Class ReflectionUtils


  • @API(status=INTERNAL,
         since="1.0")
    public final class ReflectionUtils
    extends Object
    Collection of utilities for working with the Java reflection APIs.

    DISCLAIMER

    These utilities are intended solely for usage within the JUnit framework itself. Any usage by external parties is not supported. Use at your own risk!

    Some utilities are published via the maintained ReflectionSupport class.

    Since:
    1.0
    See Also:
    ReflectionSupport
    • Method Detail

      • isPublic

        public static boolean isPublic​(Class<?> clazz)
      • isPublic

        public static boolean isPublic​(Member member)
      • isPrivate

        public static boolean isPrivate​(Class<?> clazz)
      • isPrivate

        public static boolean isPrivate​(Member member)
      • isNotPrivate

        @API(status=INTERNAL,
             since="1.4")
        public static boolean isNotPrivate​(Class<?> clazz)
      • isNotPrivate

        @API(status=INTERNAL,
             since="1.1")
        public static boolean isNotPrivate​(Member member)
      • isAbstract

        public static boolean isAbstract​(Class<?> clazz)
      • isAbstract

        public static boolean isAbstract​(Member member)
      • isStatic

        public static boolean isStatic​(Class<?> clazz)
      • isNotStatic

        @API(status=INTERNAL,
             since="1.4")
        public static boolean isNotStatic​(Class<?> clazz)
      • isStatic

        public static boolean isStatic​(Member member)
      • isNotStatic

        @API(status=INTERNAL,
             since="1.1")
        public static boolean isNotStatic​(Member member)
      • isFinal

        @API(status=INTERNAL,
             since="1.5")
        public static boolean isFinal​(Class<?> clazz)
        Since:
        1.5
      • isNotFinal

        @API(status=INTERNAL,
             since="1.5")
        public static boolean isNotFinal​(Class<?> clazz)
        Since:
        1.5
      • isFinal

        @API(status=INTERNAL,
             since="1.5")
        public static boolean isFinal​(Member member)
        Since:
        1.5
      • isNotFinal

        @API(status=INTERNAL,
             since="1.5")
        public static boolean isNotFinal​(Member member)
        Since:
        1.5
      • isInnerClass

        public static boolean isInnerClass​(Class<?> clazz)
        Determine if the supplied class is an inner class (i.e., a non-static member class).

        Technically speaking (i.e., according to the Java Language Specification), "an inner class may be a non-static member class, a local class, or an anonymous class." However, this method does not return true for a local or anonymous class.

        Parameters:
        clazz - the class to check; never null
        Returns:
        true if the class is an inner class
      • returnsVoid

        public static boolean returnsVoid​(Method method)
      • isArray

        public static boolean isArray​(Object obj)
        Determine if the supplied object is an array.
        Parameters:
        obj - the object to test; potentially null
        Returns:
        true if the object is an array
      • isMultidimensionalArray

        @API(status=INTERNAL,
             since="1.3.2")
        public static boolean isMultidimensionalArray​(Object obj)
        Determine if the supplied object is a multidimensional array.
        Parameters:
        obj - the object to test; potentially null
        Returns:
        true if the object is a multidimensional array
        Since:
        1.3.2
      • isAssignableTo

        public static boolean isAssignableTo​(Class<?> sourceType,
                                             Class<?> targetType)
        Determine if an object of the supplied source type can be assigned to the supplied target type for the purpose of reflective method invocations.

        In contrast to Class.isAssignableFrom(Class), this method returns true if the target type represents a primitive type whose wrapper matches the supplied source type. In addition, this method also supports widening conversions for primitive target types.

        Parameters:
        sourceType - the non-primitive target type; never null
        targetType - the target type; never null
        Returns:
        true if an object of the source type is assignment compatible with the target type
        Since:
        1.8
        See Also:
        Class.isInstance(Object), Class.isAssignableFrom(Class), isAssignableTo(Object, Class)
      • isAssignableTo

        public static boolean isAssignableTo​(Object obj,
                                             Class<?> targetType)
        Determine if the supplied object can be assigned to the supplied target type for the purpose of reflective method invocations.

        In contrast to Class.isInstance(Object), this method returns true if the target type represents a primitive type whose wrapper matches the supplied object's type. In addition, this method also supports widening conversions for primitive types and their corresponding wrapper types.

        If the supplied object is null and the supplied type does not represent a primitive type, this method returns true.

        Parameters:
        obj - the object to test for assignment compatibility; potentially null
        targetType - the type to check against; never null
        Returns:
        true if the object is assignment compatible
        See Also:
        Class.isInstance(Object), Class.isAssignableFrom(Class), isAssignableTo(Class, Class)
      • getWrapperType

        public static Class<?> getWrapperType​(Class<?> type)
        Get the wrapper type for the supplied primitive type.
        Parameters:
        type - the primitive type for which to retrieve the wrapper type
        Returns:
        the corresponding wrapper type or null if the supplied type is null or not a primitive type
      • newInstance

        public static <T> T newInstance​(Constructor<T> constructor,
                                        Object... args)
        Create a new instance of type T by invoking the supplied constructor with the supplied arguments.

