DBAccess.java

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package Utilities;

import java.sql.*;

/**
 * Class to access database
 * @author flummoxed
 */
public class DBAccess {

    //DBLogin info
    private String URL;
    private String DBUsername;
    private String DBPassword;
    private String IPAddress;
    //Querying
    /**
     * Statement must be set before querying the databse
     */
    public String Query;
    /**
     * Update statement must be set before using
     */
    public String Update;
    private Statement stmt;
    private Connection con;
    private ResultSet result_query;
    private Integer result_update;
    private String ResultString;

    /**
     * Creates a new instance of DBAccess
     * @param ipaddr IPaddress of the host
     * @param schema The database to be used
     * @param dbpwd Password for the user
     * @param dbuname Username to connect to the database
     */
    public DBAccess(String ipaddr, String schema, String dbuname, String dbpwd) {
        //Set Values
        IPAddress = ipaddr;
        URL = "jdbc:postgresql://" + ipaddr + "/" + schema;
        DBUsername = dbuname;
        DBPassword = dbpwd;
        stmt = null;
        con = null;

        LoadDriver();

        ConnectToDB();

    }

    /**
     * Load Class driver
     */
    private void LoadDriver() {

        try {
            Class.forName("org.postgresql.Driver").newInstance();
        } catch (Exception e) {
            System.err.println("Failed to load Connector/J");
            System.out.println("Check PostgreSql Connector/J... Restart server.");
            e.printStackTrace();
        }
    }

    /**
     * Connect to the database
     */
    private void ConnectToDB() {

        try {
            con = java.sql.DriverManager.getConnection(
                    URL,
                    DBUsername,
                    DBPassword);
            stmt = con.createStatement();
        } catch (Exception e) {
            System.err.println("Problems connecting to " + URL);
            System.out.println("Check if PostgreSQL daemon is running... Restart server.");
            e.printStackTrace();

        }

    }

    /**
     *
     * @return the resultset for the query
     */
    public ResultSet ExecQuery() {
        if (Query == null) {
            throw new NullPointerException("Query hasn't been initialized");
        }
        try {

            result_query = stmt.executeQuery(Query);
            //CloseConnection();
            return result_query;
        } catch (SQLException ex) {
            ex.printStackTrace();

        }
        //CloseConnection();
        return null;
    }

    /**
     *
     * @return the number of elements that are modified
     */
    public Integer ExecUpdate() {
        if (Update == null) {
            throw new NullPointerException("Update statement hasn't been initialized");
        }
        try {
            result_update = stmt.executeUpdate(Update);
            //CloseConnection();
            return result_update;
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
        //CloseConnection();
        return null;
    }

    /**
     * Close the connection to the DB
     */
    void CloseConnection() {
        //close connection once done
        try {
            con.close();
        } catch (Exception e) {
            System.err.println("Error closing connection to " + URL);
            System.out.println("Check if PostgreSQL daemon is running.. Restart server");
        }
    }
}