[英]How do I define fallback method for Resilience4j 2.0 Circuit Breaker in a plain Java?
How do I define fallback method for Resillience4j 2.0 Circuit Breaker in a plain Java?如何在普通 Java 中为 Resillience4j 2.0 断路器定义回退方法?
I cannot find the example in the official docs nor in the API.我在官方文档和 API 中都找不到示例。
I have a very simple code and I'd like to register a fallback / recover method when the original one fails.我有一个非常简单的代码,我想在原始方法失败时注册一个回退/恢复方法。
WeatherApi weatherApi = new FaultyWeatherService();
CircuitBreakerRegistry registry = CircuitBreakerRegistry.of(
CircuitBreakerConfig.custom()
.failureRateThreshold(1)
.minimumNumberOfCalls(1)
.build()
);
CircuitBreaker breaker = registry.circuitBreaker("weather-service");
Function<String, String> weatherFunction = CircuitBreaker
.decorateFunction(breaker, weatherApi::getWeatherFor);
for (int i = 0; i < 10; i++) {
try {
System.out.println(weatherFunction.apply("krakow"));
} catch (Exception ex) {
ex.printStackTrace();
}
}
You can use the withFallback
method on the CircuitBreaker
object. Here's an example of how you could use it in your code:您可以在CircuitBreaker
object 上使用withFallback
方法。以下是如何在代码中使用它的示例:
// Define your fallback method
Function<String, String> fallback = (city) -> {
// Return a default value or do some other recovery logic here
return "Unknown";
};
// Use the withFallback method to register the fallback
Function<String, String> weatherFunction = CircuitBreaker
.decorateFunction(breaker, weatherApi::getWeatherFor)
.withFallback(fallback);
The withFallback
method takes a Function
object that will be called whenever the original function ( weatherApi::getWeatherFor
in this case) throws an exception. withFallback
方法采用Function
object 将在原始 function(在本例中为weatherApi::getWeatherFor
)抛出异常时调用。 This function should return the same type as the original function (in this case, String
).此 function 应返回与原始 function 相同的类型(在本例中为String
)。
You can also specify a different fallback for each exception type by using the withFallback
method that takes a Class
object as an argument.您还可以使用以Class
object 作为参数的withFallback
方法为每种异常类型指定不同的回退。 This allows you to handle different exceptions in different ways.这允许您以不同的方式处理不同的异常。 For example:例如:
// Define your fallback methods
Function<String, String> ioExceptionFallback = (city) -> {
// Return a default value or do some other recovery logic here
return "Unknown";
};
Function<String, String> runtimeExceptionFallback = (city) -> {
// Return a default value or do some other recovery logic here
return "Unavailable";
};
// Use the withFallback methods to register the fallbacks
Function<String, String> weatherFunction = CircuitBreaker
.decorateFunction(breaker, weatherApi::getWeatherFor)
.withFallback(IOException.class, ioExceptionFallback)
.withFallback(RuntimeException.class, runtimeExceptionFallback);
In this example, the ioExceptionFallback
function will be called if the weatherApi::getWeatherFor
function throws an IOException
, and the runtimeExceptionFallback
function will be called if it throws any other RuntimeException
.在此示例中,如果weatherApi::getWeatherFor
ioExceptionFallback
抛出IOException
,将调用runtimeExceptionFallback
function ,如果抛出任何其他RuntimeException
,将调用 runtimeExceptionFallback function 。
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