        The constructor will be made accessible if necessary, and any checked exception will be masked as an unchecked exception.

        Parameters:
        constructor - the constructor to invoke; never null
        args - the arguments to pass to the constructor
        Returns:
        the new instance; never null
        See Also:
        newInstance(Class, Object...), ExceptionUtils.throwAsUncheckedException(Throwable)
      • readFieldValue

        @API(status=DEPRECATED,
             since="1.4")
        @Deprecated
        public static <T> Optional<Object> readFieldValue​(Class<T> clazz,
                                                          String fieldName,
                                                          T instance)
        Deprecated.
        Read the value of a potentially inaccessible or nonexistent field.

        If the field does not exist or the value of the field is null, an empty Optional will be returned.

        Parameters:
        clazz - the class where the field is declared; never null
        fieldName - the name of the field; never null or empty
        instance - the instance from where the value is to be read; may be null for a static field
        See Also:
        readFieldValue(Field), readFieldValue(Field, Object)
      • tryToReadFieldValue

        @API(status=INTERNAL,
             since="1.4")
        public static <T> Try<Object> tryToReadFieldValue​(Class<T> clazz,
                                                          String fieldName,
                                                          T instance)
        Try to read the value of a potentially inaccessible or nonexistent field.

        If the field does not exist or an exception occurs while reading it, a failed Try is returned that contains the corresponding exception.

        Parameters:
        clazz - the class where the field is declared; never null
        fieldName - the name of the field; never null or empty
        instance - the instance from where the value is to be read; may be null for a static field
        Since:
        1.4
        See Also:
        tryToReadFieldValue(Field), tryToReadFieldValue(Field, Object)
      • readFieldValues

        public static List<Object> readFieldValues​(List<Field> fields,
                                                   Object instance)
        Read the values of the supplied fields, making each field accessible if necessary and masking any checked exception as an unchecked exception.
        Parameters:
        fields - the list of fields to read; never null
        instance - the instance from which the values are to be read; may be null for static fields
        Returns:
        an immutable list of the values of the specified fields; never null but may be empty or contain null entries
      • readFieldValues

        public static List<Object> readFieldValues​(List<Field> fields,
                                                   Object instance,
                                                   Predicate<Field> predicate)
        Read the values of the supplied fields, making each field accessible if necessary, masking any checked exception as an unchecked exception, and filtering out fields that do not pass the supplied predicate.
        Parameters:
        fields - the list of fields to read; never null
        instance - the instance from which the values are to be read; may be null for static fields
        predicate - the field filter; never null
        Returns:
        an immutable list of the values of the specified fields; never null but may be empty or contain null entries
      • tryToLoadClass

        @API(status=INTERNAL,
             since="1.4")
        public static Try<Class<?>> tryToLoadClass​(String name,
                                                   ClassLoader classLoader)
        Try to load a class by its primitive name or fully qualified name, using the supplied ClassLoader.

        See ReflectionSupport.tryToLoadClass(String) for details on support for class names for arrays.

        Parameters:
        name - the name of the class to load; never null or blank
        classLoader - the ClassLoader to use; never null
        Since:
        1.4
        See Also:
        tryToLoadClass(String)
      • getFullyQualifiedMethodName

        public static String getFullyQualifiedMethodName​(Class<?> clazz,
                                                         Method method)
        Build the fully qualified method name for the method described by the supplied class and method.

        Note that the class is not necessarily the class in which the method is declared.

        Parameters:
        clazz - the class from which the method should be referenced; never null
        method - the method; never null
        Returns:
        fully qualified method name; never null
        Since:
        1.4
        See Also:
        getFullyQualifiedMethodName(Class, String, Class...)
      • getFullyQualifiedMethodName

        public static String getFullyQualifiedMethodName​(Class<?> clazz,
                                                         String methodName,
                                                         Class<?>... parameterTypes)
        Build the fully qualified method name for the method described by the supplied class, method name, and parameter types.

        Note that the class is not necessarily the class in which the method is declared.

