322 lines
16 KiB
Java
322 lines
16 KiB
Java
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang.invoke;
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import java.lang.reflect.*;
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import java.util.*;
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import java.lang.invoke.MethodHandleNatives.Constants;
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import java.lang.invoke.MethodHandles.Lookup;
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import static java.lang.invoke.MethodHandleStatics.*;
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/**
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* A symbolic reference obtained by cracking a direct method handle
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* into its consitutent symbolic parts.
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* To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}.
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* <h1><a name="directmh"></a>Direct Method Handles</h1>
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* A <em>direct method handle</em> represents a method, constructor, or field without
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* any intervening argument bindings or other transformations.
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* The method, constructor, or field referred to by a direct method handle is called
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* its <em>underlying member</em>.
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* Direct method handles may be obtained in any of these ways:
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* <ul>
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* <li>By executing an {@code ldc} instruction on a {@code CONSTANT_MethodHandle} constant.
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* (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
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* <li>By calling one of the <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>,
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* such as {@link Lookup#findVirtual Lookup.findVirtual},
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* to resolve a symbolic reference into a method handle.
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* A symbolic reference consists of a class, name string, and type.
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* <li>By calling the factory method {@link Lookup#unreflect Lookup.unreflect}
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* or {@link Lookup#unreflectSpecial Lookup.unreflectSpecial}
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* to convert a {@link Method} into a method handle.
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* <li>By calling the factory method {@link Lookup#unreflectConstructor Lookup.unreflectConstructor}
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* to convert a {@link Constructor} into a method handle.
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* <li>By calling the factory method {@link Lookup#unreflectGetter Lookup.unreflectGetter}
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* or {@link Lookup#unreflectSetter Lookup.unreflectSetter}
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* to convert a {@link Field} into a method handle.
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* </ul>
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*
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* <h1>Restrictions on Cracking</h1>
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* Given a suitable {@code Lookup} object, it is possible to crack any direct method handle
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* to recover a symbolic reference for the underlying method, constructor, or field.
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* Cracking must be done via a {@code Lookup} object equivalent to that which created
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* the target method handle, or which has enough access permissions to recreate
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* an equivalent method handle.
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* <p>
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* If the underlying method is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>,
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* the direct method handle will have been "bound" to a particular caller class, the
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* {@linkplain java.lang.invoke.MethodHandles.Lookup#lookupClass() lookup class}
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* of the lookup object used to create it.
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* Cracking this method handle with a different lookup class will fail
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* even if the underlying method is public (like {@code Class.forName}).
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* <p>
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* The requirement of lookup object matching provides a "fast fail" behavior
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* for programs which may otherwise trust erroneous revelation of a method
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* handle with symbolic information (or caller binding) from an unexpected scope.
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* Use {@link java.lang.invoke.MethodHandles#reflectAs} to override this limitation.
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*
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* <h1><a name="refkinds"></a>Reference kinds</h1>
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* The <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>
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* correspond to all major use cases for methods, constructors, and fields.
