ReflectionUtils (JUnit 5.0.0-M4 API)

java.lang.Object
- org.junit.platform.commons.util.ReflectionUtils

```
@API(value=Internal)
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

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`ReflectionUtils.HierarchyTraversalMode` Modes in which a hierarchy can be traversed — for example, when searching for methods or fields within a class hierarchy.

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static List<Class<?>>`	`findAllClassesInClasspathRoot(Path root, Predicate<Class<?>> classTester, Predicate<String> classNameFilter)` Deprecated. Use `findAllClassesInClasspathRoot(URI, Predicate, Predicate)` instead.
`static List<Class<?>>`	`findAllClassesInClasspathRoot(URI root, Predicate<Class<?>> classTester, Predicate<String> classNameFilter)`
`static List<Class<?>>`	`findAllClassesInPackage(String basePackageName, Predicate<Class<?>> classTester, Predicate<String> classNameFilter)`
`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.
`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.
`static List<Method>`	`findMethods(Class<?> clazz, Predicate<Method> predicate)` Find all methods of the supplied class or interface that match the specified `predicate`, using top-down search semantics within the type hierarchy.
`static List<Method>`	`findMethods(Class<?> clazz, Predicate<Method> predicate, ReflectionUtils.HierarchyTraversalMode traversalMode)` Find all methods of the supplied class or interface that match the specified `predicate`.
`static List<Class<?>>`	`findNestedClasses(Class<?> clazz, Predicate<Class<?>> predicate)`
`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.
`static Set<Path>`	`getAllClasspathRootDirectories()`
`static <T> Constructor<T>`	`getDeclaredConstructor(Class<T> clazz)` Get the sole declared `Constructor` for the supplied class.
`static ClassLoader`	`getDefaultClassLoader()`
`static String`	`getFullyQualifiedMethodName(Class<?> clazz, String methodName, Class<?>... params)` Build the fully qualified name of the passed parameters.
`static Optional<Method>`	`getMethod(Class<?> clazz, String methodName, Class<?>... parameterTypes)`
`static Optional<Object>`	`getOuterInstance(Object inner, Class<?> targetType)`
`static Class<?>`	`getWrapperType(Class<?> type)` Get the wrapper type for the supplied primitive type.
`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.
`static boolean`	`isAbstract(Class<?> clazz)`
`static boolean`	`isAbstract(Member member)`
`static boolean`	`isArray(Object obj)` Determine if the supplied object is an array.
`static boolean`	`isAssignableTo(Object obj, Class<?> type)` Determine if the supplied object can be assigned to the supplied type for the purpose of reflective method invocations.
`static boolean`	`isPackage(String packageName)` Determine if the supplied package name refers to a package that is present in the classpath.
`static boolean`	`isPrivate(Class<?> clazz)`
`static boolean`	`isPrivate(Member member)`
`static boolean`	`isPublic(Class<?> clazz)`
`static boolean`	`isPublic(Member member)`
`static boolean`	`isStatic(Class<?> clazz)`
`static boolean`	`isStatic(Member member)`
`static Optional<Class<?>>`	`loadClass(String name)` Load a class by its fully qualified name.
`static Optional<Class<?>>`	`loadClass(String name, ClassLoader classLoader)` Load a class by its fully qualified name, using the supplied `ClassLoader`.
`static Optional<Method>`	`loadMethod(String fullyQualifiedMethodName)` Load a method by its fully qualified name.
`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.
`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.
`static <T> Optional<Object>`	`readFieldValue(Class<T> clazz, String fieldName, T instance)` Read the value of a potentially inaccessible field.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getDefaultClassLoader

public static ClassLoader getDefaultClassLoader()

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)

isAbstract

public static boolean isAbstract(Class<?> clazz)

isAbstract

public static boolean isAbstract(Member member)

isStatic

public static boolean isStatic(Class<?> clazz)

isStatic

public static boolean isStatic(Member member)

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

isAssignableTo
```
public static boolean isAssignableTo(Object obj,
                                     Class<?> type)
```
Determine if the supplied object can be assigned to the supplied type for the purpose of reflective method invocations.
In contrast to Class.isInstance(Object), this method returns true if the supplied type represents a primitive type whose wrapper matches the supplied object's type.
Returns true if the supplied object is null and the supplied type does not represent a primitive type.

Parameters:

obj - the object to test for assignment compatibility; potentially null

type - the type to check against; never null

Returns:

true if the object is assignment compatible

See Also:

Class.isInstance(Object), Class.isAssignableFrom(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(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

See Also:

newInstance(Constructor, Object...), ExceptionUtils.throwAsUncheckedException(Throwable)

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)

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:

ExceptionUtils.throwAsUncheckedException(Throwable)

loadClass
```
public static Optional<Class<?>> loadClass(String name)
```
Load a class by its fully qualified name.

Parameters:

name - the fully qualified name of the class to load; never null or blank

See Also:

loadClass(String, ClassLoader)

loadClass
```
public static Optional<Class<?>> loadClass(String name,
                                           ClassLoader classLoader)
```
Load a class by its fully qualified name, using the supplied ClassLoader.

Parameters:

name - the fully qualified name of the class to load; never null or blank

classLoader - the ClassLoader to use; never null

See Also:

loadClass(String)

loadMethod

public static Optional<Method> loadMethod(String fullyQualifiedMethodName)

Load a method by its fully qualified name.

The following formats are supported.

