gin的源码解读4-gin的路由算法
gin的路由算法
gin的是路由算法其实就是一个Trie树(也就是前缀树). 有关数据结构的可以自己去网上找相关资料查看.
注册路由预处理
我们在使用gin时通过下面的代码注册路由
普通注册
router.GET("/ping", func(context *gin.Context) {
context.JSON(http.StatusOK, gin.H{"message": "pong"})
})
使用中间件
router.Use(gin.Recovery())
使用Group
v1 := router.Group("v1")
v1.GET("/ping", func(context *gin.Context) {
context.JSON(http.StatusOK, gin.H{"message": "pong"})
})
具体实现
func (group *RouterGroup) handle(httpMethod, relativePath string, handlers HandlersChain) IRoutes {
absolutePath := group.calculateAbsolutePath(relativePath)
handlers = group.combineHandlers(handlers)
group.engine.addRoute(httpMethod, absolutePath, handlers)
return group.returnObj()
}
在调用POST, GET, HEAD等路由HTTP相关函数时, 会调用handle函数
如果调用了中间件的话, 会调用下面函数
// Use adds middleware to the group, see example code in GitHub.
func (group *RouterGroup) Use(middleware ...HandlerFunc) IRoutes {
group.Handlers = append(group.Handlers, middleware...)
return group.returnObj()
}
如果使用了Group的话, 会调用下面函数
func (group *RouterGroup) Group(relativePath string, handlers ...HandlerFunc) *RouterGroup {
return &RouterGroup{
Handlers: group.combineHandlers(handlers),
basePath: group.calculateAbsolutePath(relativePath),
engine: group.engine,
}
}
重点关注下面两个函数:
// routergroup.go:L208-217
func (group *RouterGroup) combineHandlers(handlers HandlersChain) HandlersChain {
finalSize := len(group.Handlers) + len(handlers)
if finalSize >= int(abortIndex) {
panic("too many handlers")
}
mergedHandlers := make(HandlersChain, finalSize)
copy(mergedHandlers, group.Handlers)
copy(mergedHandlers[len(group.Handlers):], handlers)
return mergedHandlers
}
func (group *RouterGroup) calculateAbsolutePath(relativePath string) string {
return joinPaths(group.basePath, relativePath)
}
func joinPaths(absolutePath, relativePath string) string {
if relativePath == "" {
return absolutePath
}
finalPath := path.Join(absolutePath, relativePath)
appendSlash := lastChar(relativePath) == '/' && lastChar(finalPath) != '/'
if appendSlash {
return finalPath + "/"
}
return finalPath
}
综合来看, 在预处理阶段
1.在调用中间件的时候, 是将某个路由的handler处理函数和中间件的处理函数都放在了Handlers的数组中 2.在调用Group的时候, 是将路由的path上面拼上Group的值. 也就是/user/:name, 会变成v1/user:name
真正注册
func (group *RouterGroup) handle(httpMethod, relativePath string, handlers HandlersChain) IRoutes {
absolutePath := group.calculateAbsolutePath(relativePath)
handlers = group.combineHandlers(handlers)
group.engine.addRoute(httpMethod, absolutePath, handlers)
return group.returnObj()
}
调用group.engine.addRoute(httpMethod, absolutePath, handlers)将预处理阶段的结果注册到gin Engine的trees上
gin路由树简单介绍
gin的路由树算法是一棵前缀树. 不过并不是只有一颗树, 而是每种方法(POST, GET ...)都有自己的一颗树
func (engine *Engine) addRoute(method, path string, handlers HandlersChain) {
assert1(path[0] == '/', "path must begin with '/'")
assert1(method != "", "HTTP method can not be empty")
assert1(len(handlers) > 0, "there must be at least one handler")
debugPrintRoute(method, path, handlers)
root := engine.trees.get(method)
if root == nil {
root = new(node)
root.fullPath = "/"
engine.trees = append(engine.trees, methodTree{method: method, root: root})
}
root.addRoute(path, handlers)
// Update maxParams
if paramsCount := countParams(path); paramsCount > engine.maxParams {
engine.maxParams = paramsCount
}
if sectionsCount := countSections(path); sectionsCount > engine.maxSections {
engine.maxSections = sectionsCount
}
}
gin 路由最终的样子大概是下面的样子
type node struct {
path string
indices string
wildChild bool
nType nodeType
priority uint32
children []*node // child nodes, at most 1 :param style node at the end of the array
handlers HandlersChain
fullPath string
}
其实gin的实现不像一个真正的树, children []*node所有的孩子都放在这个数组里面, 利用indices, priority变相实现一棵树
获取路由handler
当服务端收到客户端的请求时, 根据path去trees匹配到相关的路由, 拿到相关的处理handlers
...
// Find root of the tree for the given HTTP method
t := engine.trees
for i, tl := 0, len(t); i < tl; i++ {
if t[i].method != httpMethod {
continue
}
root := t[i].root
// Find route in tree
value := root.getValue(rPath, c.params, c.skippedNodes, unescape)
if value.params != nil {
c.Params = *value.params
}
if value.handlers != nil {
c.handlers = value.handlers // 看这里
c.fullPath = value.fullPath
c.Next()
c.writermem.WriteHeaderNow()
return
}
if httpMethod != "CONNECT" && rPath != "/" {
if value.tsr && engine.RedirectTrailingSlash {
redirectTrailingSlash(c)
return
}
if engine.RedirectFixedPath && redirectFixedPath(c, root, engine.RedirectFixedPath) {
return
}
}
break
}
...
主要在下面这个函数里面调用程序注册的路由处理函数
func (c *Context) Next() {
c.index++
for c.index < int8(len(c.handlers)) {
c.handlers[c.index](c)
c.index++
}
}
