handling multiple POST requests - node.js

with EXPRESS.JS i wrote a service to connect my app to a database, this service is basically an endpoint and inside i have multiple GET or POST requests.
now i have to make two different POST request on the same address.
first POST request:
app.post("/accesso", function(req, res) {
connection.getConnection(function(err, connection) {
let sql = "DELETE FROM accesso where ?";
let variabile = { idaccesso: req.body.idaccesso };
connection.query(sql, variabile, function(error, results) {
if (error) throw error;
res.send(results).end();
});
connection.release();
});
});
second POST request:
app.post("/accesso", function(req, res) {
connection.getConnection(function(err, connection) {
let sql = "INSERT INTO accesso SET ?";
let variabile = { utente: req.body.utente };
connection.query(sql, variabile, function(error, results) {
if (error) throw error;
// RISPOSTA DATABASE:
res.send(results).end();
});
connection.release();
});
});
when i test those requests obviously i can't make the post request, because basically the sql query and the body is different.
is there a way to make multiple POST request on the same TABLE?

Use the next() middleware.
The next middleware function is commonly denoted by a variable named next.
Middleware functions can perform the following tasks:
Execute any code.
Make changes to the request and the response objects.
End the request-response cycle.
Call the next middleware function in the stack.
So, in your code, change your first post request by including the next parameter and call it once the post is made like this,
app.post("/accesso", function(req, res, next) {
connection.getConnection(function(err, connection) {
let sql = "DELETE FROM accesso where ?";
let variabile = { idaccesso: req.body.idaccesso };
connection.query(sql, variabile, function(error, results) {
if (error) throw error;
res.send(results).end();
});
connection.release();
next();
});
});
Then place your second post request as is (without any change).
Hope this helps!

As your first request want to delete something from DB, you can define a app.delete method with the same path.
And let the second method be the same as post.
app.delete("/accesso", function(req, res) {
connection.getConnection(function(err, connection) {
let sql = "DELETE FROM accesso where ?";
let variabile = { idaccesso: req.body.idaccesso };
connection.query(sql, variabile, function(error, results) {
if (error) throw error;
res.send(results).end();
});
connection.release();
});
});

Related

Cannot set headers after they are sent to clients in node.js

My code is not working . I am beginner and don't know my problem. Kindly help.I have seen one or two solution on stackoverflow but didnot get .
This is code.
app.post('/post',(request,response)=>{
var description=request.body.description;
var contact_number=request.body.contact_number;
var city=request.body.city;
var budget=request.body.budget;
var category=request.body.optradio;
var query=connection.query("insert into jobs(Jobs_id,Description,Category,City,Contact_number,Budget) values(?,?,?,?,?,?)",[null,description,category,city,contact_number,budget],function(err){
if(err)
console.log(err);
else
response.send("successful");
});
response.redirect('/data');
});
app.get('/data',function(request,response){
connection.query("SELECT * FROM jobs ORDER BY Jobs_id DESC",(err, rows,fields) => {
if(err) {
console.log(err);
}
else {
response.render('feed', {title : 'Jobs Details',
items: rows })
}
});
});
app.listen(3000);
This is the error
pp.post('/post', (request, response) => {
var description = request.body.description;
var contact_number = request.body.contact_number;
var city = request.body.city;
var budget = request.body.budget;
var category = request.body.optradio;
var query = connection.query("insert into jobs(Jobs_id,Description,Category,City,Contact_number,Budget) values(?,?,?,?,?,?)", [null, description, category, city, contact_number, budget],
function (err) {
if (err) {
console.log(err);
} else {
response.redirect('/data');
}
});
});
app.get('/data', function (request, response) {
connection.query("SELECT * FROM jobs ORDER BY Jobs_id DESC", (err, rows, fields) => {
if (err) {
console.log(err);
}
else {
response.render('feed', {
title: 'Jobs Details',
items: rows
})
}
});
});
app.listen(3000);
There can be only one response to single HTTP request. In your code, you are first trying to send response with
response.send("successful");
but this on its own doesn't break the flow of the function which means that if the condition is actually met then this will execute and the execution continues and finds another response, in this case
response.redirect('/data');
and it will try to send another response to the original http request but at this point it is already too late because one response has already been send.
To solve this issue in general, you can place return in front of any line of code that is closing the the connection (response.send, response.redirect, ...). That way, the function's execution is terminated at the first response, whichever it is.
So you could do something like
var query=connection.query("insert into jobs(Jobs_id,Description,Category,City,Contact_number,Budget) values(?,?,?,?,?,?)",[null,description,category,city,contact_number,budget],function(err){
if(err)
console.log(err);
else
return response.send("successful");
});
return response.redirect('/data');
});

