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/*
 * Copyright 2013-2022 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.grails.plugins.datasource

import java.sql.Driver
import java.sql.DriverManager

import groovy.transform.CompileStatic

/**
 * @author Graeme Rocher
 * @since 2.3
 */
@CompileStatic
class DataSourceUtils {

    static List clearJdbcDriverRegistrations() {
        List driverNames = []

        /*
         * DriverManager.getDrivers() has a nasty side-effect of registering
         * drivers that are visible to this class loader but haven't yet been
         * loaded. Therefore, the first call to this method a) gets the list
         * of originally loaded drivers and b) triggers the unwanted
         * side-effect. The second call gets the complete list of drivers
         * ensuring that both original drivers and any loaded as a result of the
         * side-effects are all de-registered.
         */
        def originalDrivers = new HashSet()
        Enumeration drivers = DriverManager.getDrivers()
        while (drivers.hasMoreElements()) {
            originalDrivers << drivers.nextElement()
        }
        drivers = DriverManager.getDrivers()
        while (drivers.hasMoreElements()) {
            Driver driver = drivers.nextElement()
            // Only unload the drivers this web app loaded
            if (driver.getClass().classLoader != DataSourceUtils.classLoader) {
                continue
            }
            // Only report drivers that were originally registered. Skip any
            // that were registered as a side-effect of this code.
            if (originalDrivers.contains(driver)) {
                driverNames.add(driver.getClass().canonicalName)
            }
            DriverManager.deregisterDriver(driver)
        }
        driverNames
    }

}