AutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field and Description
static String	MSG_KEY A key is pointing to the warning message text in "messages.properties" file.

Constructor Summary

Constructors

Constructor and Description
DesignForExtensionCheck()

Method Summary

Modifier and Type	Method and Description
int[]	getAcceptableTokens() The configurable token set.
int[]	getDefaultTokens() Returns the default token a check is interested in.
int[]	getRequiredTokens() The tokens that this check must be registered for.
boolean	isCommentNodesRequired() Whether comment nodes are required or not.
void	setIgnoredAnnotations(String... ignoredAnnotations) Sets annotations which allow the check to skip the method from validation.
void	visitToken(DetailAST ast) Called to process a token.

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck

beginTree, clearMessages, destroy, finishTree, getClassLoader, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, init, leaveToken, log, log, log, setClassLoader, setFileContents, setTabWidth, setTokens

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MSG_KEY

public static final String MSG_KEY

A key is pointing to the warning message text in "messages.properties" file.

See Also:

Constant Field Values

Constructor Detail

DesignForExtensionCheck

public DesignForExtensionCheck()

Method Detail

setIgnoredAnnotations

public void setIgnoredAnnotations(String... ignoredAnnotations)

Sets annotations which allow the check to skip the method from validation.

Parameters:

ignoredAnnotations - method annotations.

getDefaultTokens

public int[] getDefaultTokens()

Description copied from class: AbstractCheck

Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.

Specified by:

getDefaultTokens in class AbstractCheck

Returns:

the default tokens

See Also:

TokenTypes

getAcceptableTokens

public int[] getAcceptableTokens()

Description copied from class: AbstractCheck

The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.

Specified by:

getAcceptableTokens in class AbstractCheck

Returns:

the token set this check is designed for.

See Also:

TokenTypes

getRequiredTokens

public int[] getRequiredTokens()

Description copied from class: AbstractCheck

The tokens that this check must be registered for.

Specified by:

getRequiredTokens in class AbstractCheck

Returns:

the token set this must be registered for.

See Also:

TokenTypes

isCommentNodesRequired

public boolean isCommentNodesRequired()

Description copied from class: AbstractCheck

Whether comment nodes are required or not.

Overrides:

isCommentNodesRequired in class AbstractCheck

Returns:

false as a default value.

visitToken

public void visitToken(DetailAST ast)

Description copied from class: AbstractCheck

Called to process a token.

Overrides:

visitToken in class AbstractCheck

Parameters:

ast - the token to process