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The addc-base library supplies classes for creating UUIDs, converting between types, outputting byte arrays with different formats, support for Julian dates, delay generators, parsing properties files and support for I18N.
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package com.addc.commons.database.derby;

import java.io.File;
import java.math.BigInteger;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.addc.commons.Constants;
import com.addc.commons.database.Database;
import com.addc.commons.database.DatabaseException;

/**
 * The DerbyDatabase represents a Derby database using the embedded Derby JDBC
 * driver.
 * 
 */
@SuppressWarnings("PMD.AvoidThrowingRawExceptionTypes")
public class DerbyDatabase implements Database {
    private static final Logger LOGGER= LoggerFactory.getLogger(DerbyDatabase.class);

    private static final String DRIVER= "org.apache.derby.jdbc.EmbeddedDriver";
    private static final String PROTOCOL= "jdbc:derby:";
    private static final String CREATE_ATTRIBUTE= ";create=true";
    private static final String SHUTDOWN_ATTRIBUTE= ";shutdown=true;deregister=false";
    private static final String ENCRYPT_ATTRIBUTE= ";dataEncryption=true;encryptionAlgorithm=AES/CBC/NoPadding;encryptionKey=";
    private static final char[] SEED= "wfhsuz+A++KNASGAfYDgxQhzsLrG3AnN".toCharArray();

    private final String dbUri;
    private final String location;

    // We need this class load as otherwise the JDBC cannot find the driver when
    // running in a web application.
    static {
        try {
            Class.forName(DRIVER).newInstance();
            LOGGER.debug("Loaded the appropriate driver");
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
            throw new RuntimeException(
                    "Unable to load or instanntiatethe JDBC driver " + DRIVER + ". Check your CLASSPATH.", e);
        }
    }

    /**
     * Create new DerbyDatabase
     * 
     * @param directory
     *            the directory where the database should be placed
     * @param isConfidential
     *            whether the database contains data in encrypted form
     * @throws DatabaseException
     *             if there is any error while loading the database engine
     */
    public DerbyDatabase(String directory, boolean isConfidential) throws DatabaseException {
        try {
            if (isConfidential) {
                this.dbUri= PROTOCOL + directory + ENCRYPT_ATTRIBUTE + generateSecret();
            } else {
                this.dbUri= PROTOCOL + directory;
            }

            createOrOpen();
            File dbPath= new File(directory);
            this.location= dbPath.getAbsolutePath();
        } catch (SQLException e) {
            throw new DatabaseException("Failed to create Derby database", e);
        }
    }

    @Override
    public void shutdown() {
        try {
            LOGGER.info("Shutdown the database");
            DriverManager.getConnection(dbUri + SHUTDOWN_ATTRIBUTE);
        } catch (SQLException e) {
            // See
            // http://db.apache.org/derby/docs/dev/getstart/rwwdactivity3.html
            // for an explanation of this check
            if (((e.getErrorCode() == 45000) && ("08006".equals(e.getSQLState())))) {
                // We got the expected exception
                // Note that for single database shutdown, the expected
                // SQL state is "08006", and the error code is 45000.
                LOGGER.info("Derby database is closed");
            } else {
                // if the error code or SQLState are different, we have
                // an unexpected exception (shutdown failed)
                LOGGER.warn("Derby database closed abnormally", e);
            }
        }
    }

    @Override
    public Connection getConnection() throws SQLException {
        return DriverManager.getConnection(dbUri);
    }

    @Override
    public boolean hasTable(String tableName) {
        boolean result= false;
        Connection conn= null;
        ResultSet tables= null;
        try {
            conn= getConnection();
            DatabaseMetaData metadata= conn.getMetaData();
            tables= metadata.getTables(conn.getCatalog(), null, tableName, null);
            result= tables.next();
        } catch (SQLException e) {
            LOGGER.error("SQL error occured while checking table " + tableName + " in the database", e);
        } finally {
            close(tables);
            close(conn);
        }

        return result;
    }

    @Override
    public String getLocation() {
        return location;
    }

    /**
     * Generates an AES encryption key - based on the hard coded value of SEED -
     * of 256 bits keys size
     * 
     * @return the key used for encryption
     */
    private String generateSecret() {
        String str= new String(SEED);
        BigInteger secret= new BigInteger(str.substring(0, 32).getBytes(Constants.UTF8));
        return secret.toString(16);
    }

    private void createOrOpen() throws SQLException {
        Connection conn= null;
        try {
            conn= DriverManager.getConnection(dbUri + CREATE_ATTRIBUTE);
        } finally {
            close(conn);
        }
    }

    private void close(AutoCloseable obj) {
        if (obj != null) {
            try {
                obj.close();
            } catch (Exception e) {
                LOGGER.error("Error closing object", e);
            }
        }
    }

}