minecraft-kajetans-mod/src/main/java/me/km/databank/DataBank.java

package me.km.databank;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;
import me.km.module.Module;
import me.km.scheduler.SnuviScheduler;
import net.minecraft.util.text.TextFormatting;

public class DataBank extends Module
{
    private Connection c = null;
    private final String user;
    private final String password;
    
    private final HashMap<String, PreparedStatement> statements = new HashMap<>();
    
    public DataBank(String prefix, TextFormatting color, String user, String password) 
    {
        super(prefix, color);
        this.user = user;
        this.password = password;
    }
    
    public boolean openDataBankConnection()
    {
        try 
        {
            // The newInstance() call is a work around for some broken Java implementations
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            c = DriverManager.getConnection("jdbc:mysql://localhost/minecraft?useSSL=false", user, password);
            this.sendToConsole("Connection to datebank etablished.");
            return true;
        } 
        catch(ClassNotFoundException | IllegalAccessException | InstantiationException | SQLException ex) 
        {
            this.sendWarningToConsole(ex.toString());
            return false;
        }
    }
    
    public void closeDataBankConnection()
    {
        try 
        {
            if(c != null)
            {
                c.close();
                statements.values().forEach(stmt -> 
                {
                    try
                    {
                        stmt.close();
                    }
                    catch(SQLException ex)
                    {
                    }
                });
            }
            this.sendToConsole("The connection was closed.");
        } 
        catch (SQLException ex) 
        {
            this.sendWarningToConsole(ex.getMessage());
        }
    }
    
    public boolean isDummyDatabank()
    {
        return c == null;
    }
    
    public PreparedStatement prepareStatement(String query)
    {
        try
        {
            PreparedStatement ps = c.prepareStatement(query);
            PreparedStatement old = statements.put(query, ps);
            if(old != null)
            {
                old.close();
            }
        }
        catch(SQLException ex)
        {
            ex.printStackTrace();
        }
        return null;
    }
    
    public PreparedStatement prepareUnsafeStatement(String query) throws SQLException
    {
        return c.prepareStatement(query);
    }
    
    public boolean execute(String query)
    {
        if(c == null)
        {
            return false;
        }
        try(java.sql.Statement stmt = c.createStatement())
        {
            stmt.executeUpdate(query);
            return true;
        }
        catch(SQLException ex)
        {
            ex.printStackTrace();
            return false;
        }
    }
    
    public void startReconnecting(SnuviScheduler scheduler)
    {
        if(c == null)
        {
            return;
        }
        scheduler.scheduleRepeatingTask(() -> 
        {
            try(java.sql.Statement stmt = c.createStatement()) 
            {
                // pointless query just for reconnecting
                stmt.executeUpdate("SHOW TABLES IN minecraft");
            }
            catch(SQLException ex) 
            {
                sendToConsole("reconnect was done");
            }
        }, 100, 12000); // doing this every 10 minutes
    }
}