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/**
* Arara, the cool TeX automation tool
* Copyright (c) 2012 -- 2018, Paulo Roberto Massa Cereda
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the project's author nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package com.github.cereda.arara.utils;
import com.github.cereda.arara.model.Pair;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
/**
* Implements utilitary methods for classloading and object instantiation.
* @author Paulo Roberto Massa Cereda
* @version 4.0
* @since 4.0
*/
public class ClassLoadingUtils {
/**
* Loads a class from the provided file, potentially a Java archive.
* @param file File containing the Java bytecode (namely, a JAR).
* @param name The canonical name of the class.
* @return A pair representing the status and the class.
*/
public static Pair<Integer, Class> loadClass(File file, String name) {
// status and class to be returned,
// it defaults to an object class
int status = 0;
Class value = Object.class;
// if file does not exist, nothing
// can be done, status is changed
if (!file.exists()) {
status = 1;
} else {
// classloading involves defining
// a classloader and fetching the
// desired class from it, based on
// the provided file archive
try {
// creates a new classloader with
// the provided file (potentially
// a JAR file)
URLClassLoader classloader = new URLClassLoader(
new URL[]{
file.toURI().toURL()
},
ClassLoadingUtils.class.getClassLoader()
);
// fetches the class from the
// instantiated classloader
value = Class.forName(name, true, classloader);
} catch (MalformedURLException nothandled1) {
// the file URL is incorrect,
// update status accordingly
status = 2;
} catch (ClassNotFoundException nothandled2) {
// the class was not found,
// update status accordingly
status = 3;
}
}
// return a new pair based on the
// current status and class holder
return new Pair<Integer, Class>(status, value);
}
/**
* Loads a class from the provided file, instantiating it.
* @param file File containing the Java bytecode (namely, a JAR).
* @param name The canonical name of the class.
* @return A pair representing the status and the class object.
*/
public static Pair<Integer, Object> loadObject(File file, String name) {
// load the corresponding class
// based on the qualified name
Pair<Integer, Class> pair = loadClass(file, name);
// status and object to be returned,
// it defaults to an object
int status = pair.getFirstElement();
Object value = new Object();
// checks if the class actually
// exists, otherwise simply
// ignore instantiation
if (status == 0) {
// object instantiation relies
// on the default constructor
// (without arguments), class
// must implement it
// OBS: constructors with arguments
// must be invoked through reflection
try {
// get the class reference from
// the pair and instantiate it
// by invoking the default
// constructor (without arguments)
value = pair.getSecondElement().newInstance();
} catch (IllegalAccessException nothandled1) {
// the object instantiation violated
// an access policy, status is updated
status = 4;
} catch (InstantiationException nothandled2) {
// an instantiation exception has
// occurred, status is updated
status = 5;
}
}
// return a new pair based on the
// current status and object holder
return new Pair<Integer, Object>(status, value);
}
}
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