Class ReflectionSupport

java.lang.Object
org.junit.platform.commons.support.ReflectionSupport

@API(status=MAINTAINED, since="1.0") public final class ReflectionSupport extends Object
ReflectionSupport provides static utility methods for common reflection tasks — for example, scanning for classes in the class-path or module-path, loading classes, finding methods, invoking methods, etc.

TestEngine and extension authors are encouraged to use these supported methods in order to align with the behavior of the JUnit Platform.

Since:
1.0
See Also:
  • Method Details

    • loadClass

      @API(status=DEPRECATED, since="1.4") @Deprecated public static Optional<Class<?>> loadClass(String name)
      Deprecated.
      Please use tryToLoadClass(String) instead.
      Load a class by its primitive name or fully qualified name, using the default ClassLoader.

      Class names for arrays may be specified using either the JVM's internal String representation (e.g., [[I for int[][], [Ljava.lang.String; for java.lang.String[], etc.) or source code syntax (e.g., int[][], java.lang.String[], etc.).

      Parameters:
      name - the name of the class to load; never null or blank
      Returns:
      an Optional containing the loaded class; never null but potentially empty if no such class could be loaded
    • tryToLoadClass

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

      Class names for arrays may be specified using either the JVM's internal String representation (e.g., [[I for int[][], [Lava.lang.String; for java.lang.String[], etc.) or source code syntax (e.g., int[][], java.lang.String[], etc.).

      Parameters:
      name - the name of the class to load; never null or blank
      Returns:
      a successful Try containing the loaded class or a failed Try containing the exception if no such class could be loaded; never null
      Since:
      1.4
    • findAllClassesInClasspathRoot

      public static List<Class<?>> findAllClassesInClasspathRoot(URI root, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied classpath root that match the specified classFilter and classNameFilter predicates.

      The classpath scanning algorithm searches recursively in subpackages beginning with the root of the classpath.

      Parameters:
      root - the URI for the classpath root in which to scan; never null
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      an immutable list of all such classes found; never null but potentially empty
      See Also:
    • streamAllClassesInClasspathRoot

      @API(status=MAINTAINED, since="1.10") public static Stream<Class<?>> streamAllClassesInClasspathRoot(URI root, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied classpath root that match the specified classFilter and classNameFilter predicates.

      The classpath scanning algorithm searches recursively in subpackages beginning with the root of the classpath.

      Parameters:
      root - the URI for the classpath root in which to scan; never null
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      a stream of all such classes found; never null but potentially empty
      Since:
      1.10
      See Also:
    • findAllClassesInPackage

      public static List<Class<?>> findAllClassesInPackage(String basePackageName, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied basePackageName that match the specified classFilter and classNameFilter predicates.

      The classpath scanning algorithm searches recursively in subpackages beginning within the supplied base package.

      Parameters:
      basePackageName - the name of the base package in which to start scanning; must not be null and must be valid in terms of Java syntax
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      an immutable list of all such classes found; never null but potentially empty
      See Also:
    • streamAllClassesInPackage

      @API(status=MAINTAINED, since="1.10") public static Stream<Class<?>> streamAllClassesInPackage(String basePackageName, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied basePackageName that match the specified classFilter and classNameFilter predicates.

      The classpath scanning algorithm searches recursively in subpackages beginning within the supplied base package.

      Parameters:
      basePackageName - the name of the base package in which to start scanning; must not be null and must be valid in terms of Java syntax
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      a stream of all such classes found; never null but potentially empty
      Since:
      1.10
      See Also:
    • findAllClassesInModule

      public static List<Class<?>> findAllClassesInModule(String moduleName, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied moduleName that match the specified classFilter and classNameFilter predicates.

      The module-path scanning algorithm searches recursively in all packages contained in the module.

      Parameters:
      moduleName - the name of the module to scan; never null or empty
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      an immutable list of all such classes found; never null but potentially empty
      Since:
      1.1.1
      See Also:
    • streamAllClassesInModule

      @API(status=MAINTAINED, since="1.10") public static Stream<Class<?>> streamAllClassesInModule(String moduleName, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter)
      Find all classes in the supplied moduleName that match the specified classFilter and classNameFilter predicates.

      The module-path scanning algorithm searches recursively in all packages contained in the module.

      Parameters:
      moduleName - the name of the module to scan; never null or empty
      classFilter - the class type filter; never null
      classNameFilter - the class name filter; never null
      Returns:
      a stream of all such classes found; never null but potentially empty
      Since:
      1.10
      See Also:
    • newInstance

      public static <T> T newInstance(Class<T> clazz, Object... args)
      Create a new instance of the specified Class by invoking the constructor whose argument list matches the types of the supplied arguments.

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

      Parameters:
      clazz - the class to instantiate; never null
      args - the arguments to pass to the constructor, none of which may be null
      Returns:
      the new instance; never null
      See Also:
    • invokeMethod

      public static Object invokeMethod(Method method, Object target, Object... args)
      Invoke the supplied method, making it accessible if necessary and masking any checked exception as an unchecked exception.
      Parameters:
      method - the method to invoke; never null
      target - the object on which to invoke the method; may be null if the method is static
      args - the arguments to pass to the method
      Returns:
      the value returned by the method invocation or null if the return type is void
      See Also:
    • findFields

      @API(status=MAINTAINED, since="1.4") public static List<Field> findFields(Class<?> clazz, Predicate<Field> predicate, HierarchyTraversalMode traversalMode)
      Find all fields of the supplied class or interface that match the specified predicate.

