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Go 装饰器模式学习文档

news 2025/9/10 6:09:20

1. 装饰器模式简介

装饰器模式是一种结构型设计模式，它允许向一个对象动态地添加新的行为，而不需要修改该对象的基类或使用继承。装饰器模式通过创建一个包装对象来包裹真实的对象，提供额外的功能。

在 Go 中，装饰器模式通常通过函数式编程的方式实现，利用 Go 的函数作为一等公民的特性，我们可以创建高阶函数来包装其他函数，添加额外的行为。

装饰器模式的优点：

在不改变原有对象结构的情况下，动态地添加功能
遵循开闭原则（对扩展开放，对修改关闭）
可以灵活地组合多个装饰器

2. Go 中实现装饰器的方式

在 Go 中，装饰器通常是通过高阶函数实现的。高阶函数是指接受函数作为参数或返回函数的函数。下面是一个简单的装饰器示例：

// 装饰器函数，接受一个函数并返回一个包装后的函数
func decorator(f func()) func() {return func() {fmt.Println("装饰器：函数调用前")f()fmt.Println("装饰器：函数调用后")}
}func hello() {fmt.Println("Hello, World!")
}func main() {// 使用装饰器包装hello函数decoratedHello := decorator(hello)decoratedHello()
}

输出：

装饰器：函数调用前
Hello, World!
装饰器：函数调用后

3. 使用 logrus 记录日志

在 Go 中，logrus 是一个流行的结构化日志库，提供了丰富的功能。首先，我们需要安装 logrus：

go get github.com/sirupsen/logrus

下面是一个简单的 logrus 使用示例：

package mainimport ("github.com/sirupsen/logrus"
)func main() {// 创建一个新的logger实例logger := logrus.New()// 设置日志级别logger.SetLevel(logrus.DebugLevel)// 设置日志格式为JSONlogger.SetFormatter(&logrus.JSONFormatter{})// 记录不同级别的日志logger.Debug("这是一条调试信息")logger.Info("这是一条普通信息")logger.Warn("这是一条警告信息")logger.Error("这是一条错误信息")// 记录带字段的日志logger.WithFields(logrus.Fields{"event": "test","topic": "logging",}).Info("这是一条带字段的日志")
}

4. 示例：为函数添加日志装饰器

现在，我们将结合装饰器模式和 logrus 来创建一个日志装饰器，用于记录函数的调用信息。

package mainimport ("fmt""time""github.com/sirupsen/logrus"
)// 创建一个logger实例
var logger = logrus.New()// 初始化logger
func init() {// 设置日志级别logger.SetLevel(logrus.DebugLevel)// 设置日志格式为JSONlogger.SetFormatter(&logrus.JSONFormatter{})
}// 日志装饰器
func logDecorator(name string, f func()) func() {return func() {start := time.Now()logger.WithFields(logrus.Fields{"function": name,"event":    "start","time":     start.Format(time.RFC3339),}).Info("Function call started")f()duration := time.Since(start)logger.WithFields(logrus.Fields{"function": name,"event":    "end","duration": duration.String(),}).Info("Function call completed")}
}// 示例函数1
func processData() {logger.Info("Processing data...")time.Sleep(100 * time.Millisecond)logger.Info("Data processed successfully")
}// 示例函数2
func saveToDatabase() {logger.Info("Saving to database...")time.Sleep(150 * time.Millisecond)logger.Info("Data saved successfully")
}func main() {// 使用装饰器包装函数decoratedProcessData := logDecorator("processData", processData)decoratedSaveToDatabase := logDecorator("saveToDatabase", saveToDatabase)// 调用装饰后的函数decoratedProcessData()decoratedSaveToDatabase()
}

输出示例（JSON格式）：

{"event":"start","function":"processData","level":"info","msg":"Function call started","time":"2023-05-20T10:00:00+08:00"}
{"level":"info","msg":"Processing data..."}
{"level":"info","msg":"Data processed successfully"}
{"duration":"100.123ms","event":"end","function":"processData","level":"info","msg":"Function call completed"}
{"event":"start","function":"saveToDatabase","level":"info","msg":"Function call started","time":"2023-05-20T10:00:00+08:00"}
{"level":"info","msg":"Saving to database..."}
{"level":"info","msg":"Data saved successfully"}
{"duration":"150.456ms","event":"end","function":"saveToDatabase","level":"info","msg":"Function call completed"}

