com.microsoft.sqlserver.jdbc.SQLServerException: The connection is closed while taking the value of Resultset

public static ResultSet getTestDatafromSQL(String QueryString) throws SQLException {
Connection conn = null;
ResultSet resultSet = null;
try {
String dbURL = "jdbc:sqlserver://localhost\\sqlexpress;DatabaseName=master;integratedSecurity=true;";
conn = DriverManager.getConnection(dbURL);
if (conn != null) {
DatabaseMetaData dm = (DatabaseMetaData) conn.getMetaData();
System.out.println("Driver name: " + dm.getDriverName());
System.out.println("Driver version: " + dm.getDriverVersion());
System.out.println("Product name: " + dm.getDatabaseProductName());
System.out.println("Product version: " + dm.getDatabaseProductVersion().toString());
Statement stmt = conn.createStatement();
// Create and execute a SELECT SQL statement.
resultSet = stmt.executeQuery(QueryString);
System.out.println(resultSet);
while(resultSet.next()) {
System.out.println(resultSet.getString(1));
//return resultSet.getString(1);
}
}
} catch (SQLException ex) {
ex.printStackTrace();
} finally {
try {
if (conn != null && !conn.isClosed()) {
conn.close();
}
} catch (SQLException ex) {
ex.printStackTrace();
}
}
return resultSet;
}

Now In other class, I am calling that...

@Test(enabled = true)
public void query() throws XPathExpressionException, IOException, SQLException {
ResultSet sql = utilities.getTestDatafromSQL("SELECT ACCOUNT_NO1,CREDIT_LMT from [BCMASTER$] Where CAST(Trim(BCM_CREDIT_LMT) as float) >5000");
//System.out.println(sql.first());
System.out.println("SQLValue:"+sql.getString(1));
System.out.println("SQLValue:"+sql.getString(2));
}

I am getting FAIL Sat Aug 15 10:25:24 IST 2020 <span class='badge white-text red'>com.microsoft.sqlserver.jdbc.SQLServerException: The connection is closed. - Test Case Failed</span>

To read the result set, db connection should be open?

From each query I will get different columns, so is there any possible can we store it in array and return is only possibility or resultset can get the value?

You close the Connection in method getTestDatafromSQL() so no point in returning a ResultSet. Consider storing the ResultSet in a java.util.List and have method getTestDatafromSQL() return a List rather than a ResultSet.

Alternatively, don't close the Connection in method getTestDatafromSQL() and return the ResultSet and the method that calls getTestDatafromSQL() (which is method query() according to the code in your question) can close the Connection. In interface ResultSet call getStatement() which returns a Statement and in interface Statement call getConnection() which returns the Connection and then you can close it.

Another alternative would be to use a CachedRowSet

Here is my implementation of the first option described above.

public static List<List<String>> getTestDatafromSQL(String QueryString) throws SQLException {
    Connection conn = null;
    ResultSet resultSet = null;
    List<List<String>> result = new ArrayList<>();
    List<String> row;
    try {
        String dbURL = "jdbc:sqlserver://localhost\\sqlexpress;DatabaseName=master;integratedSecurity=true;";
        conn = DriverManager.getConnection(dbURL);
        if (conn != null) {
            Statement stmt = conn.createStatement();
            // Create and execute a SELECT SQL statement.
            resultSet = stmt.executeQuery(QueryString);
            while (resultSet.next()) {
                row = new ArrayList<>();
                row.add(resultSet.getString(1));
                row.add(resultSet.getString(1));
                result.add(row);
            }
        }
    }
    catch (SQLException ex) {
        ex.printStackTrace();
    }
    finally {
        try {
            if (conn != null && !conn.isClosed()) {
                conn.close();
            }
        }
        catch (SQLException ex) {
            ex.printStackTrace();
        }
    }
    return result;
}

Here is my implementation of the second option.

public static ResultSet getTestDatafromSQL(String QueryString) throws SQLException {
    Connection conn = null;
    ResultSet resultSet = null;
    String dbURL = "jdbc:sqlserver://localhost\\sqlexpress;DatabaseName=master;integratedSecurity=true;";
    conn = DriverManager.getConnection(dbURL);
    Statement stmt = conn.createStatement();
    // Create and execute a SELECT SQL statement.
    resultSet = stmt.executeQuery(QueryString);
    return resultSet;
}

Then you would call the method and then close the Connection like this:

ResultSet sql = utilities.getTestDatafromSQL("SELECT ACCOUNT_NO1,CREDIT_LMT from [BCMASTER$] Where CAST(Trim(BCM_CREDIT_LMT) as float) >5000");
// Handle the ResultSet
sql.getStatement().getConnection.close();