package gin import ( "bytes" "errors" "fmt" "github.com/gin-gonic/gin/binding" "github.com/gin-gonic/gin/render" "github.com/julienschmidt/httprouter" "log" "net/http" ) const ( ErrorTypeInternal = 1 << iota ErrorTypeExternal = 1 << iota ErrorTypeAll = 0xffffffff ) // Used internally to collect errors that occurred during an http request. type errorMsg struct { Err string `json:"error"` Type uint32 `json:"-"` Meta interface{} `json:"meta"` } type errorMsgs []errorMsg func (a errorMsgs) ByType(typ uint32) errorMsgs { if len(a) == 0 { return a } result := make(errorMsgs, 0, len(a)) for _, msg := range a { if msg.Type&typ > 0 { result = append(result, msg) } } return result } func (a errorMsgs) String() string { if len(a) == 0 { return "" } var buffer bytes.Buffer for i, msg := range a { text := fmt.Sprintf("Error #%02d: %s \n Meta: %v\n", (i + 1), msg.Err, msg.Meta) buffer.WriteString(text) } return buffer.String() } // 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 Keys map[string]interface{} Errors errorMsgs Params httprouter.Params Engine *Engine handlers []HandlerFunc index int8 } /************************************/ /********** ROUTES GROUPING *********/ /************************************/ func (engine *Engine) createContext(w http.ResponseWriter, req *http.Request, params httprouter.Params, handlers []HandlerFunc) *Context { c := engine.cache.Get().(*Context) c.writermem.reset(w) c.Request = req c.Params = params c.handlers = handlers c.Keys = nil c.index = -1 c.Errors = c.Errors[0:0] return c } /************************************/ /****** FLOW AND ERROR MANAGEMENT****/ /************************************/ func (c *Context) Copy() *Context { var cp Context = *c cp.index = AbortIndex cp.handlers = nil return &cp } // Next should be used only in the middlewares. // It executes the pending handlers in the chain inside the calling handler. // See example in github. func (c *Context) Next() { c.index++ s := int8(len(c.handlers)) for ; c.index < s; c.index++ { c.handlers[c.index](c) } } // Forces the system to do not continue calling the pending handlers. // For example, the first handler checks if the request is authorized. If it's not, context.Abort(401) should be called. // The rest of pending handlers would never be called for that request. func (c *Context) Abort(code int) { if code >= 0 { c.Writer.WriteHeader(code) } c.index = AbortIndex } // Fail is the same as Abort plus an error message. // Calling `context.Fail(500, err)` is equivalent to: // ``` // context.Error("Operation aborted", err) // context.Abort(500) // ``` func (c *Context) Fail(code int, err error) { c.Error(err, "Operation aborted") c.Abort(code) } func (c *Context) ErrorTyped(err error, typ uint32, meta interface{}) { c.Errors = append(c.Errors, errorMsg{ Err: err.Error(), Type: typ, Meta: meta, }) } // Attaches an error to the current context. The error is pushed to a list of errors. // It's a good idea to call Error for each error that occurred during the resolution of a request. // A middleware can be used to collect all the errors and push them to a database together, print a log, or append it in the HTTP response. func (c *Context) Error(err error, meta interface{}) { c.ErrorTyped(err, ErrorTypeExternal, meta) } func (c *Context) LastError() error { s := len(c.Errors) if s > 0 { return errors.New(c.Errors[s-1].Err) } else { return nil } } /************************************/ /******** METADATA MANAGEMENT********/ /************************************/ // Sets a new pair key/value just for the specified context. // It also lazy initializes the hashmap. func (c *Context) Set(key string, item interface{}) { if c.Keys == nil { c.Keys = make(map[string]interface{}) } c.Keys[key] = item } // Get returns the value for the given key or an error if the key does not exist. func (c *Context) Get(key string) (interface{}, error) { if c.Keys != nil { item, ok := c.Keys[key] if ok { return item, nil } } return nil, errors.New("Key does not exist.") } // MustGet returns the value for the given key or panics if the value doesn't exist. func (c *Context) MustGet(key string) interface{} { value, err := c.Get(key) if err != nil || value == nil { log.Panicf("Key %s doesn't exist", key) } return value } /************************************/ /******** ENCOGING MANAGEMENT********/ /************************************/ // This function checks the Content-Type to select a binding engine automatically, // Depending the "Content-Type" header different bindings are used: // "application/json" --> JSON binding // "application/xml" --> XML binding // else --> returns an error // if Parses the request's body as JSON if Content-Type == "application/json" using JSON or XML as a JSON input. It decodes the json payload into the struct specified as a pointer.Like ParseBody() but this method also writes a 400 error if the json is not valid. func (c *Context) Bind(obj interface{}) bool { var b binding.Binding ctype := filterFlags(c.Request.Header.Get("Content-Type")) switch { case c.Request.Method == "GET" || ctype == MIMEPOSTForm: b = binding.Form case ctype == MIMEJSON: b = binding.JSON case ctype == MIMEXML || ctype == MIMEXML2: b = binding.XML default: c.Fail(400, errors.New("unknown content-type: "+ctype)) return false } return c.BindWith(obj, b) } func (c *Context) BindWith(obj interface{}, b binding.Binding) bool { if err := b.Bind(c.Request, obj); err != nil { c.Fail(400, err) return false } return true } func (c *Context) Render(code int, render render.Render, obj ...interface{}) { if err := render.Render(c.Writer, code, obj...); err != nil { c.ErrorTyped(err, ErrorTypeInternal, obj) c.Abort(500) } } // Serializes the given struct as JSON into the response body in a fast and efficient way. // It also sets the Content-Type as "application/json". func (c *Context) JSON(code int, obj interface{}) { c.Render(code, render.JSON, obj) } // Serializes the given struct as XML into the response body in a fast and efficient way. // It also sets the Content-Type as "application/xml". func (c *Context) XML(code int, obj interface{}) { c.Render(code, render.XML, obj) } // Renders the HTTP template specified by its file name. // It also updates the HTTP code and sets the Content-Type as "text/html". // See http://golang.org/doc/articles/wiki/ func (c *Context) HTML(code int, name string, obj interface{}) { c.Render(code, c.Engine.HTMLRender, name, obj) } // Writes the given string into the response body and sets the Content-Type to "text/plain". func (c *Context) String(code int, format string, values ...interface{}) { c.Render(code, render.Plain, format, values) } // Writes some data into the body stream and updates the HTTP code. func (c *Context) Data(code int, contentType string, data []byte) { if len(contentType) > 0 { c.Writer.Header().Set("Content-Type", contentType) } if code >= 0 { c.Writer.WriteHeader(code) } c.Writer.Write(data) } // Writes the specified file into the body stream func (c *Context) File(filepath string) { http.ServeFile(c.Writer, c.Request, filepath) }