      Fields declared in the same class or interface will be ordered using an algorithm that is deterministic but intentionally nonobvious.

      The results will not contain fields that are hidden or synthetic.

      Parameters:
      clazz - the class or interface in which to find the fields; never null
      predicate - the field filter; never null
      traversalMode - the hierarchy traversal mode; never null
      Returns:
      an immutable list of all such fields found; never null but potentially empty
      Since:
      1.4
    • streamFields

      @API(status=MAINTAINED, since="1.10") public static Stream<Field> streamFields(Class<?> clazz, Predicate<Field> predicate, HierarchyTraversalMode traversalMode)
      Find all fields of the supplied class or interface that match the specified predicate.

      Fields declared in the same class or interface will be ordered using an algorithm that is deterministic but intentionally nonobvious.

      The results will not contain fields that are hidden or synthetic.

      Parameters:
      clazz - the class or interface in which to find the fields; never null
      predicate - the field filter; never null
      traversalMode - the hierarchy traversal mode; never null
      Returns:
      a stream of all such fields found; never null but potentially empty
      Since:
      1.10
    • tryToReadFieldValue

      @API(status=MAINTAINED, since="1.4") public static Try<Object> tryToReadFieldValue(Field field, Object instance)
      Try to read the value of a potentially inaccessible field.

      If an exception occurs while reading the field, a failed Try is returned that contains the corresponding exception.

      Parameters:
      field - the field to read; never null
      instance - the instance from which the value is to be read; may be null for a static field
      Since:
      1.4
    • findMethod

      public static Optional<Method> findMethod(Class<?> clazz, String methodName, String parameterTypeNames)
      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.

      The algorithm does not search for methods in Object.

      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
      parameterTypeNames - the fully qualified names of the types of parameters accepted by the method, if any, provided as a comma-separated list
      Returns:
      an Optional containing the method found; never null but potentially empty if no such method could be found
      See Also:
    • findMethod

      public static Optional<Method> findMethod(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.

      The algorithm does not search for methods in Object.

      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:
      an Optional containing the method found; never null but potentially empty if no such method could be found
      See Also:
    • findMethods

      public static List<Method> findMethods(Class<?> clazz, Predicate<Method> predicate, HierarchyTraversalMode traversalMode)
      Find all distinct methods of the supplied class or interface that match the specified predicate.

      The results will not contain instance methods that are overridden or static methods that are hidden.

      If you are looking for methods annotated with a certain annotation type, consider using AnnotationSupport.findAnnotatedMethods(Class, Class, HierarchyTraversalMode).

      Parameters:
      clazz - the class or interface in which to find the methods; never null
      predicate - the method filter; never null
      traversalMode - the hierarchy traversal mode; never null
      Returns:
      an immutable list of all such methods found; never null but potentially empty
    • streamMethods

      @API(status=MAINTAINED, since="1.10") public static Stream<Method> streamMethods(Class<?> clazz, Predicate<Method> predicate, HierarchyTraversalMode traversalMode)
      Find all distinct methods of the supplied class or interface that match the specified predicate.

      The results will not contain instance methods that are overridden or static methods that are hidden.

      If you are looking for methods annotated with a certain annotation type, consider using AnnotationSupport.findAnnotatedMethods(Class, Class, HierarchyTraversalMode).

      Parameters:
      clazz - the class or interface in which to find the methods; never null
      predicate - the method filter; never null
      traversalMode - the hierarchy traversal mode; never null
      Returns:
      a stream of all such methods found; never null but potentially empty
      Since:
      1.10
    • findNestedClasses

      public static List<Class<?>> findNestedClasses(Class<?> clazz, Predicate<Class<?>> predicate) throws JUnitException
      Find all nested classes within the supplied class, or inherited by the supplied class, that conform to the supplied predicate.

      This method does not search for nested classes recursively.

      As of JUnit Platform 1.6, this method detects cycles in inner class hierarchies — from the supplied class up to the outermost enclosing class — and throws a JUnitException if such a cycle is detected. Cycles within inner class hierarchies below the supplied class are not detected by this method.

      Parameters:
      clazz - the class to be searched; never null
      predicate - the predicate against which the list of nested classes is checked; never null
      Returns:
      an immutable list of all such classes found; never null but potentially empty
      Throws:
      JUnitException - if a cycle is detected within an inner class hierarchy
    • streamNestedClasses

      @API(status=MAINTAINED, since="1.10") public static Stream<Class<?>> streamNestedClasses(Class<?> clazz, Predicate<Class<?>> predicate) throws JUnitException
      Find all nested classes within the supplied class, or inherited by the supplied class, that conform to the supplied predicate.

      This method does not search for nested classes recursively.

      As of JUnit Platform 1.6, this method detects cycles in inner class hierarchies — from the supplied class up to the outermost enclosing class — and throws a JUnitException if such a cycle is detected. Cycles within inner class hierarchies below the supplied class are not detected by this method.

      Parameters:
      clazz - the class to be searched; never null
      predicate - the predicate against which the list of nested classes is checked; never null
      Returns:
      a stream of all such classes found; never null but potentially empty
      Throws:
      JUnitException - if a cycle is detected within an inner class hierarchy
      Since:
      1.10