Express GET Request Results in Error: "res.send is not a function"

I am trying to get data from a SQL Server DB using node. I can make a connection and get data by running functions, but I would like to turn the functions into API endpoints.
Based on the error it seems to me that the res variable isn't getting passed down into the last if statement, but I'm not seeing the issue.
I get a res.send is not a function error when using a GET method on this address from Postman.
let mssqlQuery = function(query, res) {
sql.connect(dbConfig, function(err) {
if (err) {
console.log("Error while connecting database :- " + err)
res.send(err)
} else {
let request = new sql.Request();
request.query(query, function(err, res) {
if (err) {
console.log("Error while querying database :- " + err)
res.send(err)
} else {
res.send(res) // res.send is not a function
}
})
}
})
}
// GET API
app.get("/api/address", function(req, res) {
var query = "select * from address"
mssqlQuery(query, res)
})
Is the res variable improperly scoped or might I have the wrong approach entirely?
As #Sirko suggested, the res value was shadowed by an other variable. The corrected code:
let mssqlQuery = function(query, res) {
sql.connect(dbConfig, function(err) {
if (err) {
console.log("Error while connecting database :- " + err)
res.send(err)
} else {
let request = new sql.Request();
request.query(query, function(err, resp) { // Changed res to resp
if (err) {
console.log("Error while querying database :- " + err)
res.send(err)
} else {
res.send(resp) // res.send is not a function
}
})
}
})
}

NodeJS callback - Access to 'res'

I am using the Express framework and I have the following in one of my route files:
var allUsersFromDynamoDb = function (req, res) {
var dynamodbDoc = new AWS.DynamoDB.DocumentClient();
var params = {
TableName: "users",
ProjectionExpression: "username,loc,age"
};
dynamodbDoc.scan(params, function (err, data) {
if (err) {
console.error("Unable to query. Error:", JSON.stringify(err));
res.statusCode = 500;
res.send("Internal Server Error");
} else {
console.log("DynamoDB Query succeeded.");
res.end(JSON.stringify(data.Items));
}
});
}
I am using the above function in one of my routes:
router.get('/users', allUsersFromDynamoDb);
Now the callback that I am defining while making a call to the "scan" on dynamodbDoc can be pretty useful if defined as a separate function. I can re-use that for some of my other routes as well.
But how can I can still get access to the "res" inside this new function?
I think I should be using "closure" but I can't seem to get it exactly right. I think I would need to maintain the signature of the new callback function to expect 2 params, "err" and "data" as per the following page:
http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html#scan-property
Any ideas on how this can be done?
You can use that function as middleware of every routes you want http://expressjs.com/en/guide/using-middleware.html
The new route with the middleware:
var middlewares = require('./middlewares'),
controllers = require('./controllers');
router.get('/users', middlewares.allUsersFromDynamoDb, controllers.theRouteController);
The middleware (middlewares.js) where you pass your data to req so you can use that data everywhere you have req:
exports.allUsersFromDynamoDb = function (req, res, next) {
var dynamodbDoc = new AWS.DynamoDB.DocumentClient();
var params = {
TableName: "users",
ProjectionExpression: "username,loc,age"
};
dynamodbDoc.scan(params, function (err, data) {
if (err) {
console.error("Unable to query. Error:", JSON.stringify(err));
next("Internal Server Error");
} else {
console.log("DynamoDB Query succeeded.");
req.dataScan = JSON.stringify(data.Items);
next();
}
});
};
And finally the controller (controllers.js):
exports.theRouteController = function (req, res) {
// Here is the dataScan you defined in the middleware
res.jsonp(req.dataScan);
};
Based on Michelem's answer here I tried something which makes things a bit cleaner and code more reusable:
var allUsersFromDynamoDb = function (req, res, next) {
var dynamodbDoc = new AWS.DynamoDB.DocumentClient();
var params = {
TableName: "users",
ProjectionExpression: "username,loc,age"
};
dynamodbDoc.scan(params, function (err, data) {
req.err = err;
req.data = data;
next();
});
}
Now I declare another function:
var processUserResults = function (req, res, next) {
if (req.err) {
console.error("Unable to query. Error:", JSON.stringify(req.err));
res.statusCode = 500;
res.send("Internal Server Error");
} else {
console.log("DynamoDB Query succeeded.");
res.end(JSON.stringify(req.data.Items));
}
};
And finally this:
router.get('/users', [allUsersFromDynamoDb, processUserResults]);
All I need to do in the original "function(err, data)" callback is always set 2 values:
req.err = err
req.data = data
And call next(). And processUserResults can similarly be used for other routes.
Still curious to find out if there are any other efficient solutions.

