The AccessibleObject class is the base class for Field, Method and
Constructor objects.  It provides the ability to flag a reflected
object as suppressing default Java language access control checks
when it is used.  The access checks--for public, default (package)
access, protected, and private members--are performed when Fields,
Methods or Constructors are used to set or get fields, to invoke
methods, or to create and initialize new instances of classes,
respectively.

Setting the accessible flag in a reflected object
permits sophisticated applications with sufficient privilege, such
as Java Object Serialization or other persistence mechanisms, to
manipulate objects in a manner that would normally be prohibited.

By default, a reflected object is not accessible.

AnnotatedArrayType represents the potentially annotated use of an
array type, whose component type may itself represent the annotated use of a
type.

Represents an annotated element of the program currently running in this
VM.  This interface allows annotations to be read reflectively.  All
annotations returned by methods in this interface are immutable and
serializable. The arrays returned by methods of this interface may be modified
by callers without affecting the arrays returned to other callers.

The getAnnotationsByType(Class) and getDeclaredAnnotationsByType(Class) methods support multiple
annotations of the same type on an element. If the argument to
either method is a repeatable annotation type (JLS 9.6), then the
method will "look through" a container annotation (JLS 9.7), if
present, and return any annotations inside the container. Container
annotations may be generated at compile-time to wrap multiple
annotations of the argument type.

The terms directly present, indirectly present,
present, and associated are used throughout this
interface to describe precisely which annotations are returned by
methods:



 An annotation A is directly present on an
element E if E has a RuntimeVisibleAnnotations or RuntimeVisibleParameterAnnotations or RuntimeVisibleTypeAnnotations attribute, and the attribute
contains A.

An annotation A is indirectly present on an
element E if E has a RuntimeVisibleAnnotations or
RuntimeVisibleParameterAnnotations or RuntimeVisibleTypeAnnotations
attribute, and A 's type is repeatable, and the attribute contains
exactly one annotation whose value element contains A and whose
type is the containing annotation type of A 's type.

An annotation A is present on an element E if either:



A is directly present on E; or

No annotation of A 's type is directly present on
E, and E is a class, and A 's type is
inheritable, and A is present on the superclass of E.



An annotation A is associated with an element E
if either:



A is directly or indirectly present on E; or

No annotation of A 's type is directly or indirectly
present on E, and E is a class, and A's type
is inheritable, and A is associated with the superclass of
E.





The table below summarizes which kind of annotation presence
different methods in this interface examine.


Overview of kind of presence detected by different AnnotatedElement methods
Kind of Presence
MethodDirectly PresentIndirectly PresentPresentAssociated
TgetAnnotation(Class<T>)
X

Annotation[]getAnnotations()
X

T[]getAnnotationsByType(Class<T>)
X

TgetDeclaredAnnotation(Class<T>)
X

Annotation[]getDeclaredAnnotations()
X

T[]getDeclaredAnnotationsByType(Class<T>)
XX



For an invocation of get[Declared]AnnotationsByType( Class <
T >), the order of annotations which are directly or indirectly
present on an element E is computed as if indirectly present
annotations on E are directly present on E in place
of their container annotation, in the order in which they appear in
the value element of the container annotation.

There are several compatibility concerns to keep in mind if an
annotation type T is originally not repeatable and
later modified to be repeatable.

The containing annotation type for T is TC.



Modifying T to be repeatable is source and binary
compatible with existing uses of T and with existing uses
of TC.

That is, for source compatibility, source code with annotations of
type T or of type TC will still compile. For binary
compatibility, class files with annotations of type T or of
type TC (or with other kinds of uses of type T or of
type TC) will link against the modified version of T
if they linked against the earlier version.

(An annotation type TC may informally serve as an acting
containing annotation type before T is modified to be
formally repeatable. Alternatively, when T is made
repeatable, TC can be introduced as a new type.)

If an annotation type TC is present on an element, and
T is modified to be repeatable with TC as its
containing annotation type then:



The change to T is behaviorally compatible with respect
to the get[Declared]Annotation(Class<T>) (called with an
argument of T or TC) and get[Declared]Annotations() methods because the results of the
methods will not change due to TC becoming the containing
annotation type for T.

The change to T changes the results of the get[Declared]AnnotationsByType(Class<T>) methods called with an
argument of T, because those methods will now recognize an
annotation of type TC as a container annotation for T
and will "look through" it to expose annotations of type T.



If an annotation of type T is present on an
element and T is made repeatable and more annotations of
type T are added to the element:



 The addition of the annotations of type T is both
source compatible and binary compatible.

The addition of the annotations of type T changes the results
of the get[Declared]Annotation(Class<T>) methods and get[Declared]Annotations() methods, because those methods will now
only see a container annotation on the element and not see an
annotation of type T.

