hystrix简单使用——fallback

冷不防 2022-05-22 11:29 255阅读 0赞

本文主要介绍fallback，目的是能够在程序中看到fallback的处理。

主要参考：

[https://github.com/Netflix/Hystrix/blob/master/hystrix-examples/src/main/java/com/netflix/hystrix/examples/basic/CommandHelloFailure.java][https_github.com_Netflix_Hystrix_blob_master_hystrix-examples_src_main_java_com_netflix_hystrix_examples_basic_CommandHelloFailure.java]

官网上的原话是这么说的

Hystrix will execute this fallback for all types of failure such as run() failure, timeout, thread pool or semaphore rejection, and circuit-breaker short-circuiting.

现在实现一个默认就是出错的然后看效果是什么样子的。正常应该直接执行getFallback()里面的内容。

1、添加maven依赖

<dependency>
                <groupId>com.netflix.hystrix</groupId>
                <artifactId>hystrix-core</artifactId>
                <version>1.5.12</version>
            </dependency>

2、创建一个继承hystrixCommand的类

package com.xueyou.hystrixdemo.v2;
    
    import com.netflix.hystrix.HystrixCommand;
    import com.netflix.hystrix.HystrixCommandGroupKey;
    
    
    public class CommandHelloworldWithFallBack extends HystrixCommand<String> {
        private String name;
    
        public CommandHelloworldWithFallBack(HystrixCommandGroupKey group, String name) {
            super(group);
            this.name = name;
        }
    
        @Override
        protected String getFallback() {
            return "fall back " + name;
        }
    
        @Override
        protected String run() {
            throw new RuntimeException("this command always fails");
        }
    }

3、添加测试类进行测试

package com.xueyou.hystrixdemo.v2;
    
    import com.netflix.hystrix.HystrixCommandGroupKey;
    
    public class HelloWorldFallBack {
        public static void main(String[] args) {
            String result = new CommandHelloworldWithFallBack(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"), "aaabbbccc").execute();
            String result2 = new CommandHelloworldWithFallBack(HystrixCommandGroupKey.Factory.asKey("ExampleGroup2"), "123sss").execute();
            System.out.println(result);
            System.out.println(result2);
        }
    }

4、运行结果：

![70][]

根据官网上的解释，每次执行run()方法的时候都会出现异常，但是这里没有返回异常，而是通过执行getFallback()方法然后返回getFallback()的返回值即可。

[https_github.com_Netflix_Hystrix_blob_master_hystrix-examples_src_main_java_com_netflix_hystrix_examples_basic_CommandHelloFailure.java]: https://github.com/Netflix/Hystrix/blob/master/hystrix-examples/src/main/java/com/netflix/hystrix/examples/basic/CommandHelloFailure.java
[70]: /images/20220522/0fb70738e3054f9dafba68ab0c80d4fc.png