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

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 will 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 and 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 the list of 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

    • Field Detail

      • MSG_KEY

        public static final java.lang.String MSG_KEY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values

    • Constructor Detail

      • VisibilityModifierCheck

        public VisibilityModifierCheck()

    • Method Detail

      • setIgnoreAnnotationCanonicalNames

        public void setIgnoreAnnotationCanonicalNames​(java.lang.String... annotationNames)
        Setter to specify the list of 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​(java.util.regex.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​(java.lang.String... classNames)
        Setter to specify immutable classes canonical names.
        Parameters:
        classNames - array of immutable types canonical names.

      • 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

      • 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