The addition of the annotations of type T changes the
results of the get[Declared]AnnotationsByType(Class<T>)
methods, because their results will expose the additional
annotations of type T whereas previously they exposed only a
single annotation of type T.





If an annotation returned by a method in this interface contains
(directly or indirectly) a Class-valued member referring to
a class that is not accessible in this VM, attempting to read the class
by calling the relevant Class-returning method on the returned annotation
will result in a TypeNotPresentException.

Similarly, attempting to read an enum-valued member will result in
a EnumConstantNotPresentException if the enum constant in the
annotation is no longer present in the enum type.

If an annotation type T is (meta-)annotated with an
@Repeatable annotation whose value element indicates a type
TC, but TC does not declare a value() method
with a return type of T[], then an exception of type
AnnotationFormatError is thrown.

Finally, attempting to read a member whose definition has evolved
incompatibly will result in a AnnotationTypeMismatchException or an
IncompleteAnnotationException.

AnnotatedParameterizedType represents the potentially annotated use
of a parameterized type, whose type arguments may themselves represent
annotated uses of types.

AnnotatedType represents the potentially annotated use of a type in
the program currently running in this VM. The use may be of any type in the
Java programming language, including an array type, a parameterized type, a
type variable, or a wildcard type.

AnnotatedTypeVariable represents the potentially annotated use of a
type variable, whose declaration may have bounds which themselves represent
annotated uses of types.

AnnotatedWildcardType represents the potentially annotated use of a
wildcard type argument, whose upper or lower bounds may themselves represent
annotated uses of types.

The Array class provides static methods to dynamically create and
access Java arrays.

Array permits widening conversions to occur during a get or set
operation, but throws an IllegalArgumentException if a narrowing
conversion would occur.

Constructor provides information about, and access to, a single
constructor for a class.

Constructor permits widening conversions to occur when matching the
actual parameters to newInstance() with the underlying
constructor's formal parameters, but throws an
IllegalArgumentException if a narrowing conversion would occur.

A shared superclass for the common functionality of Method
and Constructor.

A Field provides information about, and dynamic access to, a
single field of a class or an interface.  The reflected field may
be a class (static) field or an instance field.

A Field permits widening conversions to occur during a get or
set access operation, but throws an IllegalArgumentException if a
narrowing conversion would occur.

GenericArrayType represents an array type whose component
type is either a parameterized type or a type variable.

A common interface for all entities that declare type variables.

Thrown when a syntactically malformed signature attribute is
encountered by a reflective method that needs to interpret the
generic signature information for a type, method or constructor.

InvocationHandler is the interface implemented by
the invocation handler of a proxy instance.

Each proxy instance has an associated invocation handler.
When a method is invoked on a proxy instance, the method
invocation is encoded and dispatched to the invoke
method of its invocation handler.

InvocationTargetException is a checked exception that wraps
an exception thrown by an invoked method or constructor.

As of release 1.4, this exception has been retrofitted to conform to
the general purpose exception-chaining mechanism.  The "target exception"
that is provided at construction time and accessed via the
getTargetException() method is now known as the cause,
and may be accessed via the Throwable.getCause() method,
as well as the aforementioned "legacy method."

Thrown when a semantically malformed parameterized type is
encountered by a reflective method that needs to instantiate it.
For example, if the number of type arguments to a parameterized type
is wrong.

Thrown when the
java.lang.reflect package attempts to read method parameters from
a class file and determines that one or more parameters are
malformed.

The following is a list of conditions under which this exception
can be thrown:

 The number of parameters (parameter_count) is wrong for the method
 A constant pool index is out of bounds.
 A constant pool index does not refer to a UTF-8 entry
 A parameter's name is "", or contains an illegal character
 The flags field contains an illegal flag (something other than
    FINAL, SYNTHETIC, or MANDATED)


See Executable.getParameters() for more
information.

Member is an interface that reflects identifying information about
a single member (a field or a method) or a constructor.

A Method provides information about, and access to, a single method
on a class or interface.  The reflected method may be a class method
or an instance method (including an abstract method).

A Method permits widening conversions to occur when matching the
actual parameters to invoke with the underlying method's formal
parameters, but it throws an IllegalArgumentException if a
narrowing conversion would occur.

The Modifier class provides static methods and
constants to decode class and member access modifiers.  The sets of
modifiers are represented as integers with distinct bit positions
representing different modifiers.  The values for the constants
representing the modifiers are taken from the tables in sections 4.1, 4.4, 4.5, and 4.7 of
The Java™ Virtual Machine Specification.

Information about method parameters.

A Parameter provides information about method parameters,
including its name and modifiers.  It also provides an alternate
means of obtaining attributes for the parameter.

ParameterizedType represents a parameterized type such as
Collection<String>.

