错误:未指定默认引擎并且未提供扩展名。

191

我正在使用Node.js和Engine设置HTTP服务器,但是我一直遇到一些问题,而且我缺乏解决这些问题的信息。我希望能得到帮助来解决这个问题。

Error: No default engine was specified and no extension was provided. 
at new View (...\node_modules\express\lib\view.js:41:42) 
at Function.app.render (...\node_modules\express\lib\application.js:484:12) 
at ServerResponse.res.render (...\node_modules\express\lib\response.js:783:7) 
at Layer.handle (...\app.js:123:7) 
at trim_prefix (...\node_modules\express\lib\router\index.js:225:17) 
at c (...\node_modules\express\lib\router\index.js:198:9) 
at Function.proto.process_params (...\node_modules\express\lib\router\index.js:253:12) 
at next (...\node_modules\express\lib\router\index.js:189:19) 
at next (...\node_modules\express\lib\router\index.js:202:7) 
at next (...\node_modules\express\lib\router\index.js:166:38)

以下是我准备启动此引擎时所设置的内容。

var http = require('http');  
var module = require("module")
var logger = require('morgan');
var express = require('express');
var app =  module.exports = express();
var silent = 'test' == process.env.NODE_ENV;
var httpServer = http.createServer(app);  // app middleware

app.enable('strict routing');
// app.all('*', function(req, res, next)/*** CORS support.*/
// {
//   if (!req.get('Origin')) return next();// use "*" here to accept any origin
//   res.set('Access-Control-Allow-Origin', 'http://localhost:3000');
//   res.set('Access-Control-Allow-Methods', 'GET, POST');
//   res.set('Access-Control-Allow-Headers', 'X-Requested-With, Content-Type');
//   res.set('Access-Control-Allow-Max-Age', 3600);
//   if ('OPTIONS' == req.method) return res.send(200);
//   next();
// });
app.set('views', __dirname + '/views'); // general config
app.set('view engine', 'html');
app.get('/404', function(req, res, next){
next();// trigger a 404 since no other middleware will match /404 after this one, and we're not responding here
});
app.get('/403', function(req, res, next){// trigger a 403 error
  var err = new Error('not allowed!');
  err.status = 403;
  next(err);
});
app.get('/500', function(req, res, next){// trigger a generic (500) error
  next(new Error('keyboard cat!'));
});
app.use(express.static(__dirname + '/public')); 
//error handlers
app.use(logErrors);
app.use(clientErrorHandler);
app.use(errorHandler);  
// middleware with an arity of 4 are considered error handling middleware. When you next(err)
// it will be passed through the defined middleware in order, but ONLY those with an arity of 4, ignoring regular middleware.
function clientErrorHandler(err, req, res, next) {
  if (req.xhr) {// whatever you want here, feel free to populate properties on `err` to treat it differently in here.
  res.send(err.status || 500, { error: err.message });
  } 
  else 
  { next(err);}
};
// create an error with .status. we can then use the property in our custom error handler (Connect repects this prop as well)
function error  (status, msg) {
  var err = new Error(msg);
  err.status = status;
  return err;
};
function logErrors  (err, req, res, next) {
  console.error(err.stack);
  next(err);
};
function errorHandler (err, req, res, next) {
  res.status(500);
  res.render('error', { error: err });
};

// Error handlers
// Since this is the last non-error-handling middleware use()d, we assume 404, as nothing else responded.
// $ curl http://localhost:3000/notfound
// $ curl http://localhost:3000/notfound -H "Accept: application/json"
// $ curl http://localhost:3000/notfound -H "Accept: text/plain"
app.use(function(req, res, next){
  res.status(404); 
  if (req.accepts('html')) {// respond with html page
    res.render('404', { url: req.url });
    return;
  } 
  if (req.accepts('json')) {// respond with json
    res.send({ error: 'Not found' });
    return;
  } 
  res.type('txt').send('Not found');// default to plain-text. send()
});

// error-handling middleware, take the same form as regular middleware, however they require an
// arity of 4, aka the signature (err, req, res, next).when connect has an error, it will invoke ONLY error-handling middleware.

// If we were to next() here any remaining non-error-handling middleware would then be executed, or if we next(err) to
// continue passing the error, only error-handling middleware would remain being executed, however here
// we simply respond with an error page.
app.use(function(err, req, res, next){
  // we may use properties of the error object here and next(err) appropriately, or if we possibly recovered from the error, simply next().
  res.status(err.status || 500);
  res.render('500', { error: err });
});

if (!module.parent) {// assigning to exports will not modify module, must use module.exports
  app.listen(3000);
  silent || console.log('Express started on port 3000');
};

根据要求,请尝试以下三种之一 - res.status(200).send({ id: '123' });res.status(400).send({ error: 'Bad Request' });res.status(500).send({ error: 'Unknown Request' }); - Manohar Reddy Poreddy
15个回答

165

如果您不使用视图引擎,res.render将会抛出一个错误。

如果您只想提供JSON,请将代码中的res.render('error',{error:err})行替换为:

res.json({ error: err })

PS:通常情况下,返回的对象中还包含用户的信息:

res.status(err.status || 500);
res.json({
  message: err.message,
  error: err
});

126
你缺少视图引擎,例如使用jade
更改你的
app.set('view engine', 'html');

使用

app.set('view engine', 'jade');

如果您想使用HTML友好的语法,请改用ejs
app.engine('html', require('ejs').renderFile);
app.set('view engine', 'html');

