I'm developing a simple application using CouchDB and Node.js. I have few documents in my database and created a view to retrieve the documents. How can I get the view from CouchDB in my javascript file?
app.get('/find', function(req, res){
var cradle = require('cradle');
var connection = new(cradle.Connection)('http://localhost:5984/', 443);
var db = connection.database('db');
db.view('_design/usersView/users', function (err, response) {
console.log(response);
});
The response says: undefined
Try querying the view like this
db.view('usersView/users', function (err, response) {
console.log(response);
});
You don't need a _design/ with cradle (although you need that if you query it with default couchdb api)
Also I think it would be better if you moved the connection and the require statements out of the the controller.
I solved the problem. Just sent http get request to couchDB api to retrieve the view with this command:
db.get('_design/usersView/_view/users', function (err, doc) {
res.end(JSON.stringify(doc));
});
Related
I have a Node.js server which queries MySQL database. It serves as an api end point where it returns JSON and also backend server for my Express application where it returns the retrieved list as an object to the view.
I am looking into implementing flat-cache for increasing the response time. Below is the code snippet.
const flatCache = require('flat-cache');
var cache = flatCache.load('productsCache');
//get all products for the given customer id
router.get('/all/:customer_id', flatCacheMiddleware, function(req, res){
var customerId = req.params.customer_id;
//implemented custom handler for querying
queryHandler.queryRecordsWithParam('select * from products where idCustomers = ? order by CreatedDateTime DESC', customerId, function(err, rows){
if(err) {
res.status(500).send(err.message);
return;
}
res.status(200).send(rows);
});
});
//caching middleware
function flatCacheMiddleware(req, res, next) {
var key = '__express__' + req.originalUrl || req.url;
var cacheContent = cache.getKey(key);
if(cacheContent){
res.send(cacheContent);
} else{
res.sendResponse = res.send;
res.send = (body) => {
cache.setKey(key,body);
cache.save();
res.sendResponse(body)
}
next();
}
}
I ran the node.js server locally and the caching has indeed greatly reduced the response time.
However there are two issues I am facing that I need your help with.
Before putting that flatCacheMiddleware middleware, I received the response in JSON, now when I test, it sends me an HTML. I am not too well versed with JS strict mode (planning to learn it soon), but I am sure the answer lies in the flatCacheMiddleware function.
So what do I modify in the flatCacheMiddleware function so it would send me JSON?
I manually added a new row to the products table for that customer and when I called the end point, it still showed me the old rows. So at what point do I clear the cache?
In a web app it would ideally be when the user logs out, but if I am using this as an api endpoint (or even on webapp there is no guarantee that the user will log out the traditional way), how do I determine if new records have been added and the cache needs to be cleared.
Appreciate the help. If there are any other node.js caching related suggestions you all can give, it would be truly helpful.
I found a solution to the issue by parsing the content to JSON format.
Change line:
res.send(cacheContent);
To:
res.send(JSON.parse(cacheContent));
I created cache 'brute force' invalidation method. Calling clear method will clear both cache file and data stored in memory. You have to call it after db change. You can also try delete specified key using cache.removeKey('key');.
function clear(req, res, next) {
try {
cache.destroy()
} catch (err) {
logger.error(`cache invalidation error ${JSON.stringify(err)}`);
res.status(500).json({
'message' : 'cache invalidation error',
'error' : JSON.stringify(err)
});
} finally {
res.status(200).json({'message' : 'cache invalidated'})
}
}
Notice, that calling the cache.save() function will remove other cached API function. Change it into cache.save(true) will 'prevent the removal of non visited keys' (like mentioned in comment in the flat-cache documentation.
I want to send a JSON (body) on Postman with POST method and receive a result.
Im a trainee and my boss asked me this. I've been looking in web for a week and didn't find. I said to him that method to receive a data is GET, but he said that GET has a limit on URL. If the stored procedure have a lot of parameters we will not receive the expected result, so a I have to use Post method.