A parameterized type is created the first time it is needed by a
reflective method, as specified in this package. When a
parameterized type p is created, the generic type declaration that
p instantiates is resolved, and all type arguments of p are created
recursively. See TypeVariable for details on the creation process for type
variables. Repeated creation of a parameterized type has no effect.

Instances of classes that implement this interface must implement
an equals() method that equates any two instances that share the
same generic type declaration and have equal type parameters.

InvocationHandler handler = new MyInvocationHandler(...);
Class<?> proxyClass = Proxy.getProxyClass(Foo.class.getClassLoader(), Foo.class);
Foo f = (Foo) proxyClass.getConstructor(InvocationHandler.class).
                newInstance(handler);

Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
                                     new Class<?>[] { Foo.class },
                                     handler);

 proxy instanceof Foo

 (Foo) proxy

Proxy provides static methods for creating dynamic proxy
classes and instances, and it is also the superclass of all
dynamic proxy classes created by those methods.

To create a proxy for some interface Foo:


    InvocationHandler handler = new MyInvocationHandler(...);
    Class<?> proxyClass = Proxy.getProxyClass(Foo.class.getClassLoader(), Foo.class);
    Foo f = (Foo) proxyClass.getConstructor(InvocationHandler.class).
                    newInstance(handler);
or more simply:


    Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
                                         new Class<?>[] { Foo.class },
                                         handler);

A dynamic proxy class (simply referred to as a proxy
class below) is a class that implements a list of interfaces
specified at runtime when the class is created, with behavior as
described below.

A proxy interface is such an interface that is implemented
by a proxy class.

A proxy instance is an instance of a proxy class.

Each proxy instance has an associated invocation handler
object, which implements the interface InvocationHandler.
A method invocation on a proxy instance through one of its proxy
interfaces will be dispatched to the invoke method of the instance's invocation handler, passing the proxy
instance, a java.lang.reflect.Method object identifying
the method that was invoked, and an array of type Object
containing the arguments.  The invocation handler processes the
encoded method invocation as appropriate and the result that it
returns will be returned as the result of the method invocation on
the proxy instance.

A proxy class has the following properties:


Proxy classes are public, final, and not abstract if
all proxy interfaces are public.

Proxy classes are non-public, final, and not abstract if
any of the proxy interfaces is non-public.

The unqualified name of a proxy class is unspecified.  The space
of class names that begin with the string "$Proxy"
should be, however, reserved for proxy classes.

A proxy class extends java.lang.reflect.Proxy.

A proxy class implements exactly the interfaces specified at its
creation, in the same order.

If a proxy class implements a non-public interface, then it will
be defined in the same package as that interface.  Otherwise, the
package of a proxy class is also unspecified.  Note that package
sealing will not prevent a proxy class from being successfully defined
in a particular package at runtime, and neither will classes already
defined by the same class loader and the same package with particular
signers.

Since a proxy class implements all of the interfaces specified at
its creation, invoking getInterfaces on its
Class object will return an array containing the same
list of interfaces (in the order specified at its creation), invoking
getMethods on its Class object will return
an array of Method objects that include all of the
methods in those interfaces, and invoking getMethod will
find methods in the proxy interfaces as would be expected.

The Proxy.isProxyClass method will
return true if it is passed a proxy class-- a class returned by
Proxy.getProxyClass or the class of an object returned by
Proxy.newProxyInstance-- and false otherwise.

The java.security.ProtectionDomain of a proxy class
is the same as that of system classes loaded by the bootstrap class
loader, such as java.lang.Object, because the code for a
proxy class is generated by trusted system code.  This protection
domain will typically be granted
java.security.AllPermission.

Each proxy class has one public constructor that takes one argument,
an implementation of the interface InvocationHandler, to set
the invocation handler for a proxy instance.  Rather than having to use
the reflection API to access the public constructor, a proxy instance
can be also be created by calling the Proxy.newProxyInstance method, which combines the actions of calling
Proxy.getProxyClass with invoking the
constructor with an invocation handler.


A proxy instance has the following properties:


Given a proxy instance proxy and one of the
interfaces implemented by its proxy class Foo, the
following expression will return true:


     proxy instanceof Foo
and the following cast operation will succeed (rather than throwing
a ClassCastException):


     (Foo) proxy

Each proxy instance has an associated invocation handler, the one
that was passed to its constructor.  The static
Proxy.getInvocationHandler method
will return the invocation handler associated with the proxy instance
passed as its argument.

An interface method invocation on a proxy instance will be
encoded and dispatched to the invocation handler's invoke method as described in the
documentation for that method.