        Parameters:
        clazz - the class from which the method should be referenced; never null
        methodName - the name of the method; never null or blank
        parameterTypes - the parameter types of the method; may be null or empty
        Returns:
        fully qualified method name; never null
        See Also:
        getFullyQualifiedMethodName(Class, Method)
      • parseFullyQualifiedMethodName

        public static String[] parseFullyQualifiedMethodName​(String fullyQualifiedMethodName)
        Parse the supplied fully qualified method name into a 3-element String[] with the following content.
        • index 0: the fully qualified class name
        • index 1: the name of the method
        • index 2: a comma-separated list of parameter types, or a blank string if the method does not declare any formal parameters
        Parameters:
        fullyQualifiedMethodName - a fully qualified method name, never null or blank
        Returns:
        a 3-element array of strings containing the parsed values
      • getOutermostInstance

        @API(status=DEPRECATED,
             since="1.4")
        @Deprecated
        public static Optional<Object> getOutermostInstance​(Object inner,
                                                            Class<?> requiredType)
        Deprecated.
        Please discontinue use of this method since it relies on internal implementation details of the JDK that may not work in the future.
        Get the outermost instance of the required type, searching recursively through enclosing instances.

        If the supplied inner object is of the required type, it will be returned.

        Parameters:
        inner - the inner object from which to begin the search; never null
        requiredType - the required type of the outermost instance; never null
        Returns:
        an Optional containing the outermost instance; never null but potentially empty
      • getAllClasspathRootDirectories

        public static Set<Path> getAllClasspathRootDirectories()
      • findAllClassesInClasspathRoot

        public static List<Class<?>> findAllClassesInClasspathRoot​(URI root,
                                                                   ClassFilter classFilter)
        Since:
        1.1
      • findAllClassesInPackage

        public static List<Class<?>> findAllClassesInPackage​(String basePackageName,
                                                             ClassFilter classFilter)
        Since:
        1.1
      • findAllClassesInModule

        public static List<Class<?>> findAllClassesInModule​(String moduleName,
                                                            ClassFilter classFilter)
        Since:
        1.1.1
      • findConstructors

        public static List<Constructor<?>> findConstructors​(Class<?> clazz,
                                                            Predicate<Constructor<?>> predicate)
        Find all constructors in the supplied class that match the supplied predicate.

        Note that this method may return synthetic constructors. If you wish to ignore synthetic constructors, you may filter them out with the supplied predicate or filter them out of the list returned by this method.

        Parameters:
        clazz - the class in which to search for constructors; never null
        predicate - the predicate to use to test for a match; never null
        Returns:
        an immutable list of all such constructors found; never null but potentially empty
        See Also:
        Class.getDeclaredConstructors(), Class.isSynthetic()
      • isMethodPresent

        public static boolean isMethodPresent​(Class<?> clazz,
                                              Predicate<Method> predicate)
        Determine if a Method matching the supplied Predicate is present within the type hierarchy of the specified class, beginning with the specified class or interface and traversing up the type hierarchy until such a method is found or the type hierarchy is exhausted.
        Parameters:
        clazz - the class or interface in which to find the method; never null
        predicate - the predicate to use to test for a match; never null
        Returns:
        true if such a method is present
        See Also:
        findMethod(Class, String, String), findMethod(Class, String, Class...)
      • tryToGetMethod

        @API(status=INTERNAL,
             since="1.4")
        public static Try<Method> tryToGetMethod​(Class<?> clazz,
                                                 String methodName,
                                                 Class<?>... parameterTypes)
        Try to get the Method in the specified class with the specified name and parameter types.

        This method delegates to Class.getMethod(String, Class...) but catches any exception thrown.

        Parameters:
        clazz - the class in which to search for the method; never null
        methodName - the name of the method to get; never null or blank
        parameterTypes - the parameter types of the method; may be null or empty
        Returns:
        a successful Try containing the method or a failed Try containing the NoSuchMethodException thrown by Class#getMethod(); never null
        Since:
        1.4
      • getRequiredMethod

        @API(status=STABLE,
             since="1.7")
        public static Method getRequiredMethod​(Class<?> clazz,
                                               String methodName,
                                               Class<?>... parameterTypes)
        Find the first Method of the supplied class or interface that meets the specified criteria, beginning with the specified class or interface and traversing up the type hierarchy until such a method is found or the type hierarchy is exhausted.

        Use this method as an alternative to findMethod(Class, String, Class...) for use cases in which the method is required to be present.

        Parameters:
        clazz - the class or interface in which to find the method; never null
        methodName - the name of the method to find; never null or empty
        parameterTypes - the types of parameters accepted by the method, if any; never null
        Returns:
        the Method found; never null
        Throws:
        JUnitException - if no method is found
        Since:
        1.7
        See Also:
        findMethod(Class, String, Class...)
      • makeAccessible

        public static <T extends AccessibleObject> T makeAccessible​(T object)
      • getAllAssignmentCompatibleClasses

        public static Set<Class<?>> getAllAssignmentCompatibleClasses​(Class<?> clazz)
        Return all classes and interfaces that can be used as assignment types for instances of the specified Class, including itself.
        Parameters:
        clazz - the Class to look up
        See Also:
        Class.isAssignableFrom(java.lang.Class<?>)