更新

Polly8Study.Test/Polly8FallbackStrategy.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Polly8Study.Test
-{
-    class Polly8FallbackStrategy
-    {
-    }
-}

Polly8Study.Test/Polly8FallbackStrategyTest.cs

@@ -0,0 +1,201 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Polly8Study.Test
+{
+    public class Polly8FallbackStrategyTest
+    {
+        private readonly ITestOutputHelper _output;
+
+        public Polly8FallbackStrategyTest(ITestOutputHelper testOutput)
+        {
+            _output = testOutput;
+        }
+
+        [Fact]
+        public async void Test()
+        {
+            FallbackStrategyOptions<int> optionsOnFallback = new FallbackStrategyOptions<int>
+            {
+                ShouldHandle = new PredicateBuilder<int>()
+                    .Handle<Exception>()
+                    .HandleResult(r => r > 50),
+
+                FallbackAction = static args =>
+                {
+                    var v = Random.Shared.Next(1, 50);
+                    return Outcome.FromResultAsValueTask(v);
+                },
+
+                OnFallback = args =>
+                {
+                    _output.WriteLine(args.Outcome.Result.ToString());
+                    // Add extra logic to be executed when the fallback is triggered, such as logging.
+                    return default; // Returns an empty ValueTask
+                }
+            };
+
+            // Add a fallback strategy with a FallbackStrategyOptions<TResult> instance to the pipeline
+            var pipeline = new ResiliencePipelineBuilder<int>()
+                 .AddFallback(optionsOnFallback)
+                 .Build();
+
+            var data = await pipeline.ExecuteAsync<int>(static async (innerToken) =>
+             {
+
+                 return await Task.FromResult(Random.Shared.Next(1, 100));
+
+             });
+
+            _output.WriteLine(data.ToString());
+
+        }
+
+        /// <summary>
+        /// 生成回退选项
+        /// 注意：一定是有返回值的，否则没意义
+        /// </summary>
+        [Fact]
+        public async Task Create_FallbackStrategyOption_TestAsync()
+        {
+            //以返回简单的字符串或数据为例
+
+            // 1、操作失败(异常或返回值不满足)，则回退为固定值
+            var optionsSubstitute = new FallbackStrategyOptions<string>
+            {
+                //设置回退条件
+                ShouldHandle = new PredicateBuilder<string>()
+                    //出现指定的异常类型时，回退
+                    .Handle<Exception>()
+                    //返回值满足条件时，回退
+                    .HandleResult(r => r is null),
+
+                //回退时，返回的替代值
+                FallbackAction = static args => Outcome.FromResultAsValueTask("回退时的值")
+            };
+
+            // 2、如果操作失败，则回退为动态生成值
+            var optionsFallbackAction = new FallbackStrategyOptions<string>
+            {
+                //设置回退条件
+                ShouldHandle = new PredicateBuilder<string>()
+                    //出现指定的异常类型时，回退
+                    .Handle<Exception>()
+                    //返回值满足条件时，回退
+                    .HandleResult(r => r is null),
+
+                FallbackAction = static args =>
+                {
+                    var text = Random.Shared.Next(100, 999).ToString();
+                    return Outcome.FromResultAsValueTask(text);
+                }
+            };
+
+            // 3、使用默认值或动态生成的值，如果触发回退，则执行其他操作。
+            var optionsOnFallback = new FallbackStrategyOptions<string>
+            {
+                ShouldHandle = new PredicateBuilder<string>()
+                    //出现指定的异常类型时，回退
+                    .Handle<Exception>()
+                    //返回值满足条件时，回退
+                    .HandleResult(r => r is null),
+
+                //回退时：返回替代值
+                FallbackAction = static args =>
+                {
+                    var text = Random.Shared.Next(100, 999).ToString();
+                    return Outcome.FromResultAsValueTask(text);
+                },
+
+                //回退时：执行额外方法
+                OnFallback = static args =>
+                {
+                    //从参数里可以拿到上下文和结果
+                    Console.WriteLine(args.Outcome.Result);
+
+                    // 添加在触发回退时要执行的额外逻辑，例如日志记录。
+                    return default; // Returns an empty ValueTask
+                }
+            };
+
+            // 添加到弹性管道
+            var pipeline = new ResiliencePipelineBuilder<string>()
+                 .AddFallback(optionsOnFallback)
+                 .Build();
+
+            //使用弹性管道，执行/调用 方法
+            var data = await pipeline.ExecuteAsync<string>(static async (innerToken) =>
+            {
+                var data = Random.Shared.Next(1,100);
+
+                if (data % 0 ==0)
+                {
+                    throw new Exception("");
+                }
+
+                return await ValueTask.FromResult(data.ToString());
+            });
+
+            //断言
+            Assert.NotEmpty(data);
+        }
+
+        /// <summary>
+        /// 生成回退选项
+        /// 注意：一定是有返回值的，否则没意义
+        /// </summary>
+        [Fact]
+        public async Task FallbackStrategyOption_TestAsync()
+        {
+            //方法返回 1-00 随机数，使用回退方法确保返回0-50的数据。
+
+            var optionsOnFallback = new FallbackStrategyOptions<int>
+            {
+                ShouldHandle = new PredicateBuilder<int>()
+                    .Handle<Exception>()
+                    .HandleResult(r => r >= 50),
+
+                //回退时：返回替代值
+                FallbackAction = args =>
+                {
+                    var v = Random.Shared.Next(1, 50);
+
+                    _output.WriteLine($"原方法生成的数字 {args.Outcome.Result}，大于50，使用回退替代值 {v}");
+
+                    return Outcome.FromResultAsValueTask(v);
+                },
+
+                //回退时：执行额外方法(先于FallbackAction执行)
+                OnFallback = args =>
+                {
+                    //从参数里可以拿到上下文和结果
+                    _output.WriteLine($"回退额外方法执行，原方法生成数字为：{args.Outcome.Result}");
+
+                    // 添加在触发回退时要执行的额外逻辑，例如日志记录。
+                    return default; // Returns an empty ValueTask
+                }
+            };
+
+            // Add a fallback strategy with a FallbackStrategyOptions<TResult> instance to the pipeline
+            var pipeline = new ResiliencePipelineBuilder<int>()
+                 .AddFallback(optionsOnFallback)
+                 .Build();
+
+            var data = await pipeline.ExecuteAsync<int>(async (innerToken) =>
+             {
+                 //随机返回1到100数字
+                 var v = Random.Shared.Next(1, 100);
+                 _output.WriteLine($"方法生成数字为：{v}");
+
+                 return await Task.FromResult(v);
+
+             });
+
+            Assert.True(data <= 50);
+        }
+
+    }
+}