编辑

正如您可以从view.js中阅读到的那样,Express View模块

module.exports = View;

/**
 * Initialize a new `View` with the given `name`.
 *
 * Options:
 *
 *   - `defaultEngine` the default template engine name
 *   - `engines` template engine require() cache
 *   - `root` root path for view lookup
 *
 * @param {String} name
 * @param {Object} options
 * @api private
 */

function View(name, options) {
  options = options || {};
  this.name = name;
  this.root = options.root;
  var engines = options.engines;
  this.defaultEngine = options.defaultEngine;
  var ext = this.ext = extname(name);
  if (!ext && !this.defaultEngine) throw new Error('No default engine was specified and no extension was provided.');
  if (!ext) name += (ext = this.ext = ('.' != this.defaultEngine[0] ? '.' : '') + this.defaultEngine);
  this.engine = engines[ext] || (engines[ext] = require(ext.slice(1)).__express);
  this.path = this.lookup(name);
}

你必须安装一个默认引擎。
Express通过program.template搜索默认布局视图,如下所示:
mkdir(path + '/views', function(){
      switch (program.template) {
        case 'ejs':
          write(path + '/views/index.ejs', ejsIndex);
          break;
        case 'jade':
          write(path + '/views/layout.jade', jadeLayout);
          write(path + '/views/index.jade', jadeIndex);
          break;
        case 'jshtml':
          write(path + '/views/layout.jshtml', jshtmlLayout);
          write(path + '/views/index.jshtml', jshtmlIndex);
          break;
        case 'hjs':
          write(path + '/views/index.hjs', hoganIndex);
          break;

      }
    });

而且正如您可以在下面阅读的那样:

program.template = 'jade';
if (program.ejs) program.template = 'ejs';
if (program.jshtml) program.template = 'jshtml';
if (program.hogan) program.template = 'hjs';

默认视图引擎是jade


2
你好,能否请您进一步解释一下这是如何工作的?我最初阅读了有关node.js的内容,认为这就是我所需要的全部,但当我仍然无法显示我的页面时,我查找了原因,并找到了有关express的信息。现在我按照express 4.2页面上的信息进行操作,遇到了上面提到的错误,您帮助了我解决了这个问题。现在我使用了ejs,但似乎还不是我所需要的全部。您能否请给我一个流程,说明应该如何工作呢? - Kobojunkie
我建议您阅读这个逐步教程http://utahjs.com/2010/09/25/nodejs-express-and-ejs-templates/或者这个http://robdodson.me/blog/2012/05/31/how-to-use-ejs-in-express/。 - ale
我曾经认为,即使您不渲染视图,也必须显式定义视图引擎。但事实并非如此。 - stevejpurves

18

在你的代码中注释掉res.render行,并改为添加next(err);。如果你没有使用视图引擎,则res.render部分将会抛出错误。

对不起,你还需要注释掉这一行:

app.set('view engine', 'html');

我的解决方案将不使用视图引擎。你不需要一个视图引擎,但如果这是目标,请尝试以下方法:

app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
//swap jade for ejs etc

当使用视图引擎时,您将需要 res.render 行。就像这样:

// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
    message: err.message,
    error: err
    });
  });
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  next(err);
  res.render('error', {
  message: err.message,
  error: {}
  });
});

16

如果您希望呈现一个HTML文件,请使用:

response.sendfile('index.html');

然后你移除:

app.set('view engine', 'html');

将您的*.html文件放在views目录中,或者将public目录作为静态目录并将index.html文件放在public目录中。


5
response.sendfile() 已经废弃,请使用response.sendFile()。请注意大写字母 "F"。 - Pramesh Bajracharya

9

替代

app.get('/', (req, res) => res.render('Hellooooo'))

使用

app.get('/', (req, res) => res.send('Hellooooo'))

哈哈,由于我的自动完成功能,犯了一个愚蠢的错误。 - Bharat Singh

7

请替换

app.set('view engine', 'html'); 

使用

app.set('view engine', 'ejs');

6

按照以下方式设置视图引擎

app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

4

如果只需要在代码中嵌入HTML代码,我们可以使用以下方法:

var app = express();
app.get('/test.html', function (req, res) {
   res.header('Content-Type', 'text/html').send("<html>my html code</html>");
});

res.header()是将HTML代码发送到HTML文件中的头标签的一种方式吗?我能否以类似的方式使用res.documentByID()将HTML发送到具有特定ID的文档内标签? - Marko Kolaksazov
res.header()是一种将HTML代码发送到HTML文件中的标头标签的方法吗?我能否以类似的方式使用res.documentByID()将HTML发送到具有特定ID的文档内的标签中? - undefined

1
上述答案是正确的,但我发现一个简单的打字错误也可以导致此错误。例如,我有 var router = express() 而不是 var router = express.Router(),并得到了这个错误。因此应该是以下内容:
// App.js 
var express = require('express');
var app = express();
var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({ extended:false}));
// assuming you put views folder in the same directory as app.js
app.set('views', __dirname + '/views')
app.engine('ejs', ejs.renderFile);
app.set('view engine', 'ejs');
// router - wherever you put it, could be in app.js
var router = express.Router();
router.get('/', function (req,res) {
  res.render('/index.ejs');
})

1
只需在代码中设置视图引擎。
var app = express(); 
app.set('view engine', 'ejs');

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