org.apache.catalina.loader.JdbcLeakPrevention Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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
*
* http://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.apache.catalina.loader;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* This class is loaded by {@link WebappClassLoaderBase} to enable it to deregister JDBC drivers forgotten by the web
* application. There are some classloading hacks involved - see {@link WebappClassLoaderBase#clearReferences()} for
* details - but the short version is do not just create a new instance of this class with the new keyword. Since this
* class is loaded by {@link WebappClassLoaderBase}, it cannot refer to any internal Tomcat classes as that will cause
* the security manager to complain.
*/
public class JdbcLeakPrevention {
public List clearJdbcDriverRegistrations() throws SQLException {
List driverNames = new ArrayList<>();
/*
* 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.
*/
Set originalDrivers = new HashSet<>();
Enumeration drivers = DriverManager.getDrivers();
while (drivers.hasMoreElements()) {
originalDrivers.add(drivers.nextElement());
}
drivers = DriverManager.getDrivers();
while (drivers.hasMoreElements()) {
Driver driver = drivers.nextElement();
// Only unload the drivers this web app loaded
if (driver.getClass().getClassLoader() != this.getClass().getClassLoader()) {
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().getCanonicalName());
}
DriverManager.deregisterDriver(driver);
}
return driverNames;
}
}