Package com.google.common.reflect

Class Invokable<T,​R>

  • Type Parameters:
    T - the type that owns this method or constructor.
    R - the return type of (or supertype thereof) the method or the declaring type of the constructor.
    All Implemented Interfaces:
    AnnotatedElement, GenericDeclaration, Member
    @Beta
public abstract class Invokable<T,​R>
extends AccessibleObject
implements GenericDeclaration
    Wrapper around either a Method or a Constructor. Convenience API is provided to make common reflective operation easier to deal with, such as isPublic(), getParameters() etc.

    In addition to convenience methods, TypeToken.method(java.lang.reflect.Method) and TypeToken.constructor(java.lang.reflect.Constructor<?>) will resolve the type parameters of the method or constructor in the context of the owner type, which may be a subtype of the declaring class. For example: 

    
 Method getMethod = List.class.getMethod("get", int.class);
 Invokable<List<String>, ?> invokable = new TypeToken<List<String>>() {}.method(getMethod);
 assertEquals(TypeToken.of(String.class), invokable.getReturnType()); // Not Object.class!
 assertEquals(new TypeToken<List<String>>() {}, invokable.getOwnerType());
    Since:
    14.0
    Author:
    Ben Yu

    • Method Detail

      • isOverridable

        public abstract boolean isOverridable()
        Returns true if this is an overridable method. Constructors, private, static or final methods, or methods declared by final classes are not overridable.

      • isVarArgs

        public abstract boolean isVarArgs()
        Returns true if this was declared to take a variable number of arguments.

      • invoke

        @CanIgnoreReturnValue
public final R invoke​(@Nullable T receiver,
                      Object... args)
               throws InvocationTargetException,
                      IllegalAccessException
        Invokes with receiver as 'this' and args passed to the underlying method and returns the return value; or calls the underlying constructor with args and returns the constructed instance.
        Throws:
        IllegalAccessException - if this Constructor object enforces Java language access control and the underlying method or constructor is inaccessible.
        IllegalArgumentException - if the number of actual and formal parameters differ; if an unwrapping conversion for primitive arguments fails; or if, after possible unwrapping, a parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion.
        InvocationTargetException - if the underlying method or constructor throws an exception.

      • returning

        public final <R1 extends R> Invokable<T,​R1> returning​(Class<R1> returnType)
        Explicitly specifies the return type of this Invokable. For example: 
        
 Method factoryMethod = Person.class.getMethod("create");
 Invokable<?, Person> factory = Invokable.of(getNameMethod).returning(Person.class);

      • returning

        public final <R1 extends R> Invokable<T,​R1> returning​(TypeToken<R1> returnType)
        Explicitly specifies the return type of this Invokable.

      • getDeclaringClass

        public final Class<? super T> getDeclaringClass()
        Description copied from interface: java.lang.reflect.Member
        Returns the Class object representing the class or interface that declares the member or constructor represented by this Member.
        Specified by:
        getDeclaringClass in interface Member
        Returns:
        an object representing the declaring class of the underlying member

      • isAnnotationPresent

        public final boolean isAnnotationPresent​(Class<? extends Annotation> annotationClass)
        Description copied from class: java.lang.reflect.AccessibleObject
        Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.

        The truth value returned by this method is equivalent to: getAnnotation(annotationClass) != null

        The body of the default method is specified to be the code above.

        Specified by:
        isAnnotationPresent in interface AnnotatedElement
        Overrides:
        isAnnotationPresent in class AccessibleObject
        Parameters:
        annotationClass - the Class object corresponding to the annotation type
        Returns:
        true if an annotation for the specified annotation type is present on this element, else false

      • getAnnotation

        public final <A extends Annotation> A getAnnotation​(Class<A> annotationClass)
        Description copied from interface: java.lang.reflect.AnnotatedElement
        Returns this element's annotation for the specified type if such an annotation is present, else null.
        Specified by:
        getAnnotation in interface AnnotatedElement
        Overrides:
        getAnnotation in class AccessibleObject
        Type Parameters:
        A - the type of the annotation to query for and return if present
        Parameters:
        annotationClass - the Class object corresponding to the annotation type
        Returns:
        this element's annotation for the specified annotation type if present on this element, else null

      • getAnnotations

        public final Annotation[] getAnnotations()
        Description copied from interface: java.lang.reflect.AnnotatedElement
        Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
        Specified by:
        getAnnotations in interface AnnotatedElement
        Overrides:
        getAnnotations in class AccessibleObject
        Returns:
        annotations present on this element

