public class DesignForExtensionCheck extends AbstractCheck
Nothing wrong could be with founded classes. This check makes sense only for library projects (not an 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 practise 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:
Modifier and Type | Field and Description |
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private java.util.Set<java.lang.String> |
ignoredAnnotations
A set of annotations which allow the check to skip the method from validation.
|
static java.lang.String |
MSG_KEY
A key is pointing to the warning message text in "messages.properties"
file.
|
Constructor and Description |
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DesignForExtensionCheck() |
Modifier and Type | Method and Description |
---|---|
private boolean |
canBeOverridden(DetailAST methodDef)
Checks whether a method can be overridden.
|
private static boolean |
canBeSubclassed(DetailAST classDef)
Checks if the given class (given CLASS_DEF node) can be subclassed.
|
int[] |
getAcceptableTokens()
The configurable token set.
|
private static java.lang.String |
getAnnotationName(DetailAST annotation)
Gets the name of the annotation.
|
int[] |
getDefaultTokens()
Returns the default token a check is interested in.
|
private static DetailAST |
getNearestClassOrEnumDefinition(DetailAST ast)
Returns CLASS_DEF or ENUM_DEF token which is the nearest to the given ast node.
|
int[] |
getRequiredTokens()
The tokens that this check must be registered for.
|
private static boolean |
hasDefaultOrExplicitNonPrivateCtor(DetailAST classDef)
Checks whether a class has default or explicit non-private constructor.
|
private static boolean |
hasEmptyImplementation(DetailAST ast)
Checks whether a method has only comments in the body (has an empty implementation).
|
private static boolean |
hasIgnoredAnnotation(DetailAST methodDef,
java.util.Set<java.lang.String> annotations)
Checks whether a method has any of ignored annotations.
|
private boolean |
hasJavadocComment(DetailAST methodDef)
Checks whether a method has a javadoc comment.
|
boolean |
isCommentNodesRequired()
Whether comment nodes are required or not.
|
private boolean |
isNativeMethod(DetailAST ast)
Checks whether a methods is native.
|
void |
setIgnoredAnnotations(java.lang.String... ignoredAnnotations)
Sets annotations which allow the check to skip the method from validation.
|
void |
visitToken(DetailAST ast)
Called to process a token.
|
beginTree, destroy, finishTree, getClassLoader, getFileContents, getLine, getLines, getTabWidth, getTokenNames, init, leaveToken, log, log, setClassLoader, setFileContents, setMessages, setTabWidth, setTokens
getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, log, setId, setSeverity
configure, contextualize, finishLocalSetup, getConfiguration, setupChild
public static final java.lang.String MSG_KEY
private java.util.Set<java.lang.String> ignoredAnnotations
public void setIgnoredAnnotations(java.lang.String... ignoredAnnotations)
ignoredAnnotations
- method annotations.public int[] getDefaultTokens()
AbstractCheck
getDefaultTokens
in class AbstractCheck
TokenTypes
public int[] getAcceptableTokens()
AbstractCheck
getAcceptableTokens
in class AbstractCheck
TokenTypes
public int[] getRequiredTokens()
AbstractCheck
getRequiredTokens
in class AbstractCheck
TokenTypes
public boolean isCommentNodesRequired()
AbstractCheck
isCommentNodesRequired
in class AbstractCheck
public void visitToken(DetailAST ast)
AbstractCheck
visitToken
in class AbstractCheck
ast
- the token to processprivate boolean hasJavadocComment(DetailAST methodDef)
methodDef
- method definition token.private boolean isNativeMethod(DetailAST ast)
ast
- method definition token.private static boolean hasEmptyImplementation(DetailAST ast)
ast
- method definition token.private boolean canBeOverridden(DetailAST methodDef)
methodDef
- method definition token.private static boolean hasIgnoredAnnotation(DetailAST methodDef, java.util.Set<java.lang.String> annotations)
methodDef
- method definition token.annotations
- a set of ignored annotations.private static java.lang.String getAnnotationName(DetailAST annotation)
annotation
- to get name of.private static DetailAST getNearestClassOrEnumDefinition(DetailAST ast)
ast
- the start node for searching.private static boolean canBeSubclassed(DetailAST classDef)
classDef
- class definition token.private static boolean hasDefaultOrExplicitNonPrivateCtor(DetailAST classDef)
classDef
- class ast token.