117 lines
3.4 KiB
Go
117 lines
3.4 KiB
Go
// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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/*
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Show nicely (but simple) formatted HTML error pages (or respond with JSON
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if the appropriate `Accept` header is set)) for the http package.
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*/
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package http
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import (
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"encoding/json"
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"fmt"
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"html/template"
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"net/http"
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"time"
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"github.com/ethereum/go-ethereum/log"
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)
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//templateMap holds a mapping of an HTTP error code to a template
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var templateMap map[int]*template.Template
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//parameters needed for formatting the correct HTML page
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type ErrorParams struct {
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Msg string
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Code int
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Timestamp string
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template *template.Template
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Details template.HTML
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}
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//we init the error handling right on boot time, so lookup and http response is fast
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func init() {
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initErrHandling()
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}
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func initErrHandling() {
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//pages are saved as strings - get these strings
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genErrPage := GetGenericErrorPage()
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notFoundPage := GetNotFoundErrorPage()
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//map the codes to the available pages
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tnames := map[int]string{
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0: genErrPage, //default
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400: genErrPage,
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404: notFoundPage,
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500: genErrPage,
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}
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templateMap = make(map[int]*template.Template)
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for code, tname := range tnames {
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//assign formatted HTML to the code
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templateMap[code] = template.Must(template.New(fmt.Sprintf("%d", code)).Parse(tname))
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}
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}
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//ShowError is used to show an HTML error page to a client.
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//If there is an `Accept` header of `application/json`, JSON will be returned instead
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//The function just takes a string message which will be displayed in the error page.
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//The code is used to evaluate which template will be displayed
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//(and return the correct HTTP status code)
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func ShowError(w http.ResponseWriter, r *http.Request, msg string, code int) {
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if code == http.StatusInternalServerError {
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log.Error(msg)
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}
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respond(w, r, &ErrorParams{
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Code: code,
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Msg: msg,
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Timestamp: time.Now().Format(time.RFC1123),
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template: getTemplate(code),
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})
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}
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//evaluate if client accepts html or json response
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func respond(w http.ResponseWriter, r *http.Request, params *ErrorParams) {
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w.WriteHeader(params.Code)
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if r.Header.Get("Accept") == "application/json" {
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respondJson(w, params)
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} else {
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respondHtml(w, params)
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}
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}
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//return a HTML page
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func respondHtml(w http.ResponseWriter, params *ErrorParams) {
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err := params.template.Execute(w, params)
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if err != nil {
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log.Error(err.Error())
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}
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}
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//return JSON
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func respondJson(w http.ResponseWriter, params *ErrorParams) {
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w.Header().Set("Content-Type", "application/json")
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json.NewEncoder(w).Encode(params)
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}
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//get the HTML template for a given code
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func getTemplate(code int) *template.Template {
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if val, tmpl := templateMap[code]; tmpl {
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return val
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} else {
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return templateMap[0]
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}
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}
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