scriptella.core.DriverClassLoader Maven / Gradle / Ivy
/*
* Copyright 2006-2012 The Scriptella Project Team.
*
* 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
*
* 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 scriptella.core;
import scriptella.util.IOUtils;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
/**
* A classloader for drivers specified by connection element.
* This class loader is used only if classpath connection attribute is not empty.
*
* @author Fyodor Kupolov
* @version 1.0
* @see #loadClass(String) delegation model description.
*/
class DriverClassLoader extends URLClassLoader {
public DriverClassLoader(URL[] urls) {
super(urls, DriverClassLoader.class.getClassLoader());
}
/**
* Loads a class specified by name.
*
This class loader has a specific delegation model:
*
* - If a class package is a drivers package (jdbc or drivers), the
* class is loaded and created using this classloader without delegating to the parent.
* This solution is used to overcome limitations of cross-loaders interaction and to simplify built-in drivers development.
*
- In other cases the semantics is the same as in {@link URLClassLoader}.
*
*
* @param name class name.
* @return the loaded class
* @throws ClassNotFoundException If the class was not found
*/
public Class loadClass(String name) throws ClassNotFoundException {
if (name.startsWith("scriptella.jdbc.") || name.startsWith("scriptella.driver.")) {
byte[] b = getClassBytes(name);
if (b != null) {
definePackage(name);
return defineClass(name, b, 0, b.length);
}
}
return super.loadClass(name);
}
/**
* Defines a package for a class name.
*
* @param className class name to define a package.
* @see #definePackage(String, java.util.jar.Manifest, java.net.URL)
*/
private void definePackage(String className) {
if (className == null) {
return;
}
int ind = className.lastIndexOf('.');
if (ind < 0) {
return;
}
String pName = className.substring(0, ind);
if (getPackage(pName) == null) {
definePackage(pName, null, null, null, null, null, null, null);
}
}
/**
* Loads a class content using a parent class loader.
* Please note that we load class bytes even if it has already been loaded by the parent class loader.
*
* @param name class name.
* @return class file content.
*/
private static byte[] getClassBytes(final String name) {
String path = '/' + name.replace('.', '/') + ".class";
InputStream is = DriverClassLoader.class.getResourceAsStream(path);
if (is == null) {
return null;
}
ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
byte[] b = new byte[1024];
try {
for (int c; (c = is.read(b)) >= 0;) {
baos.write(b, 0, c);
}
return baos.toByteArray();
} catch (IOException e) {
throw new IllegalStateException(e);
} finally {
IOUtils.closeSilently(is);
}
}
}