Home > Article > Backend Development > Exception handling in Golang
<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Golang</span>
has many advantages, which have been mentioned in previous articles, but there are also many shortcomings that Gopher has criticized, especially Yes <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Error handling</span>
. Before talking about errors and exceptions, let’s talk about two concepts:
Error handling: Errors are part of the business and can be foreseen.
Exception handling: Not part of the business, unforeseen.
First take a look at the sample code:
file, err := os.Open("/usr/local/test.txt")
Golang officially recommends the error handling method in the above code, and recommends <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">err</span>
is placed at the end of the return value. We also need to follow such rules to define <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">func</span>
in daily coding.
在Gopher间流传着这样一个笑话:一半时间在编写代码,一半时间在写错误处理。
示例代码:
func Open(name string) (*File, error) { return OpenFile(name, O_RDONLY, 0) }
但通常不是每个方法都需要处理 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">err</span>
,可以适当的将 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">err</span>
返回给上层函数,由上层函数统一打印或者处理错误。例如:<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">http</span>
路由中的错误可以在路由返回数据前处理,将错误信息和错误码格式化后返回给 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Client</span>
。
Golang’s exception handling is quite unique and requires <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">defer</span>
<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">err</span>
<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">recover</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
The three are used together, while Java only needs <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">try</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">{</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;"></span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">}</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Catch</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
can be done, let’s take a look at the sample code:
package main import ( "fmt" ) func main() { test() } func test() { defer func() { if e := recover(); e != nil { fmt.Println("Worng!") } }() panic("panic") }
如上代码在 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">test</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
函数及其子函数中如果发生panic的错误,就会打印:
Worng!
当然,在每个方法最上面写这么一大堆冗余的代码是很不优雅的,也不符合面向对象的特性:<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">封装</span>
,于是便可以封装成 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">CoverErrorMessage</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
,而 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">test</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
函数改写如下:
package main import ( "fmt" ) func main() { test() } func test() { defer tools.CoverErrorMessage() panic("panic") } func CoverErrorMessage() { if message := recover(); message != nil { var err error switch x := message.(type) { case string: err = errors.New(x) case error: err = x default: err = errors.New("Unknow panic") } Logger.Error("Recovered panic error : ",err) } }
defer 处理异常时只能将
<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">recover</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
写在第一层函数中,否则将无法<span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">recover</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>
到panic错误
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