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/*

* Copyright © 2012 The Feign Authors (feign@commonhaus.dev)

*

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

package feign;

import feign.InvocationHandlerFactory.MethodHandler;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodHandles.Lookup;

import java.lang.reflect.Constructor;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

/**

* Handles default methods by directly invoking the default method code on the interface. The bindTo

* method must be called on the result before invoke is called.

*/

final class DefaultMethodHandler implements MethodHandler {

// Uses Java 7 MethodHandle based reflection. As default methods will only exist when

// run on a Java 8 JVM this will not affect use on legacy JVMs.

// When Feign upgrades to Java 7, remove the @IgnoreJRERequirement annotation.

private final MethodHandle unboundHandle;

// handle is effectively final after bindTo has been called...

private MethodHandle handle;

public DefaultMethodHandler(Method defaultMethod) {

Class<?> declaringClass = defaultMethod.getDeclaringClass();

try {

Lookup lookup = readLookup(declaringClass);

this.unboundHandle = lookup.unreflectSpecial(defaultMethod, declaringClass);

} catch (NoSuchFieldException

| IllegalAccessException

| IllegalArgumentException

| InvocationTargetException ex) {

throw new IllegalStateException(ex);

}

}

private Lookup readLookup(Class<?> declaringClass)

throws IllegalAccessException, InvocationTargetException, NoSuchFieldException {

try {

return safeReadLookup(declaringClass);

} catch (NoSuchMethodException e) {

try {

return androidLookup(declaringClass);

} catch (InstantiationException | NoSuchMethodException instantiationException) {

return legacyReadLookup();

}

}

}

public Lookup androidLookup(Class<?> declaringClass)

throws InstantiationException,

InvocationTargetException,

NoSuchMethodException,

IllegalAccessException {

Lookup lookup;

try {

// Android 9+ double reflection

Class<?> classReference = Class.class;

Class<?>[] classType = new Class[] {Class.class};

Method reflectedGetDeclaredConstructor =

classReference.getDeclaredMethod("getDeclaredConstructor", Class[].class);

reflectedGetDeclaredConstructor.setAccessible(true);

Constructor<?> someHiddenMethod =

(Constructor<?>) reflectedGetDeclaredConstructor.invoke(Lookup.class, (Object) classType);

lookup = (Lookup) someHiddenMethod.newInstance(declaringClass);

} catch (IllegalAccessException ex0) {

// Android < 9 reflection

Constructor<Lookup> lookupConstructor = Lookup.class.getDeclaredConstructor(Class.class);

lookupConstructor.setAccessible(true);

lookup = lookupConstructor.newInstance(declaringClass);

}

return (lookup);

}

/**

* equivalent to:

*

* <pre>

* return MethodHandles.privateLookupIn(declaringClass, MethodHandles.lookup());

* </pre>

*

* @param declaringClass

* @return

* @throws IllegalAccessException

* @throws InvocationTargetException

* @throws NoSuchMethodException

*/

private Lookup safeReadLookup(Class<?> declaringClass)

throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {

Lookup lookup = MethodHandles.lookup();

Object privateLookupIn =

MethodHandles.class

.getMethod("privateLookupIn", Class.class, Lookup.class)

.invoke(null, declaringClass, lookup);

return (Lookup) privateLookupIn;

}

private Lookup legacyReadLookup() throws NoSuchFieldException, IllegalAccessException {

Field field = Lookup.class.getDeclaredField("IMPL_LOOKUP");

field.setAccessible(true);

Lookup lookup = (Lookup) field.get(null);

return lookup;

}

/**

* Bind this handler to a proxy object. After bound, DefaultMethodHandler#invoke will act as if it

* was called on the proxy object. Must be called once and only once for a given instance of

* DefaultMethodHandler

*/

public void bindTo(Object proxy) {

if (handle != null) {

throw new IllegalStateException(

"Attempted to rebind a default method handler that was already bound");

}

handle = unboundHandle.bindTo(proxy);

}

/**

* Invoke this method. DefaultMethodHandler#bindTo must be called before the first time invoke is

* called.

*/

@Override

public Object invoke(Object[] argv) throws Throwable {

if (handle == null) {

throw new IllegalStateException(

"Default method handler invoked before proxy has been bound.");

}

return handle.invokeWithArguments(argv);

}

}