feign中的HystrixInvocationHandler作用是什么
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序
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 dispatch; private final FallbackFactory fallbackFactory; // Nullable private final Map fallbackMethodMap; private final Map setterMethodMap; HystrixInvocationHandler(Target target, Map 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 toFallbackMethod(Map dispatch) { Map result = new LinkedHashMap(); 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 toSetters(SetterFactory setterFactory, Target target, Set methods) { Map result = new LinkedHashMap(); 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 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 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 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 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
@Configurationpublic 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)
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