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HystrixInvocationHandler.java
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HystrixInvocationHandler.java
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/*
* Copyright 2012-2023 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.hystrix;
import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommand.Setter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import feign.InvocationHandlerFactory.MethodHandler;
import feign.Target;
import feign.Util;
import rx.Completable;
import rx.Observable;
import rx.Single;
import static feign.Util.checkNotNull;
final class HystrixInvocationHandler implements InvocationHandler {
private final Target<?> target;
private final Map<Method, MethodHandler> dispatch;
private final FallbackFactory<?> fallbackFactory; // Nullable
private final Map<Method, Method> fallbackMethodMap;
private final Map<Method, Setter> setterMethodMap;
HystrixInvocationHandler(Target<?> target, Map<Method, MethodHandler> dispatch,
SetterFactory setterFactory, FallbackFactory<?> fallbackFactory) {
this.target = checkNotNull(target, "target");
this.dispatch = checkNotNull(dispatch, "dispatch");
this.fallbackFactory = fallbackFactory;
this.fallbackMethodMap = toFallbackMethod(dispatch);
this.setterMethodMap = toSetters(setterFactory, target, dispatch.keySet());
}
/**
* If the method param of InvocationHandler.invoke is not accessible, i.e in a package-private
* interface, the fallback call in hystrix command will fail cause of access restrictions. But
* methods in dispatch are copied methods. So setting access to dispatch method doesn't take
* effect to the method in InvocationHandler.invoke. Use map to store a copy of method to invoke
* the fallback to bypass this and reducing the count of reflection calls.
*
* @return cached methods map for fallback invoking
*/
static Map<Method, Method> toFallbackMethod(Map<Method, MethodHandler> dispatch) {
Map<Method, Method> result = new LinkedHashMap<Method, Method>();
for (Method method : dispatch.keySet()) {
method.setAccessible(true);
result.put(method, method);
}
return result;
}
/**
* Process all methods in the target so that appropriate setters are created.
*/
static Map<Method, Setter> toSetters(SetterFactory setterFactory,
Target<?> target,
Set<Method> methods) {
Map<Method, Setter> result = new LinkedHashMap<Method, Setter>();
for (Method method : methods) {
method.setAccessible(true);
result.put(method, setterFactory.create(target, method));
}
return result;
}
@Override
public Object invoke(final Object proxy, final Method method, final Object[] args)
throws Throwable {
// early exit if the invoked method is from java.lang.Object
// code is the same as ReflectiveFeign.FeignInvocationHandler
if ("equals".equals(method.getName())) {
try {
Object otherHandler =
args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;
return equals(otherHandler);
} catch (IllegalArgumentException e) {
return false;
}
} else if ("hashCode".equals(method.getName())) {
return hashCode();
} else if ("toString".equals(method.getName())) {
return toString();
}
HystrixCommand<Object> hystrixCommand =
new HystrixCommand<Object>(setterMethodMap.get(method)) {
@Override
protected Object run() throws Exception {
try {
return HystrixInvocationHandler.this.dispatch.get(method).invoke(args);
} catch (Exception e) {
throw e;
} catch (Throwable t) {
throw (Error) t;
}
}
@Override
protected Object getFallback() {
if (fallbackFactory == null) {
return super.getFallback();
}
try {
Object fallback = fallbackFactory.create(getExecutionException());
Object result = fallbackMethodMap.get(method).invoke(fallback, args);
if (isReturnsHystrixCommand(method)) {
return ((HystrixCommand) result).execute();
} else if (isReturnsObservable(method)) {
// Create a cold Observable
return ((Observable) result).toBlocking().first();
} else if (isReturnsSingle(method)) {
// Create a cold Observable as a Single
return ((Single) result).toObservable().toBlocking().first();
} else if (isReturnsCompletable(method)) {
((Completable) result).await();
return null;
} else if (isReturnsCompletableFuture(method)) {
return ((Future) result).get();
} else {
return result;
}
} catch (IllegalAccessException e) {
// shouldn't happen as method is public due to being an interface
throw new AssertionError(e);
} catch (InvocationTargetException | ExecutionException e) {
// Exceptions on fallback are tossed by Hystrix
throw new AssertionError(e.getCause());
} catch (InterruptedException e) {
// Exceptions on fallback are tossed by Hystrix
Thread.currentThread().interrupt();
throw new AssertionError(e.getCause());
}
}
};
if (Util.isDefault(method)) {
return hystrixCommand.execute();
} else if (isReturnsHystrixCommand(method)) {
return hystrixCommand;
} else if (isReturnsObservable(method)) {
// Create a cold Observable
return hystrixCommand.toObservable();
} else if (isReturnsSingle(method)) {
// Create a cold Observable as a Single
return hystrixCommand.toObservable().toSingle();
} else if (isReturnsCompletable(method)) {
return hystrixCommand.toObservable().toCompletable();
} else if (isReturnsCompletableFuture(method)) {
return new ObservableCompletableFuture<>(hystrixCommand);
}
return hystrixCommand.execute();
}
private boolean isReturnsCompletable(Method method) {
return Completable.class.isAssignableFrom(method.getReturnType());
}
private boolean isReturnsHystrixCommand(Method method) {
return HystrixCommand.class.isAssignableFrom(method.getReturnType());
}
private boolean isReturnsObservable(Method method) {
return Observable.class.isAssignableFrom(method.getReturnType());
}
private boolean isReturnsCompletableFuture(Method method) {
return CompletableFuture.class.isAssignableFrom(method.getReturnType());
}
private boolean isReturnsSingle(Method method) {
return Single.class.isAssignableFrom(method.getReturnType());
}
@Override
public boolean equals(Object obj) {
if (obj instanceof HystrixInvocationHandler) {
HystrixInvocationHandler other = (HystrixInvocationHandler) obj;
return target.equals(other.target);
}
return false;
}
@Override
public int hashCode() {
return target.hashCode();
}
@Override
public String toString() {
return target.toString();
}
}