Class VisibilityModifierCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class VisibilityModifierCheck
    extends AbstractCheck

    Checks visibility of class members. Only static final, immutable or annotated by specified annotation members may be public; other class members must be private unless the property protectedAllowed or packageAllowed is set.

    Public members are not flagged if the name matches the public member regular expression (contains "^serialVersionUID$" by default).

    Note that Checkstyle 2 used to include "^f[A-Z][a-zA-Z0-9]*$" in the default pattern to allow names used in container-managed persistence for Enterprise JavaBeans (EJB) 1.1 with the default settings. With EJB 2.0 it is no longer necessary to have public access for persistent fields, so the default has been changed.

    Rationale: Enforce encapsulation.

    Check also has options making it less strict:

    ignoreAnnotationCanonicalNames- the list of annotations which ignore variables in consideration. If user want to provide short annotation name that type will match to any named the same type without consideration of package.

    allowPublicFinalFields- which allows public final fields.

    allowPublicImmutableFields- which allows immutable fields to be declared as public if defined in final class.

    Field is known to be immutable if:

    • It's declared as final
    • Has either a primitive type or instance of class user defined to be immutable (such as String, ImmutableCollection from Guava, etc.)

    Classes known to be immutable are listed in immutableClassCanonicalNames by their canonical names.

    Property Rationale: Forcing all fields of class to have private modifier by default is good in most cases, but in some cases it drawbacks in too much boilerplate get/set code. One of such cases are immutable classes.

    Restriction: Check doesn't check if class is immutable, there's no checking if accessory methods are missing and all fields are immutable, we only check if current field is immutable or final. Under the flag allowPublicImmutableFields, the enclosing class must also be final, to encourage immutability. Under the flag allowPublicFinalFields, the final modifier on the enclosing class is optional.

    Star imports are out of scope of this Check. So if one of type imported via star import collides with user specified one by its short name - there won't be Check's violation.

    • Property packageAllowed - Control whether package visible members are allowed. Type is boolean. Default value is false.
    • Property protectedAllowed - Control whether protected members are allowed. Type is boolean. Default value is false.
    • Property publicMemberPattern - Specify pattern for public members that should be ignored. Type is java.util.regex.Pattern. Default value is "^serialVersionUID$".
    • Property allowPublicFinalFields - Allow final fields to be declared as public. Type is boolean. Default value is false.
    • Property allowPublicImmutableFields - Allow immutable fields to be declared as public if defined in final class. Type is boolean. Default value is false.
    • Property immutableClassCanonicalNames - Specify immutable classes canonical names. Type is java.lang.String[]. Default value is java.io.File, java.lang.Boolean, java.lang.Byte, java.lang.Character, java.lang.Double, java.lang.Float, java.lang.Integer, java.lang.Long, java.lang.Short, java.lang.StackTraceElement, java.lang.String, java.math.BigDecimal, java.math.BigInteger, java.net.Inet4Address, java.net.Inet6Address, java.net.InetSocketAddress, java.net.URI, java.net.URL, java.util.Locale, java.util.UUID.
    • Property ignoreAnnotationCanonicalNames - Specify annotations canonical names which ignore variables in consideration. Type is java.lang.String[]. Default value is com.google.common.annotations.VisibleForTesting, org.junit.ClassRule, org.junit.Rule.

    To configure the check:

     <module name="VisibilityModifier"/>
     

    To configure the check so that it allows package visible members:

     <module name="VisibilityModifier">
       <property name="packageAllowed" value="true"/>
     </module>
     

    To configure the check so that it allows no public members:

     <module name="VisibilityModifier">
       <property name="publicMemberPattern" value="^$"/>
     </module>
     

    To configure the Check so that it allows public immutable fields (mostly for immutable classes):

     <module name="VisibilityModifier">
       <property name="allowPublicImmutableFields" value="true"/>
     </module>
     

    Example of allowed public immutable fields:

     public class ImmutableClass
     {
       public final ImmutableSet<String> includes; // No warning
       public final ImmutableSet<String> excludes; // No warning
       public final java.lang.String notes; // No warning
       public final BigDecimal value; // No warning
    
       public ImmutableClass(Collection<String> includes, Collection<String> excludes,
                    BigDecimal value, String notes)
       {
         this.includes = ImmutableSet.copyOf(includes);
         this.excludes = ImmutableSet.copyOf(excludes);
         this.value = value;
         this.notes = notes;
       }
     }
     

    To configure the Check in order to allow user specified immutable class names:

     <module name="VisibilityModifier">
       <property name="allowPublicImmutableFields" value="true"/>
       <property name="immutableClassCanonicalNames" value="
       com.google.common.collect.ImmutableSet"/>
     </module>
     

