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Create and handle several DBs in SQL Server (2017) from Java

I'm developing a desktop app to organize different events, thus creating a DB for each event. So far, I've managed to create a DB with whatever name the user wants, using a simple GUI.
However, I can't create tables nor columns for said database, even though it's exactly the same syntax I use in SQL Server Manager.
My code so far:
public static void creDB(String db_name, String table_name){
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
conn = DriverManager.getConnection(connectionUrl);
String SQL = "CREATE DATABASE " + db_name;
stmt = conn.createStatement();
int result = stmt.executeUpdate(SQL);
String SQL3 = "USE " + db_name;
boolean ree = stmt.execute(SQL3);
String SQL4 = "GO";
boolean rr = stmt.execute(SQL4);
if (result == 0){
System.out.println("Se insertó :D!");
String SQL2 = "CREATE TABLE Pepe(Name_emp INT NOT NULL PRIMARY KEY)";
int res = stmt.executeUpdate(SQL2);
if (res == 0)
System.out.println("GRACIAS DIOS");
}else
System.out.println("Raios shico");
}catch (Exception e) {e.printStackTrace();}
finally {
if (rs != null) try {rs.close();} catch (Exception e) {e.printStackTrace();}
if (stmt != null) try {stmt.close();} catch (Exception e) {e.printStackTrace();}
if (conn != null) try {conn.close();} catch (Exception e) {e.printStackTrace();}
}
}
The error I get is when I try to actually use the DB, using the use [DB name] go; I tried already using that same syntax in one single SQL statement, however it didn't work, so I tried doing it separately and got this error:
com.microsoft.sqlserver.jdbc.SQLServerException: Could not find stored procedure 'GO'.
I know the code above looks like a mess, and it is, but it's just for testing purposes since I'm new to doing DB-related projects with Java; I mixed-matched some of the concepts of this site, which were successful up until the creation of the tables.
I know there's a better way of managing several databases, but as I said, I'm just starting so any advice would be greatly appreciated.

You should not use statements like USE <dbname> when using JDBC, it may lead to unexpected behavior because parts of the driver may still use metadata for the original connected database. You should either use setCatalog on the current connection to switch databases or create an entirely new connection to the new database.
In short, after creating the database, you should use:
conn.setCatalog(db_name);
That's it.
Also, go is not part of the SQL Server syntax, it is only used by tools like the Management Studio, see What is the use of GO in SQL Server Management Studio & Transact SQL? The equivalent in JDBC is to simply execute the statement.

How do I Solve the Database connection?

I have a one problem regarding Database(Oracle 10g). I have developed Web Application in JSP Servlet. now I am Performing testing on it. First I have Faced one problem (i.e. "ORA-01000: maximum open cursors exceeded"). For Solving the problem I was closed every connections in every files (eg: Foo.java and Foo.jsp) where the Database connection is established. For this, I have used the Following code:
finally {
if(rs1 != null) {
try {
rs1.close();
} catch (SQLException e) { /* ignored */ }
if(ps2 != null) {
try {
ps2.close();
} catch (SQLException e) { /* ignored */ }
}
if(con != null) {
try {
con.close();
} catch (SQLException e) { /* ignored */ }
}
}
But now the code gives another problem: Application does not fetch any records from database.
When First time I click linked (Add Menu then it shows all data but when I clicked another linked then all records are vanished.
Then after like this.
and Show Error java.sql.SQLException: Closed Connection

May be you have defined the connection object out side of the method,for the first time using the connection object it connects to the database and when you click on the link again the same methods gets invoked and the connection object is already closed in finally and hence could not connect to database again causing closed connection Exception.
First thing is to create the connection or prepared statement or statement inside the method and fetch the result set.When again the method is called the connection object is created again with help of connection pool and hence can make successful connection to data base.

Unable to connect to Azure using JDBC (based upon the connection string and samples provide) due to SSL issue

Am getting the following error: com.microsoft.sqlserver.jdbc.SQLServerException: The driver could not establish a secure connection to SQL Server by using Secure Sockets Layer (SSL) encryption. Error: "Connection reset by peer: socket write error."
import java.sql.*;
import com.microsoft.sqlserver.jdbc.*;
public class SQLDatabaseConnection {
// Connect to your database.
// Replace server name, username, and password with your credentials
public static void main(String[] args) {
String connectionString =
"jdbc:sqlserver://XXXXX.database.windows.net:1433;"
+ "database=VDB;"
+ "user=XXX#VVV;"
+ "password=XXXX;"
+ "encrypt=true;"
+ "trustServerCertificate=false;"
+ "hostNameInCertificate=*.database.windows.net;"
+ "loginTimeout=30;";
// Declare the JDBC objects.
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
// Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
connection = DriverManager.getConnection(connectionString);
// Create and execute a SELECT SQL statement.
String selectSql = "SELECT TOP 2 * from Application";
statement = connection.createStatement();
resultSet = statement.executeQuery(selectSql);
// Print results from select statement
while (resultSet.next()) {
System.out.println(resultSet.getString(2) + " "
+ resultSet.getString(3));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// Close the connections after the data has been handled.
if (resultSet != null) try {
resultSet.close();
} catch (Exception e) {
}
if (statement != null) try {
statement.close();
} catch (Exception e) {
}
if (connection != null) try {
connection.close();
} catch (Exception e) {
}
}
}
}
I'm only trying to do the "sample" connection snippet of code as referenced on the Azure site (which points to a MS entry), modified only to match my db and test table but without success.
Having reviewed all there is to know, I have:-
ensured that I'm using the right sqljdbc (I've tried all 4)
have the sqlauth.dll on the CLASSPATH
have set the sample up EXACTLY as shown; and incorporated the string that Azure offers.
I have tried various combinations of encrypt and trust without success. As I'm a newbie to Java and Azure, I'm reluctant and unsure how to fiddle with the JVM security settings.
I've proven that my machine can talk to the Azure database (through a VB ODBC connection); and I've tested with the firewall down.
Any thoughts?

