【Go】Gin源码解读

1.中间件

中间件的实现 依照设计模式中责任链模式，依次调用当前路由 注册的中间件

gin.go

// HandlerFunc defines the handler used by gin middleware as return value.
type HandlerFunc func(*Context)

// HandlersChain defines a HandlerFunc array.
type HandlersChain []HandlerFunc

context.go

// Context is the most important part of gin. It allows us to pass variables between middleware,
// manage the flow, validate the JSON of a request and render a JSON response for example.
type Context struct {
    
	writermem responseWriter
	Request   *http.Request
	Writer    ResponseWriter

	Params   Params
	handlers HandlersChain
	index    int8
	fullPath string

	engine *Engine
	params *Params

	// This mutex protect Keys map
	mu sync.RWMutex

	// Keys is a key/value pair exclusively for the context of each request.
	Keys map[string]interface{
    }

	// Errors is a list of errors attached to all the handlers/middlewares who used this context.
	Errors errorMsgs

	// Accepted defines a list of manually accepted formats for content negotiation.
	Accepted []string

	// queryCache use url.ParseQuery cached the param query result from c.Request.URL.Query()
	queryCache url.Values

	// formCache use url.ParseQuery cached PostForm contains the parsed form data from POST, PATCH,
	// or PUT body parameters.
	formCache url.Values

	// SameSite allows a server to define a cookie attribute making it impossible for
	// the browser to send this cookie along with cross-site requests.
	sameSite http.SameSite
}

c.Next()

// Next should be used only inside middleware.
// It executes the pending handlers in the chain inside the calling handler.
// See example in GitHub.
func (c *Context) Next() {
    
	c.index++
	for c.index < int8(len(c.handlers)) {
    
		c.handlers[c.index](c)
		c.index++
	}
}

Next() 这个方法只在中间件中使用有意义，调用后马上执行各个 handler（这些 handler 中包含你注册在路由上的方法），最后会返回到中间件。

c.Abort()

// Abort prevents pending handlers from being called. Note that this will not stop the current handler.
// Let's say you have an authorization middleware that validates that the current request is authorized.
// If the authorization fails (ex: the password does not match), call Abort to ensure the remaining handlers
// for this request are not called.
func (c *Context) Abort() {
    
	c.index = abortIndex
}

让ctx当前index指向最后，直接返回

路由

context实现