5. 多个装饰器的组合

装饰器模式的一个强大之处在于可以组合多个装饰器，每个装饰器负责一个特定的功能。下面我们创建多个装饰器，并演示如何组合它们：

package mainimport ("fmt""os""time""github.com/sirupsen/logrus"
)// 创建一个logger实例
var logger = logrus.New()// 初始化logger
func init() {// 设置日志级别logger.SetLevel(logrus.DebugLevel)// 设置日志格式为JSONlogger.SetFormatter(&logrus.JSONFormatter{})// 设置输出到标准输出logger.SetOutput(os.Stdout)
}// 日志装饰器
func logDecorator(name string) func(func()) func() {return func(f func()) func() {return func() {start := time.Now()logger.WithFields(logrus.Fields{"function": name,"event":    "start","time":     start.Format(time.RFC3339),}).Info("Function call started")f()duration := time.Since(start)logger.WithFields(logrus.Fields{"function": name,"event":    "end","duration": duration.String(),}).Info("Function call completed")}}
}// 计时装饰器
func timingDecorator(name string) func(func()) func() {return func(f func()) func() {return func() {start := time.Now()logger.WithField("function", name).Info("Timing started")f()duration := time.Since(start)logger.WithFields(logrus.Fields{"function": name,"duration": duration.String(),}).Info("Timing completed")}}
}// 错误处理装饰器
func errorHandlingDecorator(name string) func(func()) func() {return func(f func()) func() {return func() {defer func() {if r := recover(); r != nil {logger.WithFields(logrus.Fields{"function": name,"error":    r,}).Error("Function panicked")}}()f()}}
}// 示例函数
func processData() {logger.Info("Processing data...")time.Sleep(100 * time.Millisecond)logger.Info("Data processed successfully")
}// 可能出错的函数
func riskyOperation() {logger.Info("Starting risky operation...")time.Sleep(50 * time.Millisecond)// 模拟一个错误panic("something went wrong")
}// 装饰器工厂函数，用于组合多个装饰器
func decorate(f func(), decorators ...func(func()) func()) func() {decorated := f// 按照相反的顺序应用装饰器，这样第一个装饰器将是最外层的for i := len(decorators) - 1; i >= 0; i-- {decorated = decorators[i](decorated)}return func() {decorated()}
}func main() {// 组合多个装饰器decoratedProcessData := decorate(processData,logDecorator("processData"),timingDecorator("processData"),errorHandlingDecorator("processData"),)decoratedRiskyOperation := decorate(riskyOperation,logDecorator("riskyOperation"),timingDecorator("riskyOperation"),errorHandlingDecorator("riskyOperation"),)// 调用装饰后的函数decoratedProcessData()decoratedRiskyOperation()
}

输出示例（JSON格式）：

{"event":"start","function":"processData","level":"info","msg":"Function call started","time":"2023-05-20T10:00:00+08:00"}
{"function":"processData","level":"info","msg":"Timing started"}
{"level":"info","msg":"Processing data..."}
{"level":"info","msg":"Data processed successfully"}
{"duration":"100.123ms","function":"processData","level":"info","msg":"Timing completed"}
{"duration":"100.123ms","event":"end","function":"processData","level":"info","msg":"Function call completed"}
{"event":"start","function":"riskyOperation","level":"info","msg":"Function call started","time":"2023-05-20T10:00:00+08:00"}
{"function":"riskyOperation","level":"info","msg":"Timing started"}
{"level":"info","msg":"Starting risky operation..."}
{"duration":"50.456ms","function":"riskyOperation","level":"info","msg":"Timing completed"}
{"error":"something went wrong","function":"riskyOperation","level":"error","msg":"Function panicked"}
{"duration":"50.456ms","event":"end","function":"riskyOperation","level":"info","msg":"Function call completed"}