Cannot connect to MSSQL database using jdbc - java

I'm trying to run a simple Android application that has a button click event which connects to database and retrieves a user from Clients table depending on the text input.
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection connection = DriverManager.getConnection("jdbc:sqlserver://ServerUrl;databaseName=DBNAME;selectMethod=cursor;user=USER;password=*****");
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT * FROM Clients WHERE IMEI = "+imei+"");
However, when I run the project with a breakpoint on the line that begins with "Statement" I notice that the code does not event arrive at that line.
I tried surrounding the connection line with try-catch but it throws no exception, it simply does nothing. The database is hosted so it's not on localhost.
Please keep in mind that I'm very new to Android development and do not burn me if I'm missing something very simple :)

Related

Why is this mySQL database not connecting to Netbeans?

The mysql database will not connect to the netbeans code. I am using a Mac Device and have installed mySQL on my device (it is running fine on localhost:8080). However, the connection through Java is not working. I believe there may be an error in the following line "conn = Driver Manager..." since it is not executing. I am unsure of how to change the password / what the password is.
Restarting Xampp
Screenshot of connection code
Expected result: user input is sent to mySQL database
Actual result (error): seen in this screenshot
This is the general database connectivity code .
try
{
Class.forName("java.sql.DriverManager");
Connection con=(Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/DatabaseName","MysqlUsername","MysqlPassword");
Statement stmt = (Statement) con.createStatement();
String query = "YourMysqlQuery";
stmt.executeUpdate(query);
}
catch(Exception e)
{
JOptionPane.showMessageDialog(this, e.getMessage());
}
// You also have to add 'jdbc driver' in lib folder of your project.
If want us to solve the problem in your code then please provide the actual code you have done , Not the image .

Sql Server data extraction (java jdbc): process hangs during retrieving rows

I need to extract data from a remote Sql server database. I am using the mssql jdbc driver.
I noticed that often dwhen retrieving rows from the database the process suddenly hangs, giving no errors. It remains simply stuck and no more rows are processed.
The code to read from the database is the following:
String connectionUrl = "jdbc:sqlserver://10.10.10.28:1433;databaseName=MYDB;user=MYUSER;password=MYPWD;selectMethod=direct;sendStringParametersAsUnicode=false;responseBuffering=adaptive;";
String query = "SELECT * FROM MYTABLE";
try (Connection sourceConnection = DriverManager.getConnection(connectionUrl);
Statement stmt = sourceConnection.createStatement(SQLServerResultSet.TYPE_SS_SERVER_CURSOR_FORWARD_ONLY, SQLServerResultSet.CONCUR_READ_ONLY) ) {
stmt.setFetchSize(100);
resultSet = stmt.executeQuery(query);
while (resultSet.next()) {
// Often, after retrieving some rows, process remains stuck here
}
}
Usually the connection is established correctly, some rows are fetched, than at some point the process can become stuck in retrieving the next rows batch, giving no errors and not processing any new row. This happens some times, other times it completes succesfully.
AFAIK the only reason I can see is that at some point a connection problem occurs with the remote machine, but shouldn't I be notified of this from the driver?
I am not sure how I should handle these type of situations...is there anything I can do on my side to let the process complete even if there is a temporary connection problem with the remote server (of course if the connection is not recoverable there is nothing I can do)?
As another test, instead of the java jdbc driver I've tried the bcp utility to extract data from the remote database and even with this native utility I can observe the same problem: sometimes it completes succesfully, other times it retrieves some rows (say 20000) and then becomes stuck, no errors and no more rows processed.

How to relax autocommit in Java JDBC when updating a MySQL database online?

This statement works:
Connection m = DriverManager.getConnection("jdbc:mysql://localhost:3306/imageusers?autoReconnect=true&useSSL=false&relaxAutoCommit=true", "username", "password");
I uploaded my database to a free online website to use wherever and updated my code as follows:
Connection myConn = DriverManager.getConnection("jdbc:mysql://sql9.freesqldatabase.com:3306/serverName","serverName","serverPassword");
this works correctly but the message
java.sql.SQLException: Can't call commit when autocommit=true
Appears in red in the console. I tried to update the new statement with the relax autocommit statement but that gave me a connection error. How can I properly do it so the message no longer appears? The program works but the red exception in the console isn't pretty.

Establish connection between app server and oracle database using java

I have been given a task to write a script in java, to connect oracle database from an app server. Scheduling tool will be used to schedule the job every 10 minutes.
If connection exists, the script will do nothing and just disconnect it. (and will be run again after 10 minutes).
If cannot connect after 10 secs, the program will send an email notification.
The whole thing is to ensure connection can be established between the app server and the oracle db.
Really have no clue on this. Could you please advise what are the steps to do this and what Java APIs I'll need??
Many many thanks in advance!
You will need classes out of the java.sql package. Assuming Java 7+.
import java.sql.*;
public class Test {
public static void main(String[] args) {
String url = "..."; // Specify according to JDBC driver in use
String sql = "SELECT 1 FROM DUAL"; // Test statement. Change depending on SQL vendor
try (Connection conn = DriverManager.getConnection(url);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql)) {
while (rs.next()) {/*Nothing to do*/}
} catch (SQLException e) {
// Send email here
}
}
}
If you are using J2EE App Server, create a database connection pool there which your application is also going to use.
One of the parameters of the database pool can be to verify the connection at regular intervals by sending simple SQL. Then your task boils down just to monitor the logs to see if database connection pool throws any errors when polling.

How to connect to a database using a distributed API?

I'm having trouble with my distributed application in java netbeans the program is running perfectly on the original machine where i created it. but when i build it and make a distribute folder and follow the instructions and try to run it, I got an error that localhost on port 1527 has been refused.
here is my code on my do connect function
public void DoConnect()
{
String host = "jdbc:derby://localhost:1527/KempDB";
String uName = "main";
String uPass = "admin";
try
{
con = DriverManager.getConnection(host, uName, uPass);
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
String sql = "select cv.checkvouchernumber, c.checknumber, paytoorder, bankcode, dateissued, amount from checkvoucher cv, checks c where cv.checkvouchernumber = c.checkvouchernumber and cv.checknumber = c.checknumber";
rs = stmt.executeQuery(sql);.....
..........
}
catch(SQLException err){
.......
}
so this is the code I used to connect with the database server, the database server I used is built-in with java. Its a apache derby...
like I said in the original machine where I created the program runs ok without errors but when I distribute the program to another machine there's an error refusing the connection.
How can I connect to the local machine where my database is? maybe you can help me on this.
Are the database Servers running on these machines?
Are u starting the database server programmatically?
If you try to connect a database Server with:
jdbc:derby://localhost:1527/KempDB
This Server needs to be up and running.
For your case you should use an embedded Database.
For the case your Database is already an embedded Database, then you can try using this URL:
jdbc:derby:KempDB
instead of:
jdbc:derby://localhost:1527/KempDB
Hav a look on this one

Categories