springcloud之Hystrix初识篇—结合ResTeamplate小述HystrixCommand基本使用

蔚落 2023-07-18 14:11 10阅读 0赞

**忽略异常：**  
通过@HystrixCommand的参数配置我们可以忽略异常，不走降级方法正常返回异常信息。  
**自定义异常：**

package com.example.springcloud.testdemo.exception;
    /**
     * Created by py
     * 2020/3/25
     */
    public class HystrixIgnoreException extends RuntimeException{
        private String message;
        public HystrixIgnoreException(String message) {
            this.message = message;
        }
    }

ignoreExceptions：忽略指定异常

@Override
    //我们指定忽略HystrixIgnoreException异常，即出现这个异常不走降级方法。
    @HystrixCommand(fallbackMethod = "sendFail",ignoreExceptions={HystrixIgnoreException.class})
    public String hystrixRestTemplateSend(String body) {
    	String url = "http://test1/eureka-clinet1/hystrixRestTemplate/Code";
    	//下面是故意跑出异常代码
    	try {
    		int i = 1/0;
    	} catch (Exception e) {
    		//设置 ignoreExceptions = HystrixIgnoreException.class，抛出此异常时不走熔断机制，直接返回异常信息
    		throw new HystrixIgnoreException("熔断忽略的异常，忽略属性设置");
    	}
    	return "test";
    }

**请求结果：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70][]

更换一个未被忽略的异常：

try {
    		int i = 1/0;
    	} catch (Exception e) {
    		//抛出 ignoreExceptions 中没有设置此异常，抛出该异常时触发熔断机制
    		throw new RuntimeException("熔断忽略的异常，继承HystrixBadRequestException");
    	}

**请求结果：**

![20200328223741532.png][]

**是否启用降级方法**：fallback.enabled

//fallback.enabled:启用降级方法(默认启用：true，false:直接返回异常)
    //ignoreExceptions优先级高于fallback.enabled
    @HystrixCommand(fallbackMethod = "sendFail",
            ignoreExceptions={HystrixIgnoreException.class},
            commandProperties={
                @HystrixProperty(name = "fallback.enabled",value = "false")
            })
    public String hystrixRestTemplateSend(String body) {
        //因为fallback.enabled是false,所以不会走fallback方法（降级），会直接返回异常
        try {
    			int i = 1/0;
    		} catch (Exception e) {
    			// TODO: handle exception
    			throw new RuntimeException("熔断忽略的异常，继承HystrixBadRequestException");
             
    		}
    
    }

**请求返回：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70 1][]

**更改抛出异常：**  
fallback.enabled=true：启用降级  
ignoreExceptions=\{HystrixIgnoreException.class\}：指定忽略降级的异常

@HystrixCommand(fallbackMethod = "sendFail",
                ignoreExceptions={HystrixIgnoreException.class},
                commandProperties={
                    @HystrixProperty(name = "fallback.enabled",value = "true")
                })
        public String hystrixRestTemplateSend(String body) {
            String url = "http://test1/eureka-clinet1/hystrixRestTemplate/Code";
            //下面是故意跑出异常代码
    		try {
    			int i = 1/0;
    		} catch (Exception e) {
                //设置 ignoreExceptions = HystrixIgnoreException.class，抛出此异常时不走熔断机制，直接返回异常信息
                throw new HystrixIgnoreException("熔断忽略的异常，忽略属性设置");
    		}
            return "test";
        }

**返回信息： **

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70 2][]

**总结：**ignoreExceptions**指定异常**与fallback.enabled=true**同时存在**时ignoreExceptions**优先级更高**，因此**不走f**allback方法。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70]: /images/20230528/f9eeac334c114dce8163c7beecb03170.png
[20200328223741532.png]: /images/20230528/a8b3a5e20ddd4a81990181a03affac82.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70 1]: /images/20230528/3bbe535f14304c7b96b2a1d793361f9c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2RlbmdkYWkxMjM2NTQ_size_16_color_FFFFFF_t_70 2]: /images/20230528/4d9af33763b74d8bafe19ff793a97e5a.png