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* These use cases may be distinguished using small integers as follows:
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* <table border=1 cellpadding=5 summary="reference kinds">
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* <tr><th>reference kind</th><th>descriptive name</th><th>scope</th><th>member</th><th>behavior</th></tr>
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* <tr>
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* <td>{@code 1}</td><td>{@code REF_getField}</td><td>{@code class}</td>
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* <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
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* </tr>
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* <tr>
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* <td>{@code 2}</td><td>{@code REF_getStatic}</td><td>{@code class} or {@code interface}</td>
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* <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
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* </tr>
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* <tr>
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* <td>{@code 3}</td><td>{@code REF_putField}</td><td>{@code class}</td>
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* <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
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* </tr>
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* <tr>
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* <td>{@code 4}</td><td>{@code REF_putStatic}</td><td>{@code class}</td>
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* <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
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* </tr>
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* <tr>
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* <td>{@code 5}</td><td>{@code REF_invokeVirtual}</td><td>{@code class}</td>
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* <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
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* </tr>
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* <tr>
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* <td>{@code 6}</td><td>{@code REF_invokeStatic}</td><td>{@code class} or {@code interface}</td>
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* <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
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* </tr>
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* <tr>
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* <td>{@code 7}</td><td>{@code REF_invokeSpecial}</td><td>{@code class} or {@code interface}</td>
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* <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
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* </tr>
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* <tr>
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* <td>{@code 8}</td><td>{@code REF_newInvokeSpecial}</td><td>{@code class}</td>
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* <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
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* </tr>
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* <tr>
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* <td>{@code 9}</td><td>{@code REF_invokeInterface}</td><td>{@code interface}</td>
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* <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
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* </tr>
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* </table>
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* @since 1.8
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*/
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public
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interface MethodHandleInfo {
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/**
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* A direct method handle reference kind,
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* as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
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*/
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public static final int
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REF_getField = Constants.REF_getField,
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REF_getStatic = Constants.REF_getStatic,
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REF_putField = Constants.REF_putField,
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REF_putStatic = Constants.REF_putStatic,
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REF_invokeVirtual = Constants.REF_invokeVirtual,
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REF_invokeStatic = Constants.REF_invokeStatic,
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REF_invokeSpecial = Constants.REF_invokeSpecial,
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REF_newInvokeSpecial = Constants.REF_newInvokeSpecial,
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REF_invokeInterface = Constants.REF_invokeInterface;
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/**
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* Returns the reference kind of the cracked method handle, which in turn
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* determines whether the method handle's underlying member was a constructor, method, or field.
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* See the <a href="MethodHandleInfo.html#refkinds">table above</a> for definitions.
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* @return the integer code for the kind of reference used to access the underlying member
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*/
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public int getReferenceKind();
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/**
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* Returns the class in which the cracked method handle's underlying member was defined.
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* @return the declaring class of the underlying member
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*/
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public Class<?> getDeclaringClass();
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/**
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* Returns the name of the cracked method handle's underlying member.
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* This is {@code "<init>"} if the underlying member was a constructor,
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* else it is a simple method name or field name.
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* @return the simple name of the underlying member
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*/
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public String getName();
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/**
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* Returns the nominal type of the cracked symbolic reference, expressed as a method type.
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* If the reference is to a constructor, the return type will be {@code void}.
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* If it is to a non-static method, the method type will not mention the {@code this} parameter.
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* If it is to a field and the requested access is to read the field,
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* the method type will have no parameters and return the field type.
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* If it is to a field and the requested access is to write the field,
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* the method type will have one parameter of the field type and return {@code void}.
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* <p>
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* Note that original direct method handle may include a leading {@code this} parameter,
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* or (in the case of a constructor) will replace the {@code void} return type
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* with the constructed class.
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* The nominal type does not include any {@code this} parameter,
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* and (in the case of a constructor) will return {@code void}.
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* @return the type of the underlying member, expressed as a method type
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*/
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public MethodType getMethodType();
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// Utility methods.
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// NOTE: class/name/type and reference kind constitute a symbolic reference
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// member and modifiers are an add-on, derived from Core Reflection (or the equivalent)
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/**
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* Reflects the underlying member as a method, constructor, or field object.
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* If the underlying member is public, it is reflected as if by
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* {@code getMethod}, {@code getConstructor}, or {@code getField}.
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* Otherwise, it is reflected as if by
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* {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}.
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* The underlying member must be accessible to the given lookup object.
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* @param <T> the desired type of the result, either {@link Member} or a subtype
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* @param expected a class object representing the desired result type {@code T}
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* @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges
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* @return a reference to the method, constructor, or field object
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* @exception ClassCastException if the member is not of the expected type
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* @exception NullPointerException if either argument is {@code null}
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* @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object
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*/
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public <T extends Member> T reflectAs(Class<T> expected, Lookup lookup);
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/**
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* Returns the access modifiers of the underlying member.
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* @return the Java language modifiers for underlying member,
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* or -1 if the member cannot be accessed
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* @see Modifier
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* @see #reflectAs
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*/
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public int getModifiers();
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/**
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* Determines if the underlying member was a variable arity method or constructor.
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* Such members are represented by method handles that are varargs collectors.