I tried to reproduce the issue, but failed that I could access my SQL Azure Instance using the code which be similar with yours.
The difference between our codes is only as below, besides using the connection string of my sql azure instance.
Using the driver sqljdbc4.jar from the sqljdbc_4.0 link.
Using the code Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver"); to load MS SQL JDBC driver.
Not adding the sqlauth.dll file into the CLASSPATH.
Check my client IP which has been allowed by SQL Azure IP firewall.
Using the sql select 1+1 to test my code, and get the value 4 from code result.getInt(1).
That's fine for me. If you can supply more detals for us, I think it's very helpful for analysising the issue.
Hope it helps.

JSF page freezes when is reloaded many times

I use this code to fetch data from database table.
public List<Dashboard> getDashboardList() throws SQLException {
if (ds == null) {
throw new SQLException("Can't get data source");
}
//get database connection
Connection con = ds.getConnection();
if (con == null) {
throw new SQLException("Can't get database connection");
}
PreparedStatement ps = con.prepareStatement(
"SELECT * from GLOBALSETTINGS");
//get customer data from database
ResultSet result = ps.executeQuery();
List<Dashboard> list = new ArrayList<Dashboard>();
while (result.next()) {
Dashboard cust = new Dashboard();
cust.setUser(result.getString("SessionTTL"));
cust.setPassword(result.getString("MAXACTIVEUSERS"));
//store all data into a List
list.add(cust);
}
return list;
}
This code is a part of a JSF page which is deployed on glassfish server. The problem is that when I reload the JSF page many times(around 8 times) the web page freezes. I suspect that the thread pool is fill and there is no space for new connections. How I can solve the problem? Close the connection when the query is finished or there is another way?
Best wishes

First of all: Yes you should close your connection when your done by explicitly calling the close() method. Closing a connection will release database resources.
UPDATE: And you should close the PreparedStatement as well (with close()). I would also recommend to handle SQLExceptions in your method and not throw it, since you need to make sure that your statement and connection are closed even if an exception occurs.
Something like this:
Connection connection = dataSource.getConnection();
try {
PreparedStatement statement = connection.prepareStatement();
try {
// Work with the statement
catch (SQLException e ) {
// Handle exceptions
} catch (SQLException e {
// Handle exceptions
} finally {
statement.close();
}
} finally {
connection.close();
}
Furthermore, you should not query the database in a bean field's getter method. Getters can be called several times during each request. The more elegant way would be to prepare the DashboardList in the constructor or #PostConstruct of your bean.

Java JDBC connection status

I am (successfully) connecting to a database using the following:
java.sql.Connection connect = DriverManager.getConnection(
"jdbc:mysql://localhost/some_database?user=some_user&password=some_password");
What should I be checking to see if the connection is still open and up after some time?
I was hoping for something like connect.isConnected(); available for me to use.

Your best chance is to just perform a simple query against one table, e.g.:
select 1 from SOME_TABLE;
Oh, I just saw there is a new method available since 1.6:
java.sql.Connection.isValid(int timeoutSeconds):
Returns true if the connection has not been closed and is still valid.
The driver shall submit a query on the connection or use some other
mechanism that positively verifies the connection is still valid when
this method is called. The query submitted by the driver to validate
the connection shall be executed in the context of the current
transaction.

Nothing. Just execute your query. If the connection has died, either your JDBC driver will reconnect (if it supports it, and you enabled it in your connection string--most don't support it) or else you'll get an exception.
If you check the connection is up, it might fall over before you actually execute your query, so you gain absolutely nothing by checking.
That said, a lot of connection pools validate a connection by doing something like SELECT 1 before handing connections out. But this is nothing more than just executing a query, so you might just as well execute your business query.

Use Connection.isClosed() function.
The JavaDoc states:
Retrieves whether this Connection object has been closed. A
connection is closed if the method close has been called on it or if
certain fatal errors have occurred. This method is guaranteed to
return true only when it is called after the method Connection.close
has been called.

You also can use
public boolean isDbConnected(Connection con) {
try {
return con != null && !con.isClosed();
} catch (SQLException ignored) {}
return false;
}

If you are using MySQL
public static boolean isDbConnected() {
final String CHECK_SQL_QUERY = "SELECT 1";
boolean isConnected = false;
try {
final PreparedStatement statement = db.prepareStatement(CHECK_SQL_QUERY);
isConnected = true;
} catch (SQLException | NullPointerException e) {
// handle SQL error here!
}
return isConnected;
}
I have not tested with other databases. Hope this is helpful.

The low-cost method, regardless of the vendor implementation, would be to select something from the process memory or the server memory, like the DB version or the name of the current database. IsClosed is very poorly implemented.
Example:
java.sql.Connection conn = <connect procedure>;
conn.close();
try {
conn.getMetaData();
} catch (Exception e) {
System.out.println("Connection is closed");
}

Here is a simple solution if you are using JDBC to get the default connection
private Connection getDefaultConnection() throws SQLException, ApiException {
Connection connection = null;
try {
connection = dataSource.getConnection ();
}catch (SQLServerException sqlException) {
// DB_UNAVAILABLE EXCEPTION
}
return connection;
}