org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.java Source code

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Here is the source code for org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.java

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/*
 * Copyright 2012-2018 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
 *
 *      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.springframework.boot.web.embedded.tomcat;

import java.io.IOException;
import java.net.URL;
import java.util.Collections;
import java.util.Enumeration;

import org.apache.catalina.loader.ParallelWebappClassLoader;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Extension of Tomcat's {@link ParallelWebappClassLoader} that does not consider the
 * {@link ClassLoader#getSystemClassLoader() system classloader}. This is required to
 * ensure that any custom context class loader is always used (as is the case with some
 * executable archives).
 *
 * @author Phillip Webb
 * @since 2.0.0
 */
public class TomcatEmbeddedWebappClassLoader extends ParallelWebappClassLoader {

    private static final Log logger = LogFactory.getLog(TomcatEmbeddedWebappClassLoader.class);

    static {
        ClassLoader.registerAsParallelCapable();
    }

    public TomcatEmbeddedWebappClassLoader() {
    }

    public TomcatEmbeddedWebappClassLoader(ClassLoader parent) {
        super(parent);
    }

    @Override
    public URL findResource(String name) {
        return null;
    }

    @Override
    public Enumeration<URL> findResources(String name) throws IOException {
        return Collections.emptyEnumeration();
    }

    @Override
    public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
        synchronized (getClassLoadingLock(name)) {
            Class<?> result = findExistingLoadedClass(name);
            result = (result != null) ? result : doLoadClass(name);
            if (result == null) {
                throw new ClassNotFoundException(name);
            }
            return resolveIfNecessary(result, resolve);
        }
    }

    private Class<?> findExistingLoadedClass(String name) {
        Class<?> resultClass = findLoadedClass0(name);
        resultClass = (resultClass != null) ? resultClass : findLoadedClass(name);
        return resultClass;
    }

    private Class<?> doLoadClass(String name) throws ClassNotFoundException {
        checkPackageAccess(name);
        if ((this.delegate || filter(name, true))) {
            Class<?> result = loadFromParent(name);
            return (result != null) ? result : findClassIgnoringNotFound(name);
        }
        Class<?> result = findClassIgnoringNotFound(name);
        return (result != null) ? result : loadFromParent(name);
    }

    private Class<?> resolveIfNecessary(Class<?> resultClass, boolean resolve) {
        if (resolve) {
            resolveClass(resultClass);
        }
        return (resultClass);
    }

    @Override
    protected void addURL(URL url) {
        // Ignore URLs added by the Tomcat 8 implementation (see gh-919)
        if (logger.isTraceEnabled()) {
            logger.trace("Ignoring request to add " + url + " to the tomcat classloader");
        }
    }

    private Class<?> loadFromParent(String name) {
        if (this.parent == null) {
            return null;
        }
        try {
            return Class.forName(name, false, this.parent);
        } catch (ClassNotFoundException ex) {
            return null;
        }
    }

    private Class<?> findClassIgnoringNotFound(String name) {
        try {
            return findClass(name);
        } catch (ClassNotFoundException ex) {
            return null;
        }
    }

    private void checkPackageAccess(String name) throws ClassNotFoundException {
        if (this.securityManager != null && name.lastIndexOf('.') >= 0) {
            try {
                this.securityManager.checkPackageAccess(name.substring(0, name.lastIndexOf('.')));
            } catch (SecurityException ex) {
                throw new ClassNotFoundException(
                        "Security Violation, attempt to use " + "Restricted Class: " + name, ex);
            }
        }
    }

}