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* @implSpec
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* This produces a result equivalent to:
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* <pre>{@code
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* getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
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* }</pre>
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*
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*
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* @return {@code true} if and only if the underlying member was declared with variable arity.
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*/
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// spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector
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public default boolean isVarArgs() {
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// fields are never varargs:
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if (MethodHandleNatives.refKindIsField((byte) getReferenceKind()))
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return false;
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// not in the public API: Modifier.VARARGS
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final int ACC_VARARGS = 0x00000080; // from JVMS 4.6 (Table 4.20)
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assert(ACC_VARARGS == Modifier.TRANSIENT);
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return Modifier.isTransient(getModifiers());
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}
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/**
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* Returns the descriptive name of the given reference kind,
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* as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
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* The conventional prefix "REF_" is omitted.
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* @param referenceKind an integer code for a kind of reference used to access a class member
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* @return a mixed-case string such as {@code "getField"}
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* @exception IllegalArgumentException if the argument is not a valid
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* <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
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*/
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public static String referenceKindToString(int referenceKind) {
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if (!MethodHandleNatives.refKindIsValid(referenceKind))
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throw newIllegalArgumentException("invalid reference kind", referenceKind);
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return MethodHandleNatives.refKindName((byte)referenceKind);
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}
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/**
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* Returns a string representation for a {@code MethodHandleInfo},
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* given the four parts of its symbolic reference.
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* This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the
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* {@linkplain #referenceKindToString reference kind string} for {@code kind},
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* {@code C} is the {@linkplain java.lang.Class#getName name} of {@code defc}
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* {@code N} is the {@code name}, and
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* {@code MT} is the {@code type}.
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* These four values may be obtained from the
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* {@linkplain #getReferenceKind reference kind},
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* {@linkplain #getDeclaringClass declaring class},
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* {@linkplain #getName member name},
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* and {@linkplain #getMethodType method type}
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* of a {@code MethodHandleInfo} object.
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*
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* @implSpec
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* This produces a result equivalent to:
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* <pre>{@code
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* String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
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* }</pre>
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*
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* @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference
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* @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference
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* @param name the {@linkplain #getName member name} part of the symbolic reference
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* @param type the {@linkplain #getMethodType method type} part of the symbolic reference
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* @return a string of the form {@code "RK C.N:MT"}
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* @exception IllegalArgumentException if the first argument is not a valid
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* <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
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* @exception NullPointerException if any reference argument is {@code null}
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*/
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public static String toString(int kind, Class<?> defc, String name, MethodType type) {
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Objects.requireNonNull(name); Objects.requireNonNull(type);
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return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type);
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}
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// BEGIN Android-added: refKind...() methods needed for API compatibility with 26.
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// These methods were accidentally added into the public API in API level. They are now
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// deprecated as a prelude to being removed from the public API.
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/**
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* @deprecated This internal method was accidentally added to API 26 and must not be used. No
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* replacement is available but it is possible to replicate using information from
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* the <a href="MethodHandleInfo.html#refkinds">table above</a>, e.g.
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* {@code refKind >= 1 && refKind <= 9}. There are no guarantees that this logic
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* will work if future versions extend the table.
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*/
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@Deprecated
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static boolean refKindIsValid(int refKind) {
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return MethodHandleNatives.refKindIsValid(refKind);
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}
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/**
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* @deprecated This internal method was accidentally added to API 26 and must not be used. No
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* replacement is available but it is possible to replicate using information from
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* the <a href="MethodHandleInfo.html#refkinds">table above</a>, e.g.
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* {@code refKind >= 1 && refKind <= 4}. There are no guarantees that this logic
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* will work if future versions extend the table.
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*/
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@Deprecated
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static boolean refKindIsField(int refKind) {
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return MethodHandleNatives.refKindIsField((byte) refKind);
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}
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/**
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* @deprecated This internal method was accidentally added to API 26 and must not be used. Use
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* {@link MethodHandleInfo#referenceKindToString(int)} instead.
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*/
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@Deprecated
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static String refKindName(int refKind) {
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return MethodHandleNatives.refKindName((byte) refKind);
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}
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// END Android-added: refKind...() methods needed for API compatibility with 26.
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}
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