How to handle invalid JSON in http.request?

[Nigel Brown]

Using nodejs and express I am trying to write a proxy of sorts, to handle a set of mapped urls in different back end servers. The code is below. It seems to work pretty well. 

Unfortunately, I have a naughty client, that says it is sending application/json whereas it actually sends two json objects on different lines.

{...}

{...}

So, when I receive this I get the following error:

SyntaxError: Unexpected token {

 at Object.parse (native)

 at /Users/nigel/code/webui/nodejs-api/node_modules/express/node_modules/connect/lib/middleware/json.js:75:25

 at IncomingMessage.onEnd (/Users/nigel/code/webui/nodejs-api/node_modules/express/node_modules/connect/node_modules/raw-body/index.js:109:7)

 at IncomingMessage.g (events.js:199:16)

 at IncomingMessage.emit (events.js:104:17)

 at _stream_readable.js:908:16

 at process._tickCallback (node.js:355:11)

Which is fair enough in some ways. The trouble is, the proxied server is expecting this double JSON, so, my proxy is blocking what the client and server think is valid content. 

So the question is, is there any way I can pass this straight through (without doing the JSON parse) or trap the error and repair it?

I am pretty new to nodejs and express, so this might be obvious to one of you.

Many thanks.

  app.all(path,  function(request, response) {

 

    var turl = request.url.substring(n);

    var puri = url.parse(target);

    var proxy_request = http.request({port: puri.port, host: puri.hostname, method: request.method, path: turl, headers: request.headers});

    proxy_request.addListener('response', function (proxy_response) {

      proxy_response.addListener('data', function(chunk) {

        if(this.headers['content-type'].indexOf('json') > 0) {

          console.log('writing response ' + chunk);

          response.write(chunk);

        } else {

          response.write(chunk, 'binary');

        }

      });

      proxy_response.addListener('end', function() {

        console.log('response end');

        response.end();

      });

      response.writeHead(proxy_response.statusCode, proxy_response.headers);

    });

    request.addListener('data', function(chunk) {

      if(chunk) {

        console.log('writing to proxy ' + chunk);

        proxy_request.write(chunk, 'binary');

      }

    });

    request.addListener('end', function() {

      console.log('request end');

      proxy_request.end();

    });

    if(request._body) {

      var txt = JSON.stringify(request.body);

      if(txt =='{"somevalidjson":"yes"}') {

        console.log('bad!!!');

      }

      console.log('writing body ' + txt);

      proxy_request.write(txt, 'binary');

      proxy_request.end();

    }

  });

[Jimb Esser]

Looks like the problem is the "json" middleware, presumably (in the code above what you pasted), you're adding that to your express app?  The json middleware will not work with requests saying they're application/json and not passing data in the same format as the middleware expects.  Try not using that, or using it only for routes that actually need it?

I'm not at all familiar with recent versions of Express, so it's possible that's getting added in automatically somehow, but I'd guess you're opting in to it somewhere.

Also, you may be interested in node-http-proxy, it is very robust at proxying anything Node can deal with.

Hope this helps!

  Jimb Esser