LoadTestCase

/*
 * 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.commons.logging;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

import junit.framework.TestCase;

import org.apache.commons.io.IOUtils;

/**
 * test to emulate container and application isolated from container
 */
public class LoadTestCase extends TestCase {

    /**
     * A custom class loader which "duplicates" logging classes available
     * in the parent class loader into itself.
     * <p>
     * When asked to load a class that is in one of the LOG_PCKG packages,
     * it loads the class itself (child-first). This class doesn't need
     * to be set up with a classpath, as it simply uses the same classpath
     * as the class loader that loaded it.
     */
    static class AppClassLoader extends ClassLoader {

        Map<String, Class<?>> classes = new HashMap<>();

        AppClassLoader(final ClassLoader parent) {
            super(parent);
        }

        private Class<?> def(final String name) throws ClassNotFoundException {
            Class<?> result = classes.get(name);
            if (result != null) {
                return result;
            }
            try {
                final ClassLoader cl = this.getClass().getClassLoader();
                final String classFileName = name.replace('.', '/') + ".class";
                try (InputStream is = cl.getResourceAsStream(classFileName)) {
                    final byte[] data = IOUtils.toByteArray(is);
                    result = super.defineClass(name, data, 0, data.length);
                    classes.put(name, result);
                    return result;
                }
            } catch (final IOException ioe) {
                throw new ClassNotFoundException(name + " caused by " + ioe.getMessage());
            }
        }

        // not very trivial to emulate we must implement "findClass",
        // but it will delegate to JUnit class loader first
        @Override
        public Class<?> loadClass(final String name) throws ClassNotFoundException {
            // isolates all logging classes, application in the same class loader too.
            // filters exceptions to simplify handling in test
            for (final String element : LOG_PCKG) {
                if (name.startsWith(element) && !name.contains("Exception")) {
                    return def(name);
                }
            }
            return super.loadClass(name);
        }

    }

    //TODO: need some way to add service provider packages
    static private String[] LOG_PCKG = {"org.apache.commons.logging",
                                        "org.apache.commons.logging.impl"};

    private ClassLoader origContextClassLoader;

    private void execute(final Class<?> cls) throws Exception {
        cls.getConstructor().newInstance();
    }

    /**
     * Load class UserClass via a temporary class loader which is a child of
     * the class loader used to load this test class.
     */
    private Class<?> reload() throws Exception {
        Class<?> testObjCls = null;
        final AppClassLoader appLoader = new AppClassLoader(this.getClass().getClassLoader());
        try {

            testObjCls = appLoader.loadClass(UserClass.class.getName());

        } catch (final ClassNotFoundException cnfe) {
            throw cnfe;
        } catch (final Throwable t) {
            t.printStackTrace();
            fail("AppClassLoader failed ");
        }

        assertSame("app isolated", testObjCls.getClassLoader(), appLoader);

        return testObjCls;

    }

    /**
     * Call the static setAllowFlawedContext method on the specified class
     * (expected to be a UserClass loaded via a custom class loader), passing
     * it the specified state parameter.
     */
    private void setAllowFlawedContext(final Class<?> c, final String state) throws Exception {
        final Class<?>[] params = {String.class};
        final java.lang.reflect.Method m = c.getDeclaredMethod("setAllowFlawedContext", params);
        m.invoke(null, state);
    }

    @Override
    public void setUp() {
        // save state before test starts so we can restore it when test ends
        origContextClassLoader = Thread.currentThread().getContextClassLoader();
    }

    @Override
    public void tearDown() {
        // restore original state so a test can't stuff up later tests.
        Thread.currentThread().setContextClassLoader(origContextClassLoader);
    }

    /**
     * Test what happens when we play various class loader tricks like those
     * that happen in web and j2ee containers.
     * <p>
     * Note that this test assumes that commons-logging.jar and log4j.jar
     * are available via the system classpath.
     */
    public void testInContainer() throws Exception {

        //problem can be in this step (broken app container or missconfiguration)
        //1.  Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
        //2.  Thread.currentThread().setContextClassLoader(this.getClass().getClassLoader());
        // we expect this :
        // 1. Thread.currentThread().setContextClassLoader(appLoader);
        // 2. Thread.currentThread().setContextClassLoader(null);

        // Context class loader is same as class calling into log
        Class<?> cls = reload();
        Thread.currentThread().setContextClassLoader(cls.getClassLoader());
        execute(cls);

        // Context class loader is the "bootclass loader". This is technically
        // bad, but LogFactoryImpl.ALLOW_FLAWED_CONTEXT defaults to true so
        // this test should pass.
        cls = reload();
        Thread.currentThread().setContextClassLoader(null);
        execute(cls);

        // Context class loader is the "bootclass loader". This is same as above
        // except that ALLOW_FLAWED_CONTEXT is set to false; an error should
        // now be reported.
        cls = reload();
        Thread.currentThread().setContextClassLoader(null);
        try {
            setAllowFlawedContext(cls, "false");
            execute(cls);
            fail("Logging config succeeded when context class loader was null!");
        } catch (final InvocationTargetException ex) {
            final Throwable targetException = ex.getTargetException();
            // LogConfigurationException is expected; the boot class loader doesn't *have* JCL available
            if (!(targetException instanceof LogConfigurationException)) {
                throw ex;
            }
        }

        // Context class loader is the system class loader.
        //
        // This is expected to cause problems, as LogFactoryImpl will attempt
        // to use the system class loader to load the Log4JLogger class, which
        // will then be unable to cast that object to the Log interface loaded
        // via the child class loader. However as ALLOW_FLAWED_CONTEXT defaults
        // to true this test should pass.
        cls = reload();
        Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
        execute(cls);

        // Context class loader is the system class loader. This is the same
        // as above except that ALLOW_FLAWED_CONTEXT is set to false; an error
        // should now be reported.
        cls = reload();
        Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
        try {
            setAllowFlawedContext(cls, "false");
            execute(cls);
            fail("Error: somehow downcast a Logger loaded via system class loader"
                    + " to the Log interface loaded via a custom class loader");
        } catch (final InvocationTargetException ex) {
            final Throwable targetException = ex.getTargetException();
            // LogConfigurationException is expected
            if (!(targetException instanceof LogConfigurationException)) {
                throw ex;
            }
        }
    }
}