    Example of allowed public immutable fields:

     public class ImmutableClass
     {
       public final ImmutableSet<String> includes; // No warning
       public final ImmutableSet<String> excludes; // No warning
       public final java.lang.String notes; // Warning here because
                                            //'java.lang.String' wasn't specified as allowed class
       public final int someValue; // No warning
    
       public ImmutableClass(Collection<String> includes, Collection<String> excludes,
                    String notes, int someValue)
       {
         this.includes = ImmutableSet.copyOf(includes);
         this.excludes = ImmutableSet.copyOf(excludes);
         this.value = value;
         this.notes = notes;
         this.someValue = someValue;
       }
     }
     

    Note, if allowPublicImmutableFields is set to true, the check will also check whether generic type parameters are immutable. If at least one generic type parameter is mutable, there will be a violation.

     <module name="VisibilityModifier">
       <property name="allowPublicImmutableFields" value="true"/>
       <property name="immutableClassCanonicalNames"
         value="com.google.common.collect.ImmutableSet, com.google.common.collect.ImmutableMap,
           java.lang.String"/>
     </module>
     

    Example of how the check works:

     public final class Test {
       public final String s;
       public final ImmutableSet<String> names;
       public final ImmutableSet<Object> objects; // violation (Object class is mutable)
       public final ImmutableMap<String, Object> links; // violation (Object class is mutable)
    
       public Test() {
         s = "Hello!";
         names = ImmutableSet.of();
         objects = ImmutableSet.of();
         links = ImmutableMap.of();
       }
     }
     

    To configure the Check passing fields annotated with @com.annotation.CustomAnnotation:

     <module name="VisibilityModifier">
       <property name="ignoreAnnotationCanonicalNames" value=
       "com.annotation.CustomAnnotation"/>
     </module>
     

    Example of allowed field:

     class SomeClass
     {
       @com.annotation.CustomAnnotation
       String annotatedString; // no warning
       @CustomAnnotation
       String shortCustomAnnotated; // no warning
     }
     

    To configure the Check passing fields annotated with @org.junit.Rule, @org.junit.ClassRule and @com.google.common.annotations.VisibleForTesting annotations:

     <module name="VisibilityModifier"/>
     

    Example of allowed fields:

     class SomeClass
     {
       @org.junit.Rule
       public TemporaryFolder publicJUnitRule = new TemporaryFolder(); // no warning
       @org.junit.ClassRule
       public static TemporaryFolder publicJUnitClassRule = new TemporaryFolder(); // no warning
       @com.google.common.annotations.VisibleForTesting
       public String testString = ""; // no warning
     }
     

    To configure the Check passing fields annotated with short annotation name:

     <module name="VisibilityModifier">
       <property name="ignoreAnnotationCanonicalNames"
       value="CustomAnnotation"/>
     </module>
     

    Example of allowed fields:

     class SomeClass
     {
       @CustomAnnotation
       String customAnnotated; // no warning
       @com.annotation.CustomAnnotation
       String customAnnotated1; // no warning
       @mypackage.annotation.CustomAnnotation
       String customAnnotatedAnotherPackage; // another package but short name matches
                                             // so no violation
     }
     

    To understand the difference between allowPublicImmutableFields and allowPublicFinalFields options, please, study the following examples.

    1) To configure the check to use only 'allowPublicImmutableFields' option:

     <module name="VisibilityModifier">
       <property name="allowPublicImmutableFields" value="true"/>
     </module>
     

    Code example:

     public class InputPublicImmutable {
       public final int someIntValue; // violation
       public final ImmutableSet<String> includes; // violation
       public final java.lang.String notes; // violation
       public final BigDecimal value; // violation
       public final List list; // violation
    
       public InputPublicImmutable(Collection<String> includes,
             BigDecimal value, String notes, int someValue, List l) {
         this.includes = ImmutableSet.copyOf(includes);
         this.value = value;
         this.notes = notes;
         this.someIntValue = someValue;
         this.list = l;
       }
     }
     

    2) To configure the check to use only 'allowPublicFinalFields' option:

     <module name="VisibilityModifier">
       <property name="allowPublicFinalFields" value="true"/>
     </module>
     

    Code example:

     public class InputPublicImmutable {
       public final int someIntValue;
       public final ImmutableSet<String> includes;
       public final java.lang.String notes;
       public final BigDecimal value;
       public final List list;
    
       public InputPublicImmutable(Collection<String> includes,
             BigDecimal value, String notes, int someValue, List l) {
         this.includes = ImmutableSet.copyOf(includes);
         this.value = value;
         this.notes = notes;
         this.someIntValue = someValue;
         this.list = l;
       }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • variable.notPrivate
    Since:
    3.0
    • Method Detail

