Class AnnotationUseStyleCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public final class AnnotationUseStyleCheck
    extends AbstractCheck

    Checks the style of elements in annotations.

    Annotations have three element styles starting with the least verbose.

    • ElementStyleOption.COMPACT_NO_ARRAY
    • ElementStyleOption.COMPACT
    • ElementStyleOption.EXPANDED

    To not enforce an element style a ElementStyleOption.IGNORE type is provided. The desired style can be set through the elementStyle property.

    Using the ElementStyleOption.EXPANDED style is more verbose. The expanded version is sometimes referred to as "named parameters" in other languages.

    Using the ElementStyleOption.COMPACT style is less verbose. This style can only be used when there is an element called 'value' which is either the sole element or all other elements have default values.

    Using the ElementStyleOption.COMPACT_NO_ARRAY style is less verbose. It is similar to the ElementStyleOption.COMPACT style but single value arrays are flagged. With annotations a single value array does not need to be placed in an array initializer.

    The ending parenthesis are optional when using annotations with no elements. To always require ending parenthesis use the ClosingParensOption.ALWAYS type. To never have ending parenthesis use the ClosingParensOption.NEVER type. To not enforce a closing parenthesis preference a ClosingParensOption.IGNORE type is provided. Set this through the closingParens property.

    Annotations also allow you to specify arrays of elements in a standard format. As with normal arrays, a trailing comma is optional. To always require a trailing comma use the TrailingArrayCommaOption.ALWAYS type. To never have a trailing comma use the TrailingArrayCommaOption.NEVER type. To not enforce a trailing array comma preference a TrailingArrayCommaOption.IGNORE type is provided. Set this through the trailingArrayComma property.

    By default the ElementStyleOption is set to COMPACT_NO_ARRAY, the TrailingArrayCommaOption is set to NEVER, and the ClosingParensOption is set to NEVER.

    According to the JLS, it is legal to include a trailing comma in arrays used in annotations but Sun's Java 5 & 6 compilers will not compile with this syntax. This may in be a bug in Sun's compilers since eclipse 3.4's built-in compiler does allow this syntax as defined in the JLS. Note: this was tested with compilers included with JDK versions and and the compiler included with eclipse 3.4.1.

    See Java Language specification, §9.7.

    • Property elementStyle - Define the annotation element styles. Type is$ElementStyleOption. Default value is compact_no_array.
    • Property closingParens - Define the policy for ending parenthesis. Type is$ClosingParensOption. Default value is never.
    • Property trailingArrayComma - Define the policy for trailing comma in arrays. Type is$TrailingArrayCommaOption. Default value is never.

    To configure the check:

     <module name="AnnotationUseStyle"/>


     @Deprecated // OK
     @SomeArrays(pooches={DOGS.LEO}) // Violation - COMPACT_NO_ARRAY
     @SuppressWarnings({""}) // Violation - COMPACT_NO_ARRAY
     public class TestOne
     @SomeArrays(pooches={DOGS.LEO}, um={}, test={"bleh"}) // Violation - COMPACT_NO_ARRAY
     @SuppressWarnings("") // OK
     @Deprecated() // Violation - cannot have closing parenthesis
     class TestTwo {

    To configure the check to enforce an expanded style, with a trailing array comma set to never and always including the closing parenthesis.

     <module name="AnnotationUseStyle">
       <property name="elementStyle" value="expanded"/>
       <property name="trailingArrayComma" value="never"/>
       <property name="closingParens" value="always"/>


     @Deprecated // Violation - must have closing parenthesis
     @SomeArrays(pooches={DOGS.LEO}) // OK
     @SuppressWarnings({""}) // Violation - EXPANDED
     public class TestOne
     @SomeArrays(pooches={DOGS.LEO}, um={}, test={"bleh"}) // OK
     @SuppressWarnings("") // Violation - EXPANDED
     @Deprecated() // OK
     class TestTwo {

    Parent is

    Violation Message Keys:

    • annotation.parens.missing
    • annotation.parens.present
    • annotation.trailing.comma.missing
    • annotation.trailing.comma.present