No operations allowed after connection closed MYSQL

Question

Basically I have:

String query = \"SELECT * FROM table WHERE UNIQUEID=? AND DIR IS NOT NULL AND NAME IS NOT NULL AND PAGETYPE IS NOT NULL\";
DBConnect Databa         


        

Answer 1

It's because of two reasons:

• Connection is closed after the execution of first PreparedStatement
• getcon uses an instance variable instead of local variable. Due to this, same conn variable (the one that was closed earlier) gets returned when getcon is called next time.

To fix this, getcon and DBConnect need to be modified to declare a local conn variable and return it (in fact, you don't need DBConnect at all), e.g.:

public Connection getcon(){
    try{
        Class.forName("com.mysql.jdbc.Driver");
        String unicode="useSSL=false&autoReconnect=true&useUnicode=yes&characterEncoding=UTF-8";
        return DriverManager.getConnection("jdbc:mysql://localhost:15501/duckdb?"+unicode, "root", "_PWD");
    }catch(Exception ex){
        System.out.println(ex.getMessage());
        System.out.println("couldn't connect!");
        throw new RuntimeException(ex);
    }
}

Answer 2

This is a MySQL settings issue. The response time of the MySQL server (60,621 ms in the example above) exceeds the MySQL server's configured wait_timeout value.

Solution

To resolve this issue, work with the MySQL database administrator to increase the value of the wait_timeout parameter.

Align Hibernate Configuration with you MySQL server to fix this problem.

This setting is configurable in the my.cnf file. By default, mysql sets this value to "28800" seconds. If this value has been modified from the default, consider reverting it back to the default to restore connectivity to the Datameer server.

Answer 3

A good approach is to use one try - finally block like this

String query = "SELECT * FROM table WHERE UNIQUEID=? AND DIR IS NOT NULL AND NAME IS NOT NULL AND PAGETYPE IS NOT NULL";
        DBConnect Database = new DBConnect();
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs=null;
        try {
            con = Database.getcon();
            ps = con.prepareStatement(query);
            ps.setString(1, URI);
            rs=ps.executeQuery();
            if(rs.next()){
            }

            query = "SELECT COUNTCOMMENTS FROM videosinfos WHERE UNIQUEID=?";

            ps = con.prepareStatement(query); // Getting error here
            rs=ps.executeQuery();
            ps.setString(1, URI);
            rs=ps.executeQuery();
            if(rs.next()){
                comments = rs.getInt(1);
            }
        } finally {
            if(ps != null)
                ps.close();
            if(rs != null)
                rs.close();
            if(con != null)
                con.close();
        }