      • setIgnoreAnnotationCanonicalNames

        public void setIgnoreAnnotationCanonicalNames​(String... annotationNames)
        Setter to specify annotations canonical names which ignore variables in consideration.
        Parameters:
        annotationNames - array of ignore annotations canonical names.
      • setProtectedAllowed

        public void setProtectedAllowed​(boolean protectedAllowed)
        Setter to control whether protected members are allowed.
        Parameters:
        protectedAllowed - whether protected members are allowed
      • setPackageAllowed

        public void setPackageAllowed​(boolean packageAllowed)
        Setter to control whether package visible members are allowed.
        Parameters:
        packageAllowed - whether package visible members are allowed
      • setPublicMemberPattern

        public void setPublicMemberPattern​(Pattern pattern)
        Setter to specify pattern for public members that should be ignored.
        Parameters:
        pattern - pattern for public members to ignore.
      • setAllowPublicImmutableFields

        public void setAllowPublicImmutableFields​(boolean allow)
        Setter to allow immutable fields to be declared as public if defined in final class.
        Parameters:
        allow - user's value.
      • setAllowPublicFinalFields

        public void setAllowPublicFinalFields​(boolean allow)
        Setter to allow final fields to be declared as public.
        Parameters:
        allow - user's value.
      • setImmutableClassCanonicalNames

        public void setImmutableClassCanonicalNames​(String... classNames)
        Setter to specify immutable classes canonical names.
        Parameters:
        classNames - array of immutable types canonical names.
      • 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
      • beginTree

        public void beginTree​(DetailAST rootAst)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAst - the root of the tree
      • isAnonymousClassVariable

        private static boolean isAnonymousClassVariable​(DetailAST variableDef)
        Checks if current variable definition is definition of an anonymous class.
        Parameters:
        variableDef - VARIABLE_DEF
        Returns:
        true if current variable definition is definition of an anonymous class.
      • visitVariableDef

        private void visitVariableDef​(DetailAST variableDef)
        Checks access modifier of given variable. If it is not proper according to Check - puts violation on it.
        Parameters:
        variableDef - variable to check.
      • hasIgnoreAnnotation

        private boolean hasIgnoreAnnotation​(DetailAST variableDef)
        Checks if variable def has ignore annotation.
        Parameters:
        variableDef - VARIABLE_DEF
        Returns:
        true if variable def has ignore annotation.
      • visitImport

        private void visitImport​(DetailAST importAst)
        Checks imported type. If type's canonical name was not specified in immutableClassCanonicalNames, but its short name collides with one from immutableClassShortNames - removes it from the last one.
        Parameters:
        importAst - Import
      • isStarImport

        private static boolean isStarImport​(DetailAST importAst)
        Checks if current import is star import. E.g.:

        import java.util.*;

        Parameters:
        importAst - Import
        Returns:
        true if it is star import
      • hasProperAccessModifier

        private boolean hasProperAccessModifier​(DetailAST variableDef,
                                                String variableName)
        Checks if current variable has proper access modifier according to Check's options.
        Parameters:
        variableDef - Variable definition node.
        variableName - Variable's name.
        Returns:
        true if variable has proper access modifier.
      • isStaticFinalVariable

        private static boolean isStaticFinalVariable​(DetailAST variableDef)
        Checks whether variable has static final modifiers.
        Parameters:
        variableDef - Variable definition node.
        Returns:
        true of variable has static final modifiers.
      • isIgnoredPublicMember

        private boolean isIgnoredPublicMember​(String variableName,
                                              String variableScope)
        Checks whether variable belongs to public members that should be ignored.
        Parameters:
        variableName - Variable's name.
        variableScope - Variable's scope.
        Returns:
        true if variable belongs to public members that should be ignored.
      • isAllowedPublicField

        private boolean isAllowedPublicField​(DetailAST variableDef)
        Checks whether the variable satisfies the public field check.
        Parameters:
        variableDef - Variable definition node.
        Returns:
        true if allowed.
      • isImmutableFieldDefinedInFinalClass

        private boolean isImmutableFieldDefinedInFinalClass​(DetailAST variableDef)
        Checks whether immutable field is defined in final class.
        Parameters:
        variableDef - Variable definition node.
        Returns:
        true if immutable field is defined in final class.
      • getModifiers

