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‎spring-cloud/README.md

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@@ -128,7 +128,7 @@ Spring Cloud 系列课程致力于以实战的方式覆盖 Spring Cloud 的功
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### 第九节 Spring Cloud Hystrix 源码解读
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### [第九节 Spring Cloud Hystrix 源码解读](https://segmentfault.com/l/1500000011386273/play) （[课件](https://github.com/mercyblitz/segmentfault-lessons/tree/master/spring-cloud/lesson-9)） [[问答](https://segmentfault.com/l/1500000011386273/d/1560000012218757)]
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* 受众群体：具备一定的`Java`服务端编程经验更佳
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‎spring-cloud/lesson-9/README.md

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# Spring Cloud Hystrix 源码分析
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## Spring Cloud Hystrix 源码解读
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### `@EnableCircuitBreaker`
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职责：
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* 激活 Circuit Breaker
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#### 初始化顺序
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* `@EnableCircuitBreaker `
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* `EnableCircuitBreakerImportSelector`
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* `HystrixCircuitBreakerConfiguration`
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### HystrixCircuitBreakerConfiguration
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#### 初始化组件
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* `HystrixCommandAspect`
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* `HystrixShutdownHook`
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* `HystrixStreamEndpoint` ： Servlet
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* `HystrixMetricsPollerConfiguration`
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## Netflix Hystrix 源码解读
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### `HystrixCommandAspect`
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#### 依赖组件
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* `MetaHolderFactory`
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* `HystrixCommandFactory`: 生成`HystrixInvokable`
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* `HystrixInvokable`
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* `CommandCollapser`
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* `GenericObservableCommand`
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* `GenericCommand`
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### Future 实现 服务熔断
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```java
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package com.segumentfault.springcloudlesson9.future;
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import java.util.Random;
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import java.util.concurrent.*;
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/**
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* 通过 {@link Future} 实现 服务熔断
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*
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* @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
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*/
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public class FutureCircuitBreakerDemo {
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public static void main(String[] args) throws InterruptedException, ExecutionException {
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// 初始化线程池
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ExecutorService executorService = Executors.newSingleThreadExecutor();
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RandomCommand command = new RandomCommand();
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Future<String> future = executorService.submit(command::run);
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String result = null;
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// 100 毫秒超时时间
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try {
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result = future.get(100, TimeUnit.MILLISECONDS);
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} catch (TimeoutException e) {
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// fallback 方法调用
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result = command.fallback();
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}
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System.out.println(result);
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executorService.shutdown();
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}
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/**
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* 随机对象
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*/
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private static final Random random = new Random();
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/**
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* 随机事件执行命令
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*/
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public static class RandomCommand implements Command<String> {
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@Override
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public String run() throws InterruptedException {
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long executeTime = random.nextInt(200);
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// 通过休眠来模拟执行时间
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System.out.println("Execute Time : " + executeTime + " ms");
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Thread.sleep(executeTime);
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return "Hello,World";
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}
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@Override
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public String fallback() {
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return "Fallback";
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}
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}
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public interface Command<T> {
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/**
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* 正常执行，并且返回结果
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*
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* @return
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*/
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T run() throws Exception;
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/**
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* 错误时，返回容错结果
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*
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* @return
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*/
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T fallback();
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}
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}
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```
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## RxJava 基础
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### 单数据：Single
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```java
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Single.just("Hello,World") // 仅能发布单个数据
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.subscribeOn(Schedulers.io()) // 在 I/O 线程执行
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.subscribe(RxJavaDemo::println) // 订阅并且消费数据
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;
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```
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### 多数据：Observable
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```java
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List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
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Observable.from(values) //发布多个数据
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.subscribeOn(Schedulers.computation()) // 在 I/O 线程执行
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.subscribe(RxJavaDemo::println) // 订阅并且消费数据
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;
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// 等待线程执行完毕
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Thread.sleep(100);
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```
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### 使用标准 Reactive 模式
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```java
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List<Integer> values = Arrays.asList(1, 2, 3);
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Observable.from(values) //发布多个数据
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.subscribeOn(Schedulers.newThread()) // 在 newThread 线程执行
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.subscribe(value -> {
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if (value > 2)
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throw new IllegalStateException("数据不应许大于 2");
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//消费数据
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println("消费数据：" + value);
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}, e -> {
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// 当异常情况，中断执行
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println("发生异常 , " + e.getMessage());
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}, () -> {
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// 当整体流程完成时
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println("流程执行完成");
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})
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;
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// 等待线程执行完毕
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Thread.sleep(100);
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```
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## Java 9 Flow API
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```java
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package concurrent.java9;
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import java.util.concurrent.Flow;
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import java.util.concurrent.SubmissionPublisher;
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/**
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* {@link SubmissionPublisher}
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*
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* @author mercyblitz
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**/
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public class SubmissionPublisherDemo {
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public static void main(String[] args) throws InterruptedException {
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try (SubmissionPublisher<Integer> publisher =
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new SubmissionPublisher<>()) {
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//Publisher(100) => A -> B -> C => Done
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publisher.subscribe(new IntegerSubscriber("A"));
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publisher.subscribe(new IntegerSubscriber("B"));
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publisher.subscribe(new IntegerSubscriber("C"));
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// 提交数据到各个订阅器
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publisher.submit(100);
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}
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Thread.currentThread().join(1000L);
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}
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private static class IntegerSubscriber implements
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Flow.Subscriber<Integer> {
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private final String name;
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private Flow.Subscription subscription;
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private IntegerSubscriber(String name) {
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this.name = name;
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}
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@Override
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public void onSubscribe(Flow.Subscription subscription) {
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System.out.printf(
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"Thread[%s] Current Subscriber[%s] " +
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"subscribes subscription[%s]\n",
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Thread.currentThread().getName(),
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name,
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subscription);
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this.subscription = subscription;
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subscription.request(1);
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}
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@Override
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public void onNext(Integer item) {
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System.out.printf(
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"Thread[%s] Current Subscriber[%s] " +
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"receives item[%d]\n",
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Thread.currentThread().getName(),
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name,
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item);
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subscription.request(1);
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}
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@Override
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public void onError(Throwable throwable) {
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throwable.printStackTrace();
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}
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@Override
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public void onComplete() {
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System.out.printf(
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"Thread[%s] Current Subscriber[%s] " +
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"is completed!\n",
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Thread.currentThread().getName(),
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name);
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}
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}
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}
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```
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‎spring-cloud/lesson-9/[课件] Spring Cloud Hystrix 源码解读.pdf

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‎spring-cloud/lesson-9/spring-cloud-lesson-9/.gitignore

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target/
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!.mvn/wrapper/maven-wrapper.jar
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### STS ###
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.apt_generated
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.classpath
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.factorypath
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.project
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.settings
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.springBeans
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### IntelliJ IDEA ###
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.idea
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*.iws
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*.iml
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*.ipr
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### NetBeans ###
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nbproject/private/
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build/
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nbbuild/
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dist/
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nbdist/
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.nb-gradle/

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