bentobox/src/main/java/us/tastybento/bskyblock/database/AbstractDatabaseHandler.java

package us.tastybento.bskyblock.database;

import java.beans.IntrospectionException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.sql.SQLException;
import java.util.List;

import us.tastybento.bskyblock.BSkyBlock;

/**
 * An abstract class that handles insert/select-operations into/from a database
 * 
 * @param <T>
 */
/**
 * @author tastybento
 *
 * @param <T>
 */
public abstract class AbstractDatabaseHandler<T> {

    /**
     * The type of the objects that should be created and filled with values
     * from the database or inserted into the database
     */
    protected Class<T>     type;

    /**
     * Contains the settings to create a connection to the database like
     * host/port/database/user/password
     */
    protected DatabaseConnecter     databaseConnecter;

    /** The SQL-select- and insert query */
    protected final String     selectQuery;
    protected final String     insertQuery;


    protected BSkyBlock plugin;


    /**
     * Constructor
     * 
     * @param type
     *            The type of the objects that should be created and filled with
     *            values from the database or inserted into the database
     * @param databaseConnecter
     *            Contains the settings to create a connection to the database
     *            like host/port/database/user/password
     */
    protected AbstractDatabaseHandler(BSkyBlock plugin, Class<T> type, DatabaseConnecter databaseConnecter) {

        this.plugin = plugin;
        this.databaseConnecter = databaseConnecter;
        this.type = type;
        this.selectQuery = createSelectQuery();
        this.insertQuery = createInsertQuery();
    }

    /**
     * Create the SQL-String to insert into / select from the database
     * Not used in the flat file database
     * @return the SQL-String
     */
    protected abstract String createSelectQuery();
    protected abstract String createInsertQuery();

    /**
     * 
     * Creates a comma-separated-String with the names of the variables in this
     * class
     * Not used in Flat File database.
     * @param usePlaceHolders
     *            true, if PreparedStatement-placeholders ('?') should be used
     *            instead of the names of the variables
     * @return
     */
    protected String getColumns(boolean usePlaceHolders) {
        StringBuilder sb = new StringBuilder();

        boolean first = true;
        /* Iterate the column-names */
        for (Field f : type.getDeclaredFields()) {
            if (first)
                first = false;
            else
                sb.append(", ");

            if (usePlaceHolders)
                sb.append("?");
            else
                sb.append(f.getName());
        }

        return sb.toString();
    }

    /**
     * Loads all the records in this table and returns a list of them
     * @return list of <T>
     * @throws InstantiationException
     * @throws IllegalAccessException
     * @throws IllegalArgumentException
     * @throws InvocationTargetException
     * @throws IntrospectionException
     * @throws SecurityException 
     * @throws SQLException 
     */
    protected abstract List<T> selectObjects() throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException, SQLException, SecurityException;

    /**
     * Creates a <T> filled with values from the corresponding
     * database file
     * @param uniqueId
     * @return <T>
     * @throws IntrospectionException 
     * @throws InvocationTargetException 
     * @throws IllegalArgumentException 
     * @throws IllegalAccessException 
     * @throws InstantiationException 
     */
    protected abstract T selectObject(String uniqueId) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException;

    /**
     * Inserts T into the corresponding database-table
     * 
     * @param instance that should be inserted into the database
     * @throws IllegalAccessException
     * @throws IllegalArgumentException
     * @throws InvocationTargetException
     * @throws IntrospectionException
     * @throws InstantiationException 
     * @throws SecurityException 
     * @throws SQLException 
     */
    protected abstract void insertObject(T instance) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException, SQLException, SecurityException, InstantiationException;

}