        private static Set<StringgetModifiers​(DetailAST defAST)
        Returns the set of modifier Strings for a VARIABLE_DEF or CLASS_DEF AST.
        Parameters:
        defAST - AST for a variable or class definition.
        Returns:
        the set of modifier Strings for defAST.
      • getVisibilityScope

        private static String getVisibilityScope​(DetailAST variableDef)
        Returns the visibility scope for the variable.
        Parameters:
        variableDef - Variable definition node.
        Returns:
        one of "public", "private", "protected", "package"
      • isImmutableField

        private boolean isImmutableField​(DetailAST variableDef)
        Checks if current field is immutable: has final modifier and either a primitive type or instance of class known to be immutable (such as String, ImmutableCollection from Guava, etc.). Classes known to be immutable are listed in immutableClassCanonicalNames
        Parameters:
        variableDef - Field in consideration.
        Returns:
        true if field is immutable.
      • isCanonicalName

        private static boolean isCanonicalName​(DetailAST type)
        Checks whether type definition is in canonical form.
        Parameters:
        type - type definition token.
        Returns:
        true if type definition is in canonical form.
      • getGenericTypeArgs

        private static DetailAST getGenericTypeArgs​(DetailAST type,
                                                    boolean isCanonicalName)
        Returns generic type arguments token.
        Parameters:
        type - type token.
        isCanonicalName - whether type name is in canonical form.
        Returns:
        generic type arguments token.
      • getTypeArgsClassNames

        private static List<StringgetTypeArgsClassNames​(DetailAST typeArgs)
        Returns a list of type parameters class names.
        Parameters:
        typeArgs - type arguments token.
        Returns:
        a list of type parameters class names.
      • areImmutableTypeArguments

        private boolean areImmutableTypeArguments​(Collection<String> typeArgsClassNames)
        Checks whether all generic type arguments are immutable. If at least one argument is mutable, we assume that the whole list of type arguments is mutable.
        Parameters:
        typeArgsClassNames - type arguments class names.
        Returns:
        true if all generic type arguments are immutable.
      • isFinalField

        private static boolean isFinalField​(DetailAST variableDef)
        Checks whether current field is final.
        Parameters:
        variableDef - field in consideration.
        Returns:
        true if current field is final.
      • getTypeName

        private static String getTypeName​(DetailAST type,
                                          boolean isCanonicalName)
        Gets the name of type from given ast TYPE node. If type is specified via its canonical name - canonical name will be returned, else - short type's name.
        Parameters:
        type - TYPE node.
        isCanonicalName - is given name canonical.
        Returns:
        String representation of given type's name.
      • isPrimitive

        private static boolean isPrimitive​(DetailAST type)
        Checks if current type is primitive type (int, short, float, boolean, double, etc.). As primitive types have special tokens for each one, such as: LITERAL_INT, LITERAL_BOOLEAN, etc. So, if type's identifier differs from IDENT token - it's a primitive type.
        Parameters:
        type - Ast TYPE node.
        Returns:
        true if current type is primitive type.
      • getCanonicalName

        private static String getCanonicalName​(DetailAST type)
        Gets canonical type's name from given TYPE node.
        Parameters:
        type - DetailAST TYPE node.
        Returns:
        canonical type's name
      • getNextSubTreeNode

        private static DetailAST getNextSubTreeNode​(DetailAST currentNodeAst,
                                                    DetailAST subTreeRootAst)
        Gets the next node of a syntactical tree (child of a current node or sibling of a current node, or sibling of a parent of a current node).
        Parameters:
        currentNodeAst - Current node in considering
        subTreeRootAst - SubTree root
        Returns:
        Current node after bypassing, if current node reached the root of a subtree method returns null
      • getClassShortNames

        private static Set<StringgetClassShortNames​(Set<String> canonicalClassNames)
        Converts canonical class names to short names.
        Parameters:
        canonicalClassNames - the set of canonical class names.
        Returns:
        the set of short names of classes.
      • getClassShortName

        private static String getClassShortName​(String canonicalClassName)
        Gets the short class name from given canonical name.
        Parameters:
        canonicalClassName - canonical class name.
        Returns:
        short name of class.
      • findMatchingAnnotation

        private DetailAST findMatchingAnnotation​(DetailAST variableDef)
        Checks whether the AST is annotated with an annotation containing the passed in regular expression and return the AST representing that annotation.

        This method will not look for imports or package statements to detect the passed in annotation.

        To check if an AST contains a passed in annotation taking into account fully-qualified names (ex: java.lang.Override, Override) this method will need to be called twice. Once for each name given.

        Parameters:
        variableDef - variable def node.
        Returns:
        the AST representing the first such annotation or null if no such annotation was found