com.googlecode.flyway.core.util.ClassUtils.java Source code

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Here is the source code for com.googlecode.flyway.core.util.ClassUtils.java

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/**
 * Copyright (C) 2010-2013 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 com.googlecode.flyway.core.util;

import com.googlecode.flyway.core.FlywayBeanAware;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;

/**
 * Utility methods for dealing with classes.
 */
public class ClassUtils {

    /**
     * Prevents instantiation.
     */
    private ClassUtils() {
        // Do nothing
    }

    /**
     * Creates a new instance of this class.
     *
     * @param className The fully qualified name of the class to instantiate.
     * @param <T> The type of the new instance.
     * @return The new instance.
     * @throws Exception Thrown when the instantiation failed.
     */
    @SuppressWarnings({ "unchecked" })
    // Must be synchronized for the Maven Parallel Junit runner to work
    public static synchronized <T> T instantiate(String className) throws Exception {
        // diff to original is using (configurable) beans from application context
        // start
        ApplicationContext applicationContext = FlywayBeanAware.getApplicationContext();
        if (applicationContext != null) {
            Object instance = null;
            try {
                instance = applicationContext.getBean(Class.forName(className, false, getClassLoader()));
            } catch (NoSuchBeanDefinitionException e) {
            }
            if (instance != null) {
                return (T) instance;
            }
        }
        // end
        return (T) Class.forName(className, true, getClassLoader()).newInstance();
    }

    /**
     * @return The classloader to use for loading classes.
     */
    private static ClassLoader getClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

    /**
     * Determine whether the {@link Class} identified by the supplied name is
     * present and can be loaded. Will return {@code false} if either the class
     * or one of its dependencies is not present or cannot be loaded.
     *
     * @param className the name of the class to check
     * @return whether the specified class is present
     */
    public static boolean isPresent(String className) {
        try {
            getClassLoader().loadClass(className);
            return true;
        } catch (Throwable ex) {
            // Class or one of its dependencies is not present...
            return false;
        }
    }

    /**
     * Computes the short name (name without package) of this class.
     *
     * @param aClass The class to analyse.
     * @return The short name.
     */
    public static String getShortName(Class<?> aClass) {
        String name = aClass.getName();
        return name.substring(name.lastIndexOf(".") + 1);
    }

    /**
     * Retrieves the physical location on disk of this class.
     *
     * @param aClass The class to get the location for.
     * @return The absolute path of the .class file.
     */
    public static String getLocationOnDisk(Class<?> aClass) {
        try {
            String url = aClass.getProtectionDomain().getCodeSource().getLocation().getPath();
            return URLDecoder.decode(url, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            //Can never happen.
            return null;
        }
    }
}