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Diffstat (limited to 'support/arara/source/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java')
-rw-r--r-- | support/arara/source/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/support/arara/source/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java b/support/arara/source/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java new file mode 100644 index 0000000000..c40536ce08 --- /dev/null +++ b/support/arara/source/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java @@ -0,0 +1,166 @@ +/** + * 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); + } + +} |