Package com.puppycrawl.tools.checkstyle.checks.design

Class MutableExceptionCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.puppycrawl.tools.checkstyle.checks.design.MutableExceptionCheck

All Implemented Interfaces:

Configurable, Contextualizable

public final class MutableExceptionCheck
extends AbstractCheck

Ensures that exception classes (classes with names conforming to some pattern and explicitly extending classes with names conforming to other pattern) are immutable, that is, that they have only final fields.

The current algorithm is very simple: it checks that all members of exception are final. The user can still mutate an exception's instance (e.g. Throwable has a method called setStackTrace which changes the exception's stack trace). But, at least, all information provided by this exception type is unchangeable.

Rationale: Exception instances should represent an error condition. Having non-final fields not only allows the state to be modified by accident and therefore mask the original condition but also allows developers to accidentally forget to set the initial state. In both cases, code catching the exception could draw incorrect conclusions based on the state.

• Property extendedClassNameFormat - Specify pattern for extended class names. Type is java.util.regex.Pattern. Default value is "^.*Exception$|^.*Error$|^.*Throwable$".
• Property format - Specify pattern for exception class names. Type is java.util.regex.Pattern. Default value is "^.*Exception$|^.*Error$|^.*Throwable$".

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• mutable.exception

Since:

3.2

Nested Class Summary

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

AbstractAutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	checking	Should we check current class or not.
private final Deque<Boolean>	checkingStack	Stack of checking information for classes.
private static final String	DEFAULT_FORMAT	Default value for format and extendedClassNameFormat properties.
private Pattern	extendedClassNameFormat	Specify pattern for extended class names.
private Pattern	format	Specify pattern for exception class names.
static final String	MSG_KEY	A key is pointing to the warning message text in "messages.properties" file.

Constructor Summary

Constructors

Constructor	Description
MutableExceptionCheck()

Method Summary

Modifier and Type	Method	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.
private boolean	isExtendedClassNamedAsException(DetailAST ast)	Checks that if extended class name conforms to specified format.
private boolean	isNamedAsException(DetailAST ast)	Checks that a class name conforms to specified format.
private void	leaveClassDef()	Called when we leave class definition.
void	leaveToken(DetailAST ast)	Called after all the child nodes have been process.
void	setExtendedClassNameFormat(Pattern extendedClassNameFormat)	Setter to specify pattern for extended class names.
void	setFormat(Pattern pattern)	Setter to specify pattern for exception class names.
private void	visitClassDef(DetailAST ast)	Called when we start processing class definition.
void	visitToken(DetailAST ast)	Called to process a token.
private void	visitVariableDef(DetailAST ast)	Checks variable definition.

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

beginTree, clearViolations, destroy, finishTree, getFileContents, getFilePath, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, log, log, log, 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.AbstractAutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

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

Field Details

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

DEFAULT_FORMAT

private static final String DEFAULT_FORMAT

Default value for format and extendedClassNameFormat properties.

See Also:

• Constant Field Values

checkingStack

private final Deque<Boolean> checkingStack

Stack of checking information for classes.

extendedClassNameFormat

private Pattern extendedClassNameFormat

Specify pattern for extended class names.

checking

private boolean checking

Should we check current class or not.

format

private Pattern format

Specify pattern for exception class names.

Constructor Details

MutableExceptionCheck

public MutableExceptionCheck()

Method Details

setExtendedClassNameFormat

public void setExtendedClassNameFormat(Pattern extendedClassNameFormat)

Setter to specify pattern for extended class names.

Parameters:

extendedClassNameFormat - a String value

Since:

6.2

setFormat

public void setFormat(Pattern pattern)

Setter to specify pattern for exception class names.

Parameters:

pattern - the new pattern

Since:

3.2

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

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

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

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

leaveToken

public void leaveToken(DetailAST ast)

Description copied from class: AbstractCheck

Called after all the child nodes have been process.

Overrides:

leaveToken in class AbstractCheck

Parameters:

ast - the token leaving

visitClassDef

private void visitClassDef(DetailAST ast)

Called when we start processing class definition.

Parameters:

ast - class definition node

leaveClassDef

private void leaveClassDef()

Called when we leave class definition.

visitVariableDef

private void visitVariableDef(DetailAST ast)

Checks variable definition.

Parameters:

ast - variable def node for check

isNamedAsException

private boolean isNamedAsException(DetailAST ast)

Checks that a class name conforms to specified format.

Parameters:

ast - class definition node

Returns:

true if a class name conforms to specified format

isExtendedClassNamedAsException

private boolean isExtendedClassNamedAsException(DetailAST ast)

Checks that if extended class name conforms to specified format.

Parameters:

ast - class definition node

Returns:

true if extended class name conforms to specified format