[fully qualified class name]#[methodName]
[fully qualified class name]#[methodName](parameter type list)
- The parameter type list is a comma-separated list of fully qualified class names for the types of parameters accepted by the method.

Examples

Method	Fully Qualified Method Name
`CharSequence.chars()`	`java.lang.String#chars`
`CharSequence.chars()`	`java.lang.String#chars()`
`String.equalsIgnoreCase(String)`	`java.lang.String#equalsIgnoreCase(java.lang.String)`
`String.substring(int, int)`	`java.lang.String#substring(int, int)`

Parameters:: fullyQualifiedMethodName - the fully qualified name of the method to load; never null or blank
Returns:: an Optional containing the method; never null but potentially empty

getFullyQualifiedMethodName
```
public static String getFullyQualifiedMethodName(Class<?> clazz,
                                                 String methodName,
                                                 Class<?>... params)
```
Build the fully qualified name of the passed parameters.

Parameters:

clazz - the class that declares the method; never null

methodName - the name of the method; never null

params - the parameter types of the method; may be null or empty

Returns:

fully qualified method name; never null

See Also:

loadMethod(String)

getOuterInstance

public static Optional<Object> getOuterInstance(Object inner,
                                                Class<?> targetType)

isPackage
```
public static boolean isPackage(String packageName)
```
Determine if the supplied package name refers to a package that is present in the classpath.
The default package is represented by an empty string ("").

Parameters:

packageName - the package name to check; never null and never containing whitespace only

getAllClasspathRootDirectories

public static Set<Path> getAllClasspathRootDirectories()

findAllClassesInClasspathRoot

@Deprecated
public static List<Class<?>> findAllClassesInClasspathRoot(Path root,
                                                                       Predicate<Class<?>> classTester,
                                                                       Predicate<String> classNameFilter)

Deprecated. Use findAllClassesInClasspathRoot(URI, Predicate, Predicate) instead.

findAllClassesInClasspathRoot

public static List<Class<?>> findAllClassesInClasspathRoot(URI root,
                                                           Predicate<Class<?>> classTester,
                                                           Predicate<String> classNameFilter)

See Also:: ReflectionSupport.findAllClassesInClasspathRoot(URI, Predicate, Predicate)

findAllClassesInPackage

public static List<Class<?>> findAllClassesInPackage(String basePackageName,
                                                     Predicate<Class<?>> classTester,
                                                     Predicate<String> classNameFilter)

See Also:: ReflectionSupport.findAllClassesInPackage(String, Predicate, Predicate)

findNestedClasses

public static List<Class<?>> findNestedClasses(Class<?> clazz,
                                               Predicate<Class<?>> predicate)

getDeclaredConstructor
```
public static <T> Constructor<T> getDeclaredConstructor(Class<T> clazz)
```
Get the sole declared Constructor for the supplied class.
Throws a PreconditionViolationException if the supplied class declares more than one constructor.

Parameters:

clazz - the class to get the constructor for

Returns:

the sole declared constructor; never null

See Also:

Class.getDeclaredConstructors()

getMethod

public static Optional<Method> getMethod(Class<?> clazz,
                                         String methodName,
                                         Class<?>... parameterTypes)

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.
Note, however, that the current algorithm traverses the entire type hierarchy even after having found a match.

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(Class, String, Class...), ReflectionUtils.HierarchyTraversalMode.BOTTOM_UP

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.
Note, however, that the current algorithm traverses the entire type hierarchy even after having found a match.

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:

findMethod(Class, String, String), ReflectionUtils.HierarchyTraversalMode.BOTTOM_UP

findMethods
```
public static List<Method> findMethods(Class<?> clazz,
                                       Predicate<Method> predicate)
```
Find all methods of the supplied class or interface that match the specified predicate, using top-down search semantics within the type hierarchy.

Parameters:

clazz - the class or interface in which to find the methods; never null

predicate - the method filter; never null

Returns:

an immutable list of all such methods found; never null

See Also:

ReflectionUtils.HierarchyTraversalMode.TOP_DOWN, findMethods(Class, Predicate, HierarchyTraversalMode)

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

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

See Also:

ReflectionSupport.findMethods(Class, Predicate, org.junit.platform.commons.support.HierarchyTraversalMode)

readFieldValue
```
public static <T> Optional<Object> readFieldValue(Class<T> clazz,
                                                  String fieldName,
                                                  T instance)
```
Read the value of a potentially inaccessible field.
If the field does not exist, an exception occurs while reading it, or the value of the field is null, an empty Optional is 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

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 lookup

See Also:

Class.isAssignableFrom(java.lang.Class<?>)

Class ReflectionUtils

DISCLAIMER

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

getDefaultClassLoader

isPublic

isPublic

isPrivate

isPrivate

isAbstract

isAbstract

isStatic

isStatic

isArray

isAssignableTo

getWrapperType

newInstance

newInstance

invokeMethod

loadClass

loadClass

loadMethod

Examples

getFullyQualifiedMethodName

getOuterInstance

isPackage

getAllClasspathRootDirectories

findAllClassesInClasspathRoot

findAllClassesInClasspathRoot

findAllClassesInPackage

findNestedClasses

getDeclaredConstructor

getMethod

findMethod

findMethod

findMethods

findMethods

readFieldValue

getAllAssignmentCompatibleClasses