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本文主要研究一下feign的HystrixInvocationHandler
HystrixInvocationHandler
feign-hystrix-10.2.3-sources.jar!/feign/hystrix/HystrixInvocationHandler.java
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();
}
}
- HystrixInvocationHandler实现了InvocationHandler接口，其构造器接收target、dispatch、setterFactory、fallbackFactory；invoke方法主要是创建hystrixCommand，然后执行hystrixCommand的execute或toObservable等方法；hystrixCommand的run方法执行HystrixInvocationHandler.this.dispatch.get(method).invoke(args)，其getFallback方法主要是执行fallbackMethodMap.get(method).invoke(fallback, args)
InvocationHandlerFactory
feign-core-10.2.3-sources.jar!/feign/InvocationHandlerFactory.java
public interface InvocationHandlerFactory {
InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch);
/**
* Like {@link InvocationHandler#invoke(Object, java.lang.reflect.Method, Object[])}, except for a
* single method.
*/
interface MethodHandler {
Object invoke(Object[] argv) throws Throwable;
}
static final class Default implements InvocationHandlerFactory {
@Override
public InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch) {
return new ReflectiveFeign.FeignInvocationHandler(target, dispatch);
}
}
}
- InvocationHandlerFactory接口定义了create方法用于创建InvocationHandler；它有一个Default的实现，其create方法创建的是ReflectiveFeign.FeignInvocationHandler
HystrixFeign
feign-hystrix-10.2.3-sources.jar!/feign/hystrix/HystrixFeign.java
public final class HystrixFeign {
//......
public static final class Builder extends Feign.Builder {
private Contract contract = new Contract.Default();
private SetterFactory setterFactory = new SetterFactory.Default();
//......
@Override
public Feign build() {
return build(null);
}
/** Configures components needed for hystrix integration. */
Feign build(final FallbackFactory<?> nullableFallbackFactory) {
super.invocationHandlerFactory(new InvocationHandlerFactory() {
@Override
public InvocationHandler create(Target target,
Map<Method, MethodHandler> dispatch) {
return new HystrixInvocationHandler(target, dispatch, setterFactory,
nullableFallbackFactory);
}
});
super.contract(new HystrixDelegatingContract(contract));
return super.build();
}
//......
}
//......
}
- HystrixFeign.Builder的build方法使用的InvocationHandlerFactory创建的是HystrixInvocationHandler
FeignClientsConfiguration
spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/FeignClientsConfiguration.java
@Configuration
public class FeignClientsConfiguration {
//......
@Configuration
@ConditionalOnClass({ HystrixCommand.class, HystrixFeign.class })
protected static class HystrixFeignConfiguration {
@Bean
@Scope("prototype")
@ConditionalOnMissingBean
@ConditionalOnProperty(name = "feign.hystrix.enabled")
public Feign.Builder feignHystrixBuilder() {
return HystrixFeign.builder();
}
}
//......
}
- FeignClientsConfiguration的HystrixFeignConfiguration在有HystrixCommand.class, HystrixFeign.class以及feign.hystrix.enabled为true的情况下，其创建的Feign.Builder为HystrixFeign.builder
小结
HystrixInvocationHandler实现了InvocationHandler接口，其构造器接收target、dispatch、setterFactory、fallbackFactory；invoke方法主要是创建hystrixCommand，然后执行hystrixCommand的execute或toObservable等方法；hystrixCommand的run方法执行HystrixInvocationHandler.this.dispatch.get(method).invoke(args)，其getFallback方法主要是执行fallbackMethodMap.get(method).invoke(fallback, args)
