Verify PostGIS connection, username and password

Question

I wrote the code below, but I need that the PostGIS connection to be verified, to be sure that the username and password are right. I tried this: How to access user credentials in database connection? , but it didn't worked.

I am using QGIS 3.8.3

uri = QgsDataSourceUri()
uri.setConnection('LPOSTDES-CL2', '5432', 'ugpi', None, None)
connInfo = uri.connectionInfo()
(success ,user, passwd) = QgsCredentials.instance().get(connInfo, None, None)
if success:
    QgsCredentials.instance().put(connInfo, user, passwd)
uri.setConnection('LPOSTDES-CL2', '5432', 'ugpi', user, passwd)

Replace (a, user, passwd) with (success, user, passwd), it works with me. — J. Monticolo, Feb 12 '20 at 15:48
@J.Monticolo Thanks! Edited the post and tried again, but didn't work, because, if I enter an incorrect username or password, it doesn't return me back some error message. To see what the QGIS receive, type in the end: print(uri.connectionInfo()) — vitorcsm, Feb 13 '20 at 11:01

score 3 · Accepted Answer · answered Feb 13 '20 at 13:18

You can directly verify this with QtSql, see the following Python3 code :

from PyQt5.QtSql import QSqlDatabase

host = "LPOSTDES-CL2"
port = 5432
database = "ugpi"

db = QSqlDatabase.addDatabase("QPSQL")
db.setHostName(host)
db.setPort(port)
db.setDatabaseName(database)

(success, user, passwd) = QgsCredentials.instance().get(connInfo, None, None)
if success:
    db.setUserName(user)
    db.setPassword(passwd)

if db.open():
    print("Connection successful !")
else:
    print("Connection failed.")

Here I just copy the method without have connInfo and there is no really reason for use QgsCredentials here, just a dialog with two QLineEdit widgets will do the stuff.

Verify PostGIS connection, username and password

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