This is my code to connect to ms sql server:
var express = require('express');
var app = express();
var sql = require('mssql');
var config = {
user: 'MY_USER',
password: 'MY_PASS',
server: 'MY_SERVER',
database: 'MY_DB'
};
Searching in google I found a way to execute a procedure with GET method. In the browser I put the value I want and I receive the result, but is not still what he wants. The code is:
app.get('/get/:pNU_EST001', function (req, res) {
//conexão com o DB
sql.connect(config, function(){
var request = new sql.Request();
request.input('pNU_EST001', req.params.pNU_EST001);
request.execute('dbo.ESTSP004_ConsultaLivrosEmprestadosAluno_XX', function(err, recordsets, returnValue, affected) {
if(err) console.log(err);
res.send(recordsets);
//res.end(JSON.stringify(recordsets)); /*--- result in JSON format ---*/
});
});
});
On Postman he showed me a example with DB2, but I couldn't see the code. On Post Method, on HEADERS it has two key:
KEY => Content-Type (value: application/json) // KEY => Accept (value: application/json)
And in his example, on BODY, he wrote a JSON like: { "pNU_EST001" : "3"} and received the related result below. That's what I need.
Express has a few other verbs to use you are using
app.get but there is also app.post if you change your code to use the latter instead it will handle a post request
app.post('/path', function (req, res) {
Then in express to get values from the POST body you get that from
req.body property
So in your case you would want to use req.body.pNU_EST001 instead of req.params.pNU_EST001
I have read all the questions on SO that I could find. They all use Express, Mongoose or they leave something out. I understand that Node.js is the server. I understand the MongoDB require is the driver the Node.js server uses to open a connection to the MongoDB. Then, on the server, I can do (from the documentation):
var MongoClient = require('mongodb').MongoClient;
var assert = require('assert');
var ObjectId = require('mongodb').ObjectID;
var url = 'mongodb://localhost:27017/test';
var findRestaurants = function(db, callback) {
var cursor =db.collection('restaurants').find( );
cursor.each(function(err, doc) {
assert.equal(err, null);
if (doc != null) {
console.dir(doc);
} else {
callback();
}
});
};
// Connect to the db
MongoClient.connect(url, function(err, db) {
assert.equal(null, err);
findRestaurants(db, function() { //I don't want to do this as soon as the server starts
db.close();
});
});
//if I put findRestaurant here,
function findRestaurant(data){
}
How do I call it from the client?
I do not want to find data as soon as I start the server. I realize those are examples, but what I cannot find is a way where the client requests some data and where the Node.js server returns it.
I have seen close examples using jQuery, Angular on the client, and then Express, Mongoose, Meteor, , etc.
All I want to understand is how I make this request from the client's browser. I can do that with XMLhttpRequest(), so I can put that part together, I believe. But, any example is appreciated.
But what is waiting on the Node.js side of things (how do I set up my function to be called once the server is listening)?
How do I create a function on the server side, maybe "GetRestaurants" and have that return the data it gets using find()?
I cannot find this information, this simple, anywhere. Is it too complicated to do the example without a framework?
I do not wish to copy and paste from something using Express, etc. without understanding what's going on. Most explanations never say, this goes on the Node.js side. This is client. I know I am expected to do my own research, but I am not putting it together, too used to RDBMSes, IIS, Apache, PHP, and so on.
I believe I have a fundamental misunderstanding of what's going on in the paradigm.
Please. No REST API creation, no frameworks of any kind on Node.js other than using the MongoDB library (unless there is an absolute requirement), not even jQuery, Angular, Jade, or anything else for the client side, straight up JavaScript on all sides.
I have seen questions like this,
How to display data from MongoDB to the frontend via Node.js without using a framework
But they do not show what I am asking. They do it all at once, as soon as the database connects. What if I want to do a delete or insert or find? There are many SO questions like this, but I have not hit the one that shows what I am looking for.
This should give the guidance. Once you go to a browser and type http://localhost:5155 the callback function (request, response) { will be called and the request to db will be made. Make sure you get response and then start working on the client side code:
const http = require('http');
const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
const url = 'mongodb://localhost:27017/test';
const server = http.createServer(function (request, response) {
getData(function (data) {
response.end(data);
});
});
function getData(callback) {
// Connect to the db
MongoClient.connect(url, function (err, db) {
assert.equal(null, err);
findRestaurants(db, function (data) {
db.close();
callback(data);
});
});
const findRestaurants = function (db, callback) {
const cursor = db.collection('restaurants').find();
const data = [];
cursor.each(function (err, doc) {
assert.equal(err, null);
data.push(doc);
if (doc === null) {
callback(data);
}
});
};
}
server.listen(5155);
I've got some data from a JSON file, which I use in my HTML getting it first from AngularJS like this:
$http.get('js/data.json').success(function(data) {
$scope.data = data;
});
And I want to update this JSON file after clicking a button in the HTML:
<button ng-click="postData(id)">Post</button>
You cannot write on files via JavaScript only (AngularJS).
