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DefaultMethodHandler.java
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77 lines (70 loc) · 2.83 KB
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/**
* Copyright 2012-2019 The Feign Authors
*
* 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 org.jvnet.animal_sniffer.IgnoreJRERequirement;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Field;
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.
*/
@IgnoreJRERequirement
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) {
try {
Class<?> declaringClass = defaultMethod.getDeclaringClass();
Field field = Lookup.class.getDeclaredField("IMPL_LOOKUP");
field.setAccessible(true);
Lookup lookup = (Lookup) field.get(null);
this.unboundHandle = lookup.unreflectSpecial(defaultMethod, declaringClass);
} catch (NoSuchFieldException ex) {
throw new IllegalStateException(ex);
} catch (IllegalAccessException ex) {
throw new IllegalStateException(ex);
}
}
/**
* 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);
}
}