      • getDeclaredAnnotations

        public final Annotation[] getDeclaredAnnotations()
        Description copied from interface: java.lang.reflect.AnnotatedElement
        Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
        Specified by:
        getDeclaredAnnotations in interface AnnotatedElement
        Overrides:
        getDeclaredAnnotations in class AccessibleObject
        Returns:
        annotations directly present on this element

      • setAccessible

        public final void setAccessible​(boolean flag)
                         throws SecurityException
        Description copied from class: java.lang.reflect.AccessibleObject
        Set the accessible flag for this reflected object to the indicated boolean value. A value of true indicates that the reflected object should suppress checks for Java language access control when it is used. A value of false indicates that the reflected object should enforce checks for Java language access control when it is used, with the variation noted in the class description.

        This method may be used by a caller in class C to enable access to a member of declaring class D if any of the following hold:

        • C and D are in the same module.
        • The member is public and D is public in a package that the module containing D exports to at least the module containing C.
        • The member is protected static, D is public in a package that the module containing D exports to at least the module containing C, and C is a subclass of D.
        • D is in a package that the module containing D opens to at least the module containing C. All packages in unnamed and open modules are open to all modules and so this method always succeeds when D is in an unnamed or open module.

        This method cannot be used to enable access to private members, members with default (package) access, protected instance members, or protected constructors when the declaring class is in a different module to the caller and the package containing the declaring class is not open to the caller's module.

        If there is a security manager, its checkPermission method is first called with a ReflectPermission("suppressAccessChecks") permission.

        Overrides:
        setAccessible in class AccessibleObject
        Parameters:
        flag - the new value for the accessible flag
        Throws:
        SecurityException - if the request is denied by the security manager
        See Also:
        AccessibleObject.trySetAccessible(), MethodHandles.privateLookupIn(java.lang.Class<?>, java.lang.invoke.MethodHandles.Lookup)

      • getName

        public final String getName()
        Description copied from interface: java.lang.reflect.Member
        Returns the simple name of the underlying member or constructor represented by this Member.
        Specified by:
        getName in interface Member
        Returns:
        the simple name of the underlying member

      • getModifiers

        public final int getModifiers()
        Description copied from interface: java.lang.reflect.Member
        Returns the Java language modifiers for the member or constructor represented by this Member, as an integer. The Modifier class should be used to decode the modifiers in the integer.
        Specified by:
        getModifiers in interface Member
        Returns:
        the Java language modifiers for the underlying member
        See Also:
        Modifier

      • isSynthetic

        public final boolean isSynthetic()
        Description copied from interface: java.lang.reflect.Member
        Returns true if this member was introduced by the compiler; returns false otherwise.
        Specified by:
        isSynthetic in interface Member
        Returns:
        true if and only if this member was introduced by the compiler.

      • isPublic

        public final boolean isPublic()
        Returns true if the element is public.

      • isProtected

        public final boolean isProtected()
        Returns true if the element is protected.

      • isPackagePrivate

        public final boolean isPackagePrivate()
        Returns true if the element is package-private.

      • isPrivate

        public final boolean isPrivate()
        Returns true if the element is private.

      • isStatic

        public final boolean isStatic()
        Returns true if the element is static.

      • isFinal

        public final boolean isFinal()
        Returns true if this method is final, per Modifier.isFinal(getModifiers()).

        Note that a method may still be effectively "final", or non-overridable when it has no final keyword. For example, it could be private, or it could be declared by a final class. To tell whether a method is overridable, use isOverridable().

      • isAbstract

        public final boolean isAbstract()
        Returns true if the method is abstract.

      • isNative

        public final boolean isNative()
        Returns true if the element is native.

      • isSynchronized

        public final boolean isSynchronized()
        Returns true if the method is synchronized.

      • equals

        public boolean equals​(@Nullable Object obj)
        Description copied from class: java.lang.Object
        Indicates whether some other object is "equal to" this one.

        The equals method implements an equivalence relation on non-null object references:

        • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
        • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
        • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
        • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
        • For any non-null reference value x, x.equals(null) should return false.

        The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

        Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

        Overrides:
        equals in class Object
        Parameters:
        obj - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • hashCode

        public int hashCode()
        Description copied from class: java.lang.Object
        Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

        The general contract of hashCode is:

        • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
        • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
        • It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

        As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

        Overrides:
        hashCode in class Object
        Returns:
        a hash code value for this object.
        See Also:
        Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

      • toString

        public String toString()
        Description copied from class: java.lang.Object
        Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

        The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of: 

         getClass().getName() + '@' + Integer.toHexString(hashCode())
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.