You are to go via server side and point your "post" request to a server side script (i.e: PHP) and make that script do the job.
This sort of thing won't work. The file you are trying to write to would be on a server; and as it is right now, it would be a static resource. I'd suggest reading up on Angular resources, here. You can set up your server-side code to perform CRUD operations on the json file, but an actually database would be best. If you prefer to use a json format, Mongodb is your best choice; here is a link to Mongodb University, which offers free courses. I've done it in the past, and it's been great.
Now, for some actually help in your situation:
You can perform a GET request on your json file because it's seen as a static resource. The POST request, however, needs server-side scripting to do anything.
$http.get('api/YOUR_RESOURCE').success(function(data) {
$scope.database = data;
});
$http.post('api/YOUR_RESOURCE', {
data_key: data_value,
data_key2: data_value2
}).success(function(data) {
data[id].available = false;
});
This may be further ahead on your path to learning Angular, but here is a snippet of Node.js server code, with a Mongo database and Mongoose to handle the 'Schema', to help you get an idea of how this works:
var mongoose = require('mongoose'),
YOUR_RESOURCE = mongoose.model('YOUR_RESOURCE');
app.route('/api/YOUR_RESOURCE')
// This should be your GET request; 'api/
.get(
// Get all docs in resource
YOUR_RESOURCE.find().exec(function (err, data) {
if (err) {
return res.status(400).send({
message: SOME_ERROR_HANDLER
});
} else {
res.json(data); // return list of all docs found
}
});)
// Add new doc to database
.post(function (req, res) {
// The keys of the object sent from your Angular app should match
// those of the model
var your_resource = new YOUR_RESOURCE(req.body);
your_resource.save(function (err) {
if (err) {
return res.status(400).send({
message: SOME_ERROR_HANDLER
});
} else {
// returns newly created doc to Angular after successful save
res.json(your_resource);
}
});
);
Here is an SO page with a list of resources on getting started with Node; I recommend Node because of it's ease of use and the fact that it is written in JS. The Mongo University lessons also go through setting up you server for use with the database; you can choose between several flavors, such as Java, .NET, Python or Node.
There is a bit left out in the examples above, such as the Mongoose model and Node setup, but those will be covered in the resources I've linked to on the page, if you choose to read them. Hope this helps :)
I'm using the MEAN stack for a web app. In my controller.js, I have the following:
var refresh3 = function() {
$http.get('/users').success(function(response) {
console.log("I got the data I requested");
$scope.users = response;
$scope.contact3 = "";
});
};
refresh3();
This pulls back every object in the "users" collection from my MongoDB. How could I add parameters to this to bring back, for example, only objects where "name" : "Bob" ? I have tried adding parameters in the '/users' parentheses using:
$http.get('/users', {params:{"name":"Bob"}})
I've also tried variants of that, but no luck. Any help would be appreciated!
If your server is receiving the data
(and it should, as $http.get('/users', {params:{"name":"Bob"}}) is correct)
On server side, make use of the query string:
req.query
like so:
app.get('/users', function(req,res){
if(req.query.name){
db.users.find({"name":req.query.name},function (err, docs) { console.log(docs); res.json(docs); });
}
else{
db.users.find(function (err, docs) { console.log(docs); res.json(docs); });
}
});
WHAT WAS THE ISSUE?
You hinted in your comments that your server was set to respond to the app.get('/users') GET request like so:
db.users.find(function (err, docs) {
// docs is an array of all the documents in users collection
console.log(docs); res.json(docs); }); });
So I believe that your angularjs $http get is correct, and your server is receiving the parameters {"name":"Bob"} as it should;
it just doesn't know what to do with them:
all it is set to do is to return the whole collection in the particular case of a app.get('/users') GET request.
HOW TO CONFIGURE YOUR SERVER FOR REST
You do not have to re-invent the wheel on the server.
Rather, you could consider using a middleware to automate the task (in the present case, the task is to issue a proper MongoDb request when you receive a get query with parameters from the client)
e.g. express-restify-mongoose middleware