An invocation of the hashCode,
equals, or toString methods declared in
java.lang.Object on a proxy instance will be encoded and
dispatched to the invocation handler's invoke method in
the same manner as interface method invocations are encoded and
dispatched, as described above.  The declaring class of the
Method object passed to invoke will be
java.lang.Object.  Other public methods of a proxy
instance inherited from java.lang.Object are not
overridden by a proxy class, so invocations of those methods behave
like they do for instances of java.lang.Object.


Methods Duplicated in Multiple Proxy Interfaces

When two or more interfaces of a proxy class contain a method with
the same name and parameter signature, the order of the proxy class's
interfaces becomes significant.  When such a duplicate method
is invoked on a proxy instance, the Method object passed
to the invocation handler will not necessarily be the one whose
declaring class is assignable from the reference type of the interface
that the proxy's method was invoked through.  This limitation exists
because the corresponding method implementation in the generated proxy
class cannot determine which interface it was invoked through.
Therefore, when a duplicate method is invoked on a proxy instance,
the Method object for the method in the foremost interface
that contains the method (either directly or inherited through a
superinterface) in the proxy class's list of interfaces is passed to
the invocation handler's invoke method, regardless of the
reference type through which the method invocation occurred.

If a proxy interface contains a method with the same name and
parameter signature as the hashCode, equals,
or toString methods of java.lang.Object,
when such a method is invoked on a proxy instance, the
Method object passed to the invocation handler will have
java.lang.Object as its declaring class.  In other words,
the public, non-final methods of java.lang.Object
logically precede all of the proxy interfaces for the determination of
which Method object to pass to the invocation handler.

Note also that when a duplicate method is dispatched to an
invocation handler, the invoke method may only throw
checked exception types that are assignable to one of the exception
types in the throws clause of the method in all of
the proxy interfaces that it can be invoked through.  If the
invoke method throws a checked exception that is not
assignable to any of the exception types declared by the method in one
of the proxy interfaces that it can be invoked through, then an
unchecked UndeclaredThrowableException will be thrown by
the invocation on the proxy instance.  This restriction means that not
all of the exception types returned by invoking
getExceptionTypes on the Method object
passed to the invoke method can necessarily be thrown
successfully by the invoke method.

The Permission class for reflective operations.

The following table
provides a summary description of what the permission allows,
and discusses the risks of granting code the permission.



Permission Target Name
What the Permission Allows
Risks of Allowing this Permission



  suppressAccessChecks
  ability to suppress the standard Java language access checks
      on fields and methods in a class; allow access not only public members
      but also allow access to default (package) access, protected,
      and private members.
  This is dangerous in that information (possibly confidential) and
      methods normally unavailable would be accessible to malicious code.


  newProxyInPackage.{package name}
  ability to create a proxy instance in the specified package of which
      the non-public interface that the proxy class implements.
  This gives code access to classes in packages to which it normally
      does not have access and the dynamic proxy class is in the system
      protection domain. Malicious code may use these classes to
      help in its attempt to compromise security in the system.

Type is the common superinterface for all types in the Java
programming language. These include raw types, parameterized types,
array types, type variables and primitive types.

TypeVariable is the common superinterface for type variables of kinds.
A type variable is created the first time it is needed by a reflective
method, as specified in this package.  If a type variable t is referenced
by a type (i.e, class, interface or annotation type) T, and T is declared
by the nth enclosing class of T (see JLS 8.1.2), then the creation of t
requires the resolution (see JVMS 5) of the ith enclosing class of T,
for i = 0 to n, inclusive. Creating a type variable must not cause the
creation of its bounds. Repeated creation of a type variable has no effect.

Multiple objects may be instantiated at run-time to
represent a given type variable. Even though a type variable is
created only once, this does not imply any requirement to cache
instances representing the type variable. However, all instances
representing a type variable must be equal() to each other.
As a consequence, users of type variables must not rely on the identity
of instances of classes implementing this interface.

Thrown by a method invocation on a proxy instance if its invocation
handler's invoke method throws a
checked exception (a Throwable that is not assignable
to RuntimeException or Error) that
is not assignable to any of the exception types declared in the
throws clause of the method that was invoked on the
proxy instance and dispatched to the invocation handler.

An UndeclaredThrowableException instance contains
the undeclared checked exception that was thrown by the invocation
handler, and it can be retrieved with the
getUndeclaredThrowable() method.
UndeclaredThrowableException extends
RuntimeException, so it is an unchecked exception
that wraps a checked exception.

As of release 1.4, this exception has been retrofitted to
conform to the general purpose exception-chaining mechanism.  The
"undeclared checked exception that was thrown by the invocation
handler" that may be provided at construction time and accessed via
the getUndeclaredThrowable() method is now known as the
cause, and may be accessed via the Throwable.getCause() method, as well as the aforementioned "legacy
method."

WildcardType represents a wildcard type expression, such as
?, ? extends Number, or ? super Integer.