Node js Insert a data in redis via url

i'm having a problem in posting/inserting a data in my redis database via POST method. By the way i'm using expressjs as framework and here is my code:
app.post('/create/:id', function (req, res) {
return client.set(req.params.id, req.params.val, function (err, data) {
if (!err) {
return res.send(data);
} else {
return console.log(err);
}
});
});
Is there any correction here? My goal is to post data like this http://mydomain:45/create/2/test is it possible? or do I need only to POST it to /create with the id and the value of that id? Thanks guys. I hope you can help me. :)
You are setting the value of req.params.id as the key, and the possibly undefined value of req.params.val as the value. You should set the req.body.val instead of req.params.val, if you are POST-ing with a request body.
Try with the following changes:
app.post('/create/:id', function (req, res) {
return client.set(req.params.id, req.body.val, function (err, data) {
if (!err) {
return res.send(data);
} else {
return console.log(err);
}
});
});
And run POST /create/123 with the body val=myValue.

Node.JS / JavaScript Async Call back issue

I am trying to accomplish the following (should be quite basic and I must be missing something trivial):
Call a function with string that has a select statement
Wait until the DB call completes and the rows (or json equivalent) is returned
Populate http object to return back
Here is code:
util.js
exports.execute = function( query){
if (connection) {
connection.query(query, function(err, rows, fields) {
if (err) throw err;
console.log("from Util - " + JSON.stringify(rows));
return JSON.stringify(rows);
});
}
};
repo.js
var q = "select * from xxx";
var response;
util.execute(q, function (err, r){
if (err){
throw err;
console.log(err);
}
else {
console.log(r);
res.contentType('application/json');
res.write(r);
res.end();
}
});
My problem is while the code within util.js is called and I can see the json in console, it never comes back to the anonymous call back function in the repo.js.
What am I doing wrong here ?
Update
Thanks Ben
I also found the solution in same line ... here is new code:
repo.js:
var send_data = function (req, res, r){
res.contentType('application/json');
res.write(r);
res.end();
}
exports.all = function(req, res){
var q = "select * from XXX";
var response;
util.execute(req, res,q, send_data);
};
util.js:
exports.execute = function(req, res, query, callback){
if (connection) {
connection.query(query, function(err, rows, fields) {
if (err) throw err;
callback(req, res, JSON.stringify(rows)) ;
});
}
};
util.execute only accepts one parameter in your code. It needs to accept a second callback parameter in order to use it the way you do. (Callbacks aren't magic, they're just function calls)
Something like:
exports.execute = function(query,callback){
if (connection) {
connection.query(query, function(err, rows, fields) {
if (err) throw err;
console.log("from Util - " + JSON.stringify(rows));
callback(null,JSON.stringify(rows));
});
}
};
If you'd like it to behave consistently and accept an error parameter, you might want fill that in:
exports.execute = function(query,callback){
if (connection) {
connection.query(query, function(err, rows, fields) {
callback(err,null);
console.log("from Util - " + JSON.stringify(rows));
callback(null,JSON.stringify(rows));
});
}
};

Resources