form表单的提交和对URL的解析

原文地址：http://www.hacksparrow.com/form-handling-processing-in-express-js.html

Handle / Process GET requests in Express

There are two ways of passing parameters to an Express application:i. Using named placeholders, ii. GET parameters.

i. NamedPlaceholders

Named placeholders are defined in Express routes (very likely inthe

app.js

file),and use URL fragments for relaying information to the app. A namedplaceholder might
be defined and accessed this way in Express:

app.get('/user/:id', function(req, res) {

res.send('user ' + req.params.id);

});

ii. GETParameters

Another method of sending information to an app in the URL is topass them via GET parameters.

If this is the URL

http://localhost/books?category=biographies&type=paperback

you access the GET parameters in Express, this way:

console.log('Category: ' + req.query['category']);

console.log('Type: ' + req.query['type']);

Handle / Process POST requests inExpress

The POST request method also has two aspects to it: i. text data,ii. file uploads. Let's see how they are handled in Express.

i. Text Data

All default Express applications are ready to handle text POSTrequests using the bodyParsermiddleware.Look for

app.use(express.bodyParser())

in

app.js

,if
you see that, you are good to go.

If your form looks like this:

<form method="post">

<input type="text" name="username">

<input type="password" name="password">

<input type="submit">

</form>

you can access the POST submitted text data this way:

console.log('Username: ' + req.body.username);

console.log('Password: ' + req.body.password);

ii. File Uploads

This part of the article is not recommended if you are working withthe latest version of Express. Read thisinstead.

File uploads in Express is not that straightforward as of thiswriting. But it isn't that complicated either, you just need to doa few things and you'll be all set up to handle file uploadstoo.

First of all you'll need to install

connect-form

.

$ npm install connect-form

connect-form@0.2.1 ./node_modules/connect-form

└── formidable@1.0.8

You might have read/seen somewhere that you canuse

node-formidable

toofor uploading files. Confused whether touse

node-formidable

or

connect-form

?Let
all confusion be cleared, for

connect-form

isnothing but

node-formidable

itself!Yes,

connect-form

isjust
an Express-friendly wrapper on topof

node-formidable

.

After you have installed

connect-form

,you need to make some changes to

app.js

.Require
the

connect-form

module,and pass a form object to

express.createServer

.

var form = require('connect-form');

var app = module.exports = express.createServer(form({ keepExtensions: true, uploadDir:'./uploads' }));

The

uploadDir

parameteris used to specify where we want the files to be uploaded to. Formore details about

connect-form

,visit
the

connect-form

GitHubpage.

So here is the updated HTML form:

<form method="post" enctype="multipart/form-data" action="/file-upload">

<input type="text" name="username">

<input type="password" name="password">

<input type="file" name="thumbnail">

<input type="submit">

</form>

Make sure

method

isset to

post

and

enctype

to

multipart/form-data

,else
file uploads just won't work. It is very important to notethat once you have set your form to

multipart/form-data

,you will no longer be able to access the post datafrom

req.body

!

Here is the Express route and an example code to handle the aboveform:

app.post('/file-upload', function(req, res, next) {

req.form.complete(function(err, fields, files) {

if (err) { next(err); }

else {

console.log(fields);

console.log('---------------');

console.log(files);

res.redirect(req.url);

}

});

});

All the POST text fields and values are available inthe

fields

objectof the

req.form.complete

callbackobject,
and all the files in the

files

object.Since you have the references to the POST objects now, process themwhatever way suits you.